Prevealance of Salmonella, E. Coli O157 and Staphylococci in Stree Vended Ready-to-eat Meat in Nsukk and its Environs.O- EAT MEAT IN NSUKKA AND ITS ENVIRONS

Abstract

The possible health hazard associated with ready-to-eat (RTE) meat in Nsukka and its environ in Enugu State was evaluated by determining the prevalence of salmonellae, E. coli O157 and Staphylococcus species and investigating the toxigenic potential of E. coli O157 and Staphylococcus and antibiotics profiles of these zoonotic bacterial isolates. A total of 255 RTE meat samples were purchased based on the availability of the ready-to-eat (RTE) meat vended in the markets. Purposive sampling technique was used to select the four meat sampling spots. The samples collected were transported to the laboratory for microbiological analysis. Each ready-to-eat meat sample was pre-enriched in nutrient broth for 24 hours at 37oC and subsequently processed for E. coli O157, salmonellae and staphylococci isolation using cefixime-tellurite sorbitol MacConkey (CT-SMAC) agar, brilliance salmonella agar (BSA) and mannitol salt agar (MSA) respectively. Non-sorbitol fermenting colonies on CT-SMAC were subjected to E. coli O157 latex agglutination test and molecular detection of rbfO157 gene for confirmation. Purple colonies on BSA were subjected to biochemical tests for Salmonella identification. Suspected staphylococcal (yellow or white) colonies on MSA were Gram stained and Gram-positive cocci in bunches were tested for catalase production. Identification of the staphylococcal isolates to species level was done by a combination of polymerase chain reaction (PCR) amplification of nuc and spa genes and sequencing of sodA and 16S rDNA genes. PCR amplification of genes coding for TSST-1 (tst), ETA (eta), ETB (etb), ETD (etd) were investigated by PCR. Phenotypic determination of resistance to 17 antimicrobial agents was carried out using the disc diffusion method, while genes coding for resistance to aminoglycosides (aph(2)-aac(6),ant(4), aph(3)-III), erythromycin (ermA, ermB, ermC, ermT, mphC, msrA, and msrB) and tetracyclines (tet(M), tet(O), tet(K),tet(L) lincomycins and streptogramins (linA, linB, vgaA, vgaC) and fusidic acid (fusA, fusB, fusC) were determined in the isolates by PCR amplification using their specific primers. None (0%) of the 255 street vended R-T-E meat samples analysed was contaminated with E. coli O157 or Salmonella organisms. Twenty-eight (11%) of the R-T-E meat samples contained staphylococci. Twenty-four of the Staphylococcus strains were identified to species level and they belonged to 6 species namely S. scuiri (54.1%), S. lentus (16.6%), S. saprophyticus (12.5%), S. carnosus (8.4%), S. piscifermentans (4.2%) and S. epidermidis (4.2%). Four (16.7%) of the identified Staphylococcus species haboured the virulence gene exfoliative toxin-A (eta). The staphylococci exhibited highest resistance to fusidic acid (79.2%) while lowest resistance was demonstrated against gentamicin, kanamycin, streptomycin and tobramycin; with 4.2% of the isolates resistant to each of the antimicrobial agents. None of the Staphylococcus isolates was resistant to chloramphenicol, ciprofloxacin, linezolid and teicoplanin. Resistance genes detected in the Staphylococcus species were: mecA (25%), tetK (25%), mphC (12.5%), ermT (8.3%) and ermC (4.2%). The most contaminated R-T-E meat type the R-T-E meat vended in the study area were contaminated with staphylococci and is of public health importance, especially as the isolates contain mecA gene which could transfer their resistance to pathogenic strains. The implication is that infection from such resistant organism will be difficult to treat with commonly available and affordable antibiotics which may result to increase in morbidity, mortality and cost of treatment.