Vol. 12, Special Issue 12 (2023)

Aim: The following study was aimed to detect Escherichia coli in raw milk samples, determine the virulence gene profile by PCR and to evaluate the ESBL producing ability of the isolates phenotypically.

Materials and Methods: 125 raw milk samples were collected from nearby local farms and milk merchants of Chandragiri mandal, Tirupati district, Andhra Pradesh. In order to isolate and identify E. coli, the collected samples were processed and put through standard procedures. Later by using PCR, all of these suspected E. coli isolates were verified for species-specific characterisation targeting uspA gene. Further, these isolates were evaluated for the presence of virulence genes viz., stx1 and stx2 by PCR. Using the double disk diffusion method, the ability of these E. coli isolates to produce Extended Spectrum Beta-lactamase (ESBL) was determined. And also risk factors were evaluated by an observational survey with semi structured questionnaire that was constructed using Epi Info^™ software.

Results: Out of 48 presumptive E. coli isolates, only 35 isolates were confirmed by PCR targeting uspA gene with an amplicon size of 884bp. Among these, 14 (40%) isolates harboured stx1 gene, 8 (22.85%) isolates positive for stx2 gene, while 4 (11.43%) isolates harboured both stx1 and stx2 genes. Further, out of 35 isolates only 9 (25.7%) isolates were positive for ESBL production and shown varied sensitivity response to different antibiotics.

Among ESBL antibiotics studied, Aztreonam (68.5%) had the highest sensitivity, followed by Cefotaxime (48.5%), Ceftazidime + Clavulanic acid (45.7%) and the least sensitivity was shown by Cefoxitin (8.5%).

Conclusions: The findings of this study suggest that hygienic, sanitary, and biosafety precautions should be taken during the milk-production process to prevent the spread of pathogens, as raw milk may serve as a source of virulent and antibiotic-resistant E. coli.