Staphylococcal species associated with bovine mastitis in the North West of Iran: Emerging of coagulase-negative staphylococci

Phage-Derived Endolysins Against Resistant Staphylococcus spp.: A Review of Features, Antibacterial Activities, and Recent Applications

Antimicrobial resistance is a significant global public health issue, and the dissemination of antibiotic resistance in Gram-positive bacterial pathogens has significantly increased morbidity, mortality rates, and healthcare costs. Among them, Staphylococcus, especially methicillin-resistant Staphylococcus aureus (MRSA), causes a wide range of diseases due to its diverse pathogenic factors and infection strategies. These bacteria also present significant issues in veterinary medicine and food safety. Effectively managing staphylococci-related problems necessitates a concerted effort to implement preventive measures, rapidly detect the pathogen, and develop new and safe antimicrobial therapies. In recent years, there has been growing interest in using endolysins to combat bacterial infections. These enzymes, which are also referred to as lysins, are a unique class of hydrolytic enzymes synthesized by double-stranded DNA bacteriophages. They possess glycosidase, lytic transglycosylase, amidase, and endopeptidase activities, effectively destroying the peptidoglycan layer and resulting in bacterial lysis. This unique property makes endolysins powerful antimicrobial agents, particularly against Gram-positive organisms with more accessible peptidoglycan layers. Therefore, considering the potential benefits of endolysins compared to conventional antibiotics, we have endeavored to gather and review the characteristics and uses of endolysins derived from staphylococcal bacteriophages, as well as their antibacterial effectiveness against Staphylococcus spp. based on conducted experiments and trials.

Genomic features and pathophysiological impact of a multidrug-resistant Staphylococcus warneri variant in murine mastitis

Non-aureus staphylococci (NAS) represent a major etiological agent in dairy animal mastitis, yet their role and impact remain insufficiently studied. This study aimed to elucidate the genomic characteristics of a newly identified multidrug-resistant NAS strain, specifically Staphylococcus warneri G1M1F, isolated from murine feces in an experimental mastitis model. Surprisingly, NAS species accounted for 54.35 % of murine mastitis cases, with S. warneri being the most prevalent at 40.0 %. S. warneri G1M1F exhibited resistance to 10 major antibiotics. Whole-genome sequencing established a genetic connection between G1M1F and S. warneri strains isolated previously from various sources including mastitis milk in dairy animals, human feces and blood across diverse geographical regions. Genomic analysis of S. warneri G1M1F unveiled 34 antimicrobial resistance genes (ARGs), 30 virulence factor genes (VFGs), and 278 metabolic features. A significant portion of identified ARGs (64 %) conferred resistance through antibiotic efflux pumps, while VFGs primarily related to bacterial adherence and biofilm formation. Inoculation with G1M1F in mice resulted in pronounced inflammatory lesions in mammary and colon tissues, indicating pathogenic potential. Our findings highlight distinctive genomic traits in S. warneri G1M1F, signifying the emergence of a novel multidrug-resistant NAS variant. These insights contribute to understanding NAS-related mastitis pathophysiology and inform strategies for effective treatment in dairy animals.

Characterization of Staphylococcus Species Isolates from Sheep Milk with Subclinical Mastitis: Antibiotic Resistance, Enterotoxins, and Biofilm Production

Subclinical mastitis represents one of the most contagious diseases affecting animals involved in dairy production systems. Although coagulase-negative staphylococci (CoNSs) have been considered minor pathogens for many years, they have recently emerged as opportunistic pathogens in mastitis disorders. The objectives of this work were to assess the antimicrobial resistance profile and the ability to produce a biofilm in comparison with a reference strain and to search for genes related to biofilm production, antimicrobial resistance, and enterotoxins in 18 isolates of Staphylococcus species from the milk of sheep with subclinical mastitis, collected from different Sicilian farms. This knowledge is essential to provide basic information on the pathogenicity and virulence of staphylococcal species and their impact on animal health. All isolates were resistant to ampicillin, 88.8% to streptomycin, 77.7% to gentamicin, 44.4% to chloramphenicol, 27.7% to erythromycin, and 11.1% to tetracycline, and two isolates were strong biofilm producers. Antibiotic resistance gene profiling showed that 16.6% of isolates possess the blaZ gene, whereas the search of biofilm-associated genes revealed the occurrence of the sasC gene in 33.3% of isolates, the ica gene in 27.7%, and bap and agr (accessory gene regulator) genes in 16.6% of isolates. Altogether, the results of this study indicate that CoNSs can acquire virulence genes and could have a role as pathogens in subclinical mastitis.

Prevalence of mecA and pvl genes in coagulase negative staphylococci isolated from bovine mastitis in smallholder dairy farms in Turkey

This study aimed to investigate the presence of mecA and pvl genes in coagulase negative Staphylococcus (CNS) species isolated from bovine mastitis in smallholder dairy farms by using PCR. A total of 602 mammary quarter milk samples belong to 170 cows with mastitis were used. Identification of species was achieved by using the commercial Gram-positive identification kit and a total of 52 (8.6%) CNS species were isolated. The most frequently isolated species was Staphylococcus capitis (n = 15, 28.8%), followed by Staphylococcus saccharolyticus (n = 12, 23.1%), Staphylococcus simulans (n = 8, 15.4%), Staphylococcus haemolyticus (n = 5, 9.6%), Staphylococcus cohnii (n = 4, 7.7%), Staphylococcus lentus (n = 4, 7.7%), Staphylococcus epidermidis (n = 2, 3.8%) and Staphylococcus saprophyticus (n = 2, 3.8%). The mecA gene positivity was found in the 13 (25%) of strains. Of the strains carrying mecA gene, eight also harbored the pvl gene. A total of pvl gene positivity was found as 30.8% (n = 16) in 52 CNS species. In conclusion, the present study showed that CNS isolated from cows with mastitis may be reservoir of mecA and pvl genes. To our knowledge, this is the first study showing the presence of mecA and pvl genes in CNS species isolated from bovine with mastitis in the smallholder dairy farms in Turkey.

Molecular identification, antimicrobial resistance and virulence gene profiling of Staphylococcus spp. associated with bovine sub-clinical mastitis in Bangladesh

This study was conducted to investigate the diversity and antimicrobial resistance profiling of Staphylococcus species causing sub-clinical mastitis (SCM) in dairy herds in Bangladesh as well as putative risk factors associated with the infections. Individual quarter milk samples were collected from a total of 284 lactating cows from 30 dairy farms were screened by means of California mastitis test; 178 (62.7%) of them had at least of quarter affected by SCM. After conventional microbiological isolation procedures, PCR tests were used for Staphylococcus species identification and detection of antimicrobial resistance and virulence genes. S. chromogenes (65.7%) was the most predominant species followed by, S. epidermidis (20.2%), S. haemolyticus (19.1%), S. aureus (15.7%), and S. sciuri (5.6%). High levels of antimicrobial resistance to ampicillin and amoxicillin/clavulanic acid were observed in S. aureus (82.1% and 75%) and S. sciuri (80% and 70%), while resistance to cefepime was markedly higher in S. chromogenes (95.7%), S. haemolyticus (94.1%), and S. epidermidis (97.2%). Multidrug resistance isolates were identified in all five species. The mecA gene was detected in S. aureus (32.1%) and S. chromogenes (5.98%). In addition, 20% S. sciuri and 17.7% S. haemolyticus carried the cytotoxin (pvl) gene, while 14.3% S. aureus harbored the toxic shock syndrome toxin (tst) gene. Multivariable logistic regression analysis identified "Old aged" (OR [CI]: 3.5 [1-12.4]); "Early stage of lactation" (OR [CI]: 3.4 [1.2-9.7]) and, "Firm udder condition" (OR [CI]: 4.2 [1.2-14.6]) as risk factors associated with SCM caused by S. aureus, S. chromogenes, and S. haemolyticus, respectively. Moreover, "Use of antimicrobials" (OR [CI]: 10.4 [3.4-32.1] and "History of previous clinical mastitis" (OR [CI]: 4.9 [1.2-19.7] for the carriage of methicillin-resistant Staphylococcus spp.

Molecular epidemiology of Bartonella species from sympatric mammals collected in urban and rural areas of Punjab, Pakistan

Bartonella can infect a variety of mammals including humans and has been detected in the Americas, Europe, Africa, and Asia. Roughly two-thirds of identified Bartonella species are found and maintained in rodent reservoirs, with some of these species linked to human infections. Rodents (N=236) were caught from the Sahiwal division of Punjab, Pakistan and tested for Bartonella using PCR targeting gltA and rpoB genes, followed by sequencing of rpoB-positive samples. Genetic relatedness to other published Bartonella spp. rpoB gene sequences were examined using BLAST and phylogenetic analysis. Overall, 7.62% (18/236) of rodents were positive for both gltA and rpoB fragments. Rattus rattus and R. norvegicus had 7.94% (12/151) and 7.05% (6/85) positivity rates for Bartonella DNA, respectively. Phylogenetic analysis revealed a close relatedness between Bartonella spp. from Pakistan to Bartonella spp. from China, Nepal, and Malaysia. This study is the first reported detection of Bartonella spp. in R. rattus and R. norvegicus from the Sahiwal area of Punjab, Pakistan.

Whole-Genome Sequence of the Multidrug-Resistant Staphylococcus warneri Strain G1M1F, Isolated from Mice with Mastitis

We sequenced the genome of Staphylococcus warneri G1M1F, a multidrug-resistant strain isolated from fecal samples of mice with induced mastitis. The complete genome of G1M1F consists of one chromosome of 2,504,515 bp and two plasmid replicons of 28,679 and 8,615 bp; it comprises 32.7% GC content, with 60× genome coverage.

Paeoniflorin alleviates inflammation in bovine mammary epithelial cells induced by Staphylococcus haemolyticus through TLR2/NF-κB signaling pathways

Staphylococcus haemolyticus (S. haemolyticus) is one of the most common coagulase-negative staphylococci (CoNS) isolates from bovine mastitis. Paeoniflorin (PF) shows anti-inflammatory effects on different inflammatory diseases in vitro studies and in vivo animal experiments. In this study, the viability of bovine mammary epithelial cells (bMECs) was detected by the cell counting kit-8 experiment. Subsequently, bMECs were induced with S. haemolyticus, and the induction dosage was determined. The expression of pro-inflammatory cytokines and toll-like receptor (TLR2) and nuclear factor kappa-B (NF-κB) signaling pathway-related genes were investigated by quantitative real-time PCR. The critical pathway proteins were detected by western blot. The results showed that the multiplicity of infection (MOI; the ratio of bacteria to bMECs) 5:1 of S. haemolyticus for 12 h could cause cellular inflammation, which was selected to establish the inflammatory model. Incubation with 50 μg/ml PF for 12 h was the best intervention condition for cells stimulated by S. hemolyticus. Quantitative real-time PCR and western blot analysis showed that PF inhibited the activation of TLR2 and NF-κB pathway-related genes and the expression of related proteins. Western blot results showed that PF suppressed the expression of NF-κB unit p65, NF-κB unit p50, and MyD88 in bMECs stimulated by S. haemolyticus. The inflammatory response pathway and molecular mechanism caused by S. haemolyticus on bMECs are related to TLR2-mediated NF-κB signaling pathways. The anti-inflammatory mechanism of PF may also be through this pathway. Therefore, PF is expected to develop potential drugs against CoNS-induced bovine mastitis.

Staphylococcus microti Strains Isolated from an Italian Mediterranean Buffalo Herd

S. microti is a new species among non-aureus staphylococci (NAS) frequently found in bovine milk samples and associated with subclinical mastitis (SCM). The aim of this study was to analyze the presence of S. microti in 200 composite milk samples and 104 milking parlor surface swabs collected at a buffalo farm in Southern Italy to define its presence in milk and a milking parlor environment. The samples were inoculated onto different agar plates, and the isolates were identified by MALDI-TOF MS. The strains identified as S. microti (54/304 samples, 17.8%) were collected, and their purified genomic DNA was subjected to PCR amplification and whole 16S rRNA gene sequencing. Furthermore, their phenotypic resistance profiles were evaluated by a disk diffusion method, and the genotypic characterization of the tetracycline resistance was performed for the tetM and tetK genes by multiplex PCR. Four and forty-seven S. microti isolates from milk samples of lactating animals with subclinical mastitis (SCM) and intramammary infection (IMI), respectively, and three isolates from milking parlor surfaces were recovered. The genomic DNA was purified from the bacterial isolates, and the amplification and sequencing of the 16S gene further supported the proteomic identification as S. microti. No clinical mastitis was detected in the herd during the study period. The antimicrobial susceptibility testing revealed a worrisome 100% resistance to tetracyclines, genotypically mediated by the tetM gene for all strains. This study highlights that S. microti may be commonly isolated from dairy buffalo milk and milking parlor equipment. Its association with SCM or IMI remains to be established.

Molecular detection of Toxoplasma gondii among commensal rodents from the Sahiwal division, Punjab, Pakistan

Toxoplasmosis is a zoonotic disease in humans and animals caused by the protozoan parasite Toxoplasma gondii. Rodents not only act as intermediate hosts for T. gondii but are also a significant source of T. gondii infection for other hosts. There is limited information about the prevalence of this protozoan within rodents in Pakistan. The current study was conducted to determine the prevalence of T. gondii in commensal rodents as well as associated risk factors. A total of 236 rats including Rattus rattus and Rattus norvegicus were captured from three districts of the Sahiwal division in Punjab province, Pakistan. Brain samples were collected from each specimen. Data was gathered about rodent species, gender, age, location, districts, seasonality, and habitat type. PCR assays were used to screen for T. gondii from the brain samples. A Chi-square analysis was used to investigate the association between positive samples and risk factors. A total of 236 rodent spleen samples were examined for detection of the B1 and SAG3 genes of T. gondii DNA by conventional PCR, and 14 (5.9%) were positive. T. gondii prevalence was higher in R. norvegicus (8.2%) compared to R. rattus (4.6%). All risk factors were statistically non-significant. This study provides evidence of T. gondii in rodents in the Sahiwal division and indicates that other animals and humans are at risk of infection.

Robusta coffee extracts inhibit quorum sensing activity in Chromobacterium violaceum and reduce biofilms against Bacillus cereus and Staphylococcus aureus

Background and Aim: Bacillus cereus and Staphylococcus aureus cause foodborne intoxication in humans and animals. Pathogens can produce biofilms controlled by the quorum sensing system. The study aimed to investigate the antibacterial, antibiofilm, and anti-quorum sensing activities of Coffea canephora P. ex Fr. (Robusta coffee) extracts against B. cereus and S. aureus. Materials and Methods: Ethanol extracts of fruit peels and seeds of Robusta coffee were tested for antibacterial activity against B. cereus and S. aureus using a broth microdilution assay. Reduction of the biofilm formation and elimination of the viability of mature biofilm-grown cells of B. cereus and S. aureus were determined. Inhibition of quorum sensing activity in Chromobacterium violaceum by the extracts was investigated using the disk diffusion method and flask incubation assay. Results: Fresh fruit peel extract showed the strongest antibacterial activity against B. cereus and S. aureus with minimum inhibitory concentration (MIC) values of 2 and 4 mg/mL, respectively. However, the extracts did not inhibit Escherichia coli, avian pathogenic E. coli, and Pseudomonas aeruginosa at 8 mg/mL. Significant inhibition of biofilm formation at 1/2 × MIC of the fresh peel extract was detected in B. cereus (56.37%) and S. aureus (39.69 %), respectively. At 8 × MIC of the fresh peel extract, a significant elimination of the mature biofilm viability was detected in B. cereus (92.48%) and S. aureus (74.49%), respectively. The results showed that fresh and dried peel fruit extracts at 1/2 × MIC significantly reduced violacein production with the highest percentage inhibition ranging from 44.53 to 47.48% at 24 h (p ≤ 0.05). Conclusion: The results of the present study suggest the potential therapeutic benefits of Robusta coffee extracts in inhibiting the growth, biofilm, and quorum sensing of both B. cereus and S. aureus. The results put forward an alternative strategy to control the foodborne intoxications caused by both pathogens.

Genotypic characterization of mecA gene and antibiogram profile of coagulase-negative staphylococci in subclinical mastitic cows

Background and Aim

Coagulase-negative staphylococci (CNS) are becoming the major cause of clinical and subclinical bovine mastitis around the world. This study aims to estimate the prevalence, antibiogram, and frequency of the methicillin-resistant (MR) (mecA) gene in CNS collected from cows with subclinical mastitis.

Materials and Methods

Thirty-four milk samples were collected from 20 cows. Fifteen subclinical mastitis samples (~44.12%) were identified as CNS isolates. The Vitek2 compact system method was employed for the identification of the species. Furthermore, antibiotic sensitivity tests were performed against 10 different antibiotics for CNS strains. The mecA gene from isolated CNS was detected by conventional polymerase chain reaction (PCR).

Results

Staphylococcus haemolyticus was the most predominant isolated species with an incidence of 33.3% (5/15 isolates), followed by 26.7% for Staphylococcus sciuri and Staphylococcus vitamins (4/15 isolates), and 13.3% for Staphylococcus vitulinus (2/15 isolates), respectively. The highest resistance rates were determined to be 40% (6/15 isolates) against penicillin and oxacillin (OX), 33.3% (5/15 isolates) against clindamycin, 13% (2/15 isolates) against chloramphenicol, amoxicillin, and erythromycin, and 5% (1/15 isolates) against ciprofloxacin, respectively. The results revealed that the isolates were resistant to one or more antimicrobial agents, with five isolates displaying multiple antimicrobial resistance. Furthermore, the results exhibit that all CNS isolates had the mecA gene at 310 bp with a 100% frequency. Moreover, for detecting MR isolates, there are significant discrepancies between phenotypic and genotypic approaches, and only 6/15 CNS isolates phenotypically demonstrated OX resistance.

Conclusion

The results emphasize the necessity of frequent monitoring of phenotypic and genotypic profiles of CNS isolates to ensure effective control measures and the prevention of multidrug resistance strain evolution.

Dairy Cows' Udder Pathogens and Occurrence of Virulence Factors in Staphylococci

This study investigated 960 Slovak and Czech spotted cattle from four different conventional (non-organic) dairy herds located in Eastern Slovakia and Czechia during early lactation (14-100 days after calving). Dairy cows were examined clinically; milk from fore-stripping of each udder quarter was subjected to sensory examination and assessed by the California mastitis test (CMT), and laboratory analyses of bacterial pathogens in milk, including virulence factors, were conducted. Positive CMT scores (1-3) for one or more quarters were detected in 271 (28.2%) of the examined animals. Out of 230 infected milk samples, representing 24.0% of all dairy cows, staphylococci (59.1% of positive findings) were the most commonly isolated organisms, followed by E. coli (11.3%), streptococci Str. uberis (9.1%) and Str. agalactiae (3.4%), and enterococci (6.1%). From 136 isolates of S. aureus (38 isolates) and non-aureus staphylococci (NAS; 98 isolates), virulence factors and their resistance to 14 antimicrobials were detected using the disk diffusion method, with PCR detection of the methicillin resistance gene, mecA. An increased incidence of clinical and chronic forms of mastitis has been reported in mastitic cows in which staphylococci, especially S. aureus and NAS (S. chromogenes, S. warneri, and S. xylosus), have been detected and compared to other isolated udder pathogens. From those species, S. aureus and isolates of NAS mentioned above showed multiple virulence factors that are more likely to hydrolyze DNA, hemolysis, produce gelatinase and biofilm, and have multi-drug resistance as compared to other less virulent staphylococci. Generally, the isolated staphylococci showed 77.2% resistance to one or more antimicrobials, in particular to aminoglycosides, β-lactams, macrolides, or cephalosporins. Isolates that showed the ability to form a biofilm were more resistant to more than one antimicrobial than isolates without biofilm production. Multi-drug resistance to three or more antimicrobial classes was recorded in 16 isolates (11.7%), and the presence of the mecA gene was also confirmed in two isolates of S. aureus and two species of NAS.

Prevalencia y efecto de la infección intramamaria debida a especies de estafilococos coagulasa negativo (ECN) en el conteo de células somáticas en leche de vacas Holstein en Boyacá, Colombia

La mastitis es una de las enfermedades más importantes en los rebaños lecheros especializados alrededor de todo el mundo debido a los efectos sobre la producción y la salud animal. Los tipos ocasionados por estafilococos coagualasa negativo (ECN) tienen una importancia especial en una producción en la que los principales patógenos están controlados. El objetivo del presente trabajo es determinar la prevalencia del ECN en un hato lechero en Boyacá y cuantificar los efectos de cada especie de ECN en el conteo de células somáticas (CCS). Se seleccionaron 40 vacas y se tomaron muestras durante 6 meses, se realizó california mastitis test (CMT) y se tomaron muestras de los resultados desde 1 hasta donde hubo trazas. También se realizó la prueba bacteriológica de rutina para la identificación del ECN y el aislamiento del ECN se realizó mediante la identificación del gen rpoB y del tipo de cepa, usando el procedimiento de electroforesis en gel de pulso. De 960 muestras, 619 fueron positivas para el crecimiento del ECN. Las especies más prevalentes fueron Staphylococcus epidermidis, S. chromogenes, S. sciuri, S. simulans, S. haemolyticus y S. capitis. Los resultados encontrados aquí son similares a resultados en diferentes partes del mundo, lo que confirma que son patógenos que deben ser evaluados constantemente porque pueden pasar desapercibidos en los controles de rutina, especialmente en aquellas fincas donde los patógenos mayores no son un problema grave. Los resultados determinados en este estudio demuestran que el SNC genera un ligero aumento de células somáticas.

An Understanding of the Global Status of Major Bacterial Pathogens of Milk Concerning Bovine Mastitis: A Systematic Review and Meta-Analysis (Scientometrics)

In this study, the major mastitis pathogen prevalence in the cattle and buffalo of the world was estimated by a meta-analysis. Staphylococcus (S) species, Streptococcus (St) species, and Escherichia coli (Ec) prevalence studies reported during 1979–2019 were collected using online databases, and offline resources. A meta-analysis of these data was done with the meta package in R-Software. The Staphylococcus aureus was the major mastitis pathogen, mostly causing subclinical mastitis, Ec causing clinical mastitis and St causing subclinical and clinical mastitis. The pooled prevalence estimates of S, St, and Ec were 28%, 12%, and 11% in the world from 156, 129, and 92 studies, respectively. The S, St, and Ec prevalences were high in Latin America (51%), Oceania (25%), and Oceania (28%), respectively. Higher S, St, and Ec prevalences were observed by molecular methods, signifying high sensitivity and usefulness for future studies. Among bacterial species, S. aureus (25%) followed by coagulase-negative Staphylococcus species (20%), Escherichia coli (11%), St. agalactiae (9%), St. uberis (9%) were the important pathogens present in the milk of the world. We hypothesize that there is a urgent need to reduce mastitis pathogen prevalence by ensuring scientific farm management practices, proper feeding, therapeutic interventions to augment profits in dairying, and improving animal and human health.

Evaluation of the new differential somatic cell count parameter as a rapid and inexpensive supplementary tool for udder health management through regular milk recording

Mastitis, particularly in its subclinical form, is the costliest disease in milk production causing substantial financial losses to the dairy industry, impairing animal welfare, and one of the main reasons for treating dairy cows with antimicrobials. Somatic cell count (SCC) is broadly used as an indicator for mastitis or intramammary infection (IMI) and is the basis for udder health management programmes, e.g., through monthly dairy herd improvement (DHI) testing. While SCC shows the total number of cells in milk, the new Differential SCC (DSCC) shows also the combined proportion of polymorphonuclear neutrophils (PMN) and lymphocytes as a percentage of the total SCC. In this study, we investigated the test characteristics of DSCC as a new supplementary indicator for mastitis screening. We collaborated with 11 herds totalling 969 dairy cows and collected metered DHI samples once a month over four months. The IMI status was assessed through analysis of aseptic composite hand-stripped samples using culture and followed by species identification using MALDI-ToF. The pathogens detected were categorised as 'no', 'minor', 'major', or 'other' pathogens. The results of our study showed that the DSCC parameter was significantly associated with the IMI status and the cow's parity but not with days in milk or test-day milk weight. On the other hand, SCC was associated with all these four factors. DSCC counts were significantly higher in samples of cows with IMI caused by major pathogens as compared to cows with no IMI or IMI by minor or other pathogens. SCC alone, DSCC alone, and the combination of DSCC and SCC were further compared based on test characteristics using exemplary cut-offs. For example, working with a cut-off of 200,000 cells/ for SCC alone compared to working with the combination of DSCC of 65 % and/or 200,000 cells/mL to classify cows as infected by major pathogens, the sensitivity increased from 78 % to 92 % and the specificity decreased from 87 % to 66 %. With the combination, the positive predictive value changed from 52 % to 34 %, and the negative predictive value stayed at the same level (96 % vs 98 %). In summary, our study provides first insights on test characteristics of the DSCC parameter used in combination with the well-established SCC for monitoring udder health using DHI testing. This combination opens up the possibility to further improve udder health monitoring programmes (e.g., improved identification of IMI caused by major pathogens) but more work on the subject is needed.

Predicting Disease in Transition Dairy Cattle Based on Behaviors Measured Before Calving

Simple Summary

Dairy cattle often become ill after calving. We developed models designed to predict which cows are likely to become ill based upon measures of the cows’ feeding and competitive behaviors before calving. Our models had high sensitivity (73–71%), specificity (80–84%), positive predictive values (73–77%), and negative predictive values (80–80%) for both cows that had previously calved and for those calving for the first time. We conclude that behaviors at the feed bunk before calving can predict cows at risk of becoming sick in the weeks after calving.

Abstract

Dairy cattle are particularly susceptible to metritis, hyperketonemia (HYK), and mastitis in the weeks after calving. These high-prevalence transition diseases adversely affect animal welfare, milk production, and profitability. Our aim was to use prepartum behavior to predict which cows have an increased risk of developing these conditions after calving. The behavior of 213 multiparous and 105 primiparous Holsteins was recorded for approximately three weeks before calving by an electronic feeding system. Cows were also monitored for signs of metritis, HYK, and mastitis in the weeks after calving. The data were split using a stratified random method: we used 70% of our data (hereafter referred to as the “training” dataset) to develop the model and the remaining 30% of data (i.e., the “test” dataset) to assess the model’s predictive ability. Separate models were developed for primiparous and multiparous animals. The area under the receiver operating characteristic (ROC) curve using the test dataset for multiparous cows was 0.83, sensitivity and specificity were 73% and 80%, positive predictive value (PPV) was 73%, and negative predictive value (NPV) was 80%. The area under the ROC curve using the test dataset for primiparous cows was 0.86, sensitivity and specificity were 71% and 84%, PPV was 77%, and NPV was 80%. We conclude that prepartum behavior can be used to predict cows at risk of metritis, HYK, and mastitis after calving.

Pastoral community practices, microbial quality and associated health risks of raw milk in the milk value chain of Nakasongola District, Uganda

The informal milk value chain in Uganda controls most of the raw marketed milk, albeit of poor quality. A study was conducted to assess the milk handling practices, the bacterial quality and the associated health concerns of raw milk along the informal milk value in Nakasongola District. The cross-sectional study used both qualitative and quantitative methods to obtain information from key players. The qualitative data was categorized and presented into emerging themes. Bacterial contamination of 200 milk samples was determined by morphological and biochemical tests. The antibiotic susceptibility test was done by the disc diffusion method.

Hand milking was carried out mainly by men (92.5%), and most never or rarely practised hand washing (67.5%) during milking. Milk was mainly delivered to mobile milk-collecting centres located under tree shades (50%). The quality of raw milk was affected by poor hygienic, handling and transportation practices. Most participants (75%) were aware of the dangers of drinking raw milk and the requirements to transport milk in metallic cans. Viable bacterial counts above the recommended limit were recorded in 76 samples (38%) that included Staphylococcus aureus (46%), coagulase-negative Staphylococcus (29%), Escherichia coli (12%), Streptococcus agalactiae (8%) and Salmonella spp. (5%). The overall antibiotic resistance was 45% (34/76), which included resistant isolates of S. aureus (17/34), coagulase-negative Staphylococcus (11/22), S. agalactiae (3/6), Salmonella spp. (2/4) and E. coli (2/9).

The raw milk contaminated with antibiotic drug-resistant bacterial pathogens is of public health concern. Thus, measures to improve the quality of milk need to be designed for the pastoral community in Nakasongola district.

Staphylococcus argenteus: An emerging subclinical bovine mastitis pathogen in Thailand

Background and Aim:

Staphylococcus argenteus is an emerging species of the Staphylococcus aureus complex. It has usually been misidentified as S. aureus by conventional methods and its characteristics. S. argenteus is potentially emerging in both humans and animals with an increasing global distribution. This study aimed to differentiate and identify S. argenteus from S. aureus collected and isolated from milk samples of subclinical bovine mastitis cases in Maha Sarakham Province, Northeastern Thailand.

Materials and Methods:

Forty-two isolates of S. aureus were studied from 132 individual milk samples collected from subclinical bovine mastitis cases of 15 dairy farms in three districts of Maha Sarakham, Thailand. The identification was confirmed by conventional and immune-agglutination methods. Fifteen representative isolates which were suspected as being S. argenteus were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

Results:

The result from MALDI-TOF MS confirmed that seven from 15 isolates were S. argenteus and eight isolates were S. aureus.

Conclusion:

This study indicated that MALDI-TOF MS used as an identification and classification method could accurately differentiate the novel species, S. argenteus, from the S. aureus complex which is usually misdiagnosed. In addition, the identification of S. argenteus seems to be very limited in technical difficulty despite the fact that it may be the important causative pathogen in bovine mastitis as well as a pathogenic bacterium in food and milk. Therefore, it is essential for both bovine medicine and veterinary public health to emphasize and recognize this bacterial pathogen as an emerging disease of staphylococcal bacteria that there is a need for further study of S. argenteus infections.

Staphylococcus spp. associated with subclinical bovine mastitis in central and northeast provinces of Thailand

Background

Staphylococcus spp. are major cause of bovine mastitis (BM) worldwide leading to economic damage to dairy farms and public health threat. Recently, a newly emerged Staphylococcus argenteus has been found as a human and animal pathogen. Molecular characteristics, virulence and antibiotic resistant phenotypes of bacteria causing BM in Thailand are rare. This study aimed to investigated Staphylococcus spp. associated with subclinical bovine mastitis (SCM) in Thailand.

Methods

Milk samples were collected from 224 cows of 52 dairy herds in four central and northeast provinces. Total somatic cell counts (SCC) and California mastitis test (CMT) were used to identify SCM cows. Milk samples were cultured for Staphylococcus spp. Coagulase-positive isolates were subjected to pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Organisms suspected as S. argenteus were verified by detecting nonribosomal peptide synthetase gene. All isolates were checked for antibiograms and the presence of various virulence genes.

Results

From the 224 milk samples of 224 cows, 132 (59%) were positive for SCM by SCC and CMT and 229 staphylococcal isolates were recovered. They were 32 coagulase-positive (24 S. aureus and eight S. argenteus) and 197 coagulase-negative. PFGE of the S. aureus and S. argenteus revealed 11 clusters and a non-typeable pattern. MLST of representatives of the 11 PFGE clusters, three PFGE non-typeable S. aureus isolates from different locations and S. argenteus showed 12 sequence types. The eight S. argenteus isolates belonged to ST1223 (three isolates), ST2250 (two isolates), and ST2793 (two isolates). The antimicrobial tests identified 11 (46%) methicillin-resistant S. aureus and 25 (13%) methicillin-resistant coagulase-negative isolates, while seven S. argenteus were methicillin-susceptible and one isolate was methicillin-resistant. All of the 229 isolates were multiply resistant to other antibiotics. The most prevalent virulence genes of the 24 S. aureus isolates were clfA, coa and spa (X and IgG-binding region) (100%), hla (96%), pvl (96%) and sec (79%). Six S. argenteus isolates carried one enterotoxin gene each and other virulence genes including coa, clfA, hla/hlb, spa, tsst and pvl, indicating their pathogenic potential.

Conclusion and perspective

This is the first report on the S. argenteus from cow milk samples with SCM. Data on the molecular characteristics, virulence genes and antibiograms of the Staphylococcus spp. obtained from the present study showed a wide spread and increasing trend of methicillin-resistance and multiple resistance to other antibiotics. This suggests that the "One Health" practice should be nurtured, not only at the dairy farm level, but also at the national or even the international levels through cooperation of different sectors (dairy farmers, veterinarians, medical and public health personnel and scientists) in order to effectively combat and control the spread of these pathogens.

Variability of resistance plasmids in coagulase-negative staphylococci and their importance as a reservoir of antimicrobial resistance

Coagulase-negative staphylococci (CoNS) are an important cause of human and animal diseases. Treatment of these diseases is complicated by their common antimicrobial resistance, caused by overuse of antibiotics in hospital and veterinary environment. Therefore, they are assumed to serve as a reservoir of resistance genes often located on plasmids. In this study, we analyzed plasmid content in 62 strains belonging to 10 CoNS species of human and veterinary origin. In 48 (77%) strains analyzed, 107 different plasmids were detected, and only some of them showed similarities with plasmids found previously. In total, seven different antimicrobial-resistance genes carried by plasmids were identified. Five of the CoNS staphylococci carried plasmids identical with either those of other CoNS species tested, or a well characterized Staphylococcus aureus strain COL, suggesting plasmid dissemination through horizontal transfer. To demonstrate the possibility of horizontal transfer, we performed electroporation of four resistance plasmids among Staphylococcus epidermidis, Staphylococcus petrasii, and coagulase-positive S. aureus strains. Plasmids were transferred unchanged, were stably maintained in recipient strains, and expressed resistance genes. Our work demonstrates a great variability of plasmids in human and veterinary staphylococcal strains and their ability to maintain and express resistance plasmids from other staphylococcal species.

Antimicrobial resistance and genotypic relatedness of environmental staphylococci in semi-extensive dairy farms

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Staphylococci are commonly found in the environment of semi-extensive dairy farms and milk is the main source of contamination.

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Manual milking can play a role in the dissemination of Staphylococcus spp. in semi-extensive dairy farms.

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Methicillin-resistant Staphylococcus aureus (MRSA) was detected in milk and milker's hand swabs and might be of public health significance.

This study aimed to investigate the occurrence, genotypic relatedness and antimicrobial resistance of Staphylococcus aureus and coagulase-negative Staphylococcus from milk and environmental sources in dairy herds. A total of 110 staphylococci recovered from 147 samples collected at 21 semi-extensive dairy farms in Northeastern Brazil were investigated. Staphylococcus aureus isolates were identified and screened for methicillin resistance by means of a duplex-PCR. The highest frequency of contamination by S. aureus was observed for milk samples (38.1%), while contamination by coagulase-negative staphylococci (CoNS) was most commonly detected in milkers’ hand swabs (52.4%) and environmental samples (29.5%). Two mecA-positive Staphylococcus aureus (2/40; 5%) were detected, while the same gene was found in fourteen (14/70; 20%) CoNS. Clonally related isolates from milk and environmental sources, such as the surface of gates, were detected by PFGE. This study reports the occurrence of MRSA in dairy farms under semi-extensive production practices and reinforces the importance of environment as a source of Staphylococcus contamination in dairy herds.

Molecular characterization of Staphylococcus aureus strains in bovine mastitis milk in Bangladesh

Staphylococcus aureus is a common causative agent of bovine mastitis in dairy herds worldwide. This study was designed to assess the prevalence of mastitis in cows through screening tests and molecular characterization of Staphylococcus aureus strains. Out of 175 randomly screened cows, mastitis was detected in 50 cows by California Mastitis Test (CMT), and from those mastitic cows, 200 quarter milk samples were collected for subsequent culture and PCR based identification. The herd, cow and quarter level prevalence of mastitis was 73.3, 28.6 and 29.5% respectively, and subclinical mastitis (SCM) was the predominant type in all cases. According to bacteriology the overall prevalence of herd, cow and quarter level Staphylococcus aureus mastitis was 72.7, 74.0 and 62.0%, respectively, and the pathogen was mostly associated with clinical mastitis (CM). Cows breed, parity, daily milk yield, regular teat dipping, and dry cow therapy were significantly associated (P < 0.05) risk factors for mastitis onset. This study identifies 145 Staphylococcus aureus isolates which varied greatly with the categories of mastitis (higher in CM), udder quarter location (highest in right rear quarters), and to a lesser extent in the study areas (P < 0.05). Antimicrobial susceptibility testing revealed that 79.3% Staphylococcus aureus strains were resistant to at least one antimicrobial, 49.0% to two or more antimicrobials, and clinical isolates showed more resistance to all tested antibiotics. The highest resistance rate was found to oxytetracyclin, and no resistance to ceftriaxone and azithromycin. Seven enterotoxin gene profile were detected in the tested isolates, and mecA was found in 20.0% isolates indicating the emergence and spread of methicillin-resistant Staphylococcus aureus (MRSA). The isolates were carrying genes in combination, and were found higher in SCM cases. In this study, plasmids (>23 kb to 2.9 kb) were detected in 70.3% strains, and 54.9% plasmid bearing strains were multiple drug resistant (MDR). Thus, the high prevalence of Staphylococcus aureus mastitis is an important concern for diary industry of Bangladesh since the strains of this pathogen is becoming more resistant to commercially available antimicrobials, and this is an alarming concern for both animal and public health.

Characterization of a genetically distinct subpopulation of Staphylococcus haemolyticus isolated from milk of cows with intramammary infections

The aim of this paper is to describe a novel subpopulation of Staphylococcus haemolyticus isolated from intramammary gland infections (IMI) in cattle. In total, eight isolates originating from milk samples from two unrelated dairy farms were examined phenotypically (using the ID 32 STAPH system) and genotypically. These isolates had almost identical sequences of each of the housekeeping genes examined (dnaJ, rpoB and sodA) but these sequences displayed similarity of only ∼92.5%, 95.0% and 96.8%, respectively, with known S. haemolyticus sequences. The atypical isolates could also be distinguished biochemically by the positive β-galactosidase test (with 2-naphthyl-β-d-galactopyranoside as the substrate). All the isolates were identified as S. haemolyticus upon MALDI-TOF analysis but half of them, that achieved scores 1.7-1.999 (not reliable species identification), required expanding the commercial database for secure identification. Our study has shown that IMI in cattle may be caused by two distinct subpopulations of S. haemolyticus, differing clearly by some genotypic and phenotypic properties. The first of these subpopulations seems to be common to many hosts (including humans), whereas the second (possibly at the subspecies rank) is, so far, found only in cattle.

Epizootiological characteristics of viable bacteria and fungi in indoor air from porcine, chicken, or bovine husbandry confinement buildings

Microorganisms found in bioaerosols from animal confinement buildings not only foster the risk of spreading diseases among livestock buildings, but also pose health hazards to farm workers and nearby residents. This study identified the various microorganisms present in the air of swine, chicken, and cattle farms with different kinds of ventilation conditions in Korea. Microbial air samples were collected onto Petri dishes with bacterial or fungal growth media using a cascade impactor. Endotoxin levels in total dust were determined by the limulus amebocyte lysate kinetic QCL method. Prevalent Gram-positive bacteria were Staphylococcus (S.) lentus, S. chromogenes, Bacillus (B.) cereus, B. licheniformis, and Enterococcus faecalis, while the dominant fungi and Gram-negative bacteria were Candida albicans and Sphingomonas paucimobilis, respectively. Considering no significant relationship between the indoor dust endotoxin levels and the isolation of Gram-negative bacteria from the indoor air, monitoring the indoor airborne endotoxin level was found to be also critical for risk assessment on health for animals or workers. The present study confirms the importance of microbiological monitoring and control on animal husbandry indoor air to ensure animal and worker welfare.

Safety Evaluation of the Coagulase-Negative Staphylococci Microbiota of Salami: Superantigenic Toxin Production and Antimicrobial Resistance

The risks of contracting staphylococci food poisoning by the consumption of improperly manufactured salami and the possibility of this food being reservoirs for antibiotic resistance were evaluated. Nineteen coagulase-negative staphylococci (CNS) strains were found in commercial and artisanal salami. The species in commercial salami were S. saprophyticus, S. sciuri, S. xylosus, and S. carnosus. Artisanal salami showed S. succinus, S. epidermidis, and S. hominis but no S. carnosus. Phylogenetic analyses grouped the strains into three major staphylococcal species groups, comprised of 4 refined clusters with similarities superior to 90%. Fifteen strains harbored multiple enterotoxin genes, with high incidence of seb/sec and sea, 57% and 50%, respectively, intermediate incidence of sed/seh/selm and sei/seln/tst-H, 33% and 27%, correspondingly, and low incidence of see/selj/selo and seg, of respectively 13% and 1%. Real time RT-PCR and enzyme-linked-immunosorbent assays confirmed the enterotoxigenicity of the strains, which expressed and produced enterotoxins in vitro. The CNS strains showed multiresistance to several antimicrobials of therapeutic importance in both human and veterinarian medicine, such as β-lactams, vancomycin, and linezolid. The effective control of undue staphylococci in fermented meat products should be adopted to prevent or limit the risk of food poisoning and the spread of antimicrobial-resistant strains.

Prevalence of bovine subclinical mastitis, its etiology and diagnosis of antibiotic resistance of dairy farms in four municipalities of a tropical region of Mexico

A region-wide survey was conducted in the tropical area of Tierra Caliente, State of Guerrero, Mexico to estimate the prevalence of subclinical bovine mastitis (SCM), distribution of mastitis pathogens, and in vitro antimicrobial susceptibility of different mastitis pathogens in dairy farms. In total, 1036 quarter milk samples were obtained from 259 cows at 87 different dairy farms. Collected quarter milk samples were submitted for California Mastitis Test (CMT), bacteriological examination, and testing for antimicrobial susceptibility. Overall prevalence of SCM in the studied area was 20.5 %. Prevalence in the different regions was as follows: 28 % in Arcelia municipality, 21 % in Tlalchapa municipality, 19.4 % in Pungarabato municipality, and 14.3 % in Finch Cutzamala municipality. Of all positive isolates, 97.5 % were Gram-negative bacteria. Moreover, of all positive isolates, 37.5 % were Proteus vulgaris, 25 % Salmonella spp., 12.5 % Enterobacter aerogenes, and 10 % Escherichia coli. Klebsiella pneumonia and E. coli were sensitive for netilmicin antimicrobial. However, E. coli was sensitive for pefloxacin and gentamicin with a sensitivity for pefloxacin for E. aerogenes, while Staphylococci were sensitive for gentamicin and dicloxacillin. It could be concluded that practices such as the implementation of mastitis control programs, improved milking hygiene together with an intramammary treatment with netilmicin, pefloxacin, and gentamicin antimicrobials should be considered for mastitis prevention in the study area of Tierra Caliente, in the tropical area of Guerrero, Mexico.