Bacteriological Assessment of Escherichia coli and Salmonella spp. from Local Meat Shops in Dhaka, Bangladesh

Retail meat and contact surfaces of meat have been identified as reservoirs of foodborne pathogens and can be used to transmit antimicrobial-resistant bacteria to consumers. In this research, the prevalence, phenotypic identification, molecular confirmation, antimicrobial resistance, and biofilm-forming capability of Escherichia coli and Salmonella spp. were determined in local meat shop in Dhaka, Bangladesh. Twelve samples (raw meat portions and environmental swabs) were sampled, 8 of which were subjected to microbiological analysis. Presumptive isolates were subcultured on MacConkey (MAC) and Xylose Lysine Deoxycholate (XLD) agar and identified by Triple Sugar Iron (TSI), citrate utilization and Motility-Indole-Urease (MIU) assays. The biochemical characteristics of most XLD-derived isolates were similar to Salmonella spp. and the majority of MAC-derived isolates were similar to E. coli. Molecular verification was added with the help of Polymerase chain reaction (PCR) on the invA gene of Salmonella spp. and the uidA gene of E. coli. The Kirby-Bauer disk diffusion method of antimicrobial susceptibility testing showed widespread resistance, with about 70% of the tested isolates having a multidrug-resistant phenotype and no isolates being completely susceptible to all antibiotics tested. Biofilm formation, as measured using the microtiter plate assay, revealed that all the isolates tested were biofilm formers with optical densities of 0.105 to 0.35. It was also found that stronger biofilm formation was mostly seen in XLD-derived isolates compared to MAC-derived isolates. The results indicate an important food safety issue and the necessity of heightened hygiene, regular monitoring, and sensible antimicrobial usage.