Multidrug Resistant Salmonella Spp. and Staphylococcus Spp. Isolated from milk in Dhaka City

Abstract

The foodborne pathogen Salmonella spp. and Staphylococcus spp. are responsible for a food borne disease affecting both humans and animals. To evaluate the presence of these nuisance bacteria, a total of 61 samples comprising 39 raw milk and 22 brand milk samples were collected, using convenience sampling from different points/markets of Dhaka and the local farms at Mohakhali, Hemayetpur, and BLRI. The Samples were examined for identification of Salmonella spp. and Staphylococcus spp., total viable bacterial count (TVBC), and total coliform count (TCC). The raw milk samples had TVBC with values that ranged between 3– 8.2 log10 CFU/mL in contrast brand milk samples had TVBC values ranging between 0-8.6 log10 CFU/mL. A total of 5 (8.2%) Salmonella isolates were confirmed by conventional PCR with the inV gene. Of these, 4 (10%) and 1 (4%) Salmonella spp. were isolated from raw milk and commercially packaged brand milk samples respectively. A total of 27 (44.3%) Staphylococcus spp. were isolated from 39 (69.2%) raw milk samples. Antibiotic susceptibility testing indicated that all 5 isolates of Salmonella spp. were resistant to at least 14 antibiotics especially tetracycline-class antibiotics. Fourteen (51.6%) of the Staphylococcus spp. isolates showed resistance to ampicillin and penicillin, which is indicative of the presence of β lactamase producing gene. In conclusion, the high bacterial load beyond the permissible level in the milk samples, the presence of Salmonella spp. in the milk, and also multidrug-resistant strains of Salmonella and Staphylococcus spp. are of serious public health significance.