Milk supply chain as a reservoir of antimicrobial-resistant Staphylococcus species.

Milk is a source of essential nutrients, but food safety across the milk supply chain has emerged as an integral part of food trade. Of the several food safety hazards, antimicrobial-resistant Staphylococcus species have emerged as one of the major microbial hazards with significant public health concerns. The present crosssectional study was undertaken with the objective to isolate Staphylococcus species from the milk supply chain, characterize isolates for antimicrobial resistance, and trace the origin of isolates using molecular techniques. Samples collected from the formal and informal milk supply chains showed prevalence of Staphylococcus species of 4.3% (n=720); isolates were identified as coagulase-positive (S. aureus 67.7% and S. intermedius 6.4%) and coagulase-negative (S. lentus 9.6%, S. sciuri 3.2%, S. xylosus 3.2%, S. schleiferi 3.2%, S. felis 3.2%, and S. gallinarum 3.2%) species. Staphylococcus isolates showed antimicrobial resistance to methicillin (32.2%), ß-lactam (41.9%), and macrolide-lincosamide-streptogramin B (3.2%). Staphylococcus isolates phenotypically resistant to methicillin also carried the mecA gene and displayed diverse pulsed field gel electrophoresis (PFGE) profiles, indicating their diverse origins in the milk supply chain. Based on the similarity of PFGE profile, the origin of one of the Staphylococcus isolates was traced to the soil in contact with milch cows. The findings of this study highlight the need for more comprehensive microbial risk analysis studies across the milk supply chain, capacity building, creation of awareness among stakeholders about the judicious use of antimicrobials, and protection of public health using a One-Health approach.

Non-diarrhoeic pigs as source of highly virulent and multidrug-resistant non-typhoidal Salmonella.

Food-producing animals act as reservoirs of non-typhoidal Salmonella (NTS) serovars with potential food safety and public health implications. The present cross-sectional study aimed at determining the prevalence of Salmonella serotypes in non-diarrhoeic pigs and characterizing the isolates using molecular tools. Salmonella isolates (n = 22) recovered from faecal samples of 194 randomly selected pigs were characterized for virulence and antimicrobial resistance and subtyped using XbaI-PFGE. The prevalence of Salmonella in apparently healthy non-diarrhoeic pigs was 11.3% (95%CI, 4.3-19.5%), with S. Weltevreden (81.8%) and S. Enteritidis (18.2%) being the serotypes detected. Salmonella isolates harboured virulence genes such as invA (100%), stn (100%), spvR/spvC (86.3%) and fimA (22.7%). Phenotypically, isolates showed sensitivity to chloramphenicol, levofloxacin and ciprofloxacin and resistance to tetracycline and ampicillin (100%), streptomycin (86.4%), amoxicillin-clavulanate (63.6%), cefotaxime (22.7%) and ceftriaxone (9.1%). Notably, 18.2% isolates were multidrug-resistant (≥ 3 antimicrobial class) with multiple antimicrobial resistance (MAR) index of 0.56-0.67 (18.2%), 0.44 (45.5%), 0.33 (31.8%) and 0.22 (4.5%). Genotypically, isolates carried various antibiotic resistance genes: ESBL (blaTEM and blaOXA), aminoglycoside (strA, strB and aadA1), sulphonamide (sul1, sul2 and dfrA1), tetracycline (tetA and tetB) and plasmid AmpC beta-lactamase (ACC, FOX, MOX, DHA, CIT and EBC). The present investigation emphasizes the epidemiological significance of PFGE typing in the detection of emerging strains of highly virulent and multidrug-resistant S. Weltevreden and S. Enteritidis in non-diarrhoeic pigs that pose serious public health implications in the pork supply chain environment. More extensive longitudinal study is warranted to provide epidemiological links between environmental reservoirs and animal and human infections in piggery settings.