Streptococcus agalactiae in the environment of bovine dairy herds--rewriting the textbooks?

Dietary anti-inflammatory and anti-bacterial medicinal plants and its compounds in bovine mastitis associated impact on human life

Bovine mastitis (BM) is the most common bacterial mediated inflammatory disease in the dairy cattle that causes huge economic loss to the dairy industry due to decreased milk quality and quantity. Milk is the essential food in the human diet, and rich in crucial nutrients that helps in lowering the risk of diseases like hypertension, cardiovascular diseases and type 2 diabetes. The main causative agents of the disease include various gram negative, and positive bacteria, along with other risk factors such as udder shape, age, genetic, and environmental factors also contributes much for the disease. Currently, antibiotics, immunotherapy, probiotics, dry cow, and lactation therapy are commonly recommended for BM. However, these treatments can only decrease the rise of new cases but can't eliminate the causative agents, and they also exhibit several limitations. Hence, there is an urgent need of a potential source that can generate a typical and ideal treatment to overcome the limitations and eliminate the pathogens. Among the various sources, medicinal plants and its derived products always play a significant role in drug discovery against several diseases. In addition, they are also known for its low toxicity and minimum resistance features. Therefore, plants and its compounds that possess anti-inflammatory and anti-bacterial properties can serve better in bovine mastitis. In addition, the plants that are serving as a food source and possessing pharmacological properties can act even better in bovine mastitis. Hence, in this evidence-based study, we particularly review the dietary medicinal plants and derived products that are proven for anti-inflammatory and anti-bacterial effects. Moreover, the role of each dietary plant and its compounds along with possible role in the management of bovine mastitis are delineated. In this way, this article serves as a standalone source for the researchers working in this area to help in the management of BM.

Role of infrastructure and operation in disease prevalence in dairy farms: groundwork for disease prevention-based antibiotic stewardship

Attempts at regulating misuse of antibiotics in the dairy industry have been ineffective, especially in low- and middle-income countries, who also typically have high burden of preventable infectious disease, we propose a disease prevention-based approach to minimize the need and in turn consumption of antibiotics in dairy farms. Since the immediate environment of the animals is key to disease prevalence, we targeted the infrastructure- and operation-related factors in dairy farms and their link with prevalence of most common diseases and symptoms. We conducted four focused group discussions and a cross-sectional survey in 378 dairy farms to investigate disease prevalence and associated infrastructural (housing system, and manger shape), and operational (waste management, feed management, and type of cleaning agent) parameters. The most common diseases (Mastitis and secondary infections related to Foot-and-mouth disease) and symptoms (fever and diarrhoea) in the focus area were linked with the infrastructural and operational factors on the dairy farm with higher disease prevalence reported in dairy farms, where the animals were exposed to variations in diurnal temperatures or were hard to clean. We further used ML classifiers - Neural Network (NN), k-Nearest Neighbour (kNN), Support Vector Machine (SVM), Decision Tree (DT), and Random Forest (RF) - to corroborate the relationship between infrastructure and operations of the dairy farms and disease prevalence- The DT classifier on randomly sampled data could predict the prevalence of the two most common diseases (accuracy = 92%, F1-score = 0.919) Our results open new avenues for cost-effective interventions such as use of curve-edged mangers, use of rubber mats on floors, not reusing leftover feed etc. in dairy farms to prevent the most common diseases and symptoms in dairy farms and reduce the need and consumption of antibiotics.

Milk as diagnostic fluid for udder health management

BACKGROUND

Mastitis is the major disease affecting milk production of dairy cattle, and milk is an obvious substrate for the detection of both the inflammation and its causative infectious agents at quarter, cow, or herd levels. In this review, we examine the use of milk to detect inflammation based on somatic cell count (SCC) and other biomarkers, and for the detection of mastitis pathogens through culture-based and culture-free methods.

FINDINGS

The use of SCC at a cow or bulk milk level to guide udder health management in lactation is well-established, and SCC is increasingly used to guide selective dry cow treatment. Other markers of inflammation include electrical conductivity, which is used commercially, and markers of disease severity such as acute phase proteins but are not pathogen-specific. Some pathogen-specific markers based on humoral immune responses are available, but their value in udder health management is largely untested. Commercial pathogen detection is based on culture or polymerase chain reaction, with other tests, for example, loop-mediated isothermal amplification or 16S microbiome analysis still at the research or development stage. Matrix-assisted laser desorption ionisation time of flight (MALDI-ToF) is increasingly used for the identification of cultured organisms whilst application directly to milk needs further development. Details of test sensitivity, specificity, and use of the various technologies may differ between quarter, cow, and bulk milk applications.

CONCLUSIONS

There is a growing array of diagnostic assays that can be used to detect markers of inflammation or infection in milk. The value of some of these methods in on-farm udder health improvement programs is yet to be demonstrated whilst methods with proven value may be underutilised.

Molecular characterisation and antimicrobial resistance of Streptococcus agalactiae isolates from dairy farms in China

Introduction

Streptococcus agalactiae (S. agalactiae) is a pathogen causing bovine mastitis that results in considerable economic losses in the livestock sector. To understand the distribution and drug resistance characteristics of S. agalactiae from dairy cow mastitis cases in China, multilocus sequence typing (MLST) was carried out and the serotypes and drug resistance characteristics of the bacteria in the region were analysed.

Material and Methods

A total of 21 strains of bovine S. agalactiae were characterised based on MLST, molecular serotyping, antimicrobial susceptibility testing, and the presence of drug resistance genes.

Results

The serotypes were mainly Ia and II, accounting for 47.6% and 42.9% of all serotypes, respectively. Five sequence types (STs) were identified through MLST. The ST103 and ST1878 strains were predominant, with rates of 52.4% and 28.6%, respectively. The latter is a novel, previously uncharacterised sequence type. More than 90% of S. agalactiae strains were susceptible to penicillin, oxacillin, cephalothin, ceftiofur, gentamicin, florfenicol and sulfamethoxazole. The bacteria showed high resistance to tetracycline (85.7%), clindamycin (52.1%) and erythromycin (47.6%). Resistant genes were detected by PCR, the result of which showed that 47.6%, 33.3% and 38.1% of isolates carried the tet(M), tet(O) and erm(B) genes, respectively.

Conclusion

The results of this study indicate that S. agalactiae show a high level of antimicrobial resistance. It is necessary to monitor the pathogens of mastitis to prevent the transmission of these bacteria.

The Efficacy of Bacteriocins Against Biofilm-Producing Bacteria Causing Bovine Clinical Mastitis in Dairy Farms: A New Strategy

Using an alternative bio-product is one of the most promising ways to control bovine mastitis and avoid new intra-mammary infections. The aims of this study were to ascertain the prevalence of biofilm-forming bacteria responsible for causing clinical mastitis in dairy herds and to assess the effectiveness of bacteriocins, produced by Bacillus subtilis, in controlling the growth of these bacteria in the milk of animals. A total of 150 milk samples were collected from cows and buffalos suffering from mastitis and the etiological agents were isolated and identified by the VITEK-2-COMPACT-SYSTEM®. Additionally, the capability of the bacterial isolates to produce biofilms was determined. RT-PCR was used to detect enterotoxin-producing genes (sed and seb), resistance genes (mecA and blaZ), and biofilm-associated genes (icaA and fnbA) in the isolated bacteria. The susceptibility patterns of the bacterial isolates to bacteriocins were assessed using an agar well-diffusion assay. S. aureus was significantly more capable of producing biofilms than coagulase-negative Staphylococcus isolates. S. ubris was the strongest biofilm producer among the Streptococcus species. The sensitivity profiles of the Staphylococcus spp. (S. aureus and coagulase-negative Staphylococcus) and their biofilm producers to bacteriocins were significantly higher (100% and 90%, respectively) at the same concentration. Bacteriocins had a lethal effect on Staphylococci, Streptococci, and biofilm development at a dose of 250 µg/mL. In dairy farms, bacteriocins are a viable alternative treatment for the prevention and control of bovine clinical mastitis.

Interspecies Interactions within the Host: the Social Network of Group B Streptococcus

Group B Streptococcus (GBS) is a pervasive neonatal pathogen accounting for a combined half a million deaths and stillbirths annually. The most common source of fetal or neonatal GBS exposure is the maternal microbiota. GBS asymptomatically colonizes the gastrointestinal and vaginal mucosa of 1 in 5 individuals globally, although its precise role in these niches is not well understood. To prevent vertical transmission, broad-spectrum antibiotics are administered to GBS-positive mothers during labor in many countries. Although antibiotics have significantly reduced GBS early-onset neonatal disease, there are several unintended consequences, including an altered neonatal microbiota and increased risk for other microbial infections. Additionally, the incidence of late-onset GBS neonatal disease remains unaffected and has sparked an emerging hypothesis that GBS-microbe interactions in developing neonatal gut microbiota may be directly involved in this disease process. This review summarizes our current understanding of GBS interactions with other resident microbes at the mucosal surface from multiple angles, including clinical association studies, agriculture and aquaculture observations, and experimental animal model systems. We also include a comprehensive review of in vitro findings of GBS interactions with other bacterial and fungal microbes, both commensal and pathogenic, along with newly established animal models of GBS vaginal colonization and in utero or neonatal infection. Finally, we provide a perspective on emerging areas of research and current strategies to design microbe-targeting prebiotic or probiotic therapeutic intervention strategies to prevent GBS disease in vulnerable populations.

CDK5RAP3, a key defender of udder, modulates NLRP3 inflammasome activation by regulating autophagolysosome degradation in S. agalactiae-infected mastitis

Streptococcus agalactiae, as one of the main pathogens of clinical and subclinical mastitis, affects animal welfare and leads to huge economic losses to farms due to the sharp decline in milk yield. However, both the real pathogenic mechanisms of S. agalactiae-induced mastitis and the regulator which controls the inflammation and autophagy are largely unknown. Served as a substrate of ubiquitin-like proteins of E3 ligase, CDK5RAP3 is widely involved in the regulation of multiple signaling pathways. Our findings revealed that CDK5RAP3 was significantly down-regulated in mastitis infected by S. agalactiae. Surprisingly, inflammasome activation was triggered by CDK5RAP3 knockdown: up-regulated NLRP3, IL1β and IL6, and cleaved caspase1 promoting by NF-κB, thereby resulting in pyroptosis. Additionally, the accumulation of autophagy markers (LC3B and p62) after CDK5RAP3 knockdown suggested that the autophagolysosome degradation pathway was inhibited, thereby activating the NF-κB pathway and NLRP3 inflammasome. Hence, our findings suggest that downregulation or ablation of CDK5RAP3 inhibits autophagolysosome degradation, causes inflammation by activating the NF-κB /NLRP3 inflammasome, and triggers cell death. In conclusion, CDK5RAP3 holds the key to understanding the interaction between autophagy and immune responses, its anti-inflammatory role in this study will throw new light on the clinical drug discovery to cure S. agalactiae mastitis.

Relationship between Biofilm Production and High Somatic Cell Count in Streptococcus agalactiae Isolated from Milk of Cows with Subclinical Mastitis

Streptococcus agalactiae (S. agalactiae) is one of the main agents that causes mastitis in dairy cows, mainly inducing the subclinical form, which is characterized by a high somatic cell count (SCC). The aim of this study was to correlate the increase in SCC caused by S. agalactiae in cows with subclinical mastitis to the presence of genes related to adhesion and invasion in bovine mammary epithelial cells (BMEC) and biofilm formation. Considering the 145 isolates tested, 57.2% presented the capsular type Ia and 42.8% presented type III. We identified the virulence genes among the isolates and determined nine genetic profiles. The most common profile was identified in 69 isolates (47.5%): Ia, fbsA⁺, fbsB^-, pI1^-, pI2a^-, pI2b⁺, and hylb⁺. All isolates produced biofilm, with 58.6% classified as strong producers, 29% as moderate producers and 12.4% as weak producers. No statistical correlation was found between the presence of virulence genes and increased SCC or biofilm production. However, biological evidence was observed between increased SCC and biofilm production. One isolate from each profile was randomly subjected to adhesion and invasion assays, and all of them adhered to BEMC, but none were able to invade. Our results showed that different genetic profiles do not provide advantages for bacteria to invade BMEC in vitro. In addition, biofilm production appears to be related to high SCC.

Molecular epidemiology, drug resistance, and virulence gene analysis of Streptococcus agalactiae isolates from dairy goats in backyard farms in China

Streptococcus agalactiae infections may lead to clinical or subclinical mastitis in dairy animals when it invades the mammary gland. In this study, 51 S. agalactiae strains were isolated from 305 milk samples that were collected from goats with mastitis in 13 provinces of China. The antimicrobial resistance of S. agalactiae was determined by disk diffusion methods against 18 antibiotics from six classes. In addition, multilocus sequence typing (MLST), and the presence of resistance and virulence genes was determined by PCR analysis. Seven sequence types in five clonal complexes were identified according to MLST; CC103 and CC67 strains were predominant, with rates of 45.1% and 39.2%, respectively. All isolates (100%) were multiresistant to three or more antimicrobial agents. S. agalactiae isolates had a 100% resistance rate to penicillin, oxacillin, and amoxicillin, followed by doxycycline (82.4%), tetracycline (76.5%), and amikacin (74.5%). The lowest resistance was observed for ciprofloxacin (29.4%), which varied in five different regions. The detection rates of six classes of antimicrobial-related genes were calculated as follows: 33 (64.7%) for β-lactam-related resistance gene, 12 (23.5%) for tetracyclines, 11 (21.6%) for quinolone-related resistance genes, 10 (19.6%) for aminoglycosides, 7 (13.7%) for macrolides (ermA, ermB, and mefA), and 3 (5.9%) for lincosamide (lnu(B)). Regarding virulence genes, profile 1 (bca cfb-cspA-cylE-hylB-bibA-pavA-fbsA-fbsB) was the most prevalent, with a detection rate of 54.9%. This work provides a primary source related to the molecular epidemiology of S. agalactiae in dairy goat herds in China and will aid in the clinical treatment, prevention, and control of mastitis.

Antimicrobial Resistance and Virulence Genes of Streptococcus Agalactiae Isolated from Mastitis Milk Samples in China

Introduction

Streptococcus agalactiae is an important zoonotic pathogen that affects milk production and quality and poses a threat to public health. Treatment of infections with this bacterium exploits antimicrobials, to which the resistance of S. agalactiae is a growing problem. Addressing the possibility of a correlation between this pathogen's genetic factors for antimicrobial resistance and virulence, this study attempted to identify the relevant genes.

Material and Methods

Antimicrobial resistance of S. agalactiae isolated from 497 Chinese bovine mastitic milk samples was detected by the broth microdilution method. Eight drug resistance genes and eleven virulence genes were detected using PCR.

Results

Streptococcus agalactiae was 100% susceptible to rifampicin and vancomycin, 93.33% susceptible to sulfisoxazole and sulfamethoxazole, but 100% resistant to ≥3 of the 16 antimicrobial agents, thereby being multidrug resistant, with resistance to oxacillin, tetracycline, erythromycin, clindamycin, and gentamicin being common. The ermB, ermA and lnuA genes were carried by 73.33%, 66.67% and 60.00% of the strains, respectively. The carriage rates of the glnA, clyE, hylB, bibA, iagA, and fbsA virulence genes were greater than 40%, lmb and bac were not observed in any strain, and glnA+hylB+bibA+iagA+fbsA+clyE combined virulence gene patterns were the most commonly detected.

Conclusion

Antimicrobial resistance of S. agalactiae is still a great concern for cattle health in China, and multidrug resistance coupled with the high positive rates of this bacterium's strains for virulence genes indicates the importance of S. agalactiae surveillance and susceptibility tests.

The landscape of antimicrobial resistance in the neonatal and multi-host pathogen group B Streptococcus: review from a One Health perspective

Group B Streptococcus (GBS) stands out as a major agent of pediatric disease in humans, being responsible for 392,000 invasive disease cases and 91,000 deaths in infants each year across the world. Moreover, GBS, also known as Streptococcus agalactiae, is an important agent of infections in animal hosts, notably cattle and fish. GBS population structure is composed of multiple clades that differ in virulence, antimicrobial resistance (AMR), and niche adaptation; however, there is growing evidence of interspecies transmission, both from evolutionary analysis and from disease investigations. The prevention of GBS infections through vaccination is desirable in humans as well as animals because it reduces the burden of GBS disease and reduces our reliance on antimicrobials, and the risk of adverse reactions or selection for AMR. In this perspective article, we navigate through the landscape of AMR in the pediatric and multi-host pathogen GBS under the One Health perspective and discuss the use of antimicrobials to control GBS disease, the evolution of AMR in the GBS population, and the future perspectives of resistant GBS infections in the post-pandemic era.

Evaluation of Control Program Against Streptococcus agalactiae Infection in Dairy Herds During 2019–2021 in Emilia-Romagna Region, Northern Italy

Streptococcus agalactiae (group B Streptococcus, GBS) is a causative agent of mastitis in dairy cattle, mainly causing a subclinical disease associated with a high somatic cell count (SCC), and a consequent decrease in production yield and quality of milk. GBS has been almost eradicated in many Northern European countries, but there are warnings of its re-emergence as a zoonotic threat. In Italy, only two regions carry out a GBS control program: Lombardy and Emilia-Romagna. In Emilia-Romagna, the program has been in place since 2019 and provides for the bacteriological culture of bulk-tank milk (BTM) of all dairy farms every 6 months and the voluntary application of herd eradication programs in the case of positive results. To assess the progress of the program in Emilia Romagna, in terms of herd-level prevalence and GBS transmission between herds, we analyzed the results of 17,056 BTM cultures from 2,831 dairy herds, sampled bi-annually in the period 2019–2021 (six rounds total). The impact of GBS infection on SCC and milk production was also evaluated. The results show a decreasing trend in both the incidence rate (from 3.0 to 1.5%) and apparent prevalence (from 8.9 to 5.2%) of GBS over the study period. By using a susceptible-infected-susceptible (SIS) model for the estimation of the transmission parameters, a basic reproductive number R₀ of 1.4 was calculated, indicating an active spread of GBS in the dairy cattle population of the Emilia-Romagna region. GBS infected farms have a consistently higher BTM SCC than negative ones (+77,000 cells/ml), corresponding to a 0.4 kg/cow/day milk loss. Moreover, GBS infected herds resulted in almost three times more likelihood of having non-marketable milk by exceeding the legal SCC limit. This study demonstrates the need to maintain the current control program against GBS to lower its occurrence and prevent significant market losses to farmers.

Virulence Factor Genes and Cytotoxicity of Streptococcus agalactiae Isolated from Bovine Mastitis in Poland

Streptococcus agalactiae can produce a wide variety of virulence factors, including toxins and proteins which facilitate adhesion to and colonization and invasion of the host cells. There are few reports on the characteristics of field isolates from bovine mastitis in Poland. Thus, the aim of this study was to determine the occurrence of types of hemolysis on blood agar, virulence factor genes, and cytotoxicity of S. agalactiae isolates derived from cows with mastitis across Poland. The study included 68 isolates. Virulence genes were tested using standard PCR, and cytotoxicity was determined using methylthiazol tetrazolium (MTT) and lactate dehydrogenase (LDH) tests. Among the tested isolates, 89.7% were β-hemolytic, 8.8% γ-hemolytic, and 1.5% alpha-hemolytic. The only genes detected in all isolates were the cfb, cspA, hylB, and sip genes. Cytotoxicity assessment based on the LDH test revealed that isolates were cytotoxic only to Vero cells. However, according to the results obtained from the MTT test, more than half of the isolates exhibited low cytotoxicity to both SK and Vero cells, whereas the other isolates showed moderate or no cytotoxicity to both cell lines. Our research confirms the prevalence of various virulence genes in S. agalactiae isolated from Polish dairy herds, which have previously been found in isolates recovered from human and animal infections. For the first time, the presence of bac- and scpB-positive isolates of S. agalactiae was determined in Polish dairy cattle, and the cytotoxicity of bovine isolates was assessed. IMPORTANCE We believe that this manuscript is one of the few reports on the characteristics of field S. agalactiae isolates derived from cases of bovine mastitis in cows in Poland in terms of the occurrence of virulence genes and cytotoxicity. For the first time, the presence of bac- and scpB-positive isolates of S. agalactiae was determined in Polish dairy cattle, and the cytotoxicity of bovine isolates was assessed.

Circulation of Streptococcus agalactiae ST103 in a Free Stall Italian Dairy Farm

We report here on an outbreak of mastitis caused by Streptococcus agalactiae, or group B Streptococcus, in a northern Italy (Lombardy Region) free stall dairy farm. This outbreak was unusual because it occurred in a closed dairy herd and proved to be extremely difficult to resolve even after the application of the classical control procedures, which are specifically focused on the contagious nature of S. agalactiae. In order to better understand the potential origins of the pathogen and the critical points that could impair the eradication program and to investigate the possible presence of S. agalactiae in sources outside the mammary gland, we collected 656 individual composite milk samples, 577 samples from extramammary body sites (289 rectal, 284 vaginal, and four throat samples from milking cows, dry cows, heifers, and calves), and 81 samples from the cattle environment, including the milking parlor and the barn. Twenty-two S. agalactiae isolates were obtained from lactating cows or their environment. Of these, nine were isolated from milk, two were from rectal swabs, and two were from vaginal swabs, while nine were isolated from environmental samples. Based on molecular serotyping, pilus island (PI) typing and multilocus sequence typing, all isolates belonged to serotype III, pilus type PI-1/2b, and sequence type 103 (ST103), a type previously described to have an environmental transmission cycle and a potential human origin. Once the classical mastitis control measures were supplemented with environmental hygiene measures, herd monitoring using bulk tank milk revealed no further positive results for S. agalactiae, and the outbreak was considered resolved. IMPORTANCE Streptococcus agalactiae is an important pathogen in humans and cattle. Bovine mastitis caused by this bacterium and its control are generally associated with contagious transmission between animals. More recently, the presence of a fecal-oral transmission cycle in cattle has been proposed, linked to the ability of some S. agalactiae strains to survive in the bovine gastrointestinal tract and environment. Based on analysis of 1,316 specimens from cattle and their environment on a single dairy farm, we demonstrate the presence of sequence type 103 (ST103), which may have an environmental mode of transmission. This possibility was supported by the fact that the mastitis outbreak could not be controlled through measures to prevent contagious transmission alone and required additional environmental hygiene measures to be brought to a halt. This case study highlights that measures to control animal disease need to evolve alongside the microorganisms that cause them.

Molecular typing and prevalence of antibiotic resistance and virulence genes in Streptococcus agalactiae isolated from Chinese dairy cows with clinical mastitis

Bovine mastitis is a common disease occurring in dairy farms and can be caused by more than 150 species of pathogenic bacteria. One of the most common causative organisms is Streptococcus agalactiae, which is also potentially harmful to humans and aquatic animals. At present, research on S. agalactiae in China is mostly concentrated in the northern region, with limited research in the southeastern and southwestern regions. In this study, a total of 313 clinical mastitis samples from large-scale dairy farms in five regions of Sichuan were collected for isolation of S. agalactiae. The epidemiological distribution of S. agalactiae was inferred by serotyping isolates with multiplex polymerase chain reaction. Susceptibility testing and drug resistance genes were detected to guide the clinical use of antibiotics. Virulence genes were also detected to deduce the pathogenicity of S. agalactiae in Sichuan Province. One hundred and five strains of S. agalactiae (33.6%) were isolated according to phenotypic features, biochemical characteristics, and 16S rRNA sequencing. Serotype multiplex polymerase chain reaction analysis showed that all isolates were of type Ia. The isolates were up to 100% sensitive to aminoglycosides (kanamycin, gentamicin, neomycin, and tobramycin), and the resistance rate to β-lactams (penicillin, amoxicillin, ceftazidime, and piperacillin) was up to 98.1%. The TEM gene (β-lactam-resistant) was detected in all isolates, which was in accordance with a drug-resistant phenotype. Analysis of virulence genes showed that all isolates harbored the cfb, cylE, fbsA, fbsB, hylB, and α-enolase genes and none harbored bac or lmb. These data could aid in the prevention and control of mastitis and improve our understanding of epidemiological trends in dairy cows infected with S. agalactiae in Sichuan Province.

Streptococcus agalactiae-induced autophagy of bovine mammary epithelial cell via PI3K/AKT/mTOR pathway

Streptococcus agalactiae (S. agalactiae) infection is a significant cause of mastitis, resulting in loss of cellular homeostasis and tissue damage. Autophagy plays an essential function in cell survival, defense, and the preservation of cellular homeostasis, and is often part of the response to pathogenic challenge. However, the effect of autophagy induced by S. agalactiae in bovine mammary epithelial cells (bMECs) is mainly unknown. So in this study, an intracellular S. agalactiae infection model was established. Through evaluating the autophagy-related indicators, we observed that after S. agalactiae infection, a significant quantity of LC3-I was converted to LC3-II, p62 was degraded, and levels of Beclin1 and Bcl2 increased significantly in bMECs, indicating that S. agalactiae induced autophagy. The increase in levels of LAMP2 and LysoTracker Deep Red fluorescent spots indicated that lysosomes had participated in the degradation of autophagic contents. After autophagy was activated by rapamycin (Rapa), the amount of p-Akt and p-mTOR decreased significantly, whilst the amount of intracellular S. agalactiae increased significantly. Whereas the autophagy was inhibited by 3-methyladenine (3MA), the number of intracellular pathogens decreased. In conclusion, the results demonstrated that S. agalactiae could induce autophagy through PI3K/Akt/mTOR pathway and utilize autophagy to survive in bMECs.

The Influence of Bacteria Causing Subclinical Mastitis on the Structure of the Cow’s Milk Microbiome

Mastitis is the most expensive disease of dairy cattle across the world and is the main reason for the use of antibiotics in animal husbandry. The aim of this study was to analyze the microbiome of raw milk obtained from a semi-subsistence farm located in the Kuyavian–Pomeranian Voivodeship in Poland. Milk from healthy cows and from cows with subclinical mastitis was analyzed. The following pathogenic bacteria were found in milk from individuals with subclinical mastitis: Escherichia coli or Streptococcus agalactiae. The composition of drinking milk was assessed on the basis of 16S rRNA gene sequencing using the Ion Torrent platform. Based on the conducted research, significant changes in the composition of the milk microbiome were found depending on the physiological state of the cows. The microbiome of milk from healthy cows differed significantly from the milk from cows with subclinical mastitis. Two phyla dominated in the milk from healthy cows: Firmicutes and Proteobacteria, in equal amounts. On the contrary, in the milk from cows with diagnosed subclinical mastitis, one of the types dominated: either Firmicutes or Proteobacteria, and was largely predominant. Moreover, the milk microflora from the ill animals were characterized by lower values of the determined biodiversity indicators than the milk from healthy cows. The presence of pathogenic bacteria in the milk resulted in a significant reduction in the share of lactic acid bacteria in the structure of the population of microorganisms, which are of great importance in the production technology of regional products.

The prevalence, molecular characterization and antimicrobial resistance profiling of Streptococcus agalactiae isolated from clinical mastitis cases on large dairy farms in China

This research communication aims to characterize the prevalence, molecular characterization and antimicrobial resistance profiling of Streptococcus agalactiae isolated from clinical mastitis in China. A total of 140 Strep. agalactiae isolates were identified from 12 out of 201 farms in 6 provinces, overall herd prevalence was 18.6% and the MLST analysis showed clonal complexes (CC) 103 and CC 67 were present in these herds with CC 103 predominant, accounting for 97.9%. Isolates were mostly sensitive to the tested antimicrobials: penicillin, ceftiofur, amoxi/clav, cefquinome, and vancomycin (100%), followed by cefalexin (97.9%), oxacillin (96.4%), enrofloxacin (95.7%), erythromycin (89.3%), and clindamycin (88.6%). Only 19.3 and 0.7% of isolates were sensitive to tetracycline and daptomycin, respectively, and sequence type (ST) 103 was most resistant to antimicrobials. In conclusion, CC 103 was the predominant subgroup of bovine mastitis Strep. agalactiae in China, and most antimicrobials apart from tetracycline and daptomycin were effective.

Investigation of extramammary sources of Group B Streptococcus reveals its unusual ecology and epidemiology in camels

Camels are vital to food production in the drylands of the Horn of Africa, with milk as their main contribution to food security. A major constraint to camel milk production is mastitis, inflammation of the mammary gland. The condition negatively impacts milk yield and quality as well as household income. A leading cause of mastitis in dairy camels is Streptococcus agalactiae, or group B Streptococcus (GBS), which is also a commensal and pathogen of humans and cattle. It has been suggested that extramammary reservoirs for this pathogen may contribute to the occurrence of mastitis in camels. We explored the molecular epidemiology of GBS in camels using a cross-sectional study design for sample collection and phenotypic, genomic and phylogenetic analysis of isolates. Among 88 adult camels and 93 calves from six herds in Laikipia County, Kenya, GBS was detected in 20% of 50 milk samples, 25% of 152 nasal swabs, 8% of 90 oral swabs and 3% of 90 rectal swabs, but not in vaginal swabs. Per camel herd, two to four sequence types (ST) were identified using Multi Locus Sequence Typing (MLST). More than half of the isolates belonged to ST617 or its single-locus variant, ST1652, with these STs found across all sample types. Capsular serotype VI was detected in 30 of 58 isolates. In three herds, identical STs were detected in milk and swab samples, suggesting that extramammary sources of GBS may contribute to the maintenance and spread of GBS within camel herds. This needs to be considered when developing prevention and control strategies for GBS mastitis. The high nasal carriage rate, low recto-vaginal carriage rate, and high prevalence of serotype VI for GBS in camels are in stark contrast to the distribution of GBS in humans and in cattle and reveal hitherto unknown ecological and molecular features of this bacterial species.

Assessing potential routes of Streptococcus agalactiae transmission between dairy herds using national surveillance, animal movement data and molecular typing

Streptococcus agalactiae, also known as group B Streptococcus (GBS), is a pathogen of humans and animals. It is an important cause of mastitis in dairy cattle, causing decreased milk quality and quantity. Denmark is the only country to have implemented a national surveillance and control campaign for GBS in dairy cattle. After a significant decline in the 20th century, prevalence has increased in the 21st century. Using a unique combination of national surveillance, cattle movement data and molecular typing, we tested the hypothesis that transmission mechanisms differ between GBS strains that are almost exclusive to cattle and those that affect humans as well as cattle, which would have implications for control recommendations. Three types of S. agalactiae, sequence type (ST) 1, ST23 and ST103 were consistently the most frequent strains among isolates obtained through the national surveillance programme from 2009 to 2011. Herds infected with ST103, which is common in cattle but rarely found in people in Europe, were spatially clustered throughout the study period and across spatial scales. By contrast, strains that are also commonly found in humans, ST1 and ST23, showed no spatial clustering in most or any years of the study, respectively. Introduction of cattle from a positive herd was associated with increased risk of infection by S. agalactiae in the next year (risk ratio of 2.9 and 4.7 for 2009-2010 and 2010-2011, respectively). Moreover, mean exposure to infection was significantly higher for newly infected herds and significantly lower for persistently susceptible herds, as compared to random simulated networks with the same properties, which suggests strong association between the cattle movement network and new infections. At strain-level, new infections with ST1 between 2009 and 2010 were significantly associated with cattle movements, while other strains showed only some degree of association. Sharing of veterinary services, which may serve as proxy for local or regional contacts at a range of scales, was not significantly associated with increased risk of introduction of S. agalactiae or one of the three predominant strains on a farm. Our findings support the reinstatement of restrictions on cattle movements from S. agalactiae positive herds, which came into effect in 2018, but provide insufficient evidence to support strain-specific control recommendations.

Investigations on Transfer of Pathogens between Foster Cows and Calves during the Suckling Period

Simple Summary

Regarding the increasing importance of alternative calf rearing systems, such as the foster cow system, better knowledge about the transfer of pathogens via suckling calves would be very helpful. In this context, the present study was conducted on a large organic dairy farm practising calf rearing on foster cows. For microbiological examinations, quarter milk samples were collected both from foster cows and biological dams. Additionally, swabs were taken from the oral cavities of the associated foster calves. The concordance of pathogens between cows and calves was further examined by strain comparisons. The same strains of isolates were detected for Pasteurella multocida, Staphylococcus aureus, S. sciuri and Streptococcus (Sc.) suis. Based on the present results and the available literature, transmission of P. multocida and S. aureus via suckling calves is considered very likely. Transmission of pathogens from the dam to the foster cow with the suckling calf as a vector could not be detected.

Abstract

To date, there have been few studies on the health effects of foster cow systems, including the transmission of mastitis-associated pathogens during suckling. The present study aimed to compare the pathogens detected in the mammary glands of the foster cow with those in the oral cavities of the associated foster calves and to evaluate the resulting consequences for udder health, calf health and internal biosecurity. Quarter milk sampling of 99 foster cows from an organic dairy farm was conducted twice during the foster period. Oral cavity swabs were taken from 345 foster calves. Furthermore, quarter milk samples were collected from 124 biological dams to investigate possible transmission to the foster cows via the suckling calves. All samples were microbiologically examined and confirmed by MALDI-TOF (matrix-assisted laser desorption time-of-flight mass-spectrometry). Using RAPD-PCR (randomly amplified polymorphic DNA polymerase chain reaction), strain similarities were detected for Pasteurella multocida, Staphylococcus aureus, S. sciuri and Streptococcus (Sc.) suis. Transmission of P. multocida and S. aureus probably occurred during suckling. For S. sciuri and Sc. suis, environmental origins were assumed. Transmission from dam to foster cow with the suckling calf as vector could not be clearly demonstrated.

The fall and rise of group B Streptococcus in dairy cattle: reintroduction due to human-to-cattle host jumps?

Group B Streptococcus (GBS; Streptococcus agalactiae) is a major neonatal and opportunistic bacterial pathogen of humans and an important cause of mastitis in dairy cattle with significant impacts on food security. Following the introduction of mastitis control programmes in the 1950s, GBS was nearly eradicated from the dairy industry in northern Europe, followed by re-emergence in the 21st century. Here, we sought to explain this re-emergence based on short and long read sequencing of historical (1953–1978; n=44) and contemporary (1997–2012; n=76) bovine GBS isolates. Our data show that a globally distributed bovine-associated lineage of GBS was commonly detected among historical isolates but never among contemporary isolates. By contrast, tetracycline resistance, which is present in all major GBS clones adapted to humans, was commonly and uniquely detected in contemporary bovine isolates. These observations provide evidence for strain replacement and suggest a human origin of newly emerged strains. Three novel GBS plasmids were identified, including two showing >98 % sequence similarity with plasmids from Streptococcus pyogenes and Streptococcus dysgalactiae subsp. equisimilis, which co-exist with GBS in the human oropharynx. Our findings support introduction of GBS into the dairy population due to human-to-cattle jumps on multiple occasions and demonstrate that reverse zoonotic transmission can erase successes of animal disease control campaigns.

Genomic analysis of group B Streptococcus from milk demonstrates the need for improved biosecurity: a cross-sectional study of pastoralist camels in Kenya

BACKGROUND

Streptococcus agalactiae (Group B Streptococcus, (GBS)) is the leading cause of mastitis (inflammation of the mammary gland) among dairy camels in Sub-Saharan Africa, with negative implications for milk production and quality and animal welfare. Camel milk is often consumed raw and presence of GBS in milk may pose a public health threat. Little is known about the population structure or virulence factors of camel GBS. We investigated the molecular epidemiology of camel GBS and its implications for mastitis control and public health.

RESULTS

Using whole genome sequencing, we analysed 65 camel milk GBS isolates from 19 herds in Isiolo, Kenya. Six sequence types (STs) were identified, mostly belonging to previously described camel-specific STs. One isolate belonged to ST1, a predominantly human-associated lineage, possibly as a result of interspecies transmission. Most (54/65) isolates belonged to ST616, indicative of contagious transmission. Phylogenetic analysis of GBS core genomes showed similar levels of heterogeneity within- and between herds, suggesting ongoing between-herd transmission. The lactose operon, a marker of GBS adaptation to the mammary niche, was found in 75 % of the isolates, and tetracycline resistance gene tet(M) in all but two isolates. Only the ST1 isolate harboured virulence genes scpB and lmb, which are associated with human host adaptation.

CONCLUSIONS

GBS in milk from Kenyan camel herds largely belongs to ST616 and shows signatures of adaptation to the udder. The finding of similar levels of within- and between herd heterogeneity of GBS in camel herds, as well as potential human-camel transmission highlights the need for improved internal as well as external biosecurity to curb disease transmission and increase milk production.

The Recombinant Expression Proteins FnBP and ClfA From Staphylococcus aureus in Addition to GapC and Sip From Streptococcus agalactiae Can Protect BALB/c Mice From Bacterial Infection

Dairy cow mastitis is a serious disease that is mainly caused by intramammary infection with Staphylococcus aureus and Streptococcus agalactiae [group B streptococcus (GBS)]. FnBP and ClfA are the virulence factors of S. aureus, while GapC is the respective factor for S. agalactiae. Sip is a highly immunogenic protein, and it is conserved in all GBS serotypes. In this study, we analyzed the abovementioned four genes prepared a FnBP+ClfA chimeric protein (FC), a GapC+Sip chimeric protein (GS), and a FnBP+ClfA+GapC+Sip chimeric protein (FCGS) based on the antigenic sites to evaluate their use in vaccine development. After expression and purification of the recombinant proteins in Escherichia coli, BALB/c mice were immunized with them to examine resistance effects. The total lethal and half lethal doses of S. aureus and S. agalactiae were then measured, and the immunoprotective effects of the fusion proteins were evaluated. The FC and FCGS chimeric proteins could induce mice to produce high levels of antibodies, and bacterial loads were significantly reduced in the spleens and livers after challenge. After immunization with FCGS, the recipients resisted the attacks of both S. aureus and S. agalactiae, indicating the potential of the fusion protein as a mastitis vaccine.

Evidence of Common Isolates of Streptococcus agalactiae in Bovines and Humans in Emilia Romagna Region (Northern Italy)

Streptococcus agalactiae (group B Streptococcus, GBS) is one of the most important agents of bovine mastitis and causes remarkable direct and indirect economic losses to the livestock sector. Moreover, this species can cause severe human diseases in susceptible individuals. To investigate the zoonotic potential of S. agalactiae, 203 sympatric isolates from both humans and cattle, isolated in the same time frame (2018) and in the same geographic area (Emilia Romagna region, Northern Italy), were characterized by molecular capsular typing (MCT), pilus island typing (PI), and multi-locus sequence typing (MLST). In addition, antibiotic-resistant phenotypes were investigated. The distribution of the allelic profiles obtained by combining the three genotyping methods (MCT-PI-MLST) resulted in 64 possible genotypes, with greater genetic variability among the human compared to the bovine isolates. Although the combined methods had a high discriminatory power (>96,2%), five genotypes were observed in both species (20,9% of the total isolates). Furthermore, some of these strains shared the same antibiotic resistance profiles. The finding of human and bovine isolates with common genotypes and antibiotic resistance profiles supports the hypothesis of interspecies transmission of S. agalactiae between bovines and humans.

Transmission dynamics of Staphylococcus aureus and Streptococcus agalactiae in a Dutch dairy herd using an automatic milking system

Staphylococcus aureus and Streptococcus agalactiae are important contagious mastitis pathogens and are considered to mainly transmit between cows through the milking machine. Controlling contagious mastitis on dairy farms requires a reduction of the transmission rate or the duration of intramammary infections (IMI), or both. These parameters may differ in dairy herds milked with an automatic milking system (AMS) as compared to those milked with a conventional milking system (CMS). The aims of this prospective longitudinal study were to estimate the transmission rate, the median duration of IMI and the basic reproduction number (R₀) of Staph. aureus and Strep. agalactiae in a Dutch AMS herd. Bacteriological cultures of quarter milk samples were collected every 2 wks. Using 3 different definitions of IMI, we estimated the transmission rate for Staph. aureus to be within the range of 0.002 (95 % CI: 0-0.005) quarter-day^-1 to 0.019 (95 % CI: 0.010-0.032) quarter-day^-1, and for Strep. agalactiae of 0.007 (95 % CI: 0.005-0.010) quarter-day^-1 to 0.019 (95 % CI: 0.011-0.032) quarter-day^-1, the median duration of chronic IMI at 95 (95 % CI: 72-125) days for Staph. aureus and at 86 (95 % CI: 67-111) days for Strep. agalactiae, and the R₀ between 0.16 (95 % CI: 0.05-0.27) and 0.34 (95 % CI: 0.20-0.48) for Staph. aureus, and between 0.64 (95 % CI: 0.41-0.87) and 0.68 (95 % CI: 0.48-0.88) for Strep. agalactiae. Transmission of these two contagious pathogens in this herd was limited and theoretically the IMI would not sustain, given that R₀ of both pathogens was lower than 1. The estimated transmission rate of Staph. aureus in this AMS herd was found to be comparable to those described for CMS herds, while for Strep. agalactiae, it was slightly higher than in CMS herds. The duration of Staph. aureus IMI was in line with results from CMS farms, while the duration of Strep. agalactiae was lower than what has been described in CMS herds. The R₀ of these contagious pathogens was found to be lower than the estimates in CMS herds. Our study suggests that the transmission rate of these two contagious pathogens in this AMS herd were comparable to what has been reported about well-performing CMS herds that have a low rate of transmission.

Antimicrobial and antibiofilm potentials of cinnamon oil and silver nanoparticles against Streptococcus agalactiae isolated from bovine mastitis: new avenues for countering resistance

BACKGROUND

Streptococcus agalactiae (S. agalactiae) is a contagious pathogen of bovine mastitis. It has financial implications for the dairy cattle industry in certain areas of the world. Since antimicrobial resistance increases in dairy farms, natural antimicrobials from herbal origins and nanoparticles have been given more attention as an alternative therapy. Hence, this study reported the antimicrobial and antibiofilm potentials of cinnamon oil, silver nanoparticles (AgNPs), and their combination against multidrug-resistant (MDR) S. agalactiae recovered from clinical bovine mastitis in Egypt.

RESULTS

Our findings revealed that 73% (146/200) of the examined milk samples collected from dairy cows with clinical mastitis were infected with Streptococci species. Of these, 9.59% (14/146) were identified as S. agalactiae and categorized as MDR. S. agalactiae isolates expressed four virulence genes (Hyl, cylE, scpB, and lmb) and demonstrated an ability to produce biofilms. Cinnamon oil showed high antimicrobial (MICs ≤0.063 μg /mL) and antibiofilm (MBIC50 = 4 μg/mL) potentials against planktonic and biofilms of S. agalactiae isolates, respectively. However, AgNPs showed reasonable antimicrobial (MICs ≤16 μg/mL) and relatively low antibiofilm (MBIC50 = 64 μg/mL) activities against screened isolates. Synergistic antimicrobial or additive antibiofilm interactions of cinnamon oil combined with AgNPs were reported for the first time. Scanning electron microscope (SEM) analysis revealed that biofilms of S. agalactiae isolates treated with cinnamon oil were more seriously damaged than observed in AgNPs cinnamon oil combination. Moreover, reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) showed that cinnamon oil exerted a remarkable down-regulation of pili biosynthesis genes (pilA and pilB) and their regulator (rogB) against S. agalactiae biofilms, meanwhile the AgNPs cinnamon oil combination demonstrated a lower efficacy.

CONCLUSIONS

This is an in vitro preliminary approach that documented the antibiofilm potential of cinnamon oil and the inhibitory activity of cinnamon oil and its combination with AgNPs against MDR S. agalactiae recovered from clinical mastitis. Further in vivo studies should be carried out in animal models to provide evidence of concept for implementing these alternative candidates in the treatment of dairy farms infected by streptococcal mastitis in the future.

Effect of enhanced hygiene on transmission of Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus dysgalactiae in dairy herds with automatic milking systems

The objective of the study was to evaluate the effect of hygiene measures in automatic milking units on the transmission of 3 mastitis pathogens considered to be mainly or partly transmitted from cow to cow during milking events. Two studies were conducted as within-herd experimental trials in 2 Danish commercial dairy herds (A and B) with automatic milking systems. Interventions to enhance hygiene were implemented on the automatic milking units. The 2 studies evaluated separate interventions. In herd A, the hygiene interventions were manual wash with the Lely foam unit and adjustments on the brush-mediated teat cleaning procedure. In herd B, the hygiene intervention included automatic disinfection spray on the upper surface of the brush motor and daily change of brushes. Composite milk samples were collected longitudinally at 3- or 4-wk intervals from all lactating cows. Additional milk samples were taken from cows entering or leaving the study groups. Milk samples were analyzed with quantitative PCR. A hidden Markov model implemented within a Bayesian framework was used to estimate the transmission probability. For analysis, 701 samples from 156 cows were used for herd A, and 1,349 samples from 390 cows were used for herd B. In the intervention group in herd B, transmission of Streptococcus agalactiae was reduced to 19% (95% posterior credibility interval: 0.00-64%) of the transmission in the control group, whereas transmission of Streptococcus dysgalactiae was reduced to 17% (95% posterior credibility interval: 0.00-85%) of transmission in the control group. This suggests that automatic spray on the upper surface of the brush motor with disinfectant along with daily change of brushes collectively reduced transmission of Strep. agalactiae and Strep. dysgalactiae. Results on Staphylococcus aureus in herd B and results on manual foam cleaning and brush-mediated teat cleaning adjustments in herd A were inconclusive.

Prudent Use of Antibiotics in Dairy Cows: The Nordic Approach to Udder Health

Global concerns regarding bacterial antibiotic resistance demand prudent use of antibiotics in livestock production. Dairy production in the Nordic countries has a low consumption of antibiotics, while animal health, productivity and milk quality are at high levels. Here, we describe the basis of Nordic mastitis control and treatment strategies, as a model for production of high-quality milk with prudent use of antibiotics. We hope this will be beneficial for dairy producers and advisors in other countries and regions that consider limiting antibiotic use in cattle herds. In this perspectives paper we describe the dairy sector in the Nordic countries, and present regulatory aspects of antibiotic use, diagnostics and current guidelines for treatment of clinical mastitis as well as dry cow therapy. We also show summary statistics of udder health indicators in Denmark, Finland, Norway and Sweden, to illustrate the effects of the implemented udder health management practices.

Molecular epidemiology, antimicrobial activity, and virulence gene clustering of Streptococcus agalactiae isolated from dairy cattle with mastitis in China

Streptococcus agalactiae is a contagious pathogen that causes bovine mastitis worldwide, resulting in considerable economic losses. In this study, we isolated 42 S. agalactiae strains in 379 milk samples from cows with subclinical mastitis on 15 dairy farms in 12 Chinese provinces. Analysis based on capsular typing and multilocus sequence typing, combined with patterns of virulence gene scanning and antimicrobial resistance, identified the lineages and populations of the isolates. We grouped the 42 isolates into 7 sequence types belonging to 6 clonal complexes, mainly CC103 (31/42 isolates; 73.8%). We identified an ST-23 strain named Sa 129 for the first time on Chinese dairy farms-this strain is usually associated with human isolates. Capsular types Ia and II were predominant in capsular typing. The prevalence of virulence profile 1 (bibA, cfb, cspA, cylE, fbsA, fbsB, hylB, and pavA) was 64.3%, and represented the main trend in China. With respect to antimicrobial resistance, most isolates were susceptible to β-lactams, rifamycin, glycopeptides, and oxazolidone; resistance to several antimicrobial agents, including lincomycin, clindamycin, and doxycycline, varied in 4 different regions. Our research provides a profile for the molecular epidemiology, multilocus sequence typing, antimicrobial resistance, and virulence gene clustering of S. agalactiae, and may be beneficial for the clinical monitoring, prevention, and control of mastitis in dairy cattle.

Molecular characterization of pathogenic group B streptococcus from a tertiary hospital in Shanxi, China: High incidence of sequence type 10 strains in infants/pregnant women

BACKGROUND

Group B streptococcus (GBS) is a leading cause of serious infection in infants. Understanding its regional molecular epidemiology is helpful for regulating efficient prevention practice.

METHODS

A retrospective study was conducted to collected data from infants and pregnant women with culture-proven GBS disease in the largest women and children's medical center in Shanxi between January 2017 and September 2019. All GBS isolates were analyzed by multi-locus sequence typing (MLST) as well as distribution of pilus island (PI) genes.

RESULTS

A total of 54 GBS isolates were obtained from 36 (66.7%) pregnant women and 18 (33.3%) infants with invasive disease. Among invasive GBS strains, the most common sequence type was ST10 (72.2%, P < 0.05), followed by ST23 and ST19. The ST10 strain was also the leading sequence type in colonizing pregnant women (44.4%, P < 0.05). All of the isolates carried at least one pilus island. The most frequently detected pilus island was PI-1+PI-2a (85.2%, P < 0.05), followed in turn by PI-2a and PI-2b.

CONCLUSIONS

Our study demonstrates that one hypervirulent clone, sequence type 10, accounts for a large proportion of invasive GBS disease in infants and colonizing pregnant women, and the PI-1+PI-2a sub-lineages should be noted in infant infections.

Bovine mastitis: risk factors, therapeutic strategies, and alternative treatments - A review

Bovine mastitis, an inflammation of the mammary gland, is the most common disease of dairy cattle causing economic losses due to reduced yield and poor quality of milk. The etiological agents include a variety of gram-positive and gram-negative bacteria, and can be either contagious (e.g., Staphylococcus aureus, Streptococcus agalactiae, Mycoplasma spp.) or environmental (e.g., Escherichia coli, Enterococcus spp., coagulase-negative Staphylococcus, Streptococcus uberis). Improving sanitation such as enhanced milking hygiene, implementation of post-milking teat disinfection, maintenance of milking machines are general measures to prevent new cases of mastitis, but treatment of active mastitis infection is dependant mainly on antibiotics. However, the extensive use of antibiotics increased concerns about emergence of antibiotic-resistant pathogens and that led the dairy industries to reduce the use of antibiotics. Therefore, alternative therapies for prevention and treatment of bovine mastitis, particularly natural products from plants and animals, have been sought. This review provides an overview of bovine mastitis in the aspects of risk factors, control and treatments, and emerging therapeutic alternatives in the control of bovine mastitis.

Subclinical mastitis in pastoralist dairy camel herds in Isiolo, Kenya: Prevalence, risk factors, and antimicrobial susceptibility

Mastitis is an important constraint to milk production in pastoralist camel (Camelus dromedarius) herds in Kenya. The objective of this study was to investigate the prevalence, risk factors, and bacterial panorama of subclinical mastitis (SCM) in pastoralist camel herds in Isiolo County, Kenya. Furthermore, antimicrobial susceptibility in udder pathogens was studied. A cross-sectional sample of 206 camels from 20 milking herds was screened using the California Mastitis Test (CMT), and quarter milk was subjected to bacterial culturing. Isolates were confirmed using MALDI-TOF mass spectrometry analysis, and antimicrobial susceptibility was determined using the broth microdilution method. Interviews focusing on herd management were conducted with camel owners. Subclinical mastitis, defined as a CMT score ≥ 3 (scale 1 to 5) and absence of clinical symptoms in the udder, were present in all visited herds. On the individual level, 46% of the camels had at least 1 quarter affected with SCM, and on the quarter level the prevalence was 26%. Intramammary infections (IMI) were common; out of 798 quarter milk samples, 33% yielded conclusive bacterial growth. The sensitivity and specificity of CMT for correctly identifying quarters with IMI were 82% and 92%, respectively. The most prevalent pathogen was Streptococcus agalactiae (72% of IMI-positive quarters), followed by non-aureus staphylococci (19%) and Staphylococcus aureus (13%). Antimicrobial susceptibility testing revealed that only a low proportion (4.9%) of Strep. agalactiae isolates was sensitive to tetracycline. For Staph. aureus, 59.1% of isolates exhibited sensitivity to penicillin. Skin lesions on the teats or udder were a risk factor for SCM. Increased age, parity, and stage of lactation were associated with increased risk of both SCM and IMI. Older camels with a blind teat or a previous history of mastitis were more likely to be infected with Strep. agalactiae. Hygiene routines for milking were largely absent in the observed herds, and knowledge of adequate milk handling was limited. The poor udder health is likely to depend on multiple factors, most prominently the within-herd maintenance of contagious udder pathogens, in combination with difficult sanitary conditions and lack of awareness among camel keepers. This study showed that in pastoralist camel herds around Isiolo town, SCM and IMI specifically caused by Strep. agalactiae are common udder health problems and are associated with increasing age, parity, and stage of lactation, and skin lesions on the teats and udder. Resistance to tetracycline in Strep. agalactiae was common. Control strategies specifically targeting SCM and adapted to pastorally managed camel herds need to be developed to reduce disease, combat antimicrobial resistance, and improve the livelihoods of pastoralists.

Recombinant of the Staphylococcal Bacteriophage Lysin CHAPk and Its Elimination against Streptococcus agalactiae Biofilms

Bovine mastitis is the most important infectious disease, causing significant losses in the dairy industry, in which Streptococcus agalactiae is a major pathogen. In this study, lysin CHAP_k, derived from bacteriophage K, was expressed heterogeneously, and its antimicrobial and anti-biofilm effects against S. agalactiae isolated from bovine mastitis were further analyzed. CHAP_k was expressed in Escherichia coli BL21 (DE3), in which the purified yield of CHAP_k was up to 14.6 mg/L with the purity of 95%. Time-killing kinetic curves showed that CHAP_k fastly killed S. agalactiae in TSB medium and in milk within 25 min (by 3.3 log₁₀ CFU/mL and 2.4 log₁₀ CFU/mL, respectively). Observation of scanning electron microscope (SEM) showed cells wrinkled and ruptured after the treatment of CHAP_k. CHAP_k effectively inhibited early biofilms by 95% in 8 × MIC, and eradicated mature biofilms by 89.4% in 16 × MIC. Moreover, CHAP_k killed 99% bacteria in mature biofilms. Confocal laser scanning microscopy (CLSM) also demonstrated the potent antimicrobial and anti-biofilm action of CHAP_k. It was firstly demonstrated CHAP_k had the characters of inhibition/elimination of S. agalactiae biofilms and killing the bacteria in biofilms. CHAP_k has the potential to develop a new antibacterial agent for mastitis treatment of S. agalactiae infections.

Microbiome and Metabolome Analyses of Milk From Dairy Cows With Subclinical Streptococcus agalactiae Mastitis-Potential Biomarkers

The microbial ecosystem in the udders of dairy cows directly influences the flavor and quality of milk. However, to our knowledge, no published research has analyzed the complex relationship between the udder microbiome and its associated metabolism in animals with subclinical mastitis. We identified the bacterial species and measured relative population numbers in the milk of cows with subclinical Streptococcus agalactiae mastitis (GBS) and compared this information to that from the milk of healthy cows. Metabolite profiles were determined to investigate correlations between the milk microbiota and metabolic factors in healthy vs. GBS dairy cows. Six milk samples from GBS cows and six from healthy cows were subjected to 16S rRNA gene sequencing to identify the microbial species using a MiSeq high-throughput sequencing apparatus. The metabolites present in the milk were identified by gas chromatography time-of-flight mass spectrometry. Both principal component analysis and orthogonal partial least squares discriminant analysis indicated that the metabolites were well-separated from each other in the milk samples from the two groups. GBS dramatically altered microbial diversity, and the GBS group had significantly fewer Proteobacteria, Actinobacteria, and Acidobacteria than the CON group, with greater relative abundance of Firmicutes (p < 0.01). Several bacterial genera, such as Streptococcus, were significantly more abundant in milk from the GBS group than in milk from the CON group, and there was a tendency for greater abundance of Turicibacter (p = 0.07) and Enterococcus spp. (p = 0.07) in the GBS group. The levels of five milk metabolites were significantly higher in the GBS group than in the CON group: phenylpyruvic acid, the homogentisic acid: 4-hydroxyphenylpyruvic acid ratio, the xanthine: guanine ratio, uridine and glycerol. Metabolic pathway analysis of the different metabolites revealed that the following were enriched in both groups: galactose metabolism; pentose and glucuronate interconversion; starch and sucrose metabolism; alanine, aspartate and glutamate metabolism; arginine biosynthesis; citrate cycle (TCA cycle); D-glutamine and D-glutamate metabolism; and the neomycin, kanamycin, and gentamicin biosynthesis pathways. Several typical metabolites were highly correlated with specific ruminal bacteria, such as Streptococcaceae, Lachnospiraceae, Lactobacillaceae and Corynebacteriaceae, demonstrating the functional correlations between the milk microbiome and associated metabolites. These findings revealed that the milk microbiota and metabolite profiles were significantly different between the two groups of cows, raising the question of whether the microbiota associated with the bovine mammary gland could be related to mammary gland health. There was also a relationship between milk quality and the presence of spoilage bacteria. Other bacterial taxa should be investigated, as related information may provide insights into how perturbations in milk metabolomics profiles relate to differences in milk synthesis between healthy cows and those with subclinical mastitis.

Population Gene Introgression and High Genome Plasticity for the Zoonotic Pathogen Streptococcus agalactiae

The influence that bacterial adaptation (or niche partitioning) within species has on gene spillover and transmission among bacterial populations occupying different niches is not well understood. Streptococcus agalactiae is an important bacterial pathogen that has a taxonomically diverse host range making it an excellent model system to study these processes. Here, we analyze a global set of 901 genome sequences from nine diverse host species to advance our understanding of these processes. Bayesian clustering analysis delineated 12 major populations that closely aligned with niches. Comparative genomics revealed extensive gene gain/loss among populations and a large pan genome of 9,527 genes, which remained open and was strongly partitioned among niches. As a result, the biochemical characteristics of 11 populations were highly distinctive (significantly enriched). Positive selection was detected and biochemical characteristics of the dispensable genes under selection were enriched in ten populations. Despite the strong gene partitioning, phylogenomics detected gene spillover. In particular, tetracycline resistance (which likely evolved in the human-associated population) from humans to bovine, canines, seals, and fish, demonstrating how a gene selected in one host can ultimately be transmitted into another, and biased transmission from humans to bovines was confirmed with a Bayesian migration analysis. Our findings show high bacterial genome plasticity acting in balance with selection pressure from distinct functional requirements of niches that is associated with an extensive and highly partitioned dispensable genome, likely facilitating continued and expansive adaptation.

Potential group B Streptococcus interspecies transmission between cattle and people in Colombian dairy farms

Group B Streptococcus (GBS), is a leading cause of neonatal death and an emerging pathogen in adults. Additionally, GBS is a bovine pathogen causing intramammary infections. The likelihood of GBS interspecies transmission is largely unknown. We explored the potential transmission of GBS between cattle and people on dairy farms in Colombia and compared the antimicrobial resistance (AMR) profiles of isolates from both host species. Across 33 farms, throat swabs and rectal swabs were collected from 191 people, and rectal swabs and composite milk samples from 2092 cattle, yielding 60 human isolates and 301 bovine isolates. The majority (64%) of isolates belonged to shared sequence types (ST). Sequence type (ST) 1 was the most common strain in both host species, suggesting that interspecies transmission may be possible. Two members of the bovine-specific clonal complex 61/67 were detected in human samples (ST718 and ST1175), providing evidence for the lack of genuine species barriers. Apparent prevalence of penicillin resistance was surprisingly high in human and bovine isolates. Further investigation of this phenomenon is needed and could lead to modification of standard testing and treatment recommendations in human and veterinary medicine.

Potential group B Streptococcus interspecies transmission between cattle and people in Colombian dairy farms

Group B Streptococcus (GBS), is a leading cause of neonatal death and an emerging pathogen in adults. Additionally, GBS is a bovine pathogen causing intramammary infections. The likelihood of GBS interspecies transmission is largely unknown. We explored the potential transmission of GBS between cattle and people on dairy farms in Colombia and compared the antimicrobial resistance (AMR) profiles of isolates from both host species. Across 33 farms, throat swabs and rectal swabs were collected from 191 people, and rectal swabs and composite milk samples from 2092 cattle, yielding 60 human isolates and 301 bovine isolates. The majority (64%) of isolates belonged to shared sequence types (ST). Sequence type (ST) 1 was the most common strain in both host species, suggesting that interspecies transmission may be possible. Two members of the bovine-specific clonal complex 61/67 were detected in human samples (ST718 and ST1175), providing evidence for the lack of genuine species barriers. Apparent prevalence of penicillin resistance was surprisingly high in human and bovine isolates. Further investigation of this phenomenon is needed and could lead to modification of standard testing and treatment recommendations in human and veterinary medicine.

Non-aureus staphylococci in fecal samples of dairy cows: First report and phenotypic and genotypic characterization

The aims of this study were to determine whether non-aureus staphylococci (NAS) are present in rectal feces of healthy dairy cows, and if so, to delineate species to which they belong and to study several phenotypic and genotypic traits as a first step toward determining the potential impact of fecal shedding of NAS on bovine udder health. Fecal samples were aseptically collected from the rectum of 25 randomly selected clinically healthy dairy cows in a commercial dairy herd using an automated milking system. Fecal NAS were isolated and then identified at the species level using transfer RNA-intergenic spacer PCR and sequencing of the 16S rRNA housekeeping gene. Strain typing was performed using random amplification of polymorphic DNA (RAPD)-PCR. The antimicrobial resistance profiles, biofilm formation, and growth and inhibitory characteristics of all NAS isolates were evaluated. Half of the cows were shedding NAS, resulting in 31 NAS isolates belonging to 11 different species. The most prevalent species were Staphylococcus rostri (23%, n = 7), Staphylococcus cohnii (16%, n = 5), and Staphylococcus haemolyticus (13%, n = 4) with all Staphylococcus agnetis, Staphylococcus chromogenes, and Staph. rostri isolates belonging to the same strain according to RAPD banding patterns. Acquired antimicrobial resistance was observed in 28 of the 31 NAS isolates, mainly due to β-lactamase production. Most of the isolates (84%, n = 27) had a weak biofilm-forming potential, but only 2 contained the bap gene. The ica and aap genes were not detected in any of the isolates. In vitro growth of Staphylococcus aureus and Streptococcus dysgalactiae was inhibited by Staph. agnetis isolates, and Staph. chromogenes isolates were able to inhibit the growth of Strep. dysgalactiae and Streptococcus uberis. All fecal isolates were able to grow when oxygen and iron were limitedly available, mimicking the growth conditions in the mammary gland.

Transcription Profiling of Monocyte-Derived Macrophages Infected In Vitro With Two Strains of Streptococcus agalactiae Reveals Candidate Pathways Affecting Subclinical Mastitis in Cattle

Macrophages are key cells of innate immune response and serve as the first line of defense against bacteria. Transcription profiling of bacteria-infected macrophages could provide important insights on the pathogenicity and host defense mechanisms during infection. We have examined transcription profiles of bovine monocyte-derived macrophages (bMDMs) isolated from the blood of 12 animals and infected in vitro with two strains of Streptococcus agalactiae. Illumina sequencing of RNA from 36 bMDMs cultures exposed in vitro to either one of two sequence types of S. agalactiae (ST103 or ST12) for 6 h and unchallenged controls was performed. Analyses of over 1,656 million high-quality paired-end sequence reads revealed 5,936 and 6,443 differentially expressed genes (p < 0.05) in bMDMs infected with ST103 and ST12, respectively, versus unchallenged controls. Moreover, 588 genes differentially expressed between bMDMs infected with ST103 versus ST12 were identified. Ingenuity pathway analysis of the differentially up-regulated genes in the bMDMs infected with ST103 revealed significant enrichment for granulocyte adhesion and diapedesis, while significant enrichment for the phagosome formation pathway was found among down-regulated genes. Moreover, Ingenuity pathway analysis of the differentially up-regulated genes in the bMDMs infected with ST12 showed significant enrichment for type 1/type 2 T helper cell activation, while the complement activation pathway was overrepresented in the down-regulated genes. Our study identified pathogen-induced regulation of key genes and pathways involved in the immune response of macrophages against infection but also likely involved in bacterial evasion of the host immune system. These results may contribute to better understanding of the mechanisms underlying subclinical infection such as bovine streptococcal mastitis.

A cohort study of the effect of Streptococcus agalactiae on milk yield and somatic cell count in Norwegian dairy cows

The primary objective of the present study was to estimate the effect of Streptococcus agalactiae intramammary infection on milk production and somatic cell count (SCC) in Norwegian dairy cows. A secondary objective was to assess differences in the effect of common Strep. agalactiae sequence types (ST) found in Norwegian dairy herds. We performed a cohort study combining registry data with sequence-type data from Strep. agalactiae isolates. Herds in which Strep. agalactiae had been detected in individual animals (bacteriological culture or quantitative PCR) between 2012 and 2015 were included. We accessed monthly test-day milk yield records for the entire period to compare milk yield and SCC between cows that were Strep. agalactiae positive and all other cows, within each herd. The study sample consisted of 150 herds, 15,757 cows, 30,850 lactations, and 204,126 test days. We evaluated the effects of Strep. agalactiae on test-day milk yield and SCC using mixed linear regression models, controlling for clustering by herd, cow, and lactation. Multilocus sequence typing of Strep. agalactiae was available for isolates from 86 herds. Additional models were fit to a subset of herds (n = 59) in which ST1, ST23, ST103, and ST196 had been found, to compare the effects of ST on milk production and SCC. In the period 3 to 2 mo before diagnosis, Strep. agalactiae-positive cows produced an average of 1.3 kg more DIM-adjusted milk/d than their negative herd mates. At the time of diagnosis, production was on average 0.13 kg less DIM-adjusted milk/d in Strep. agalactiae-positive cows than in negative cows; 2 to 3 mo after diagnosis, they produced 1.24 kg less DIM-adjusted milk/d than negative cows. Losses persisted for the rest of the investigated period. Cows with ST23, ST103, and ST196 followed a similar pattern as the overall analysis with respect to milk production, whereas ST1-affected cows produced similar amounts of milk before diagnosis as the negative cows. Cows with ST1 experienced the largest milk loss 1 to 2 mo after diagnosis but then recovered to some extent; for cows with ST103, the severe milk loss persisted for the rest of the investigation period. The cow-associated ST103 elicited a lower response in peak SCC compared with ST23, ST103, and ST196. The results indicate an effect of Strep. agalactiae on milk production and SCC. Production was lowest 2 to 3 mo after a positive sample. Peak SCC was reached the month before diagnosis, with notable differences between sequence types.

Genomic Insights Into the Distribution and Evolution of Group B Streptococcus

Streptococcus agalactiae, also known as Group B Streptococcus (GBS), is a bacteria with truly protean biology. It infects a variety of hosts, among which the most commonly studied are humans, cattle, and fish. GBS holds a singular position in the history of bacterial genomics, as it was the substrate used to describe one of the first major conceptual advances of comparative genomics, the idea of the pan-genome. In this review, I describe a brief history of GBS and the major contributions of genomics to understanding its genome plasticity and evolution as well as its molecular epidemiology, focusing on the three hosts mentioned above. I also discuss one of the major recent paradigm shifts in our understanding of GBS evolution and disease burden: foodborne GBS can cause invasive infections in humans.

One hypervirulent clone, sequence type 283, accounts for a large proportion of invasive Streptococcus agalactiae isolated from humans and diseased tilapia in Southeast Asia

Background

In 2015, Singapore had the first and only reported foodborne outbreak of invasive disease caused by the group B Streptococcus (GBS; Streptococcus agalactiae). Disease, predominantly septic arthritis and meningitis, was associated with sequence type (ST)283, acquired from eating raw farmed freshwater fish. Although GBS sepsis is well-described in neonates and older adults with co-morbidities, this outbreak affected non-pregnant and younger adults with fewer co-morbidities, suggesting greater virulence. Before 2015 ST283 had only been reported from twenty humans in Hong Kong and two in France, and from one fish in Thailand. We hypothesised that ST283 was causing region-wide infection in Southeast Asia.

Methodology/Principal findings

We performed a literature review, whole genome sequencing on 145 GBS isolates collected from six Southeast Asian countries, and phylogenetic analysis on 7,468 GBS sequences including 227 variants of ST283 from humans and animals. Although almost absent outside Asia, ST283 was found in all invasive Asian collections analysed, from 1995 to 2017. It accounted for 29/38 (76%) human isolates in Lao PDR, 102/139 (73%) in Thailand, 4/13 (31%) in Vietnam, and 167/739 (23%) in Singapore. ST283 and its variants were found in 62/62 (100%) tilapia from 14 outbreak sites in Malaysia and Vietnam, in seven fish species in Singapore markets, and a diseased frog in China.

Conclusions

GBS ST283 is widespread in Southeast Asia, where it accounts for a large proportion of bacteraemic GBS, and causes disease and economic loss in aquaculture. If human ST283 is fishborne, as in the Singapore outbreak, then GBS sepsis in Thailand and Lao PDR is predominantly a foodborne disease. However, whether transmission is from aquaculture to humans, or vice versa, or involves an unidentified reservoir remains unknown. Creation of cross-border collaborations in human and animal health are needed to complete the epidemiological picture.

An outbreak due to a bacterium called Streptococccus agalactiae in Singapore in 2015 was caused by a clone called ST283, and was associated with consumption of raw freshwater-fish. It was considered unique as it was the only reported foodborne outbreak of this bacterium. Our new data show that invasive ST283 disease is far from unique. ST283 has been causing disease in humans and farmed fish in SE Asian countries for decades. Reports of ST283 are almost absent outside Asia. We suspect that human ST283 is fishborne in other Asian countries, as it was in Singapore, but we haven’t looked at this yet. We don’t know where ST283 originally came from; it may have been transmitted from humans to fish, or come from another animal. More studies are needed to determine ST283’s geographical extent and burden of disease, as well as its origin, how it is transmitted, and what enables it to be so aggressive. We may then be able to interrupt transmission, to the benefit of fish, farmers, and the general public.

Influence of bovine sub-clinical mastitis and associated risk factors on calving interval in a population of crossbred lactating cows in Sri Lanka

A study was carried out to identify prevalence and risk factors for bovine subclinical mastitis (SCM) in crossbred lactating cows within the Kurunagala district of Sri Lanka. In this study, 283 crossbred cows (Jersey x Shahiwal) from randomly selected medium- and relatively large-scale dairy farms were screened for SCM. The Californian mastitis test (CMT) plus microbiological analyses were employed for screening. A pre-tested questionnaire was used to collect information on the cows and their management. When screening was based only on CMT, the prevalence of SCM was 49%, and it was 44% if based on both CMT and pathogen isolation. The isolated pathogens were Staphylococcus spp. (80%, 98/123), Escherichia coli (14%, 17/123), Streptococcus spp. (3%, 4/123) and Pasteurella multocida (3%, 4/123). The age, parity and milk yield showed positive correlations with SCM (p < 0.05). The prevalence of SCM was relatively high after the fifth parity (p = 0.03, odds ratio = 9.49). A positive correlation of increase in calving interval (more than 18 months) with SCM was observed. The prevalence of SCM on the dairy farms can be reduced by implementing more hygienic management practices.

Expert evaluation of different infection types in dairy cow quarters naturally infected with Staphylococcus aureus or Streptococcus agalactiae

The purpose of this study was to improve the diagnostic recommendations for Staphylococcus aureus and Streptococcus agalactiae control using bacterial culture (BC), polymerase chain reaction (PCR) and somatic cell count (SCC) as diagnostic methods. The study was carried out in three steps: firstly, diagnostic test patterns for naturally infected quarters with Staph. aureus (24 quarters) and Strep. agalactiae (16 quarters) were created by sampling the quarters each day for 21 days and analysing the daily quarter milk samples using BC, PCR and SCC. Secondly, 30 mastitis experts were asked to group and describe the diagnostic test patterns and to establish a diagnosis for each group. The experts' statements regarding the groups they established were subsequently examined using qualitative content analysis to assign "infection types" to the statements. Lastly, the test performance was estimated for BC, PCR and SCC using generalised logistic regression models with the interpreted statements as a reference for infection. The experts mainly identified the Staph. aureus quarter-patterns as persistent infections, while some had more dynamic patterns. Strep. agalactiae quarter-patterns mainly involved persistent infection, yet some appeared hard to diagnose and were assigned to almost all different infection types, while experts did not agree on the interpretation. Estimates of Se for detection of Staph. aureus infection were 95.9% [93.7; 97.3] for BC, 99.5% [98.3; 99.8] for PCR, and 96.1% [94.0; 97.5] for SCC. The corresponding Sp estimates were 74.5% [65.7; 81.7], 66% [57.2; 73.8] and 43.7% [36.2; 51.5] for BC, PCR and SCC, respectively. The Se estimates of BC and PCR for Strep. agalactiae infection were 100% [83.5; 100] and 99.9% [99.6; 100], respectively, whereas the Se of SCC detecting Strep. agalactiae infection was only 34.3% [26.4; 43.3]. This indicated that Strep. agalactiae-positive BC and PCR test results were more important than SCC results to the experts when diagnosing a quarter as infected. The Sp estimates of BC, PCR and SCC for Strep. agalactiae infection were 99% [72.8; 100], 97.7% [62.1; 99.9], and 65.7% [56.7; 73.7], respectively. We conclude that PCR and BC are highly sensitive in the detection of persistent and new infections as defined by the experts, although the Se was not always 100%. An accepted lower Sp suggests that experts place less emphasis on false-positive results. We recommend that efforts are made to develop consistent terminology to characterise intramammary infections over time so that the course of infection can be taken into account at diagnosis.

Streptococcus agalactiae is not always an obligate intramammary pathogen: Molecular epidemiology of GBS from milk, feces and environment in Colombian dairy herds

For many years Streptococcus agalactiae has been considered an obligate intramammary and strictly contagious pathogen in dairy cattle. However, recent reports of S. agalactiae isolation from extramammary sources have contradicted that premise. To gain further insight into the epidemiology of S. agalactiae infection in cattle, we examined its distribution and heterogeneity of strains in bovine milk, bovine feces, and the environment in Colombian dairy farms. First, a longitudinal study was conducted at herd level in 152 dairy herds. Bulk tank milk samples from each herd where collected twice a month for six months. A follow-up study with a cross sectional design at the cow level was conducted in a subset of 25 farms positive for S. agalactiae. Cow-level milk samples from 1712 lactatting cows and 1545 rectal samples were collected, as well as 120 environmental samples. Samples were used for S. agalactiae detection and genotyping using Multi Locus Sequence Typing. Results showed sporadic rather than repeated isolation of S. agalactiae from bulk tank milk in 40% of the positive herds, challenging the idea that S. agalactiae is a highly contagious pathogen causing chronic infections. S. agalactiae was isolated from rectal or environmental samples in 32% and 12% of cross-sectional study farms, respectively, demonstrating that the bacteria can survive in extramammary sources and that S. agalactiae is not an obligate intramammary pathogen. The same strain was isolated from rectal and bulk tank milk samples in eight farms, suggesting that fecal shedding is frequent, and contributes to the presence of S. agalactiae in bulk tank. High within-herd heterogeneity of strains was found, which is distinct from the situation in developed dairy industries. These new epidemiological findings should be considered to adjust surveillance and control recommendations for S. agalactiae.

Association between teat skin colonization and intramammary infection with Staphylococcus aureus and Streptococcus agalactiae in herds with automatic milking systems

The objective of this study was to investigate the association between teat skin colonization and intramammary infection (IMI) with Staphylococcus aureus or Streptococcus agalactiae at the quarter level in herds with automatic milking systems. Milk and teat skin samples from 1,142 quarters were collected from 300 cows with somatic cell count >200,000 cells/mL from 8 herds positive for Strep. agalactiae. All milk and teat skin samples were cultured on calf blood agar and selective media. A subset of samples from 287 quarters was further analyzed using a PCR assay (Mastit4 PCR; DNA Diagnostic A/S, Risskov, Denmark). Bacterial culture detected Staph. aureus in 93 (8.1%) of the milk samples and 75 (6.6%) of the teat skin samples. Of these, 15 (1.3%) quarters were positive in both the teat skin and milk samples. Streptococcus agalactiae was cultured in 84 (7.4%) of the milk samples and 4 (0.35%) of the teat skin samples. Of these, 3 (0.26%) quarters were positive in both the teat skin and milk samples. The PCR detected Staph. aureus in 29 (10%) of the milk samples and 45 (16%) of the teat skin samples. Of these, 2 (0.7%) quarters were positive in both the teat skin and milk samples. Streptococcus agalactiae was detected in 40 (14%) of the milk samples and 51 (18%) of the teat skin samples. Of these, 16 (5.6%) quarters were positive in both the teat skin and milk samples. Logistic regression was used to investigate the association between teat skin colonization and IMI at the quarter level. Based on bacterial culture results, teat skin colonization with Staph. aureus resulted in 7.8 (95% confidence interval: 2.9; 20.6) times higher odds of Staph. aureus IMI, whereas herd was observed as a major confounder. However, results from the PCR analyses did not support this association. Streptococcus agalactiae was isolated from the teat skin with both PCR and bacterial culture, but the number of positive teat skin samples detected by culture was too low to proceed with further analysis. Based on the PCR results, Strep. agalactiae on teat skin resulted in 3.8 (1.4; 10.1) times higher odds of Strep. agalactiae IMI. Our results suggest that Staph. aureus and Strep. agalactiae on teat skin may be a risk factor for IMI with the same pathogens. Focus on proper teat skin hygiene is therefore recommended also in AMS.

Accuracy of qPCR and bacterial culture for the diagnosis of bovine intramammary infections and teat skin colonisation with Streptococcus agalactiae and Staphylococcus aureus using Bayesian analysis

Streptococcus agalactiae (Strep. agalactiae) and Staphylococcus aureus (Staph. aureus) are originally regarded as contagious mastitis pathogens, however, both pathogens have recently been isolated from extramammary and environmental sites, indicating that other sites than the udder might contribute to the spread of these pathogens potentially causing intramammary infections. Diagnostic tools to identify pathogens at extramammary sites are available but still needs to be validated. The objective of this cross-sectional field study was to estimate the diagnostic sensitivity (Se) and specificity (Sp) of the commercially available Mastit4 qPCR assay and bacterial culture (BC) in identifying Strep. agalactiae and Staph. aureus from milk and teat skin samples. We randomly selected 30-40 cows with high somatic cell counts from eight Danish Strep. agalactiae-positive dairy herds with automatic milking systems. Teat skin samples and aseptic milk samples were collected from right rear quarters (n = 287) for BC and PCR analysis. Se and Sp were estimated in a Bayesian latent class analysis. For milk samples, the Se and Sp of qPCR for Strep. agalactiae were estimated to 0.97 and 0.99, respectively, whereas the Se and Sp of BC were 0.41 and 1.00, respectively. The Se and Sp of qPCR for Staph. aureus were estimated to 0.95 and 0.99, respectively, whereas the Se and Sp of BC were 0.54 and 0.77, respectively. For teat skin samples, the Se and Sp of qPCR for Strep. agalactiae were estimated to be 0.97 and 0.96, respectively, whereas the Se and Sp of BC were 0.33 and 1.00, respectively. The Se and Sp of qPCR for Staph. aureus were estimated to 0.94 and 0.98, respectively, whereas the Se and Sp of BC were 0.44 and 0.74, respectively. In conclusion, the Se for diagnosing Strep. agalactiae and Staph. aureus IMI was higher for qPCR than BC, suggesting that qPCR is a valuable method for detecting both pathogens from quarter-level milk samples. The performance of BC in the detection of Strep. agalactiae and Staph. aureus on teat skin was poor compared to qPCR, indicating that differences in the target condition of the two methods should be considered when implementing them as routine diagnostic tests for detecting teat skin colonisers. The low Se of BC may preclude the use of BC for skin testing, and qPCR is better for this task.