Vol. 10, Issue 4, Part D (2024)

Raw milk and raw milk cheese were collected from Puducherry and Cuddalore. After collection of samples, in case of raw milk, bacterial Pre-enrichment was performed in 225 ml of 1% buffered peptone water with 25 ml of raw milk sample and in case of raw milk cheese, Pre-enrichment was performed in 225 ml of 1% buffered peptone water with 25 g of raw milk cheese. After Pre-enrichment, isolation and identification of the target organism was carried out. The Pre-enriched raw milk and raw milk cheese samples were streaked in EMB agar plate and Mac Conkey agar plates. Then they were incubated at 37 ℃ for 24hrs. E. coli was identified by the pink colour colonies in Mac Conkey agar. If EMB agar plate contains dark centered colonies with greenish metallic sheen, they were considered as positive for E. coli. The isolates were sub cultured to get pure culture. The isolates were identified based on morphological and biochemical characterization. The antibiotic susceptibility testing was carried out for the isolates against the selected antibiotics Ampicillin, Tetracycline, Kanamycin, Erythromycin, Oxacillin, Streptomycin, Amikacin, Gentamicin, Cephalothin, Ciprofloxacin and Chloramphenicol. Among the ten raw milk isolates and ten raw milk cheese isolates, raw milk isolate RMS 4 showed resistance towards five selected antibiotics. RMS 4 isolate was identified by 16S r RNA sequencing and it was identified with 99.92% of similarity as E. coli.