Isolation And Phenotypic Characterization of E. Coli O157 And Salmonella SPP in a Slaughter House And Meat Sale Tables at Nsukka Market, Enugu State

Abstract

: Escherichia coli O157 and Salmonella spp. are major food borne pathogens and the emergence of these pathogens has been reported in many countries. The objectives of this study were to examine the meat contact surfaces in Nsukka slaughterhouse and meat sales environment for E. coli O157 and Salmonella species, determine the enterotoxigenic potential and antibacterial resistance profile of the isolated bacteria. For this study, a total of 448 swab samples randomly collected from slaughter slab (112), slaughter floor (112), meat holding drums (112) and meat sales tables (112) were pre-enriched in nutrient broth at 37oC for 24hours. For E. coli O157 isolation, a loopful of each pre-enrichment broth was streaked on Cefixime Tellurite Sorbitol MaConkey (CT-SMAC) agar (Oxoid®). After 24 hours of incubation, colourless colonies were subcultured on plain MacConkey, incubated at 37oC for 24 hours and thereafter a rose pink colony was subcultured on Eosin Methylene Blue (EMB) agar and observed for colonies with greenish metallic sheen appearance. E.coli O157 was further confirmed using Oxoid O157 latex agglutination kit. For Salmonella isolation, a loopful of the pre-enrichment broth was inoculated into Selenith F broth and incubated at 42oC for 24hours after which loopful of the broth was streaked on Brilliance Salmonella agar (Oxoid®). After incubation at 37oC for 18-24hrs, purple colonies (presumptive Salmonella organism) were further subjected to biochemical tests for confirmation. The saccharytic activity of the organisms were verified using 13 sugars – sorbitol, glucose, cellobiose, sucrose, saccharose, arabinose, maltose mannitol, mannose, dulcitol, xylose, Inositol and lactose. The ability to produce heat-labile and heat-stable enterotoxin was determined using infant mouse assay. Antibiogram of the test isolates was determined using disc diffusion technique with the following 11 antimicrobial agents - chloramphenicol, ciprofloxacin, ceftazidime, gentamicin, cefotaxime, ampicillin, aztreonam, ceftriaxone, sulphamethoxazole/trimethoprim, enrofloxacine and streptomycin. The results of this study have shown that Escherichia coli O157 was isolated from 3(0.68%) of the 448 samples analysed while Salmonella species were recovered from 10(8.93%) of the samples. The E.coli O157 strains were isolated from the slaughter floor 1(0.9), slaughter slabs 1(0.9), and sales tables 1(0.9). Four (3.57%) of the salmonellae were obtained from meat holding drums, and 4 (3.57%) from sales tables while 2 (1.79%) were isolated from slaughter floor. All the E.coli O157 isolated fermented glucose, sucrose, lactose, mannitol, dulcitol, saccharose, arabinose, maltose, cellobiose, xylose and mannose and none fermented inositol and sorbitol. All the Salmonella isolated fermented glucose, mannitol, dulcitol, saccharose, cellobiose and mannose, while 80% fermented xylose and none fermented sucrose, inositol, lactose, arabinose and maltose. The three E.coli O157 and Salmonella isolates produced heat-labile enterotoxins as evidenced by death of all infected mice none of the E.coli O157 and Salmonella isolates produced heat-stable enterotoxins since the gut to carcass ratio produced ranged from 0.043-0.062. The three E.coli O157 isolates were sensitive to ceftriaxone, enrofloxacin, streptomycin, cefotaxime and gentamicin, but resistant to ampicillin and ceftazidime. All the Salmonella isolates were sensitive to enrofloxacin but resistant to ampicillin and ceftazidime. This study has shown that E.coli O157 and Salmonella are present on meat contact surfaces in Nsukka Slaughterhouse. This suggests that meat from these surfaces is likely to be contaminated by these organisms and may therefore predispose the consumer to bacterial food poisoning. The multiple antibiotic resistances displayed by zoonotic bacteria is of serious public health significance because infections in humans caused by these bacteria will be difficult to treat with the commonly available antibiotics.