Sources of Klebsiella and Raoultella species on dairy farms: be careful where you walk

Antimicrobial resistance in E. Coli of animal origin and discovery of a novel ICE mobile element in Northeast China

BACKGROUND

Multidrug resistance in Enterobacteriaceae including resistance to quinolones is rising worldwide. The development of resistance may lead to the emergence of new transmission mechanisms. In this study, the collection of different E. coli was performed from animals and subjected to subsequent procedures including pulsed-field gel electrophoresis, micro-broth dilution method, polymerase chain reaction. Whole genome sequencing of E. coli C3 was performed to detect the affinity, antimicrobial resistance and major carriers of the isolates.

RESULTS

A total of 66 E. coli were isolated and their antibiotic resistance genes, frequency of horizontal transfer and genetic environment of E. coli C3 were determined. The results showed there were both different and same types in PFGE typing, indicating clonal transmission of E. coli among different animals. The detection of antimicrobial resistance and major antibiotic resistance genes and the plasmid transfer results showed that strains from different sources had high levels of resistance to commonly used clinical antibiotics and could be spread horizontally. Whole-genome sequencing discovered a novel ICE mobile element.

CONCLUSION

In summary, the antimicrobial resistance of E. coli in northeast China is a serious issue and there is a risk of antimicrobial resistance transmission. Meanwhile, a novel ICE mobile element appeared in the process of antimicrobial resistance formation.

Microbiota of maize kernels as influenced by Aspergillus flavus infection in susceptible and resistant inbreds

Background

Nearly everything on Earth harbors a microbiome. A microbiome is a community of microbes (bacteria, fungi, and viruses) with potential to form complex networks that involve mutualistic and antagonistic interactions. Resident microbiota on/in an organism are determined by the external environment, both biotic and abiotic, and the intrinsic adaptability of each organism. Although the maize microbiome has been characterized, community changes that result from the application of fungal biocontrol strains, such as non-aflatoxigenic Aspergillus flavus, have not.

Methods

We silk channel inoculated field-grown maize separately with a non-aflatoxigenic biocontrol strain (K49), a highly toxigenic strain (Tox4), and a combination of both A. flavus strains. Two maize inbreds were treated, A. flavus-susceptible B73 and A. flavus-resistant CML322. We then assessed the impacts of A. flavus introduction on the epibiota and endobiota of their maize kernels.

Results

We found that the native microbial communities were significantly affected, irrespective of genotype or sampled tissue. Overall, bacteriomes exhibited greater diversity of genera than mycobiomes. The abundance of certain genera was unchanged by treatment, including genera of bacteria (e.g., Enterobacter, Pantoea) and fungi (e.g., Sarocladium, Meyerozyma) that are known to be beneficial, antagonistic, or both on plant growth and health.

Conclusion

Beneficial microbes like Sarocladium that responded well to A. flavus biocontrol strains are expected to enhance biocontrol efficacy, while also displacing/antagonizing harmful microbes.

The role of EII complex in the bacterial responses to the glucose-survey in clinical Klebsiella pneumoniae isolates

Type 3 fimbriae in Klebsiella pneumoniae are important for bacterial colonization on abiotic and biotic surfaces. The major subunit of type 3 fimbriae (MrkA) is increased by overexpression of EtcABC, an EII complex of phosphoenolpyruvate:carbohydrate phosphotransferase systems (PTSs), through cAMP-cAMP receptor protein (cAMP-CRP) in K. pneumoniae STU1. Here, we further characterized the relations between the amount of etcABC mRNA and MrkA in 78 clinical K. pneumoniae isolates incubated in high levels of glucose. By Western blotting, we observed that MrkA of 29 isolates were not decreased much by high levels of glucose (Group A) but MrkA of other 49 isolates were significantly reduced (Group B) in the same condition. The bacterial biofilms on abiotic surfaces and colonization in the Caenorhabditis elegans of representative isolates in the Group A were not affected by high levels of glucose. However, the biofilm and colonization in the worm of clinical isolates in the Group B were much reduced by high levels of glucose. After quantification by real time RT-PCR, 76% of Group A but just 10% of Group B showed high amount of etcA mRNA. In summary, our results suggested that for most of K. pneumoniae clinical isolates, the amount of etcABC mRNA was positively related to their type 3 fimbriae production in a high level of glucose, thereby to their biofilm formation and colonization in the worm.

Staphylococcus aureus, Escherichia coli, and Klebsiella spp. prevalence in bulk tank milk of Colombian herds and associated milking practices

Background and Aim

Bovine mastitis is one of the most costly and prevalent diseases in dairy herds, which can be prevented and controlled through proper milking practices, diagnosis, and elimination of chronic animals, among others. Contagious pathogens such as Staphylococcus aureus and environmental pathogens such as Escherichia coli and Klebsiella spp. can affect cows and milk for human consumption, generating a public health risk. This study aimed to estimate the prevalence of herds with somatic cell count (SCC) ≥200,000 cells/mL, S. aureus, E. coli, and Klebsiella spp., in bulk tank milk (BTM) and its associated risk factors in Colombian dairy cow herds.

Materials and Methods

A cross-sectional probabilistic study was carried out in 150 dairy herds located in the north of the Antioquia province. A single visit per herd was conducted, during which three BTM samples were aseptically collected. General data and milking practices were collected through an epidemiological survey applied in each herd.

Results

The prevalence of S. aureus, E. coli, and Klebsiella spp. were 14% (21/150), 2% (3/150), and 8% (12/150), respectively. Moreover, 95% of the herds presented an SCC of ≥200,000 cells/mL. Practices such as in-paddock milking, change of milker during the last month, use of disposable gloves, and hand disinfection were associated with increased prevalence of S. aureus, whereas proper dipping was a protective factor. Proper washing and disinfection of the milking machine, use of chlorinated disinfectants for hand hygiene, and use of disposable gloves decreased the prevalence of E. coli and Klebsiella spp. Bulk tank SCC increased in herds with 30-60 milking cows, herds with >60 milking cows, and herds with a change of milker during the last month. Hand disinfection and dipping decreased the SCC.

Conclusion

Staphylococcus aureus, E. coli, and Klebsiella spp. were prevalent in BTM from dairy cow herds. The risk of S. aureus isolation was higher in herds with an in-paddock milking system. The risk of E. coli and Klebsiella spp. isolation were higher in herds with >60 milking cows, with a change of milker during the last month. Processes such as avoiding changing the milker and greater control in medium and large herds could improve the SCC in BTM.

The differential plasma and ruminal metabolic pathways and ruminal bacterial taxa associated with divergent residual body weight gain phenotype in crossbred beef steers

We applied ruminal and plasma metabolomics and ruminal 16S rRNA gene sequencing to determine the metabolic pathways and ruminal bacterial taxa associated with divergent residual body weight gain phenotype in crossbred beef steers. A group of 108 crossbred growing beef steers (average BW = 282.87 ± 30 kg) were fed a forage-based diet for a period of 56 d in a confinement dry lot equipped with GrowSafe intake nodes to determine their residual body weight gain (RADG) phenotype. After RADG identification, blood and rumen fluid samples were collected from beef steers with the highest RADG (most efficient; n = 16; 0.76 kg/d) and lowest RADG (least efficient; n = 16; -0.65 kg/d). Quantitative untargeted metabolome analysis of the plasma and rumen fluid samples were conducted using chemical isotope labelling/liquid chromatography-mass spectrometry. Differentially abundant metabolites in each of the plasma and rumen fluid samples between the two groups of beef steers were determined using a false discovery rate (FDR)-adjusted P-values ≤ 0.05 and area under the curve (AUC) > 0.80. Rumen and plasma metabolic pathways that were differentially enriched or depleted (P ≤ 0.05) in beef steers with positive RADG compared to those with negative RADG were determined by the quantitative pathway enrichment analysis. A total of 1,629 metabolites were detected and identified in the plasma of the beef steers; eight metabolites including alanyl-phenylalanine, 8-hydroxyguanosine, and slaframine were differentially abundant (FDR ≤ 0.05; AUC > 0.80) in beef steers with divergent RADG; five metabolic pathways including steroid hormone biosynthesis, thiamine metabolism, propanoate metabolism, pentose phosphate pathway, and butanoate metabolism were enriched (P ≤ 0.05) in beef steers with positive RADG, relative to negative RADG steers. A total of 1,908 metabolites were detected and identified in the rumen of the beef steers; results of the pathway enrichment analysis of all the metabolites revealed no metabolic pathways in the rumen were altered (P > 0.05). The rumen fluid samples were also analyzed using 16S rRNA gene sequencing to assess the bacterial community composition. We compared the rumen bacterial community composition at the genus level using a linear discriminant analysis effect size (LEfSe) to identify the differentially abundant taxa between the two groups of beef steers. The LEfSe results showed greater relative abundance of Bacteroidetes_vadinHA17 and Anaerovibrio in steers with positive RADG compared to the negative RADG group, while steers in the negative RADG group had greater relative abundance of Candidatus_Amoebophilus, Clostridium_sensu_stricto_1, Pseudomonas, Empedobacter, Enterobacter, and Klebsiella compared to the positive RADG group. Our results demonstrate that beef steers with positive or negative RADG exhibit differences in plasma metabolic profiles and some ruminal bacterial taxa which probably explain their divergent feed efficiency phenotypes.

Molecular Epidemiology and Antimicrobial Resistance of Outbreaks of Klebsiella pneumoniae Clinical Mastitis in Chinese Dairy Farms

Klebsiella pneumoniae is an opportunistic pathogen that causes serious infections in humans and animals. However, the availability of epidemiological information on clinical mastitis due to K. pneumoniae is limited. To acquire new information regarding K. pneumoniae mastitis, data were mined about K. pneumoniae strains on dairy cattle farms (farms A to H) in 7 Chinese provinces in 2021. Hypermucoviscous strains of K. pneumoniae were obtained by the string test. MICs of antimicrobial agents were determined via the broth microdilution method. Ten antimicrobial resistance genes and virulence genes were identified by PCR. The prevalence of K. pneumoniae was 35.91% (65/181), and 100% of the bacteria were sensitive to enrofloxacin. Nine antimicrobial resistance genes and virulence genes were identified and compared among farms. The hypermucoviscous phenotype was present in 94.44% of isolates from farm B, which may be a function of the rmpA virulence gene. Based on these data, the multidrug-resistant strains SD-14 and HB-21 were chosen and sequenced. Genotypes were assayed for K. pneumoniae isolates from different countries and different hosts using multilocus sequence typing (MLST). Ninety-four sequence types (STs) were found, and 6 STs present a risk for spreading in specific regions. Interestingly, ST43 was observed in bovine isolates for the first time. Our study partially reveals the current distribution characteristics of bovine K. pneumoniae in China and may provide a theoretical basis for the prevention and treatment of bovine K. pneumoniae mastitis. IMPORTANCE K. pneumonia is ubiquitous in nature and infects a wide range of hosts, including animals, and humans. It is one of the leading inducements of clinical mastitis (CM) in dairy cows, a prevalent and costly disease that is predominantly associated with bacterial infection. In general, CM caused by Gram-negative bacteria is more difficult to cure than that associated with Gram-positive pathogens, with an average cost per case of 211.03 U.S. dollars (USD) for Gram-negative bacterial infections compared with 133.73 USD for Gram-positive bacterial CM cases. After Escherichia coli, K. pneumoniae is the second most common Gram-negative cause of bovine CM, but it is the most detrimental in terms of decreased milk yield, discarded milk, treatment costs, death, and culling. In view of the economic implications of K. pneumoniae infection in dairy farming, research into population structure and antibiotic resistance is particularly important.

Limited Transmission of Klebsiella pneumoniae among Humans, Animals, and the Environment in a Caribbean Island, Guadeloupe (French West Indies)

Guadeloupe (French West Indies), a Caribbean island, is an ideal place to study the reservoirs of the Klebsiella pneumoniae species complex (KpSC) and identify the routes of transmission between human and nonhuman sources due to its insularity, small population size, and small area. Here, we report an analysis of 590 biological samples, 546 KpSC isolates, and 331 genome sequences collected between January 2018 and May 2019. The KpSC appears to be common whatever the source. Extended-spectrum-β-lactamase (ESBL)-producing isolates (21.4%) belonged to K. pneumoniae sensu stricto (phylogroup Kp1), and all but one were recovered from the hospital setting. The distribution of species and phylogroups across the different niches was clearly nonrandom, with a distinct separation of Kp1 and Klebsiella variicola (Kp3). The most frequent sequence types (STs) (≥5 isolates) were previously recognized as high-risk multidrug-resistant (MDR) clones, namely, ST17, ST307, ST11, ST147, ST152, and ST45. Only 8 out of the 63 STs (12.7%) associated with human isolates were also found in nonhuman sources. A total of 22 KpSC isolates were defined as hypervirulent: 15 associated with human infections (9.8% of all human isolates), 4 (8.9%) associated with dogs, and 3 (15%) associated with pigs. Most of the human isolates (33.3%) belonged to the globally successful sublineage CG23-I. ST86 was the only clone shared by a human and a nonhuman (dog) source. Our work shows the limited transmission of KpSC isolates between human and nonhuman sources and points to the hospital setting as a cornerstone of the spread of MDR clones and antibiotic resistance genes. IMPORTANCE In this study, we characterized the presence and genomic features of isolates of the Klebsiella pneumoniae species complex (KpSC) from human and nonhuman sources in Guadeloupe (French West Indies) in order to identify the reservoirs and routes of transmission. This is the first study in an island environment, an ideal setting that limits the contribution of external imports. Our data showed the limited transmission of KpSC isolates between the different compartments. In contrast, we identified the hospital setting as the epicenter of antibiotic resistance due to the nosocomial spread of successful multidrug-resistant (MDR) K. pneumoniae clones and antibiotic resistance genes. Ecological barriers and/or limited exposure may restrict spread from the hospital setting to other reservoirs and vice versa. These results highlight the need for control strategies focused on health care centers, using genomic surveillance to limit the spread, particularly of high-risk clones, of this important group of MDR pathogens.

Effects of Cellulase and Lactiplantibacillus plantarum on the Fermentation Parameters, Nutrients, and Bacterial Community in Cassia alata Silage

Silage Cassia alata (CA) can alleviate feed shortage in some areas to a certain extent and reduce feed costs. The present research evaluated the effect of cellulase (CE) and Lactiplantibacillus plantarum (LP) on the fermentation parameters, nutrients, and bacterial community of CA silage. Chopped CA was ensiled with three different treatments, namely, no inoculant (CK), CE, and LP, and the indexes were determined on the 2nd, 6th, 14th, and 30th days of silage fermentation. The fermentation parameters indicate that the pH value of the three groups decreased and then increased with the ensilage process, and the lowest value was observed on the 14th day. The CK and LP groups attained the highest value on the 30th day, while the CE group attained the highest value on the 2nd day. Additionally, the pH value and NH₃-N content were significantly lower (P < 0.05) in the CE and LP groups than in the CK group. In terms of nutrients, crude protein (CP) contents significantly increased (P < 0.05) in the CE and LP groups on the 30th day. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of the CE group were significantly and negatively associated with fermentation time, and the water-soluble carbohydrate (WSC) contents of the three groups were significantly lower during ensiling. In comparison with the CK group, the NDF and ADF contents were significantly reduced (P < 0.05), and the WSC content increased (P < 0.05) in the CE group on day 30. Sequencing analysis of bacterial communities showed that Lactobacillus became the most dominant genus in the ensilage process. Moreover, both CE and LP groups increased the abundance of Lactobacillus and decreased that of Klebsiella, Weissella, and Acetobacter in comparison to the CK group, in which LP had a better effect. CE and LP could further improve the silage quality of CA, and LP had a more significant effect in reconstructing the bacterial community in the silage environment.

The Prevalence of Klebsiella spp. Associated With Bovine Mastitis in China and Its Antimicrobial Resistance Rate: A Meta-Analysis

Understanding distribution of bovine mastitis pathogen Klebsiella spp. can contribute to the treatment decision and the control within programs of bovine mastitis, we conducted a meta-analysis to investigate the epidemiology and antimicrobial resistance rates of Klebsiella spp. associated with bovine mastitis in China. Three databases, namely, PubMed, Google scholar, and China National Knowledge Infrastructure database, were utilized to obtain relevant publications. According to PRISMA reporting standards, a total of 38 publications were included in the research, among them, 7 papers included an AMR test. The pooled prevalence of Klebsiella spp. was 5.41% (95% CI: 3.87–7.50%). Subgroup analysis revealed that the prevalence was higher in South China (8.55%, 95% CI: 3.57–19.09%) than in North China (4.22%, 95% CI: 2.46–7.14%), in 2010–2020 (7.45%, 95% CI: 5.29–110.40%) than in 2000–2010 (3.14%, 95% CI: 1.90–15.14%), and in the clinical bovine mastitis cases (7.49%, 95% CI: 3.71–14.54%) than in the subclinical cases (4.03%, 95% CI: 1.55–10.08%). The pooled AMR rate revealed that Klebsiella spp. were most resistant to sulfonamides (45.07%, 95% CI: 27.72–63.71%), followed by tetracyclines (36.18%, 95% CI: 23.36–51.34%), aminoglycosides (27.47%, 95% CI: 17.16–40.92%), β-lactams (27.35%, 95% CI: 16.90–41.05%), amphenicol (26.82%, 95% CI: 14.17–44.87%), lincosamides (21.24%, 95% CI: 7.65–46.75%), macrolides (20.98%, 95% CI: 7.20–47.58%), polypeptides (15.51%, 95% CI: 6.46–32.78%), and quinolones (7.8%, 95% CI: 3.25–17.56%). The climate difference between South and North China and the natural pathogenicity of Klebsiella spp. may be the primary reasons for its distribution, and the prevalence of Klebsiella spp. indicated that the genus is an increasing hazard to the dairy industry. The prevalence of AMR in China is commonly higher than in the European countries and Canada, this is a very important concern for strategy programs to control bovine mastitis caused by Klebsiella spp. in China.

Multidrug-Resistant Klebsiella variicola Isolated in the Urine of Healthy Bovine Heifers, a Potential Risk as an Emerging Human Pathogen

Klebsiella variicola, a member of Klebsiella pneumoniae complex, is found to infect plants, insects, and animals and is considered an emerging pathogen in humans. While antibiotic resistance is often prevalent among K. variicola isolates from humans, this has not been thoroughly investigated in isolates from nonhuman sources. Prior evidence suggests that K. variicola can be transmitted between agricultural products as well as between animals, and the use of antibiotics in agriculture has increased antibiotic resistance in other emerging pathogens. Furthermore, in animals that contain K. variicola as a normal member of the rumen microbiota, the same bacteria can also cause infections, such as clinical mastitis in dairy cows. Here, we describe K. variicola UFMG-H9 and UFMG-H10, both isolated from the urine of healthy Gyr heifers. These two genomes represent the first isolates from the urine of cattle and exhibit greater similarity with strains from the human urinary tract than isolates from bovine fecal or milk samples. Unique to the UFMG-H9 genome is the presence of flagellar genes, the first such observation for K. variicola. Neither of the sampled animals had symptoms associated with K. variicola infection, even though genes associated with virulence and antibiotic resistance were identified in both strains. Both strains were resistant to amoxicillin, erythromycin, and vancomycin, and UFMG-H10 is resistant to fosfomycin. The observed resistances emphasize the concern regarding the emergence of this species as a human pathogen given its circulation in healthy livestock animals. IMPORTANCE Klebsiella variicola is an opportunistic pathogen in humans. It also has been associated with bovine mastitis, which can have significant economic effects. While numerous isolates have been sequenced from human infections, only 12 have been sequenced from cattle (fecal and milk samples) to date. Recently, we discovered the presence of K. variicola in the urine of two healthy heifers, the first identification of K. variicola in the bovine urinary tract and the first confirmed K. variicola isolate encoding for flagella-mediated motility. Here, we present the genome sequences and analysis of these isolates. The bovine urinary genomes are more similar to isolates from the human urinary tract than they are to other isolates from cattle, suggesting niche specialization. The presence of antibiotic resistance genes is concerning, as prior studies have found transmission between animals. These findings are important to understand the circulation of K. variicola in healthy livestock animals.

High Prevalence of Klebsiella pneumoniae in European Food Products: a Multicentric Study Comparing Culture and Molecular Detection Methods

The Klebsiella pneumoniae species complex (KpSC) is a leading cause of multidrug-resistant human infections. To better understand the potential contribution of food as a vehicle of KpSC, we conducted a multicentric study to define an optimal culture method for its recovery from food matrices and to characterize food isolates phenotypically and genotypically. Chicken meat (n = 160) and salad (n = 145) samples were collected in five European countries and screened for the presence of KpSC using culture-based and zur-khe intergenic region (ZKIR) quantitative PCR (qPCR) methods. Enrichment using buffered peptone water followed by streaking on Simmons citrate agar with inositol (44°C for 48 h) was defined as the most suitable selective culture method for KpSC recovery. A high prevalence of KpSC was found in chicken meat (60% and 52% by ZKIR qPCR and the culture approach, respectively) and salad (30% and 21%, respectively) samples. Genomic analyses revealed high genetic diversity with the dominance of phylogroups Kp1 (91%) and Kp3 (6%). A total of 82% of isolates presented a natural antimicrobial susceptibility phenotype and genotype, with only four CTX-M-15-producing isolates detected. Notably, identical genotypes were found across samples-same food type and same country (15 cases), different food types and same country (1), and same food type and two countries (1)-suggesting high rates of transmission of KpSC within the food sector. Our study provides a novel isolation strategy for KpSC from food matrices and reinforces the view of food as a potential source of KpSC colonization in humans. IMPORTANCE Bacteria of the Klebsiella pneumoniae species complex (KpSC) are ubiquitous, and K. pneumoniae is a leading cause of antibiotic-resistant infections in humans. Despite the urgent public health threat represented by K. pneumoniae, there is a lack of knowledge of the contribution of food sources to colonization and subsequent infection in humans. This is partly due to the absence of standardized methods for characterizing the presence of KpSC in food matrices. Our multicentric study provides and implements a novel isolation strategy for KpSC from food matrices and shows that KpSC members are highly prevalent in salads and chicken meat, reinforcing the view of food as a potential source of KpSC colonization in humans. Despite the large genetic diversity and the low levels of resistance detected, the occurrence of identical genotypes across samples suggests high rates of transmission of KpSC within the food sector, which need to be further explored to define possible control strategies.

Unveiling lignocellulolytic trait of a goat omasum inhabitant Klebsiella variicola strain HSTU-AAM51 in light of biochemical and genome analyses

Klebsiella variicola is generally known as endophyte as well as lignocellulose-degrading strain. However, their roles in goat omasum along with lignocellulolytic genetic repertoire are not yet explored. In this study, five different pectin-degrading bacteria were isolated from a healthy goat omasum. Among them, a new Klebsiella variicola strain HSTU-AAM51 was identified to degrade lignocellulose. The genome of the HSTU-AAM51 strain comprised 5,564,045 bp with a GC content of 57.2% and 5312 coding sequences. The comparison of housekeeping genes (16S rRNA, TonB, gyrase B, RecA) and whole-genome sequence (ANI, pangenome, synteny, DNA-DNA hybridization) revealed that the strain HSTU-AAM51 was clustered with Klebsiella variicola strains, but the HSTU-AAM51 strain was markedly deviated. It consisted of seventeen cellulases (GH1, GH3, GH4, GH5, GH13), fourteen beta-glucosidase (2GH3, 7GH4, 4GH1), two glucosidase, and one pullulanase genes. The strain secreted cellulase, pectinase, and xylanase, lignin peroxidase approximately 76-78 U/mL and 57-60 U/mL, respectively, when it was cultured on banana pseudostem for 96 h. The catalytically important residues of extracellular cellulase, xylanase, mannanase, pectinase, chitinase, and tannase proteins (validated 3D model) were bound to their specific ligands. Besides, genes involved in the benzoate and phenylacetate catabolic pathways as well as laccase and DiP-type peroxidase were annotated, which indicated the strain lignin-degrading potentiality. This study revealed a new K. variicola bacterium from goat omasum which harbored lignin and cellulolytic enzymes that could be utilized for the production of bioethanol from lignocelluloses.

Exploring the bacterial community and fermentation characteristics during silage fermentation of abandoned fresh tea leaves

The potential application of silage fermentation on abandoned fresh tea leaves (AFTL) was investigated. Dynamic profiles of fermentation-related components, characteristic components and the bacterial community of AFTL during ensiling were analysed. The results showed that after ensiling for 60 days, the concentrations of lactic, acetic and propionic acid increased, whereas a high pH value (4.80) and NH₃-N content (106 g/kg TN) were detected. Characteristic components, including caffeine, polyphenols, theanine and catechins, were well preserved. The microbial community changed significantly, and Lactobacillus (63.6%) became the dominant phylum. Spearman rank correlation revealed a positive correlation between lactic acid concentration and the abundance of Lactobacillus (63.6%) and Klebsiella (25.0%), whereas the abundance of Klebsiella was negatively correlated with catechin concentration. In conclusion, ensiling could be an effective utilization for AFTL and provides a new idea for utilizing idle resources on tea plantations.

Diffuse-Type Tenosynovial Giant Cell Tumor of the Knee with Concurrent Polymicrobial Infection (Klebsiella oxytoca and Group B Streptococcus)

Tenosynovial giant cell tumors (TGCT) are a rare class of benign proliferative tumors that are classified according to their presentation: localized-type (L-TGCT) or diffuse-type (D-TGCT). TGCT is synonymous with pigmented villonodular synovitis (PVNS). We describe the unique case of a 56-year-old obese male with type 2 diabetes who had polymicrobial septic arthritis of his left knee joint with concurrent D-TGCT in the same knee. While on a vacation, he noticed spontaneous left knee pain and swelling with an acute onset of fever. He was diagnosed with septic arthritis that was attributed to hematogenous spread from a leg laceration. The septic arthritis was treated with arthroscopic lavage and debridement, including simultaneous excision of the D-TGCT lesions, followed by intravenous ceftriaxone. Cultures of the synovial tissue that were obtained during arthroscopy grew Klebsiella oxytoca and beta-hemolytic (group B) Streptococcus agalactiae. We were not able to find another reported case of any joint with (1) a polymicrobial bacterial infection that included Klebsiella oxytoca and (2) concurrent bacterial septic arthritis and TGCT.

Proposal for reunification of the genus Raoultella with the genus Klebsiella and reclassification of Raoultella electrica as Klebsiella electrica comb. nov

The order Enterobacterales was divided into seven families including the family Enterobacteriaceae in 2016. The genus Klebsiella within the family Enterobacteriaceae was divided into two genera Klebsiella and Raoultella in 2001. Here, our phylogenomic analysis shows that the genus Raoultella is nested within the genus Klebsiella. Klebsiella and Raoultella together are monophyletic and share average amino acid identities (AAIs) of 86.9-89.6% above the AAI threshold (86%) for genus delimitation within the family Enterobacteriaceae. Klebsiella and Raoultella share AAIs of 79.9%-85.0% with the other genera within the subfamily "Klebsiella clade", which are in the range of inter-genus AAIs (74‒85%) within the family Enterobacteriaceae. Klebsiella and Raoultella also share six known conserved signature indels. Therefore, we propose to reunify Klebsiella and Raoultella to the single genus Klebsiella and reclassify Raoultella electrica as Klebsiella electrica comb. nov. Our genome-based taxonomic analyses also identified seven potential novel species within the unified genus Klebsiella.

Isolation, characterization, and interaction of lignin-degrading bacteria from rumen of buffalo (Bubalus bubalis)

The purpose of this study was to isolate lignin-degrading bacteria from buffalo rumen and to explore their interactions further. Using lignin as the carbon source, three bacteria, B-04 (Ochrobactrum pseudintermedium), B-11 (Klebsiella pneumoniae), and B-45 (Bacillus sonorensis), which have shown lignin degradation potential, were successfully isolated and identified from the rumen fluid of buffalo by colony morphology, 16S ribosomal RNA gene sequencing, and biochemical and physiological analyses. The degradation rates of lignin were determined, and the maximum values were 4.86%, 11.1%, and 7.68% for B-04, B-11, and B-45, respectively. The maximum laccase activities were 0.65, 0.93, and 1.15 U/ml, while the maximum lignin peroxidase activities were 5.72, 8.29, and 18.69 U/ml, respectively. Pairwise interaction studies showed inhibitory interaction between B-04 and B-45, inhibitory interaction between B-04 and B-11, and symbiotic interaction between B-11 and B-45. This is the first report on the lignin degradation ability of bacteria isolated from the buffalo's rumen, which provides a new understanding for revealing the mechanism of roughage tolerance of buffalo.

Antimicrobial resistance in Klebsiella species from milk specimens submitted for bovine mastitis testing at the Wisconsin Veterinary Diagnostic Laboratory, 2008–2019

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Klebsiella isolates resistant to ceftiofur, cephalothin, or tetracycline did not increase.

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For sulfadimethoxine, the proportion of resistant isolates decreased over time.

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There was no trend toward increasing antimicrobial resistance among isolates.

The purpose of this retrospective study was to describe antimicrobial resistance trends in Klebsiella isolates cultured from milk samples submitted to the Wisconsin Veterinary Diagnostic Laboratory for bovine mastitis testing. In vitro antimicrobial susceptibility testing was conducted in 483 Klebsiella isolates cultured from 63,841 milk samples submitted from January 1, 2008, through December 31, 2019. The Wisconsin Veterinary Diagnostic Laboratory conducted antimicrobial susceptibility testing according to the Clinical and Laboratory Standards Institute by using a broth microdilution panel. Ten antimicrobials were tested in the panel: ampicillin, penicillin, erythromycin, oxacillin + 2% NaCl, pirlimycin, penicillin/novobiocin, tetracycline, ceftiofur, cephalothin, and sulfadimethoxine. Isolates were considered resistant to specific antimicrobials based on minimum inhibitory concentrations described in Clinical and Laboratory Standards Institute guidelines. No guidelines were available for sulfadimethoxine; isolates were categorized as resistant when bacterial growth was not inhibited. The proportion of isolates resistant to ceftiofur, cephalothin, or tetracycline did not increase over time. For sulfadimethoxine, the proportion of resistant isolates decreased over time. These results do not demonstrate a trend toward increasing antimicrobial resistance among Klebsiella isolates. Despite that, antimicrobial resistance should continue to be monitored.

Case Report: Multidrug Resistant Raoultella ornithinolytica in a Septicemic Calf

Sepsis is a frequent life-threatening condition in young calves, requiring rapid broad spectrum and bactericidal therapy to maximize survival chances. Few studies have identified and characterized bacteria involved in sepsis in calves. This report demonstrates the involvement of a multidrug resistant Raoultella ornithinolytica, an emerging pathogen in human medicine, in a calf with suspected sepsis. R. ornithinolytica was identified by MALDI-TOF MS from blood cultures of a critically ill calf. Susceptibility testing showed phenotypic resistance against ampicillin, gentamicin, potentiated sulphonamides, streptomycin, tetracyclines and intermediate susceptibility for enrofloxacin. Whole genome sequencing confirmed identification as R. ornithinolytica and the multidrug resistant character of the isolate. Antimicrobial resistance genes acting against aminoglycosides, beta-lactam antibiotics, fosfomycin, quinolones, sulphonamides, trimethoprim and tetracyclines were found. The calf recovered after empirical parenteral therapy with enrofloxacin and sodium penicillin for seven days. Ancillary therapy consisted of fluid therapy, ketoprofen and doxapram hydrochloride. To the authors' knowledge, this is the first report characterizing a multidrug resistant R. ornithinolytica isolate from blood culture in cattle. It is currently unknown whether animals and farms may act as reservoirs for multidrug resistant R. ornithinolytica strains.

Molecular characterization of antimicrobial resistance in Klebsiella pneumoniae isolated from Brazilian dairy herds

In this observational study, phenotypic and genotypic patterns of antimicrobial resistance (AMR) in Klebsiella pneumoniae isolated from intramammary infections, clinical mastitis, fresh feces, rectal swabs, animal hindlimbs, and bulk tank milk samples from Brazilian dairy herds were investigated. In addition, we identified specific genetic variants present among extended-spectrum β-lactamase (ESBL) producers. We obtained 169 isolates of K. pneumoniae from 2009 to 2011 on 24 Brazilian dairy farms located in 4 Brazilian states. The AMR profile of all isolates was determined using disk-diffusion assays. The antimicrobial panel included drugs commonly used as mastitis treatment in Brazilian dairy herds (gentamicin, cephalosporins, sulfamethoxazole-trimethoprim, tetracycline) as well as antimicrobials of critical importance for human health (meropenem, ceftazidime, fluoroquinolones). The K. pneumoniae isolates resistant to tetracycline, fluoroquinolones, sulfamethoxazole-trimethoprim, or chloramphenicol were screened for presence of drug-specific AMR genes [tet, qnr, aac(6')-Ib, floR, catA2, cm1A, dfr, sul] using PCR. In addition, we identified ESBL genes present among ESBL-producers by using whole genome sequencing. Genomes were assembled and annotated, and patterns of AMR genes were investigated. Resistance was commonly detected against tetracycline (22.5% of all isolates), streptomycin (20.7%), and sulfamethoxazole-trimethoprim (9.5%). Antimicrobial resistance rates were higher in K. pneumoniae isolated from intramammary infections in comparison with isolates from feces (19.2 and 0% of multidrug resistance in intramammary and fecal isolates, respectively). In contrast, no difference in AMR rates was observed when contrasting hind limbs and isolates from intramammary infections. The genes tetA, sul2, and floR were the most frequently observed AMR genes in K. pneumoniae resistant to tetracycline, sulfamethoxazole-trimethoprim, and chloramphenicol, respectively. The tetA gene was present exclusively in isolates from milk. The genes bla_CTX-M8 and bla_SHV-108 were present in 3 ESBL-producing K. pneumoniae, including an isolate from bulk tank milk. The 3 isolates were of sequence type 281 and had similar mobile genetic elements and virulence genes. Our study reinforced the epidemiological importance and dissemination of bla_CTX-M-8 pST114 plasmid in food-producing animals in Brazil.

The PTS Components in Klebsiella pneumoniae Affect Bacterial Capsular Polysaccharide Production and Macrophage Phagocytosis Resistance

Capsular polysaccharide (CPS) is a crucial virulence factor for Klebsiella pneumoniae infection. We demonstrated an association of CPS production with two phosphoenolpyruvate:carbohydrate phosphotransferase systems (PTSs). Deficiency of crr, encoding enzyme IIA of PTS, in K. pneumoniae enhanced the transcriptional activities of galF, wzi and gnd, which are in the cps gene cluster, leading to high CPS production. A crr mutant exhibited a higher survival rate in 1% hydrogen peroxide than the wild-type. The crr mutant showed less sensitivity to engulfment by macrophage (RAW 264.7) than the wild-type by observing the intracellular bacteria using confocal laser scanning microscopy (CLSM) and by calculating the colony-forming units (CFU) of intracellular bacteria. After long-term incubation, the survival rate of the intracellular crr mutant was higher than that of the wild-type. Deficiency of crr enhanced the transcriptional activities of etcABC which encodes another putative enzyme II complex of a PTS. Deletion of etcABC in the crr mutant reduced CPS production and the transcriptional activities of galF compared to those of the crr mutant. These results indicated that one PTS component, Crr, represses CPS production by repressing another PTS component, EtcABC, in K. pneumoniae. In addition, PTS plays a role in bacterial resistance to macrophage phagocytosis.

Genetic diversity and molecular epidemiology of outbreaks of Klebsiella pneumoniae mastitis on two large Chinese dairy farms

Klebsiella pneumoniae is an opportunistic and environmental mastitis-causing pathogen, with potential for contagious transmission. Repetitive element sequence-based PCR was used to determine genetic diversity and explore potential transmission and reservoirs for mastitis caused by K. pneumoniae on 2 large Chinese dairy farms. A total of 1,354 samples was collected from the 2 dairy farms, including milk samples from cows with subclinical and clinical mastitis, bedding, feces, feed, teat skin, and milking liners. Environmental samples were collected from all barns and milking parlors and extramammary samples from randomly selected dairy cows on both farms. In total, 272 and 93 K. pneumoniae isolates were obtained from Farms A and B, respectively (with ~8K and 2K lactating cows, respectively). Isolation rates from clinical mastitis (CM), subclinical mastitis (SCM), and environmental or extramammary samples were 34, 23 and 37%, respectively for Farm A and 42, 3, and 34% for Farm B. The K. pneumoniae isolated from CM milk and extramammary or environmental sources had high genetic diversity (index of diversity >90%) on the 2 farms and from SCM on Farm A. However, on Farm B, 9 SCM isolates were classified as 2 genotypes, resulting in a relatively low index of diversity (Simpson's index of diversity = 0.39; 95% CI = 0.08-0.70). Genotypes of K. pneumoniae causing mastitis were commonly detected in feces, bedding, and milking liners (Farm A), or from teat skin, sawdust bedding, and feed (Farm B). Based on its high level of genetic diversity, we inferred K. pneumoniae was an opportunistic and environmental pathogen causing outbreaks of CM on these 2 large Chinese dairy farms. Nevertheless, that only a few genotypes caused SCM implied some strains had increased udder adaptability and a contagious nature or a common extramammary source. Finally, control of intramammary infections caused by K. pneumoniae on large Chinese dairy farms must consider farm-level predictors, as the 2 outbreaks had distinct potential environmental sources of infection.

Development and evaluation of 4 loop-mediated isothermal amplification assays to detect mastitis-causing bacteria in bovine milk samples

Farmers prefer fast, sensitive, and on-site tests for treatment decisions on mastitis. Due to the time to results of the currently available diagnostic tools, these are rarely used for that purpose. Genotypic tests that do not require a growth step may be suitable for on-site testing, for example loop-mediated isothermal amplification (LAMP), which has been described as a sensitive test that can be used on-site. Therefore, this study aimed to develop and evaluate LAMP assays for the detection of a subset of mastitis-causing pathogens, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Streptococcus spp., in milk from cows with clinical mastitis. Furthermore, a generic nucleic acid lateral flow immunoassay (NALFIA) was evaluated as a potential on-site readout of the LAMP assays. For each assay of LAMP and NALFIA, the limit of detection and analytical specificity were determined using isolates, and the diagnostic specificity was determined using selected samples with known etiology. In addition, the diagnostic specificity of LAMP was determined using field samples with unknown etiology at testing. Bacteriological culture with identification by mass spectrometry was used as a reference method. The 4 assays had a kappa ≥0.73 with the reference method when testing the selected samples, but ≥0.47 when testing field samples. After correcting for prevalence, kappa was ≥0.80 for the E. coli, K. pneumoniae, and Staph. aureus assays. The Streptococcus spp. assay had a kappa of 0.47 (0.48 after correction) with the reference method, probably caused by the assay broadly targeting a genus instead of a particular species. The NALFIA readout was found to have kappa ≥0.81 for the E. coli, Staph. aureus, and Streptococcus spp. assays at a generic runtime, but for the K. pneumoniae assay a shorter runtime could be used. In conclusion, LAMP is a promising method for fast on-site tests for mastitis-causing pathogens if the current elaborate method for sample preparation is replaced by a simplified protocol. The NALFIA is an easy and reliable readout for on-site use, with the observation that for the current assay designs a generic runtime is not yet possible for the chosen set of pathogens. If associated with a simple and fast sample preparation protocol, the combination of LAMP and NALFIA has the potential to enable fast and reliable on-site testing of clinical mastitis milk samples.

The ZKIR Assay, a Real-Time PCR Method for the Detection of Klebsiella pneumoniae and Closely Related Species in Environmental Samples

The Klebsiella pneumoniae species complex Kp includes human and animal pathogens, some of which are emerging as hypervirulent and/or antibiotic-resistant strains. These pathogens are diverse and classified into seven phylogroups, which may differ in their reservoirs and epidemiology. Proper management of this public health hazard requires a better understanding of Kp ecology and routes of transmission to humans. So far, detection of these microorganisms in complex matrices such as food or the environment has been difficult due to a lack of accurate and sensitive methods. Here, we describe a novel method based on real-time PCR which enables detection of all Kp phylogroups with high sensitivity and specificity. We used this method to detect Kp isolates from environmental samples, and we show based on genomic sequencing that they differ in antimicrobial resistance and virulence gene content from human clinical Kp isolates. The ZKIR PCR assay will enable rapid screening of multiple samples for Kp presence and will thereby facilitate tracking the dispersal patterns of these pathogenic strains across environmental, food, animal and human sources.

Klebsiella pneumoniae is of growing public health concern due to the emergence of strains that are multidrug resistant, virulent, or both. Taxonomically, the K. pneumoniae complex (“Kp”) includes seven phylogroups, with Kp1 (K. pneumoniaesensu stricto) being medically prominent. Kp can be present in environmental sources such as soils and vegetation, which could act as reservoirs of animal and human infections. However, the current lack of screening methods to detect Kp in complex matrices limits research on Kp ecology. Here, we analyzed 1,001 genome sequences and found that existing molecular detection targets lack specificity for Kp. A novel real-time PCR method, the ZKIR (zur-khe intergenic region) assay, was developed and used to detect Kp in 96 environmental samples. The results were compared to a culture-based method using Simmons citrate agar with 1% inositol medium coupled to matrix-assisted laser desorption ionization–time of flight mass spectrometry identification. Whole-genome sequencing of environmental Kp was performed. The ZKIR assay was positive for the 48 tested Kp reference strains, whereas 88 non-Kp strains were negative. The limit of detection of Kp in spiked soil microcosms was 1.5 × 10⁻¹ CFU g⁻¹ after enrichment for 24 h in lysogeny broth supplemented with ampicillin, and it was 1.5 × 10³ to 1.5 × 10⁴ CFU g⁻¹ directly after soil DNA extraction. The ZKIR assay was more sensitive than the culture method. Kp was detected in 43% of environmental samples. Genomic analysis of the isolates revealed a predominance of phylogroups Kp1 (65%) and Kp3 (32%), a high genetic diversity (23 multilocus sequence types), a quasi-absence of antibiotic resistance or virulence genes, and a high frequency (50%) of O-antigen type 3. This study shows that the ZKIR assay is an accurate, specific, and sensitive novel method to detect the presence of Kp in complex matrices and indicates that Kp isolates from environmental samples differ from clinical isolates.

IMPORTANCE The Klebsiella pneumoniae species complex Kp includes human and animal pathogens, some of which are emerging as hypervirulent and/or antibiotic-resistant strains. These pathogens are diverse and classified into seven phylogroups, which may differ in their reservoirs and epidemiology. Proper management of this public health hazard requires a better understanding of Kp ecology and routes of transmission to humans. So far, detection of these microorganisms in complex matrices such as food or the environment has been difficult due to a lack of accurate and sensitive methods. Here, we describe a novel method based on real-time PCR which enables detection of all Kp phylogroups with high sensitivity and specificity. We used this method to detect Kp isolates from environmental samples, and we show based on genomic sequencing that they differ in antimicrobial resistance and virulence gene content from human clinical Kp isolates. The ZKIR PCR assay will enable rapid screening of multiple samples for Kp presence and will thereby facilitate tracking the dispersal patterns of these pathogenic strains across environmental, food, animal and human sources.

Characterization of Klebsiella isolates obtained from clinical mastitis cases in dairy cattle

Klebsiella spp. are important opportunistic pathogens commonly defined as environmental clinical mastitis agents. Despite Klebsiella mastitis being clinically impairing in cows and costly to the industry, only a few studies describe Klebsiella isolated from mastitis cases. The aim of this work was to characterize species of Klebsiella involved in clinical mastitis cases in Canada. Klebsiella isolated from clinical mastitis cases (n = 53) were identified to the species level using a biochemical test panel and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The rpoB gene sequence was used as the gold standard method and identified Klebsiella pneumoniae (n = 40), Klebsiella oxytoca (n = 9), Raoultella ornithinolytica (n = 2), and Raoultella planticola (n = 2). Raoultella, a genus closely related to Klebsiella, was also accurately identified using mass spectrometry but not via biochemical testing. Using the disc diffusion technique, 31 (58%) isolates were found to be susceptible to all antimicrobials tested (n = 18). The remaining 22 (42%) isolates were resistant to 1 or more of the following antimicrobials: kanamycin (2%), streptomycin (38%), spectinomycin (13%), sulfisoxazole (13%), and tetracycline (19%). The following antimicrobial resistance genes were identified: tetA, tetB, sul1, strA/strB, and aadA. Random amplified polymorphic DNA revealed the majority of our isolates as unrelated and having different patterns, indicating environmental contamination as the primary source of infection. All isolates were shown to be biofilm producers. In conclusion, although antimicrobial resistance was low for both Klebsiella and Raoultella species, genetically related Klebsiella spp. isolates appeared to be more resistant.

Molecular epidemiology of nonsevere clinical mastitis caused by Klebsiella pneumoniae occurring in cows on 2 Wisconsin dairy farms

The objective of this study was to describe diversity of Klebsiella pneumoniae isolated from milk collected at detection of nonsevere (abnormal milk or abnormal udder) clinical mastitis (CM) and during a follow-up period. Cases were detected in cows enrolled in a randomized clinical trial (n = 168) conducted using 2 related Wisconsin dairy farms. Cases were randomly assigned to receive 2 d (n = 18) or 8 d (n = 18) of intramammary infusions with an approved product containing ceftiofur hydrochloride or assigned to a negative control group (n = 17). Milk samples were collected from affected quarters at detection and during a 28-d follow-up period. Sufficient DNA was recovered from 53 of 54 Kleb. pneumoniae cultured from quarter milk samples collected at detection of the incident case. Additional Kleb. pneumoniae were recovered from milk samples collected from the same quarters at 14, 21, and 28 d after case detection (n = 35), at detection of recurrent cases in the same quarter (n = 14), and from new cases of CM (n = 3) occurring in enrolled quarters. All Kleb. pneumoniae were used for molecular typing by pulsed-field gel electrophoresis and 90% similarity was used to define homology. Of Kleb. pneumoniae recovered from incident cases, unique strains (n = 41) were identified in milk samples collected from cows on farm A (n = 19) and farm B (n = 22), whereas 12 clonal strains were identified with 8 found only in milk collected from farm A and 4 found in milk samples collected from cows on both farms. Heterogeneous strains of Kleb. pneumoniae genotypes were isolated from incident cases of CM. However, when intramammary infection persisted or when recurrence of CM occurred, clonal strains were isolated at 14, 21, or 28 d. Similar strains of Kleb. pneumoniae genotypes caused persistent CM. In conclusion, initial cases of CM were caused by a wide genetic diversity of Kleb. pneumoniae, but when IMI persisted, the same strain often persisted within the mammary gland up to 28 d.

Population genomics of Klebsiella pneumoniae

Klebsiella pneumoniae is a common cause of antimicrobial-resistant opportunistic infections in hospitalized patients. The species is naturally resistant to penicillins, and members of the population often carry acquired resistance to multiple antimicrobials. However, knowledge of K. pneumoniae ecology, population structure or pathogenicity is relatively limited. Over the past decade, K. pneumoniae has emerged as a major clinical and public health threat owing to increasing prevalence of healthcare-associated infections caused by multidrug-resistant strains producing extended-spectrum β-lactamases and/or carbapenemases. A parallel phenomenon of severe community-acquired infections caused by 'hypervirulent' K. pneumoniae has also emerged, associated with strains expressing acquired virulence factors. These distinct clinical concerns have stimulated renewed interest in K. pneumoniae research and particularly the application of genomics. In this Review, we discuss how genomics approaches have advanced our understanding of K. pneumoniae taxonomy, ecology and evolution as well as the diversity and distribution of clinically relevant determinants of pathogenicity and antimicrobial resistance. A deeper understanding of K. pneumoniae population structure and diversity will be important for the proper design and interpretation of experimental studies, for interpreting clinical and public health surveillance data and for the design and implementation of novel control strategies against this important pathogen.

A mixture of potassium sorbate and sodium benzoate improved fermentation quality of whole-plant corn silage by shifting bacterial communities

AIMS

To investigate the changes in fermentation quality of whole-plant corn silage ensiled with varying dosages of mixed organic acid salts (MS), and link these dosage changes to shifts in bacterial composition.

METHODS AND RESULTS

Fermentation quality and bacterial community of corn silage ensiled with MS at four application rates (0, 0·67 g kg^-1 , 1·33 g kg^-1 , and 2·00 g kg^-1 ) were investigated. The MS consisted of 40% potassium sorbate and 60% sodium benzoate. The corn silages were conserved for 42 days. Dry matter losses and ammonia nitrogen concentration were linearly declined by up to 19·10 and 33·3% with increasing dosages of MS. MS treatments significantly reduced the pH of silage vs the control group. Further analysis indicated that the improvement of fermentation quality was the result of shifts in bacterial composition, the relative abundance of Lactobacillus paralimentarius and Pediococcus spp. increased while Lactobacillus reuteri, Lactobacillus coryniformis and Klebsiella declined with increasing dosages of MS.

CONCLUSIONS

MS effectively improved the fermentation quality of whole-plant corn silage with an optimum dosage of 2·00 g kg^-1 .

SIGNIFICANCE AND IMPACT OF THE STUDY

The correlation between bacterial taxa and fermentation quality provides a potential for the development of novel silage inoculants and for the application of MS on controlling Klebsiella mastitis of livestock farms.

Recurrent urinary tract infections caused by Raoultella planticola after kidney transplant

Recurrent urinary tract infections are difficult to manage in patients with a history of kidney transplant and may contribute to graft loss. Few cases describe recurrent urinary tract infections due to Raoultella planticola in this population. We describe the management of recurrent urinary tract infections due to R planticola in a kidney transplant recipient and review other case reports of urinary tract infections due to this organism.

Prevalence of Potential Virulence Genes in Klebsiella spp. Isolated from Cows with Clinical Mastitis on Large Chinese Dairy Farms

Klebsiella spp. is a common cause of clinical mastitis (CM) in dairy cows. However, relatively less information is available about distribution of virulence factors of Klebsiella spp. isolated from cows with CM. Objectives of this study were, therefore, to determine the prevalence of hypermucoviscosity (HMV) phenotype, capsule serotypes, and potential virulence genes in Klebsiella spp. from cows in China with CM. A total of 241 Klebsiella spp. isolates were recovered from cows with CM on 123 dairy farms (each had >500 lactating cows) located in 13 provinces of China. Of the isolates, 124 (51%) and 117 (49%) were identified as Klebsiella pneumoniae and Klebsiella oxytoca, respectively. The prevalence of HMV was 16% for K. pneumoniae and 11% for K. oxytoca; entB (78%), fimH1 (55%), kfu (31%), and mrkD (24%) were the prevalent virulence genes among K. pneumoniae, whereas entB (50%), fimH1 (30%), and mrkD (22%) were prevalent in K. oxytoca. Prevalence of the lac gene was higher for K. pneumoniae (78%) than for K. oxytoca (13%), whereas the nif gene was more prevalent in K. oxytoca than in K. pneumoniae (12% and 1%, respectively). Fifty-six K. pneumoniae isolates were confirmed as K57, the most prevalent capsule serotype (45%). Twenty-one (18%), 20 (10%), and 9 (8%) of 117 K. oxytoca isolates were positive for K57, K5, and K54 serotypes, respectively. As the predominant serotype, K. pneumoniae K57 isolates had a higher prevalence of the HMV phenotype and fimH1 than non-K57 K. pneumoniae. In conclusion, virulence factors were commonly detected for both K. oxytoca and K. pneumoniae causing CM in Chinese dairy herds. HMV isolates were commonly identified, irrespective of species. In addition, as the predominant capsule in bovine K. pneumoniae, the K57 serotype may be better adapted to the udder environment; therefore, further studies targeting pathogenicity to mammary tissue should contribute new knowledge for vaccine development using this serotype.

Post-surgical meningitis caused by Klebsiella variicola

Klebsiella variicola, a member of K. pneumoniae phylogroup, can cause severe infectious diseases. We report a case of K. variicola meningitis after neurosurgery. The bacterium was isolated from blood and cerebrospinal fluid, and bacterial species identification was carried out by using both matrix-assisted laser-desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) and whole genome sequencing. Initially, the organism was misidentified as K. pneumoniae by VITEK®2; automated system in the clinical laboratory examination. The patient recovered with the combination of surgical drainage and antimicrobial treatment. To our knowledge, this is the first case report of post-surgical meningitis caused by K. variicola. As experienced in this case, the automated bacterial identification system popularly being used in the clinical laboratory might not be effective enough for bacterial species identification. The use of MALDI-TOF MS for microbial identification may be helpful to physicians for appropriate management of K. pneumoniae phylogroup infection.

Characterization of Clinically Relevant Strains of Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae Occurring in Environmental Sources in a Rural Area of China by Using Whole-Genome Sequencing

Klebsiella pneumoniae is a gram-negative, opportunistic pathogen, and a common cause of healthcare-associated infections such as pneumonia, septicemia, and urinary tract infection. The purpose of this study was to survey the occurrence of and characterize K. pneumoniae in different environmental sources in a rural area of Shandong province, China. Two hundred and thirty-one samples from different environmental sources in 12 villages were screened for extended-spectrum β-lactamase-(ESBL)-producing K. pneumoniae, and 14 (6%) samples were positive. All isolates were multidrug-resistant and a few of them belonged to clinically relevant strains which are known to cause hospital outbreaks worldwide. Serotypes, virulence genes, serum survival, and phagocytosis survival were analyzed and the results showed the presence of virulence factors associated with highly virulent clones and a high degree of phagocytosis survivability, indicating the potential virulence of these isolates. These results emphasize the need for further studies designed to elucidate the role of the environment in transmission and dissemination of ESBL-producing K. pneumoniae and the potential risk posed to human and environmental health.

Study of bacterial and fungal community structures in traditional koumiss from Inner Mongolia

Koumiss is notable for its nutritional functions, and microorganisms in koumiss determine its versatility. In this study, the bacterial and fungal community structures in traditional koumiss from Inner Mongolia, China, were investigated. Our results demonstrated that 6 bacterial phyla represented by 126 genera and 49 species and 3 fungal phyla represented by 59 genera and 57 species were detected in 11 samples of artisanal koumiss. Among them, Lactobacillus was the predominant genus of bacterium, and Kluyveromyces and Saccharomyces dominated at the fungal genus level. In addition, there were no differences in the bacterial and fungal richness and diversity of koumiss from 3 neighboring administrative divisions in Inner Mongolia, and the bacterial and fungal community structures (the varieties and relative abundance of bacterial and fungal genera and species) were clearly distinct in individual samples. This study provides a comprehensive understanding of the bacterial and fungal population profiles and the predominant genus and species, which would be beneficial for screening, isolation, and culture of potential probiotics to simulate traditional fermentation of koumiss for industrial and standardized production in the future.

Yeasts and bacteria associated with kocho, an Ethiopian fermented food produced from enset (Ensete ventricosum)

Enset (Ensete ventricosum) is the basis of the staple food consumed by about 20% of the Ethiopian population. Kocho is one of the food products generated from enset by spontaneous fermentation of decorticated and pulverized pseudostem and corm sections. We isolated culturable microbes associated with kocho from different stages of fermentation. Twelve yeast species, six lactic acid bacteria (LABs) species and eleven species of aerobic bacteria were identified by sequencing ITS/D1D2 regions of 26S rDNA of yeasts and 16S rDNA of bacteria, respectively. More yeast species were identified in fresh (fermented for 2–5 days) kocho, compared to long-term (7–12 months) fermented kocho, while we observed an opposite trend for LABs. In fresh kocho, the most frequently isolated yeast species were Pichia exigua, Galactomyces geotrichum, and Pichia fermentans. From mid-term (3–4 months) kocho most frequently Candida cabralensis, G. geotrichum, and Candida ethanolica were isolated. In the long-term fermentations, the most frequently isolated yeast was Saturnispora silva. Lactobacillus plantarum was the most frequently isolated LAB in both fresh and mid-term kocho. In long-term fermented kocho, Acetobacter pasteurianus and L. plantarum were most frequently isolated. L. plantarum was consistently isolated from all the three stages of fermentation. Aerobic bacteria in fresh kocho were mostly gram-negative, with Raoultella planticola and Pantoea agglomerans being the most frequently isolated species. In long-term fermented kocho, mainly gram-positive, spore-forming bacteria of the genus Bacillus were found, among them also species of the Bacillus cereus group, Bacillus anthracis and Bacillus thurigiensis.

Analysis of culturable and non-culturable bacteria and their potential to form biofilms in a primary treated dairy wastewater system

Biofilm formation in a dairy waste irrigation system can reduce treatment capacity and increase maintenance and cleaning. An extreme biofilm observed in a primary treated dairy wastewater system blocked the irrigation line requiring manual cleaning. Both next-generation genomic sequencing and the culturable fraction showed the presence of predominantly Gram-negative bacteria. Isolates identified from current samples and stored samples from the extreme biofilm included Pseudomonas, Citrobacter, Klebsiella and Enterobacter, one Gram-positive spore former (Bacillus cereus) and one unique isolate from the biofilm, a member of the Raoultella genus. Raoultella spp was only cultured from the extreme biofilm; however, next-generation sequencing analysis of a wastewater sample showed this bacterium to be present in the wastewater system. The dominance of Gram negative may be due to the wastewater from the washing equipment used to handle raw milk. Six bacteria from the fresh samples were found to be strong biofilm formers along with the Raoultella spp from the extreme biofilm. Tests using multiple isolates showed Raoultella spp to be important in biofilm formation. This is the first report of the microbial composition of a dairy wastewater biofilm giving insight into the population and growth of microorganisms in the sections of a dairy wastewater irrigation system.

Klebsiella pneumoniae as a key trafficker of drug resistance genes from environmental to clinically important bacteria

Klebsiella pneumoniae is an opportunistic bacterial pathogen known for its high frequency and diversity of antimicrobial resistance (AMR) genes. In addition to being a significant clinical problem in its own right, K. pneumoniae is the species within which several new AMR genes were first discovered before spreading to other pathogens (e.g. carbapenem-resistance genes KPC, OXA-48 and NDM-1). Whilst K. pneumoniae's contribution to the overall AMR crisis is impossible to quantify, current evidence suggests it has a wider ecological distribution, significantly more varied DNA composition, greater AMR gene diversity and a higher plasmid burden than other Gram negative opportunists. Hence we propose it plays a key role in disseminating AMR genes from environmental microbes to clinically important pathogens.

An update on environmental mastitis: Challenging perceptions

Environmental mastitis is the most common and costly form of mastitis in modern dairy herds where contagious transmission of intramammary pathogens is controlled through implementation of standard mastitis prevention programmes. Environmental mastitis can be caused by a wide range of bacterial species, and binary classification of species as contagious or environmental is misleading, particularly for Staphylococcus aureus, Streptococcus uberis and other streptococcal species, including Streptococcus agalactiae. Bovine faeces, the indoor environment and used pasture are major sources of mastitis pathogens, including Escherichia coli and S. uberis. A faeco-oral transmission cycle may perpetuate and amplify the presence of such pathogens, including Klebsiella pneumoniae and S. agalactiae. Because of societal pressure to reduce reliance on antimicrobials as tools for mastitis control, management of environmental mastitis will increasingly need to be based on prevention. This requires a reduction in environmental exposure through bedding, pasture and pre-milking management and enhancement of the host response to bacterial challenge. Efficacious vaccines are available to reduce the impact of coliform mastitis, but vaccine development for gram-positive mastitis has not progressed beyond the "promising" stage for decades. Improved diagnostic tools to identify causative agents and transmission patterns may contribute to targeted use of antimicrobials and intervention measures. The most important tool for improved uptake of known mastitis prevention measures is communication. Development of better technical or biological tools for management of environmental mastitis must be accompanied by development of appropriate incentives and communication strategies for farmers and veterinarians, who may be confronted with government-mandated antimicrobial use targets if voluntary reduction is not implemented.

Whole-Genome Sequencing of Human Clinical Klebsiella pneumoniae Isolates Reveals Misidentification and Misunderstandings of Klebsiella pneumoniae, Klebsiella variicola, and Klebsiella quasipneumoniae

Klebsiella pneumoniae is a serious human pathogen associated with resistance to multiple antibiotics and high mortality. K. variicola and K. quasipneumoniae are closely related organisms that are generally considered to be less-virulent opportunistic pathogens. We used a large, comprehensive, population-based strain collection and whole-genome sequencing to investigate infections caused by these organisms in our hospital system. We discovered that K. variicola and K. quasipneumoniae isolates are often misidentified as K. pneumoniae by routine clinical microbiology diagnostics and frequently cause severe life-threatening infections similar to K. pneumoniae. The presence of KPC in K. variicola and K. quasipneumoniae strains as well as NDM-1 metallo-beta-lactamase in one K. variicola strain is particularly concerning because these genes confer resistance to many different beta-lactam antibiotics. The sharing of plasmids, as well as evidence of homologous recombination, between these three species of Klebsiella is cause for additional concern.

Klebsiella pneumoniae is a major threat to public health, causing significant morbidity and mortality worldwide. The emergence of highly drug-resistant strains is particularly concerning. There has been a recognition and division of Klebsiella pneumoniae into three distinct phylogenetic groups: Klebsiella pneumoniae, Klebsiella variicola, and Klebsiella quasipneumoniae. K. variicola and K. quasipneumoniae have often been described as opportunistic pathogens that have less virulence in humans than K. pneumoniae does. We recently sequenced the genomes of 1,777 extended-spectrum-beta-lactamase (ESBL)-producing K. pneumoniae isolates recovered from human infections and discovered that 28 strains were phylogenetically related to K. variicola and K. quasipneumoniae. Whole-genome sequencing of 95 additional non-ESBL-producing K. pneumoniae isolates recovered from patients found 12 K. quasipneumoniae strains. Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) analysis initially identified all patient isolates as K. pneumoniae, suggesting a potential pitfall in conventional clinical microbiology laboratory identification methods. Whole-genome sequence analysis revealed extensive sharing of core gene content and plasmid replicons among the Klebsiella species. For the first time, strains of both K. variicola and K. quasipneumoniae were found to carry the Klebsiella pneumoniae carbapenemase (KPC) gene, while another K. variicola strain was found to carry the New Delhi metallo-beta-lactamase 1 (NDM-1) gene. K. variicola and K. quasipneumoniae infections were not less virulent than K. pneumoniae infections, as assessed by in-hospital mortality and infection type. We also discovered evidence of homologous recombination in one K. variicola strain, as well as one strain from a novel Klebsiella species, which challenge the current understanding of interrelationships between clades of Klebsiella.

IMPORTANCEKlebsiella pneumoniae is a serious human pathogen associated with resistance to multiple antibiotics and high mortality. K. variicola and K. quasipneumoniae are closely related organisms that are generally considered to be less-virulent opportunistic pathogens. We used a large, comprehensive, population-based strain collection and whole-genome sequencing to investigate infections caused by these organisms in our hospital system. We discovered that K. variicola and K. quasipneumoniae isolates are often misidentified as K. pneumoniae by routine clinical microbiology diagnostics and frequently cause severe life-threatening infections similar to K. pneumoniae. The presence of KPC in K. variicola and K. quasipneumoniae strains as well as NDM-1 metallo-beta-lactamase in one K. variicola strain is particularly concerning because these genes confer resistance to many different beta-lactam antibiotics. The sharing of plasmids, as well as evidence of homologous recombination, between these three species of Klebsiella is cause for additional concern.

Metabolic diversity of the emerging pathogenic lineages of Klebsiella pneumoniae

Multidrug resistant and hypervirulent clones of Klebsiella pneumoniae are emerging pathogens. To understand the association between genotypic and phenotypic diversity in this process, we combined genomic, phylogenomic and phenotypic analysis of a diverse set of K. pneumoniae and closely related species. These species were able to use an unusually large panel of metabolic substrates for growth, many of which were shared between all strains. We analysed the substrates used by only a fraction of the strains, identified some of their genetic basis, and found that many could not be explained by the phylogeny of the strains. Puzzlingly, few traits were associated with the ecological origin of the strains. One noticeable exception was the ability to use D-arabinose, which was much more frequent in hypervirulent strains. The broad carbon and nitrogen core metabolism of K. pneumoniae might contribute to its ability to thrive in diverse environments. Accordingly, even the hypervirulent and multidrug resistant clones have the metabolic signature of ubiquitous bacteria. The apparent few metabolic differences between hypervirulent, multi-resistant and environmental strains may favour the emergence of dual-risk strains that combine resistance and hypervirulence.

Klebsiella species associated with bovine mastitis in Newfoundland

Klebsiella spp. is a common cause of bovine mastitis, but information regarding its molecular epidemiology is lacking from many parts of the world. On using mass spectrometry and partial sequencing of the rpoB gene, it was found that over a one year study, K. variicola and Enterobacter cloacae were misidentified as K. pneumoniae in a small number of clinical mastitis (CM) cases from Newfoundland. Results suggest that the currently used standard biochemical/phenotypic tests lack the sensitivity required to accurately discriminate among the three mentioned Gram negative bacteria. In addition, a single strain of K. variicola was associated with CM from one farm in the study as demonstrated by Random Amplified Polymorphic DNA (RAPD) PCR. To the best of our knowledge, K. variicola, which is normally found in the environment, has not been isolated previously from milk obtained from cows with CM. Therefore, it is possible that K. variicola was not detected in milk samples in the past due to the inability of standard tests to discriminate it from other Klebsiella species.

Microbiota characterization of a Belgian protected designation of origin cheese, Herve cheese, using metagenomic analysis

Herve cheese is a Belgian soft cheese with a washed rind, and is made from raw or pasteurized milk. The specific microbiota of this cheese has never previously been fully explored and the use of raw or pasteurized milk in addition to starters is assumed to affect the microbiota of the rind and the heart. The aim of the study was to analyze the bacterial microbiota of Herve cheese using classical microbiology and a metagenomic approach based on 16S ribosomal DNA pyrosequencing. Using classical microbiology, the total counts of bacteria were comparable for the 11 samples of tested raw and pasteurized milk cheeses, reaching almost 8 log cfu/g. Using the metagenomic approach, 207 different phylotypes were identified. The rind of both the raw and pasteurized milk cheeses was found to be highly diversified. However, 96.3 and 97.9% of the total microbiota of the raw milk and pasteurized cheese rind, respectively, were composed of species present in both types of cheese, such as Corynebacterium casei, Psychrobacter spp., Lactococcus lactis ssp. cremoris, Staphylococcus equorum, Vagococcus salmoninarum, and other species present at levels below 5%. Brevibacterium linens were present at low levels (0.5 and 1.6%, respectively) on the rind of both the raw and the pasteurized milk cheeses, even though this bacterium had been inoculated during the manufacturing process. Interestingly, Psychroflexus casei, also described as giving a red smear to Raclette-type cheese, was identified in small proportions in the composition of the rind of both the raw and pasteurized milk cheeses (0.17 and 0.5%, respectively). In the heart of the cheeses, the common species of bacteria reached more than 99%. The main species identified were Lactococcus lactis ssp. cremoris, Psychrobacter spp., and Staphylococcus equorum ssp. equorum. Interestingly, 93 phylotypes were present only in the raw milk cheeses and 29 only in the pasteurized milk cheeses, showing the high diversity of the microbiota. Corynebacterium casei and Enterococcus faecalis were more prevalent in the raw milk cheeses, whereas Psychrobacter celer was present in the pasteurized milk cheeses. However, this specific microbiota represented a low proportion of the cheese microbiota. This study demonstrated that Herve cheese microbiota is rich and that pasteurized milk cheeses are microbiologically very close to raw milk cheeses, probably due to the similar manufacturing process. The characterization of the microbiota of this particular protected designation of origin cheese was useful in enabling us to gain a better knowledge of the bacteria responsible for the character of this cheese.

Short communication: Bacterial counts in recycled manure solids bedding replaced daily or deep packed in freestalls

An experiment was conducted to compare bacterial counts of mastitis pathogens in deep-packed manure solids bedding with those in manure solids bedding replaced daily from mattresses. Eighteen Holstein cows were housed in 1 pen with 18 stalls. One row of 9 stalls was equipped with mattresses topped with bedding. The back one-third of these stalls toward the alleyway was covered in 25 mm of recycled manure solids, which was removed daily for the next 6 d and replaced with bedding from the brisket board and lunge space areas of stalls. The second row of 9 stalls was bedded for 3 wk with 100 to 150 mm of deep-pack recycled manure bedding from which only fecal matter was removed daily. After 3 wk, bedding treatments were changed between rows in a switchback design. Mean total gram-negative bacterial counts did not differ between treatments throughout the experiment. Coliform and Klebsiella spp. bacterial counts were lower in daily replaced bedding compared with deep pack across the experiment and on each of d 0, 1, 2, and 6. Streptococcal counts were reduced in daily replacement stalls compared with deep-pack stalls on d 0 and greater in daily replacement stalls compared with deep-pack stalls on d 1, 2, and 6. Daily replacement of recycled manure bedding from the back one-third of the stalls appeared to be an effective approach to reducing exposure to coliforms, specifically Klebsiella, but not streptococci. However, bacterial counts in bedding from both treatments were elevated throughout the trial and resulted in considerable risk for exposure to teats and development of intramammary infections.

Comparison of the epidemiological behavior of mastitis pathogens by applying time-series analysis in results of milk samples submitted for microbiological examination

The objective of this study is to examine and compare the trends of mastitis pathogens in quarter milk samples (n = 240,232) submitted for microbiological examination at the Milk Analysis Laboratory (L.I.G.A.L.) at Galicia, Spain from June 2005 to September 2011. Autoregressive Integrated Moving Average (ARIMA) models and multivariate statistical techniques such as Cluster Analysis were used in order to detect seasonal trends and similarities between the series trends and to classify mastitis pathogens into relatively homogeneous groups. The decrease of bulk milk somatic cell counts achieved by the mastitis control program, developed in recent years in this region, is the result of the decrease in IMI caused by a limited number of mastitis pathogens. The obtained results reflect a greater complexity in the behavior of mastitis pathogens, unlike the traditional classification into contagious or environmental. Staphylococcus aureus showed a trend similar to Streptococcus dysgalactiae, a mastitis pathogen can behave in both a contagious and an environmental manner. Among the traditionally considered environmental mastitis pathogens, Strep. uberis showed a different behavior to Escherichia coli and Klebsiella pneumoniae. Coagulase-negative staphylococci (CNS) species and Streptococcus other than Strep. agalactiae showed differences in the trend model. Time-series analysis and multivariate statistical techniques, such as Cluster Analysis, could be powerful tools to assess the isolation trend of mastitis pathogens because of their ability to cope with stochastic dependence of consecutive data. Furthermore, they could be used to identify the epidemiological behavior of mastitis pathogens using the results of milk samples submitted for routine microbiological examination, by classifying them into relatively homogeneous groups.

The "other" gram-negative bacteria in mastitis: Klebsiella, serratia, and more

Mastitis caused by gram-negative infections is of increasing importance on modern and well-managed dairy farms. Without a doubt, E coli tends to be the most important cause of these gram-negative infections when the data are tallied across farms.1 However, more precise investigation of individual farms often reveals a farm-specific infection pattern where a single gram-negative bacterial species predominates. Several farms with a predominance of “other” gram-negative IMIs may be observed. We have shown the presence of outbreaks on individual dairy farms with K pneumoniae, S marcescens, and Enterobacter cloacae. On farms with a predominance of these “other” gram-negative infections, a detailed epidemiologic investigation may reveal the source of these infections. It is quite surprising to identify the difference in host immune response pattern and the associated clinical and subclinical presentations of IMIs due to the different gram-negative organisms. Experimental and field observations would suggest that among the gram-negative bacterial causes of mastitis, Klebsiella spp are causing the most severe cases, closely followed by E coli and then much less clinical severity is observed in Serratia spp and Enterobacter spp cases. The precise mechanisms that would explain the difference in clinical severity are not known, but the most likely explanation appears to be the structure of the lipid A fraction of the LPS of the bacterial species. Important differences in the lipid A fraction of LPS between and within bacterial species are observed. The prevention of IMIs with gram-negative bacteria has components that are generic across species and components that are species specific. Generic prevention may be obtained by improving hygiene and reducing exposure of teat ends to environmental contamination. Also the use of a J5 bacterin is expected to provide some reduction in severity of gram-negative IMIs across bacterial species. Specific prevention programs will depend on the actual transmission behavior of the dominant species causing IMIs in the herd. Several clonal outbreaks of gram-negative bacterial species have been described. In such situations, optimal milking procedures, segregation and culling of infected animals, and targeted treatment would be advisable. Even more specific are the prevention procedures associated with S marcescens outbreaks, where resistance against specific biocides will lead to transmission of infection through teat disinfectants. Removal of these biocides from the cow environment is than essential. Antimicrobial treatment of gram-negative bacteria has often considered to be of limited value and treatment should be more targeted toward cow survival and reduction of clinical symptoms. More recently, extended treatment with a third-generation cephalosporin was reported to be efficacious in the treatment of E coli and Klebsiella spp but not of E cloacae. Further investigations in effective treatment protocols for gram-negative IMIs are warranted.

Molecular epidemiology of mastitis pathogens of dairy cattle and comparative relevance to humans

Mastitis, inflammation of the mammary gland, can be caused by a wide range of organisms, including gram-negative and gram-positive bacteria, mycoplasmas and algae. Many microbial species that are common causes of bovine mastitis, such as Escherichia coli, Klebsiella pneumoniae, Streptococcus agalactiae and Staphylococcus aureus also occur as commensals or pathogens of humans whereas other causative species, such as Streptococcus uberis, Streptococcus dysgalactiae subsp. dysgalactiae or Staphylococcus chromogenes, are almost exclusively found in animals. A wide range of molecular typing methods have been used in the past two decades to investigate the epidemiology of bovine mastitis at the subspecies level. These include comparative typing methods that are based on electrophoretic banding patterns, library typing methods that are based on the sequence of selected genes, virulence gene arrays and whole genome sequencing projects. The strain distribution of mastitis pathogens has been investigated within individual animals and across animals, herds, countries and host species, with consideration of the mammary gland, other animal or human body sites, and environmental sources. Molecular epidemiological studies have contributed considerably to our understanding of sources, transmission routes, and prognosis for many bovine mastitis pathogens and to our understanding of mechanisms of host-adaptation and disease causation. In this review, we summarize knowledge gleaned from two decades of molecular epidemiological studies of mastitis pathogens in dairy cattle and discuss aspects of comparative relevance to human medicine.

Sources other than unused sawdust can introduce Klebsiella pneumoniae into dairy herds

A longitudinal study was carried out to detect intramammary infections caused by Klebsiella pneumoniae and to identify potential sources of this bacterial species in the environment of the cows. The study was performed in 6 well-managed Belgian dairy herds from May 2008 to May 2009. Monthly (n=13), unused and used sawdust bedding samples as well as individual quarter milk and feces samples were collected from 10 randomly selected cohort cows in each herd. Cases of clinical mastitis of all lactating cows in the 6 herds were also sampled (n=64). From the 3,518 collected samples, 153 K. pneumoniae isolates were obtained, of which 2 originated from milk (clinical mastitis cases). In feces (n=728), used bedding (n=73), and unused bedding (n=73), respectively, 125 (17.2%), 20 (27.4%), and 6 (8.2%) isolates were found. The isolates were fingerprinted by means of pulsed field gel electrophoresis. In total, 109 different pulsotypes were differentiated, indicating a high degree of genetic diversity within the isolates. All isolates from unused bedding belonged to pulsotypes other than those from the other sources, suggesting that sources other than unused sawdust may introduce K. pneumoniae into the herd. Only 2 pulsotypes contained isolates originating from different sources. Pulsotype 10 was found in milk and used bedding and pulsotype 21 was found in feces and used bedding. The 2 milk isolates originated from 2 cows in the same herd but they belonged to a different pulsotype. The results indicate that K. pneumoniae can be prevalent in the environment without causing significant mastitis problems. Most cows were shedding K. pneumoniae in feces, substantiating findings under very different conditions (i.e., American dairy herds). Contamination of used bedding in the cubicles with K. pneumoniae from feces was confirmed, whereas unused bedding was not an important source of K. pneumoniae for the environment of the cows.