Fecal Shedding of Klebsiella pneumoniae by Dairy Cows

Prevalence and risk factors of Klebsiella spp. in milk samples from dairy cows with mastitis-A global systematic review

Introduction

The overall prevalence of Klebsiella spp., a group of important zoonotic pathogens, in the global dairy herds and the risk of cross-species transmission between humans and dairy cows remain to be clarified. This systematic review aimed to determine the prevalence of Klebsiella spp. in milk samples from dairy cows with mastitis worldwide and to assess the factors influencing the prevalence of these strains.

Methods

Qualified studies published from 2007 to 2021 were retrieved from ScienceDirect, Web of Science, PubMed, WanFang Database, China National Knowledge Infrastructure (CNKI), and VIP Chinese Journal Database. Calculations of prevalence and their 95% confidence intervals (CIs) were performed for all the studies using the Freeman-Tukey double arcsine transformation (PFT).

Results

A total of 79,852 milk samples from 55 manuscripts were examined in this meta-analysis, and 2,478 samples were found to be positive for Klebsiella spp. The pooled prevalence estimates worldwide were 7.95% (95% CI: 6.07%-10.06%), with significant heterogeneity (I ² = 98.8%, p = 0). The sampling period of 2013-2020 had a higher (p < 0.05) Klebsiella-positive proportion of milk samples (12.16%, 95% CI: 8.08%-16.90%) than that of 2007-2012 (3.85%, 95% CI: 2.67%-5.21%), indicating that bovine mastitis caused by Klebsiella may become increasingly prevalent. The risk factors for the high prevalence of Klebsiella in milk samples mainly included: economic development level (developing countries; 11.76%, 95% CI: 8.25%-15.77%), mastitis type (CM; 11.99%, 95% CI: 8.62%-15.79%), and population density (>500 per sq km; 10.28%, 95% CI: 2.73%-21.58%). Additionally, a bivariate meta-regression analysis revealed that the multidrug-resistance (MDR) rate of the epidemic strains was also closely related to economic development level (R ² = 78.87%) and population density (R ² = 87.51%).

Discussion

Due to the potential risk of cross-species transmission between humans and cows, the prevalence of mastitis milk-derived Klebsiella and its high MDR rate need to be monitored, especially in developing countries with high population densities.

Biofilms in hoses utilized to divert colostrum and milk on dairy farms: A report exploring their potential role in herd health, milk quality, and public health

Biofilms in milking equipment on dairy farms have been associated with failures in cleaning and sanitizing protocols. These biofilms on milking equipment can be a source of contamination for bulk tank milk and a concern for animal and public health, as biofilms can become on-farm reservoirs for pathogenic bacteria that cause disease in cows and humans. This report describes a cross-sectional study on 3 dairy farms, where hoses used to divert waste milk, transition milk, and colostrum were analyzed by culture methods and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to assess the presence of pathogenic bacteria such as Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella spp. In addition, the presence of biofilms was analyzed using scanning electron microscopy and confocal spectral microscopy. Biofilms composed of multispecies microbial communities were observed on the surfaces of all milk hoses. In two dairy farms, S. aureus, P. aeruginosa, Klebsiella pneumoniae, and Klebsiella oxytoca were isolated from the milk hose samples collected. Cleaning and sanitation protocols of all surfaces in contact with milk or colostrum are crucial. Hoses used to collect waste milk, colostrum, and transition milk can be a source of biofilms and hence pathogenic bacteria. Waste milk used to feed calves can constitute a biosecurity issue and a source of pathogens, therefore an increased exposure and threat for the whole herd health and, potentially, for human health.

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.

Ethnobotanical, phytochemical and antimicrobial activity of Halexylon salicornicum (Ramth) as a graze and promising shrub against selected animal microbes

Folk medicine, including plants, has been utilized for humans and animals since the dawn of civilization. Because of the widespread problem of antimicrobial resistance around the world, one of the mainly significant challenges in microbiological research is to achieve a replacement antibiotic with the fewest adverse effects. Camel and ruminant grazing were provided by the wild shrub Halexylon salicornicum (Ramth). However, despite prior research demonstrating its antimicrobial action against human diseases, no investigations on its antimicrobial activity against animal pathogens have been conducted to far. The goal of this study is to investigate whether Halexylon salicornicum aqueous and solvent extracts have antimicrobial activity on a variety of animal pathogens isolated from cattle and poultry using the agar well diffusion method (Enterococcus faecium, Shigella flexneri, Bacillus Cereus, Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, Streptococcus pyogens, Pseudomonas aerogenes, Salmonella typhimurium, and Candida albicans) moreover it's ethnobotanical and phytochemical. All of the extracts tested had antimicrobial efficacy against tested strains and included bioactive chemicals, particularly the acetone extract, had the highest antibacterial activity. As a result, it can be stated that Halexylon salicornicum is a promising important shrub that might be used as a natural antimicrobial alternative for animals or as a food additive.

Timber-colonizing gram-negative bacteria as potential causative agents of respiratory diseases in woodworkers

Occurrence

Gram-negative bacteria occur commonly in the inner tissues of stored coniferous and deciduous timber, showing a marked variation in numbers. The greatest maximal numbers are found in the sapwood of coniferous timber. The common constituents of the Gram-negative biota are potentially pathogenic species of Enterobacteriaceae family of the genera Rahnella, Pantoea, Enterobacter, and Klebsiella. The air of wood-processing facilities is polluted with the wood-borne Gram-negative bacteria and produced by them endotoxin, as demonstrated worldwide by numerous studies.

Effects

There are three potential pathways of the pathogenic impact of wood-borne Gram-negative bacteria on exposed woodworkers: allergic, immunotoxic, and infectious. Allergic impact has been underestimated for a long time with relation to Gram-negative bacteria. Hopefully, the recent demonstration of the first documented case of hypersensitivity pneumonitis (HP) in woodworkers caused by Pantoea agglomerans which developed in extremely large quantities in birch sapwood, would speed up finding of new wood-related cases of HP caused by Gram-negative bacteria. The second pathway is associated with endotoxin, exerting strong immunotoxic (excessively immunostimulative) action. It has been demonstrated that endotoxin is released into wood dust in the form of nano-sized microvesicles, by peeling off the outer membrane of bacteria. Endotoxin microvesicles are easily inhaled by humans together with dust because of small dimensions and aerodynamic shape. Afterwards, they cause a nonspecific activation of lung macrophages, which release numerous inflammatory mediators causing an inflammatory lung reaction, chest tightness, fever, gas exchange disorders, and bronchospasm, without radiographic changes. The resulting disease is known as “Organic Dust Toxic Syndrome” or “toxic pneumonitis.” The potential third pathway of pathogenic impact is infection. The suspected species is Klebsiella pneumoniae that may occur commonly in wood dust; however, until now this pathway has not been confirmed.

Conclusion

Summarizing, Gram-negative bacteria-inhabiting timber should be considered, besides filamentous fungi and actinobacteria, as important risk factors of occupational disease in woodworkers that could be either HP with allergenic background or toxic pneumonitis elicited by endotoxin.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00420-021-01829-1.

Virulence profiles of Klebsiella pneumoniae isolated from 2 large dairy farms in China

We recently reported on the diversity of Klebsiella pneumoniae isolated from dairy herds in China. In our previous work, isolates from subclinical mastitis (SCM) had lower indices of diversity when compared with bacteria from other sources, possibly due to a contagious-like spread of udder adapted strains. Here we explored the virulence profile and capsular types of K. pneumoniae isolated from different sources on 2 dairy farms in China. Our overarching goal was to gain insights on the role of virulence genes toward the severity of mastitis caused by K. pneumoniae. A total of 1,484 samples were collected from clinical mastitis (CM; n = 355), SCM (n = 561), bulk tank milk (BTM; n = 130), and environmental and extramammary (EE) sites (n = 438). From those, 431 K. pneumoniae isolates were obtained, including 129, 77, 66, and 159 isolates from CM, SCM, BTM, and EE samples, respectively. Polymerase chain reactions were used to determine the capsular types and to detect potential virulence genes in all isolates. No significant farm effects were observed when comparing the distribution of most virulence genes in K. pneumoniae isolated from each source. K57 was the most prevalent capsular type in K. pneumoniae from all sources, but with increased detection rate in isolates from CM. entB, kfu, fimH1, mrkD, and β-d-lacZ were frequently detected in K. pneumoniae from all sources. β-d-lacZ, entB, and ituA were more prevalent in isolates from CM, whereas kfu, allS, and nif were more frequently detected in isolates from SCM. ybtS, aerobactin, and rpmA had increased prevalence in K. pneumoniae from BTM when compared with bacteria from other sources. No association was detected between virulence genes and the severity of CM. K57 and the nif gene had the highest discriminatory power to classify isolates from CM and SCM, respectively. Based on our findings, it is likely that K57 is the dominant capsular type in K. pneumoniae causing CM in large Chinese dairy herds. Likewise, we demonstrated that β-d-lacZ is disseminated in K. pneumoniae isolated from large Chinese dairy farms, irrespectively of the source of bacteria. Our results also suggest a low contribution of the virulence profile of K. pneumoniae toward CM severity. Finally, the role of nif in increasing the adaptability to the udder and promoting a contagious-like spread of K. pneumoniae warrants further investigation.

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.

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.

Enhanced Antibacterial Activity of Silver Nanoparticles Combined with Hydrogen Peroxide Against Multidrug-Resistant Pathogens Isolated from Dairy Farms and Beef Slaughterhouses in Egypt

Purpose

The last few decades have witnessed a rapid and global increase in multidrug-resistant bacteria (MDR) emergence.

Methods

The aim of the current study is to isolate the most common MDR bacteria from dairy farms and beef slaughterhouses followed by evaluation of their antimicrobial resistance pattern and assessment of the antibacterial activity of AgNPs-H₂O₂ as an alternative to conventional antibiotics. In this regard, 200 samples were collected from two dairy farms and one beef slaughterhouse located in Dakhliya Governorate, Egypt.

Results

Interestingly, out of 120 collected samples from dairy farms, the prevalence of the isolated strains was 26.7, 23.3, 21.7, 16.7, and 11.7% for S. typhimurium, E. coli O157:H7, L. monocytogenes, K. pneumoniae and P. aeruginosa, respectively. Meanwhile, the overall prevalence was 30, 25, 22.5, 17.5, and 5% for E. coli O157:H7, L. monocytogenes, S. typhimurium, P. aeruginosa, and K. pneumoniae, respectively, for the 80 samples collected from a beef slaughterhouse. The antimicrobial susceptibility pattern elucidated that all isolated strains exhibited resistance to at least four of the tested antimicrobials, with multiple-antibiotic resistance index values (MAR) ranging between 0.44 and 0.88. Furthermore, the commercial AgNPs-H₂O₂ product was characterized by transmission electron microscopy (TEM) and zeta potential that showed spherical particles with a surface charge of -0.192 mV. The antimicrobial activity of synergized nano-silver (AgNP) with H₂O₂ product toward MDR strains was assessed via measuring minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill curve.

Conclusion

The present data report high prevalence rates of MDR pathogens in dairy farms and abattoirs. More importantly, AgNPs-H₂O₂ exerted broad-spectrum bactericidal activity toward MDR bacterial strains, suggesting their promising usage as safe, ecofriendly, cost-effective antibacterial agents. To our knowledge, this study is a pioneer in investigating the potential alternative antimicrobial role of silver nanoparticles for control of multiple drug-resistant pathogens in Egypt.

Dynamic changes of the fecal bacterial community in dairy cows during early lactation

The dynamics of the community structure and composition of the dairy cow fecal bacterial communities during early lactation is unclear, therefore this study was conducted to characterize the fecal bacterial communities in dairy cows during early lactation using 16S rRNA gene sequencing. Feces were sampled from 20 healthy fresh Holstein dairy cows on day 1 (Fresh1d group) and day 14 (Fresh14d group) after calving. After calving, cows were fed the same fresh diet. The dominant phyla Firmicutes and Proteobacteria were decreased (P ≤ 0.01) with lactating progress and phyla Bacteroidetes were increased (P = 0.008) with lactating progress and dietary transition. At family level, the predominant families were Ruminococcaceae (35.23%), Lachnospiraceae (11.46%), Rikenellaceae (10.44%) and Prevotellaceae (6.89%). A total of 14 genera were different between fecal samples from Fresh1d and Fresh14d, included the predominant genera, such as Ruminococcaceae_UCG-005 (P = 0.008), Rikenellaceae_RC9_gut_group (P = 0.043) and Christensenellaceae_R-7_group (P = 0.008). All fecal bacterial communities shared members of the genera Ruminococcaceae_UCG-005, Bacteroides and Rikenellaceae_RC9_gut_group. These findings help to improve our understanding of the composition and structure of the fecal microbial community in fresh cows and may provide insight into bacterial adaptation time and dietary in lactating cows.

Clinical and Pathologic Features of Spontaneous Klebsiella pneumoniae Infection in 9 Rhesus Macaques (Macaca mulatta)

Klebsiella pneumoniae is a gram-negative bacterium found in the environment and as a commensal in humans and animals. In humans, K. pneumoniae is one of the most serious nosocomial infections encountered currently and is characterized by liver abscesses, pneumonia, and bacteremia resulting in meningoencephalitis and endophthalmitis. K. pneumoniae in veterinary medicine is rarely reported in NHP, and recent literature describing this disease is sparse. In our colony of predominantly outdoor-housed rhesus macaques (Macaca mulatta), K. pneumoniae is cultured infrequently from healthy animals during routine screening and is even rarer in sick animals. This report summarizes the clinical and postmortem findings associated with this pathogen in 9 rhesus macaques and compares these results with the disease outcomes reported for humans. In these cases, K. pneumoniae infection was confirmed through culture or PCR testing or both. In our experience, when this bacterium does cause clinical signs, the disease is rapidly progressive and severe. At necropsy of NHP, the findings are strikingly similar to opportunistic Klebsiella-associated syndromes described in humans and include liver abscesses, meningoencephalitis, and endophthalmitis. In addition, many of the affected macaques had similar risk factors to humans that succumb to disease, thus perhaps indicating that rhesus macaques could be a viable model for investigating these syndromes.

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.

A One Health Study of the Genetic Relatedness of Klebsiella pneumoniae and Their Mobile Elements in the East of England

BACKGROUND

Klebsiella pneumoniae is a human, animal, and environmental commensal and a leading cause of nosocomial infections, which are often caused by multiresistant strains. We evaluate putative sources of K. pneumoniae that are carried by and infect hospital patients.

METHODS

We conducted a 6-month survey on 2 hematology wards at Addenbrooke's Hospital, Cambridge, United Kingdom, in 2015 to isolate K. pneumoniae from stool, blood, and the environment. We conducted cross-sectional surveys of K. pneumoniae from 29 livestock farms, 97 meat products, the hospital sewer, and 20 municipal wastewater treatment plants in the East of England between 2014 and 2015. Isolates were sequenced and their genomes compared.

RESULTS

Klebsiella pneumoniae was isolated from stool of 17/149 (11%) patients and 18/922 swabs of their environment, together with 1 bloodstream infection during the study and 4 others over a 24-month period. Each patient carried 1 or more lineages that was unique to them, but 2 broad environmental contamination events and patient-environment transmission were identified. Klebsiella pneumoniae was isolated from cattle, poultry, hospital sewage, and 12/20 wastewater treatment plants. There was low genetic relatedness between isolates from patients/their hospital environment vs isolates from elsewhere. Identical genes encoding cephalosporin resistance were carried by isolates from humans/environment and elsewhere but were carried on different plasmids.

CONCLUSION

We identified no patient-to-patient transmission and no evidence for livestock as a source of K. pneumoniae infecting humans. However, our findings reaffirm the importance of the hospital environment as a source of K. pneumoniae associated with serious human infection.

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

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

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.

Research of Klebsiella pneumoniae in dairy herds

Klebsiella pneumoniae is a common environmental agent of clinical and subclinical mastitis affecting dairy herds, and may be present in the final product decreasing its quality. Mastitis caused by K. pneumoniae is even more severe due to its poor response to antibiotic therapy, rapid evolution to toxic shock and death of the animal. This paper aimed to study the prevalence of this pathogen among dairy herds in ten farms located in different municipalities of São Paulo State based on size and use of milking technology. All mammary glands of all lactating cows were screened using the California Mastitis Test (CMT) and a strip cup. A single aseptic milk sample (20mL) was collected from all CMT-positive quarters and bulk tanks, whereas swab samples were collected from feces, hind limbs of the animals, bedding and milking parlor. Identification of K. pneumoniae was performed using conventional microbiology culture, biochemical assay and Polimerase Chain Reaction. The primers were designed and tested at the Laboratory of Molecular Biology applied to Zoonoses (FMVZ, Unesp-Botucatu) targeting the 16S rRNA gene. This study included 1067 animals. Six cases of intramammary infection by K. pneumoniae were detected in six different cows in two farms. Moreover, K. pneumoniae was isolated in 77 swabs (34 from bedding in 9 farms, 7 from waiting rooms in 5 farms, 6 from milking parlors in 4 farms, 11 from rectums in six farms, and 19 from hindlimbs in 7 farms. Molecular analysis confirmed the agent was K. pneumoniae. At least one strain of the agent was identified in a certain site in all farms, showing the need of maintaining the hygiene in dairy farms.

Ultrastructural effect on mastitis pathogens by extract of endophytic fungi associated with ethnoveterinary plant, Hibiscus sabdariffa L

Three endophytic fungi isolated from different parts of Hibiscus sabdariffa L. were identified using morphological and molecular approaches. Ethanolic extract of endophytic fungi as well as plant extracts were evaluated for in vitro antibacterial activity by using well diffusion method and their minimum inhibitory concentration estimated. The culture extract of one endophytic fungus Glomerella acutata EF15 was found to be potent antibacterial agent against pathogenic coliform bacteria Klebsiella pneumoniae and Escherichia coli responsible for causing clinical mastitis. Scanning electron microscopy (SEM) revealed the ultrastructural alteration in the cells of K. pneumoniae and E. coli when treated with crude ethanolic extract of G. acutata. The ethanolic extract of the endophytic fungus revealed potential to be bioprospected as antibacterial agent against pathogens causing coliform mastitis, the existing havoc of dairy industries.

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.

Phenotypic, antimicrobial susceptibility profile and virulence factors of Klebsiella pneumoniae isolated from buffalo and cow mastitic milk

Studies on the prevalence and virulence genes of Klebsiella mastitis pathogens in a buffalo population are undocumented. Also, the association of rmpA kfu, uge, magA, Aerobactin, K1 and K2 virulent factors with K. pneumoniae buffalo, and cow mastitis is unreported. The virulence of K. pneumoniae was evaluated through both phenotypic and molecular assays. In vivo virulence was assessed by the Vero cell cytotoxicity, suckling mouse assay and mice lethality test. Antimicrobial susceptibility was tested by disk diffusion method. The 45 K. pneumoniae isolates from buffalo (n = 10/232) and cow (n = 35/293) milk were isolated (45/525; 8.6%) and screened via PCR for seven virulence genes encoding uridine diphosphate galactose 4 epimerase encoding gene responsible for capsule and smooth lipopolysaccharide synthesis (uge), siderophores (kfu and aerobactin), protectines or invasins (rmpA and magA), and the capsule and hypermucoviscosity (K1 and K2). The most common virulence genes were rmpA, kfu, uge, and magA (77.8% each). Aerobactin and K1 genes were found at medium rates of 66.7% each and K2 (55.6%). The Vero cell cytotoxicity and LD (50) in mice were found in 100% of isolates. A multidrug resistance pattern was observed for 40% of the antimicrobials. The distribution of virulence profiles indicate a role of rmpA, kfu, uge, magA, Aerobactin, and K1 and K2 in pathogenicity of K. pneumoniae in udder infections and invasiveness, and constitutes a threat for vulnerable animals, even more if they are in combination with antibiotic resistance.

Seasonal variation in health care-associated bloodstream infection: increase in the incidence of gram-negative bacteremia in nonhospitalized patients during summer

OBJECTIVE

Recent research has suggested that episodes of gram-negative (GN) bloodstream infection (BSI) are more common in the population during summer months. Our objective was to determine if the same phenomenon could be observed in patients with health care-associated (HCA) BSI, and if so, whether a summer peak was less apparent in patients accommodated in a climate-controlled hospital environment.

METHODS

Data from episodes of HCA BSI spanning an 11-year period were analyzed. To test for seasonal variation in HCA BSI among hospitalized and nonhospitalized patients, and between GN and gram-positive organisms, the χ(2) goodness-of-fit test was used.

RESULTS

There were 440 episodes of HCA GN BSI of which 259 (59%) occurred in inpatients and 181 (41%) occurred in noninpatients. A significant increase in the frequency of HCA GN BSI was observed in nonhospitalized patients during the summer months (P = .03) but not in climate-controlled hospitalized patients. The most common source of infection in these patents was an intravascular device (38%).

CONCLUSIONS

We found an increased incidence of GN HCA BSI during summer that was not apparent in our inpatient cohort. The cause is unknown. It might be prudent to advise patients at risk of BSI (eg, those receiving intravascular infusions) to minimize exposure to high environmental temperature and to educate on possible behavioral factors that may increase risk.

Molecular epidemiology and extended-spectrum β-lactamases production of Klebsiella pneumoniae isolated from three dairy herds

The objectives of this study were to isolate Klebsiella pneumoniae from different sources in three dairy cattle herds, to use the pulsed-field gel electrophoresis (PFGE) to measure genotypic similarities between isolates within a dairy herd, to verify the production of extended-spectrum β-lactamases (ESBLs) by the double-disk synergy test (DDST), and to use the PCR to detect the main ESBLs subgroups genes. Three dairy farms were selected based on previous mastitis outbreaks caused by K. pneumoniae. Milk samples were collected from lactating cows and from the bulk tank. Swabs were performed in different locations, including milking parlors, waiting room, soil, animal's hind limbs and rectum. K. pneumoniae was isolated from 27 cases of intramammary infections (IMI) and from 41 swabs. For farm A isolates from IMI and bulk tank were considered of the same PGFE subtype. One isolate from a bulk tank, three from IMI cases and four from environmental samples were positive in the DDST test. All eight DDST positive isolates harbored the bla shv gene, one harbored the bla tem gene, and three harbored the bla ctx-m gene, including the bulk tank isolate. Our study confirms that ESBL producing bacteria is present in different locations in dairy farms, and may be responsible for IMI. The detection of ESBLs on dairy herds could be a major concern for both public and animal health.

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.

Diversity of Ammonia Oxidation (amoA) and Nitrogen Fixation (nifH) Genes in Lava Caves of Terceira, Azores, Portugal

Lava caves are an understudied ecosystem in the subterranean world, particularly in regard to nitrogen cycling. The diversity of ammonia oxidation (amoA) and nitrogen fixation (nifH) genes in bacterial mats collected from lava cave walls on the island of Terceira (Azores, Portugal) was investigated using denaturing gradient gel electrophoresis (DGGE). A total of 55 samples were collected from 11 lava caves that were selected with regard to surface land use. Land use types above the lava caves were categorized into pasture, forested, and sea/urban, and used to determine if land use influenced the ammonia oxidizing and nitrogen fixing bacterial communities within the lava caves. The soil and water samples from each lava cave were analyzed for total organic carbon, inorganic carbon, total nitrogen, ammonium, nitrate, phosphate and sulfate, to determine if land use influences either the nutrient content entering the lava cave or the nitrogen cycling bacteria present within the cave. Nitrosospira-like sequences dominated the ammonia-oxidizing bacteria (AOB) community, and the majority of the diversity was found in lava caves under forested land. The nitrogen fixation community was dominated by Klebsiella pneumoniae-like sequences, and diversity was evenly distributed between pasture and forested land, but very little overlap in diversity was observed. The results suggest that land use is impacting both the AOB and the nitrogen fixing bacterial communities.

Milk microbiome signatures of subclinical mastitis-affected cattle analysed by shotgun sequencing

AIMS

Metagenomic analysis of milk samples collected from Kankrej, Gir (Bos indicus) and crossbred (Bos taurus × B. indicus) cattle harbouring subclinical mastitis was carried out by next-generation sequencing 454 GS-FLX technology to elucidate the microbial community structure of cattle milk.

METHODS AND RESULTS

Milk samples from Kankrej, Gir and crossbred cattle were subjected to metagenomic profiling by pyrosequencing. The Metagenomic analysis produced 63·07, 11·09 and 7·87 million base pairs (Mb) of sequence data, assembled in 264 798, 56 114 and 36 762 sequences with an average read length of 238, 197 and 214 nucleotides in Kankrej, Gir and crossbred cattle, respectively. Phylogenetic and metabolic profiles by the web-based tool MG-RAST revealed that the members of Enterobacteriales were predominant in mastitic milk followed by Pseudomonadales, Bacillales and Lactobacillales. Around 56 different species with varying abundance were detected in the subclinically infected milk. Escherichia coli was found to be the most predominant species in Kankrej and Gir cattle followed by Pseudomonas aeruginosa, Pseudomonas mendocina, Shigella flexneri and Bacillus cereus. In crossbred cattle, Staphylococcus aureus followed by Klebsiella pneumoniae, Staphylococcus epidermidis and E. coli were detected in descending order. Metabolic profiling indicated fluoroquinolones, methicillin, copper, cobalt-zinc-cadmium as the groups of antibiotics and toxic compounds to which the organisms showed resistance. Sequences indicating potential of organisms exhibiting multidrug resistance against antibiotics and resistance to toxic compounds were also present. Interestingly, presence of bacteriophages against Staph. aureus, E. coli, Enterobacter and Yersinia species was also observed.

CONCLUSIONS

The analysis identified potential infectious organisms in mastitis, resistance of organisms to antibiotics and chemical compounds and the natural resistance potential of dairy cows.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings of this study may help in formulating strategies for the prevention and treatment of mastitis in dairy animals and consequently in reducing economic losses incurred because of it.

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.

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

Klebsiella spp. are a common cause of mastitis, milk loss, and culling on dairy farms. Control of Klebsiella mastitis is largely based on prevention of exposure of the udder to the pathogen. To identify critical control points for mastitis prevention, potential Klebsiella sources and transmission cycles in the farm environment were investigated, including oro-fecal transmission, transmission via the indoor environment, and transmission via the outdoor environment. A total of 305 samples was collected from 3 dairy farms in upstate New York in the summer of 2007, and included soil, feed crops, feed, water, rumen content, feces, bedding, and manure from alleyways and holding pens. Klebsiella spp. were detected in 100% of rumen samples, 89% of water samples, and approximately 64% of soil, feces, bedding, alleyway, and holding pen samples. Detection of Klebsiella spp. in feed crops and feed was less common. Genotypic identification of species using rpoB sequence data showed that Klebsiella pneumoniae was the most common species in rumen content, feces, and alleyways, whereas Klebsiella oxytoca, Klebsiella variicola, and Raoultella planticola were the most frequent species among isolates from soil and feed crops. Random amplified polymorphic DNA-based strain typing showed heterogeneity of Klebsiella spp. in rumen content and feces, with a median of 4 strains per 5 isolates. Observational and bacteriological data support the existence of an oro-fecal transmission cycle, which is primarily maintained through direct contact with fecal contamination or through ingestion of contaminated drinking water. Fecal shedding of Klebsiella spp. contributes to pathogen loads in the environment, including bedding, alleyways, and holding pens. Hygiene of alleyways and holding pens is an important component of Klebsiella control on dairy farms.

Changing trends in mastitis

The global dairy industry, the predominant pathogens causing mastitis, our understanding of mastitis pathogens and the host response to intramammary infection are changing rapidly. This paper aims to discuss changes in each of these aspects. Globalisation, energy demands, human population growth and climate change all affect the dairy industry. In many western countries, control programs for contagious mastitis have been in place for decades, resulting in a decrease in occurrence of Streptococcus agalactiae and Staphylococcus aureus mastitis and an increase in the relative impact of Streptococcus uberis and Escherichia coli mastitis. In some countries, Klebsiella spp. or Streptococcus dysgalactiae are appearing as important causes of mastitis. Differences between countries in legislation, veterinary and laboratory services and farmers' management practices affect the distribution and impact of mastitis pathogens. For pathogens that have traditionally been categorised as contagious, strain adaptation to human and bovine hosts has been recognised. For pathogens that are often categorised as environmental, strains causing transient and chronic infections are distinguished. The genetic basis underlying host adaptation and mechanisms of infection is being unravelled. Genomic information on pathogens and their hosts and improved knowledge of the host's innate and acquired immune responses to intramammary infections provide opportunities to expand our understanding of bovine mastitis. These developments will undoubtedly contribute to novel approaches to mastitis diagnostics and control.

Seasonal variation in Klebsiella pneumoniae bloodstream infection on 4 continents

BACKGROUND

Klebsiella pneumoniae causes serious, life-threatening infections in humans in endemic and epidemic settings. The objective of this study was to determine whether the incidence of K. pneumoniae bloodstream infection (BSI) was higher during warm months.

METHODS

We analyzed surveillance data from 2001-2006 at 4 hospitals located on 4 continents. Incidence rates (IRs) and IR ratios (IRRs) were determined using multivariable Poisson regression.

RESULTS

In total, 1189 cases of K. pneumonia BSIs occurred during 6,671,337 patient-days. The IR of K. pneumoniae BSI during the 4 warmest months of the year was 2.23/10,000 patient-days, whereas the IR of K. pneumoniae BSI for the other 8 months was 1.55/10,000 patient-days (IRR, 1.46 [95% confidence interval, 1.04-2.06]; P= .03). In contrast, no seasonal variation was identified in rates of BSI due to Enterobacter or Serratia species. Using Poisson regression, we showed that temperature (P< .0001) and dew point (a marker for relative humidity; P< .0001) were both linearly predictive of increasing rates of K. pneumoniae BSI.

CONCLUSIONS

Environmental pressures may lead to an increase in the IR of K. pneumoniae BSI during the warmest months of the year.

Molecular subtyping of mastitis-associated Klebsiella pneumoniae isolates shows high levels of diversity within and between dairy herds

Despite advances in controlling mastitis (inflammation of the mammary gland), udder infections caused by Klebsiella pneumoniae continue to affect dairy cattle. Mastitis caused by K. pneumoniae responds poorly to antibiotic treatment, and as a consequence, infections tend to be severe and long lasting. We sought to determine whether a nonrandom distribution of specific genotypes of K. pneumoniae was associated with mastitis from 6 dairy herds located in 4 different states. A total of 635 isolates were obtained and fingerprinted by repetitive DNA sequence PCR. Significant genetic diversity was observed in 4 of the 6 dairy herds analyzed, and a total of 49 genotypic variants were identified. Within a herd, Simpson's diversity indices were 91.0, 94.1, 91.7, 88.6, 53.3, and 64.3% for dairies A, B, C, D, E, and F, respectively. The association between matrices of genetic similarity and matrices of temporal distance was negative in all the dairies analyzed. Four dairies had a high incidence of K. pneumoniae mastitis during the winter. The majority of genotypes were unique to herds of origin, and only 5 genotypes were detected in more than 2 dairies. Genotype 1 (arbitrary designation) occurred most frequently across dairies and was found in 25.2% of all mastitis cases and among 22.8% of reinfected and culled cows in dairy A. Specific genotypes also tended to be associated with a specific bedding type and dairy location. Analysis of molecular variance showed that 18% of the genetic diversity was due to variation among herds within states, and 82% of the genetic diversity was accounted for by variation of genotypes within herds. The data support the idea that mastitis is caused by a diverse group of K. pneumoniae genotypes and thus has major implications for the diagnosis, prevention, and treatment of udder infections in dairy cows.

Molecular epidemiology of two Klebsiella pneumoniae mastitis outbreaks on a dairy farm in New York State

Klebsiella spp. have become an important cause of clinical mastitis in dairy cows in New York State. We describe the occurrence of two Klebsiella mastitis outbreaks on a single dairy farm. Klebsiella isolates from milk, feces, and environmental sources were compared using random amplified polymorphic DNA (RAPD)-PCR typing. The first mastitis outbreak was caused by a single strain of Klebsiella pneumoniae, RAPD type A, which was detected in milk from eight cows. RAPD type A was also isolated from the rubber liners of milking machine units after milking of infected cows and from bedding in the outbreak pen. Predominance of a single strain could indicate contagious transmission of the organism or exposure of multiple cows to an environmental point source. No new cases with RAPD type A were observed after implementation of intervention measures that targeted the prevention of transmission via the milking machine as well as improvement of environmental hygiene. A second outbreak of Klebsiella mastitis that occurred several weeks later was caused by multiple RAPD types, which rules out contagious transmission and indicates opportunistic infections originating from the environment. The diversity of Klebsiella strains as quantified with Simpson's index of discrimination was significantly higher for isolates from fecal, feed, and water samples than for isolates from milk samples. Several isolates from bedding material that had the phenotypic appearance of Klebsiella spp. were identified as being Raoultella planticola and Raoultella terrigena based on rpoB sequencing.

Prevalence and distribution of mastitis pathogens in subclinically infected dairy cows in Flanders, Belgium

The main objective was to determine the prevalence of intramammary infections (IMI) in dairy cows in Flanders, Belgium. Data were obtained from quarter milk samples of dairy herds subjected to a mandatory yearly screening of all lactating cows. A total of 178,668 quarter milk samples were collected at 1087 cross-sectional dairy herd screenings performed in three consecutive years. Of the dairy cows, 40% had at least one culture-positive quarter. More than 50% of all IMI were caused by non-aureus staphylococci. Streptococcus agalactiae is almost eradicated in Flanders, whereas Staphylococcus aureus was isolated from 18% of the culture-positive quarters. In addition, the distribution of mastitis pathogens in quarter milk samples from selected dairy cows with an elevated somatic cell count (SCC) is described. From 6390 cows with a geometric mean composite SCC 250,000 cells/ml, nearly 65% had at least one culture-positive quarter. The majority of the IMI were caused by non-aureus staphylococci (41.1%), whereas Staph. aureus and aesculin-positive cocci were found in respectively 25% and 18% of the culture-positive milk samples. We conclude that more efforts are needed in the prevention and control of subclinical mastitis in Flanders. Non-aureus staphylococci are the predominant cause of IMI, warranting more research regarding the epidemiology and pathogenicity of those species.

Short Communication: Patterns of Fecal Shedding of Klebsiella by Dairy Cows

Patterns and persistency of fecal shedding of Klebsiella spp. by healthy adult dairy cattle were explored with probabilistic, statistical, and molecular methods. Fecal shedding was monitored longitudinally in 92 animals in 1 herd for 5 mo. Shedding patterns followed a random binomial distribution, and associations with host factors were not detected. For 12 animals from 4 herds, strain-typing of multiple fecal Klebsiella isolates was performed by means of random-amplified polymorphic DNA typing. For 2 animals, additional typing was performed on isolates from samples collected on several consecutive days. A large variety of Klebsiella strains was detected within samples (on average, 3.1 strains per 4 isolates) and between samples (18 of 20 strains were detected only once in feces from cows that were sampled for 5 d consecutively). Results from each method suggest that fecal shedding of Klebsiella is associated with transient rather than persistent presence of the organism in the gastrointestinal tract.