Molecular Characterization of Methicillin-Resistant Staphylococci from the Dairy Value Chain in Two Indian States

Abstract

Bovine milk and milk products may contain pathogens, antimicrobial resistant bacteria, and antibiotic residues that could harm consumers. We analyzed 282 gram-positive isolates from milk samples from dairy farmers and vendors in Haryana and Assam, India, to assess the prevalence of methicillin-resistant staphylococci using microbiological tests, antibiotic susceptibility testing, and genotyping by PCR. The prevalence of genotypic methicillin resistance in isolates from raw milk samples was 5% [95% confidence interval, CI (3–8)], with 7% [CI (3–10)] in Haryana, in contrast to 2% [CI (0.2–6)] in Assam. The prevalence was the same in isolates from milk samples collected from farmers [5% (n = 6), CI (2–11)] and vendors [5% (n = 7), CI (2–10)]. Methicillin resistance was also observed in 15% of the isolates from pasteurized milk [(n = 3), CI (3–38)]. Two staphylococci harboring a novel mecC gene were identified for the first time in Indian dairy products. The only SCCmec type identified was Type V. The staphylococci with the mecA (n = 11) gene in raw milk were commonly resistant to oxacillin [92%, CI (59–100)] and cefoxitin [74%, CI (39–94)], while the isolates with mecC (n = 2) were resistant to oxacillin (100%) only. All the staphylococci with the mecA (n = 3) gene in pasteurized milk were resistant to both oxacillin and cefoxitin. Our results provided evidence that methicillin-resistant staphylococci occur in dairy products in India with potential public health implications. The state with more intensive dairy systems (Haryana) had higher levels of methicillin-resistant bacteria in milk.

Analyses of Extended-Spectrum-β-Lactamase, Metallo-β-Lactamase, and AmpC-β-Lactamase Producing Enterobacteriaceae from the Dairy Value Chain in India

“…To our knowledge, no other study from India has reported β-lactamases in GNB isolated from pasteurized milk. This finding aligns with our previous report, which identified methicillin-resistant Gram-positive bacteria in pasteurized milk [50]. It could also be due to post-pasteurization contamination, potentially exacerbated by inadequate quality packaging and cold storage that encourages bacterial growth.…”

“…The prevalence of genotypic β-lactamases was 13% (CI (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)) in Haryana (a developed dairy sector) and 7% (CI (4-11)) in Assam (mainly informal dairy sector). These findings could indicate that intensive farms have a higher prevalence of antibiotic resistance genes, which has also been reported by others [48,49] and was similarly found in our previous study on Gram-positive bacteria in milk [50]. Even though we observed a higher prevalence of β-lactamase genes in milk isolates from Haryana compared to isolates from Assam, we discovered that milk isolates from Assam (77%, CI (70-82)) exhibited a higher phenotypic β-lactam resistance compared to isolates from Haryana (63%, CI (56-70)), and we therefore cannot conclude on the difference between the states.…”

Synanthropic Rodents and Shrews Are Reservoirs of Zoonotic Bacterial Pathogens and Act as Sentinels for Antimicrobial Resistance Spillover in the Environment: A Study from Puducherry, India

“…Although, S. aureus with mecC genetic element in milk was first reported in India [35], we report the isolation of MRSA with mec C from rodents and shrews for the first time in India. The prevalence of MRSA in shrews and rodents in our study is 73.9% and 26.3% respectively.…”

Synanthropic rodents and shrews are reservoirs of zoonotic bacterial pathogens and act as sentinels for antimicrobial resistance spillover in the environment: A study from Puducherry, India

“…Although, S. aureus with mecC genetic element in milk was first reported in India [ 37 ], we report the isolation of MRSA with mec C from rodents and shrews for the first time in India. The prevalence of MRSA in shrews and rodents in our study is 73.9% and 26.3% respectively.…”