Co-infection of methicillin-resistant Staphylococcus epidermidis, methicillin-resistant Staphylococcus aureus and extended spectrum β-lactamase producing Escherichia coli in bovine mastitis--three cases reported from India

The role of food chain in antimicrobial resistance spread and One Health approach to reduce risks

The incidence of antimicrobial resistance (AMR) is rapidly spreading worldwide. It is depleting the repertoire of antibiotics in use but the pace of development of new antibiotics is stagnant for decades. Annually, millions of people are killed by AMR. This alarming situation urged both scientific and civil bodies to take steps to curb AMR as a top priority. Here we review the various sources of AMR in the environment, especially focusing on the food chain. Food chain inculcates pathogens with AMR genes and serves as a conduit for its transmission. In certain countries, the antibiotics are more used in livestock than in humans. It is also used in agriculture crops of high value products. The indiscriminate use of antibiotics in livestock and agriculture increased rapid emergence of AMR pathogens. In addition, in many countries nosocomial settings are spewing AMR pathogens, which is a serious health hazard. Both the developed and low and middle income countries (LMIC) face the phenomenon of AMR. Therefore, a comprehensive approach for monitoring all sectors of life is required to identify the emerging trend of AMR in environment. AMR genes' mode of action must be understood to develop strategies to reduce risk. The new generation sequencing technologies, metagenomics and bioinformatics capabilities can be resorted to quickly identify and characterize AMR genes. The sampling for AMR monitoring can be done from multiples nodes of the food chain as envisioned and promoted by the WHO, FAO, OIE and UNEP under the One Health approach to overcome threat of AMR pathogens.

Is AMR in Dairy Products a Threat to Human Health? An Updated Review on the Origin, Prevention, Treatment, and Economic Impacts of Subclinical Mastitis

Background

Bovine mastitis is the most frequent and costly illness impacting dairy herds worldwide. The presence of subclinical mastitis in dairy cows has an impact on the decreased output of milk and milk quality, culling of affected cows, mortality rate, as well as mastitis-related treatment expenses, generating significant financial loss to the dairy industry. The pathogenic bacteria invade through the mammary gland, which then multiply in the milk-producing tissues causing infection, and the presence of pathogenic bacteria in milk is concerning, jeopardizes human health, and also has public health consequences. Intervention to promote herd health is essential to protect public health and the economy.

Results

This review attempts to provide an overview of subclinical mastitis, including mastitis in different species, the effect of mastitis on human health and its pathogenic mechanism, the prevalence and incidence of subclinical mastitis, and current preventive, diagnostic, and treatment methods for subclinical mastitis. It also elaborates on the management practices that should be followed by the farms to improve herd immunity and health.

Conclusion

This review brings the importance of the threat of antimicrobial resistance organisms to the dairy industry. Furthermore, this review gives a glimpse of the economic consequences faced by the farmers and a futuristic mastitis market analysis in the dairy industry.

Subclinical mastitis in dairy cows in south-Asian countries: a review of risk factors and etiology to prioritize control measures

Mastitis is a major production disease, causing significant economic losses for dairy farmers in South-Asian countries, as well as other parts of the world. Udder health control programs (UHCP) have been established in developed countries as an effective strategy for mastitis control but have not yet been introduced in South-Asian low-income countries like Bangladesh, India, Pakistan, and Sri Lanka. To launch UHCP successfully in dairy herds in South-Asia, it is important to know the current prevalence and risk factors for subclinical mastitis (SCM). Therefore, a narrative literature review was conducted with the aim to describe the dairy sector, the prevalence of SCM and its causal agents, risk factors for mastitis occurrence and the control measures suggested by different studies conducted in the selected countries. The literature revealed that India had the highest cattle population. Milking was mainly done by hand in all of the studied countries. Stall feeding was done in Bangladesh and Sri Lanka and limited access to grazing was also reported in some farms in India and Pakistan. There was substantial variation in the prevalence of SCM between studies in all 4 countries, ranging from about 20% to about 80%, but the average prevalence across all studies was high (50%). The most common causal agents for SCM were non-aureus staphylococci (NAS), Staphylococcus (S.) aureus, Streptococcus spp. and Escherichia (E.) coli. The management related risk factors reported for SCM were stall feeding of cows, a higher stock density, cracked floors, open drains, the presence of flies, poor drainage, peri-parturient diseases, infrequent dung removal and earth floors. The control measures suggested in these studies were to improve the hygiene and sanitation of cows, to improve the cleanliness of farms and milker's hands, to apply dry cow therapy, supplementing micronutrients and routine screening for SCM combined with taking intervention measures like isolation of cows or milking infected cows last, and proper treatment. Also, full hand milking, complete milking, machine milking, and providing feed and water immediately after milking have been recommended. Finally, we show that current literature often studies the same set of (non-manageable) risk factors, so more research is needed to obtain a comprehensive picture of the determinants of SCM. Randomized controlled trials are needed to truly quantify the effect of intervention under field conditions. Altogether, our work gives an overview of the udder health situation in South-Asia and provides the basis for the design of UHCP in this region.

Application of Nanomaterials in the Prevention, Detection, and Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA)

Due to differences in geographic surveillance systems, chemical sanitization practices, and antibiotic stewardship (AS) implementation employed during the COVID-19 pandemic, many experts have expressed concerns regarding a future surge in global antimicrobial resistance (AMR). A potential beneficiary of these differences is the Gram-positive bacteria MRSA. MRSA is a bacterial pathogen with a high potential for mutational resistance, allowing it to engage various AMR mechanisms circumventing conventional antibiotic therapies and the host’s immune response. Coupled with a lack of novel FDA-approved antibiotics reaching the clinic, the onus is on researchers to develop alternative treatment tools to mitigate against an increase in pathogenic resistance. Mitigation strategies can take the form of synthetic or biomimetic nanomaterials/vesicles employed in vaccines, rapid diagnostics, antibiotic delivery, and nanotherapeutics. This review seeks to discuss the current potential of the aforementioned nanomaterials in detecting and treating MRSA.

Virulence and enterotoxin gene profile of methicillin-resistant Staphylococcus aureus isolates from bovine mastitis

Bovine mastitis is a major infectious disease affecting dairy animals resulting in enormous economic losses, prolonged antibiotic treatment, reduced milk yield and death of livestock. Emergence of Methicillin-resistant Staphylococcus aureus (MRSA) among bovine mastitis is matter of concern for animal health and dairy industry. The present study was conducted to detect the distribution of virulence and enterotoxin genes among MRSA isolates from bovine mastitis. Out of 500 milk samples, 126 isolates were identified as Staphylococcus and from these only 56 were S. aureus. S.aureus were resistant to cefoxitin (75%), ceftazidime (75%), amoxicillin (71.4%), cefodaxime (67.8%), cefepime (66.1%), oxacillin (64.3%), norfloxacin (60.7%) and gentamicin (58.9%). Only 42 isolates were identified as MRSA strains among staphylococci isolates. MRSA were harbouring virulence genes; mecA (100%), coa (100%) and nuc (100%). The other virulence factors such as hlg (80.9%, 34/42), pvl (47.6%, 20/42) and spa (92.8%, 39/42) were also reported. Molecular characterisation of enterotoxin genes revealed that out of 42 tested isolates 11 were found negative (26%) for any enterotoxin gene whereas 7 (16.6%), 6 (14.3%), 18 (42.8%), 1 (2.3%), 26 (61.9%),27(64.2%),3 (7.1%) were found positive for sea, seb, sec, sed, seg, sei, and seq enterotoxin respectively.

Bacteria from bovine clinical mastitis showed multiple drug resistance

Mastitis, which often manifests as udder infection in dairy animals, is of great concern as it affects public health and results in heavy economic losses to the dairy industry. A hospital-based cross-sectional study was conducted to determine the cultivable bacterial species associated with bovine clinical mastitis and their resistance patterns towards different antimicrobials. The milk samples from cows suffering from clinical mastitis during monsoon season were investigated. The prevalence of clinical mastitis was significantly high in Holstein-Friesian crossbred cows, followed by in Jersey crossbred, Red Kandhari and Deoni. Significantly high prevalence was observed during 4th to 6th months of lactation. A total of 110 bacterial isolates belonging to 14 different genera were isolated and identified. Aminoglycosides and quinolones were found to be the most effective antibiotics. Vancomycin resistant penicillinase producing Gram positive bacteria were demonstrated. Gram negative bacteria resistant to extended spectrum β lactamases, cephalosporins, tetracyclines, vancomycin and chloramphenicol as well as vancomycin resistant enterococci, multiple drug resistant (MDR) gram negative rods, MDR Pseudomonas and MDR Acinetobacter were found. Widespread resistance of Streptococcus uberis towards cephalosporins was documented. Variable MDR patterns were recorded within a single species. MDR transfer from non-pathogens to emerging foodborne and established mastitis pathogens could be a potential problem to the dairy industry as well as to public health.

Systematic review and meta-analysis of the epidemiology of vancomycin-resistance Staphylococcus aureus isolates

BACKGROUND

Vancomycin‑resistant Staphylococcus aureus (VRSA) is a serious public health challenging concern worldwide.

OBJECTIVES

Therefore, the objective of present study of 62 published studies was to evaluate the prevalence of VRSA based on different years, areas, isolate source, antimicrobial susceptibility testing, and the genetic determinants.

METHODS

We searched the relevant articles that focused on the prevalence rates of VRSA in PubMed, Scopus, Embase, and Web of Science from 2000 to 2019. Statistical analyses were conducted using STATA software (version 14.0).

RESULTS

The prevalence of VRSA was 2% before 2006, 5% in 2006-2014, and 7% in 2015-2020 that showed a 3.5-fold increase in the frequency of VRSA between before 2006 and 2020 years. The prevalence of VRSA was 5% in Asia, 1% in Europe, 4% in America, 3% in South America, and 16% in Africa. The frequencies of VRSA isolated from clinical, non-clinical, and mixed samples were 6%, 7%, and 14%, respectively. The prevalence of VRSA was 12% using disk diffusion agar method, 7% using MIC-base methods, and 4% using mixed-methods. The prevalence of vanA, vanB, and vanC1 positive were 71%, 26%, and 4% among VRSA strains. The most prevalent genotype was staphylococcal cassette chromosomemec (SCCmec) II, which accounted for 57% of VRSA. The most prevalent staphylococcal protein A (spa) types were t002, t030, and t037.

CONCLUSION

The prevalence of VRSA has been increasing in recent years particularly in Africa/Asia than Europe/America. The most prevalent of genetic determinants associated with VRSA were vanA and SCCmec II. This study clarifies that the rigorous monitoring of definite antibiotic policy, regular surveillance/control of nosocomial-associated infections and intensive surveillance of vancomycin-resistance are required for preventing emergence and further spreading of VRSA.

Characterization of Multidrug-Resistant Biofilm-Producing Escherichia coli and Klebsiella pneumoniae in Healthy Cattle and Cattle with Diarrhea

This study describes comparative occurrence and characterization of multidrug-resistant (MDR) Escherichia coli and Klebsiella pneumoniae (KP) in healthy cattle (HC) and cattle with diarrhea (DC) in India. During 2018-2020, 72 MDR isolates, including 35 E. coli (DC: 27; HC 8) and 37 K. pneumoniae (DC: 34; HC: 3), from 251 rectal swabs (DC: 219; HC: 32) were investigated for extended-spectrum beta-lactamase (ESBL), AmpC type β-lactamase and carbapenemase production, antimicrobial susceptibility profile, biofilm production, and efflux pump activity. Fifty-five MDR isolates were ESBL producers (ESBLPs) (DC: 50; HC: 5) and ESBLPs from DC were coresistant to multiple antibiotics. The blaCTX-M gene (50) was the most frequently detected β-lactamases followed by blaAmpC (22), blaTEM1 (13), blaCMY-6 (6), blaOXA1 (5), blaPER (2), blaDHA, and blaFOX and blaSHV12 (1 each). Plasmid-mediated quinolone resistance determinants qnrB, qnrS, qnrA, and qepA were detected in 18, 16, 2, and 3 isolates, respectively. Twenty three isolates revealed mutation in gyrA and parC genes. Tetracycline-resistance markers tetA, tetB, tetC, and tetE were detected in 33, 10, 3, and 2 isolates, respectively. Only one of the 41 imipenem-resistant isolates harbored blaNDM-5 and two were colistin-resistant. Altogether, 20 MDR isolates were strong biofilm producers and 19 harbored different virulence factors. This is the first ever report from India on the presence of MDR Enterobacteriaceae with resistance to even last-resort antimicrobials in the bovine diarrhea.

A review of animal health and drug use practices in India, and their possible link to antimicrobial resistance

BACKGROUND

Livestock production, particularly the dairy sector, is important for food and nutritional wellbeing of communities in India, it supports livelihoods of many farmers, and contributes to the economy of the country. India is a high consumer of antibiotics and antimicrobial resistant (AMR) bacteria are a major public health concern.

OBJECTIVES

Our objectives were to identify animal health and drug use practices that may contribute to emergence and spread of AMR in the country, review previous AMR- mitigation strategies, and discuss "theory of change" as an approach to informing the choice of interventions.

METHODS

We undertook a desk review of literature to identify practices with potential to contribute to emergence and spread of antimicrobial resistance in India. Searches were done in PubMed, Google scholar, and Google. Data were synthesized and discussed by themes.

RESULTS

Animal disease surveillance is less developed and infrastructure to support delivery of services is inadequate. Several groups are known to offer animal health services. The untrained "animal health workers" and para-veterinarians are more popular with farmers as they charge less for consultations (compared to veterinarians who are few and charge more). Over-the-counter access of antibiotics, without prescription, and direct marketing of drugs to farmers are common. Because of this, farmers are able to treat their animals and only consult when cases become non- responsive to treatment. Antibiotics are mostly used in management of mastitis cases. Drug withdrawal periods are rarely observed and occurrence of antibiotic- contaminated milk has been reported. Awareness on AMR is low and antimicrobial stewardship in livestock is yet to be developed. Initiatives such as the National programme for containment of AMR, National Action Plan on AMR, and the National Health policy point to government's commitment in addressing the problem of AMR in the country.

CONCLUSION

Several animal health and drug use practices, with potential to cause AMR, have been described, and their contribution can be discussed further by engaging stakeholders in a "theory of change" exercise. Interventions that address AMR from the animal health perspective should be promoted, and incentives to increase their adoption explored.

Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in cattle production - a threat around the world

Food producing animal is a global challenge in terms of antimicrobial resistance spread. Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae are relevant opportunistic pathogens that may spread in many ecological niches of the One Health approach as human, animal and environment due to intestinal selection of antimicrobial resistant commensals in food production animals. Cattle production is a relevant ecological niche for selection of commensal bacteria with antimicrobial resistance from microbiota. Enterobacteriaceae show importance in terms of circulation of resistant-bacteria and antimicrobial resistance genes via food chain creating a resistance reservoir, setting up a threat for colonization of humans and consequent health risk. ESBL-producing Enterobacteriaceae are a threat in terms of human health responsible for life threatening outbreaks and silent enteric colonization of community populations namely the elder population. Food associated colonization is a risk difficult to handle and control. In a time of globalization of food trading, population intestinal colonization is a mirror of food production and in that sense this work aims to make a picture of ESBL-producing Enterobacteriaceae in animal production for food over the world in order to make some light in this reality of selection of resistant threats in food producing animal.

Characterization of MDR and ESBL-producing E. coli strains from healthy swine herds of north-eastern India

Fecal samples (225) from apparently healthy pigs were analysed for E. coli isolation. Multidrug-resistant (MDR) isolates (42) were identified from 225 E. coli isolates. Forty isolates exhibited extended-spectrum beta-lactamases (ESBL) phenotype harbouring single to multiple-sized plasmids (1 kb to ≥ 25 kb). Overall blaTEM (85.7%) was the commonest genotype, followed by blaCTX-M (61.9%), blaOXA (17%) and blaSHV was not recovered. Other antimicrobial resistant genes (ARGs) identified were sul2 (100%), strA (95.2%), tetA (92.9%), sul1 (76%), aadA (71.4%), tetB (50%), cat (42.9%) and aac(3)IV (26.2%). Plasmid-mediated quinolone resistance (PMQR) positive strains totalled to 59.5% for qnrB, 19.04% for qnrS but qnrA was not detected. Integron genes were detected either singly or combined: intI1 (76.2%), intI2 (26.2%). Conjugation experiment was successful for 4 ESBL producers. The present study detected higher carriage of ESBL producing E. coli in pigs, and highlights the dominance of resistance and integron genes circulating in MDR E. coli from swine of northeast India, posing a threat of horizontal gene transfer.

Analysis of milk-derived isolates of E. coli indicating drug resistance in central Ethiopia

Mastitis is one of the most important diseases in dairy cows throughout the world and is responsible for significant economic losses to the dairy industry. This study was performed to characterize the genetic basis of drug resistance in Escherichia coli isolated from cases of clinical and sub-clinical bovine mastitis. A total of 224 California mastitis test (CMT)-positive milk samples were collected from December 2015 to April 2016 to characterize the phenotypic and genetic basis of antimicrobial resistance in E. coli isolated from raw milk from dairy farms found in Burayu, Sebeta, and Holeta areas of Ethiopia. The prevalence of E. coli was 7.1% (16) and both phenotypic and molecular techniques were used to identify E. coli antimicrobial susceptibility trait. The most commonly observed phenotypic resistance was against ampicillin (68.7%), sulphamethazole-trimethoprim (50%), and streptomycin (25%). Multidrug resistance phenotypes were found in 11 of 16 (68.7%) of E. coli isolates. Tetracycline (tet (A)) and chloramphenicol (cml (A)) genes were the most predominant encoding resistance genes identified (50%) each, followed by gentamycin resistance encoding gene (aac (3)-IV) (37.5%). Overall, 11 (68.7%) of the isolates had multidrug resistance genes responsible to two or more classes of antibiotics. The most common pattern detected was cml (A) and tet (A) together 37.5% followed by aac (3)-IV and tet (A) 25%. The current study indicated that raw milk could be regarded as critical source of antibiotic-resistant pathogenic E. coli.

Carbapenem-resistant Enterobacteriaceae in wildlife, food-producing, and companion animals: a systematic review

OBJECTIVES

The spread of carbapenem-resistant Enterobacteriaceae (CRE) in healthcare settings challenges clinicians worldwide. However, little is known about dissemination of CRE in livestock, food, and companion animals and potential transmission to humans.

METHODS

We performed a systematic review of all studies published in the PubMed database between 1980 and 2017 and included those reporting the occurrence of CRE in samples from food-producing and companion animals, wildlife, and exposed humans. The primary outcome was the occurrence of CRE in samples from these animals; secondary outcomes included the prevalence of CRE, carbapenemase types, CRE genotypes, and antimicrobial susceptibilities.

RESULTS

We identified 68 articles describing CRE among pigs, poultry, cattle, seafood, dogs, cats, horses, pet birds, swallows, wild boars, wild stork, gulls, and black kites in Africa, America, Asia, Australia, and Europe. The following carbapenemases have been detected (predominantly affecting the genera Escherichia and Klebsiella): VIM, KPC, NDM, OXA, and IMP. Two studies found that 33-67% of exposed humans on poultry farms carried carbapenemase-producing CRE closely related to isolates from the farm environment. Twenty-seven studies selectively screened samples for CRE and found a prevalence of <1% among livestock and companion animals in Europe, 2-26% in Africa, and 1-15% in Asia. Wildlife (gulls) in Australia and Europe carried CRE in 16-19%.

CONCLUSIONS

The occurrence of CRE in livestock, seafood, wildlife, pets, and directly exposed humans poses a risk for public health. Prospective prevalence studies using molecular and cultural microbiological methods are needed to better define the scope and transmission of CRE.

Genomic Identity of Fluoroquinolone-Resistant blaCTX-M-15-Type ESBL and pMAmpC β-Lactamase Producing Klebsiella pneumoniae from Buffalo Milk, India

We investigated the occurrence of extended-spectrum β-lactamase (ESBL) and AmpC-type β-lactamase (ACBL) producing quinolone-resistant Klebsiella pneumoniae (KP) in milk samples of apparently healthy buffaloes (n = 348) and buffaloes (n = 19) with evidence of subclinical mastitis from seven districts of West Bengal, India. In total, 12 ESBL producing KP were isolated with blaCTX-M-15 gene and 7 of them were ACBL producers, as well. The blaCTX-M-15 genes were carried by transposable element ISEcp1. The plasmid-mediated quinolone resistance genes-qnrS, qnrA, qnrB, qepA, and aac(6')-Ib-cr were detected in five, one, three, four, and one isolate (s), respectively. In addition, eight isolates carried mutation in gyrase (gyrA) and six in topoisomerase IV (parC). Resistance markers/genes for sulfonamide (sul1), tetracycline [tet(A) and tet(B)], and aminoglycoside (aacC2) were also detected in eight, four, and one isolate(s), respectively. The class I integrons identified in five isolates carried aad2/aad5 and dfrA12/dfrA17 gene cassettes. The enterobacterial repetitive intergenic consensus-PCR revealed that all the isolates were genetically diverse and comprised a heterogeneous population. Isolation of multidrug-resistant KP, a typical nosocomial pathogen from buffalo milk, reiterates the need to monitor farm animals for ESBL producing Enterobacteriaceae and emphasizes on judicious use of antibiotics in animal husbandry sector.

Milk amyloid A as a biomarker for diagnosis of subclinical mastitis in cattle

Background and Aim

Mastitis is one of the most vital noteworthy monetary risks to dairy ranchers and affects reproductive performance in dairy cattle. However, subclinical mastitis (SCM) negatively affects milk quality and quantity and associated with economic losses as clinical mastitis. It is recognizable only by additional testing. Somatic cell count (SCC) is currently used worldwide for the screening of intramammary infection (IMI) infections. However, somatic cells (SC) are affected by numerous factors and not always correlate with infection of the udder. Therefore, the aim of the present study was to evaluate the milk amyloid A (MAA) in the milk of normal and SCM cows and compare the sensitivity of both MAA secretion and SCC in response to mammary gland bacterial infection.

Materials and Methods

A total of 272 quarter milk samples collected from 68 Friesian cows after clinical examination for detection of clinical mastitis were employed in this study. All quarter milk samples (272) were subjected to bacteriological examination, while SCs were assessed in samples (220). Following SCC estimation and bacteriological examination, the apparently normal quarter milk samples were categorized into 7 groups and MAA concentration was estimated in normal and subclinical mastitic milk samples.

Results

Prevalence of clinical mastitis was 19.12 % (52 quarters), while 80.88 % (220 quarters) were clinically healthy with normal milk secretion. Of those 220 clinically healthy quarter milk samples, 72 (32.73%) showed SCM as detected by SCC (SCC ≥500,000 cells/ml). The most prevalent bacteria detected in this study were streptococci (48.53%), Staphylococcus aureus (29.41%), Escherichia coli (36.76%), and coagulase-negative staphylococci (11.76%). Results of MAA estimation revealed a strong correlation between MAA secretion level and SCC in agreement with the bacteriological examination. Interestingly, there was a prompt increase in MAA concentration in Group III (G III) (group of milk samples had SCC ≤200,000 cells/ml and bacteriologically positive) than Group I (G I) (group of milk samples with SCC ≤500,000 cells/ml and bacteriologically negative), as MAA concentration in G III was about 4 times its concentration in G I.

Conclusion

Our study provides a strong evidence for the significance of MAA measurement in milk during SCM, and MAA is more sensitive to IMI than SCC. This can be attributed to rapid and sensitive marker of inflammation. The advantage of MAA over other diagnostic markers of SCM is attributed the minute or even undetectable level of MAA in the milk of healthy animals, it is not influenced by factors other than mastitis, and could be estimated in preserved samples. Therefore, we recommend that estimation of MAA concentration in milk is a more useful diagnostic tool than SCC to detect SCM and to monitor the udder health in dairy cattle.

Detection of emerging antibiotic resistance in bacteria isolated from subclinical mastitis in cattle in West Bengal

AIM

The aim of this work was to detect antibiotic resistance in Gram-negative bacteria isolated from subclinical mastitis in cattle in West Bengal.

MATERIALS AND METHODS

The milk samples were collected from the cattle suffering with subclinical mastitis in West Bengal. The milk samples were inoculated into the nutrient broth and incubated at 37°C. On the next day, the growth was transferred into nutrient agar and MacConkey agar. All the pure cultures obtained from nutrient agar slant were subjected to Gram-staining and standard biochemical tests. All the bacterial isolates were tested in vitro for their sensitivity to different antibiotics commonly used in veterinary practices. All Gram-negative isolates including positive control were subjected to polymerase chain reaction (PCR) for detection of bla_CTX-M, bla_TEM, bla_SHV, bla_VIM, tetA, tetB, tetC, and tetM genes considered for extended-spectrum β-lactamase (ESBL), metallo-β-lactamase, and tetracycline resistance.

RESULTS

In total, 50 Gram-negative organisms (Escherichia coli, Proteus, Pseudomonas, Klebsiella, and Enterobacter) were isolated from milk samples of subclinical mastitis infected cattle. Among these Gram-negative isolates, 48% (24/50) were found either ESBL producing or tetracycline resistant. Out of total 50 Gram-negative isolates, bla_CTX-M was detected in 18 (36%) isolates, and 6 (12%) harbored bla_TEM genes in PCR. None of the isolates carried bla_SHV genes. Further, in this study, 5 (10%) isolates harbored tet(A) gene, and 8 (16%) isolates carried tet(B) gene. No tet(C) gene was detected from the isolates.

CONCLUSION

This study showed emerging trend of antibiotic-resistant Gram-negative bacteria associated with subclinical mastitis in cattle in West Bengal, India.

Molecular signature of extended spectrum β-lactamase producing Klebsiella pneumoniae isolated from bovine milk in eastern and north-eastern India

The present study reports on 23 extended spectrum β-lactamase producing Klebsiella pneumoniae (KP), isolated from milk samples (n=340) of healthy cows (n=129) and cows with subclinical (n=159) and clinical (n=52) mastitis, from three different states of India viz. West Bengal, Jharkhand and Mizoram. Seven of them were AmpC type β-lactamase producers, as well. The ESBL producing KP were significantly (P=0.006, χ2=10.04, df=2) and more frequently detected in milk samples of mastitic cows than healthy ones. The β-lactamase genes - blaCTX-M, blaTEM and blaSHV were detected in 19, 8 and 3 isolates, respectively. In all but one CTX-M positive isolates, the genetic platform - ISEcp1-blaCTX-M-orf477 was detected. Ten of the isolates carried plasmid mediated quinolone resistance gene - qnrS and 1 isolate possessed qnrB. Again 11 of them were found to have sulfonamide resistance gene - sul1 and 12 possessed class I integron. Sequencing of the class 1 integron revealed the presence of dfrA12/dfrA17 and aadA2/aadA5 gene cassettes conferring resistance to trimethoprim and aminoglycosides, respectively. All the isolates, characterized by enterobacterial repetitive intergenic consensus (ERIC) PCR, yielded distinct fingerprinting profile. However, most of the isolates from Jharkhand were clustered along with two isolates each from West Bengal and Mizoram indicating their clonal relatedness even though isolated from geographically different areas. Isolation of ESBL producing KP from bovine milk samples implies its public health significance; as such pathogens may enter the human food chain causing severe health hazards.

Approaches to characterize extended spectrum beta-lactamase/beta-lactamase producing Escherichia coli in healthy organized vis-a-vis backyard farmed pigs in India

The study was undertaken to investigate the occurrence and to characterize the ESBL/beta-lactamase producing-Escherichia coli in healthy pigs of organized and backyard farms in West Bengal, India. Total 200 rectal swabs were collected randomly from healthy pigs maintained in four organized farms and 10 backyard farms (n=100 each) and 76 isolates were identified as E. coli from organized (48/100, 48%) and backyard pigs (28/100, 28%). Twelve E. coli isolates (6%) in the present study were detected to possess any of the ESBL/beta-lactamase genes studied. ESBL/beta-lactamase producers were isolated with significantly more frequency from backyard pigs than the organized farm pigs (p=0.026). Six of ESBL/beta-lactamase producing isolates were phenotypically confirmed as CTX-M producers and ten of them were confirmed as TEM/SHV producers. PCR and sequencing of the amplified product from representative isolates revealed the presence of blaCTX-M-9, blaSHV-12 and blaTEM-1. No unique combination of the studied beta lactamase genes for organized and backyard farm pig isolates was noted. The ESBL isolates belonged to O13, O55, O133, O153, O157, O158, O166, rough and OUT serogroups. The association of heat labile toxin (elt) (p<0.0005) with organized farm isolates and heat stable toxin (estA) (p=0.0143) with backyard piggery sector was significantly higher. The ESBL/beta-lactamase producers from organized farm (Ak/Ex) and indigenous pigs (Ak/Ex/Te; Ak/CoT/G) showed a characteristic phenotypical antibiotic resistance pattern. Two pairs of isolates from organized and backyard farm pigs showed clonal relationship indicating a possible transmission between the farms which were situated adjacently. Thus the present study revealed backyard farm pigs as major source of ESBL/beta-lactamase producing-E. coli associated with STa and characteristic antibiotic resistance pattern in India.