Microbial Contamination and Antibiotic Resistance in Enteric Pathogens Isolated from Cooked Foods Sold in Eateries in Ado-Ekiti, Nigeria

Background: There are indications that some ready-to-eat or street vended foods are of low microbial quality with varying degree of contaminations. The contaminants may include antibiotic-resistant bacteria that may further be spread through consumption of such foods which has epidemiological and public health implications. This study therefore, was aimed at investigating the microbial quality of ready-to-eat cooked foods sold in eateries in Ado-Ekiti, Nigeria and to determine the susceptibility of the isolates to antibiotics.
Methods: We evaluated bacterial contamination of ready-to-eat cooked foods using total bacteria plate counts (TPC) and total coliform counts (TCC). Susceptibility of isolates to antibiotics was tested using the disc diffusion method.
Results: The overall mean TPC and TCC of cooked food samples ranged from 4.96±1.01 log10 cfu/g to 5.34±0.06 log10 cfu/g for both. There was no significant difference (≤ 0.05) in the overall mean TPC and TCC of the various cooked food samples from the three categories of sampling sites. The cooked foods examined were contaminated with a total of 129 enteric bacterial species belonging to 7 genera with E. coli (31.8%) being the most prevalent, followed by Klebsiella sp. (19.4%), Proteus sp. (17.1%), Salmonella (14.0%), Pseudomonas sp. (12.4%), Shigella sp. (3.8%) and Enterobacter sp. (1.6%) in that order. Resistance to antibiotics was very high (94.0%) and resistance to amoxicillin (89.1%) was the highest, and least to nalidixic acid (23.1%) while none of the isolates was resistant to ofloxacin. More than 50% of these isolates were resistant to six of the eight antibiotics tested and 26 different antibiotic resistance phenotypes were obtained. The most common phenotype observed was AMX/GEN/AUG. The results suggest that contaminated ready-to-eat (RTE) food sold in eateries can be a major source of antibiotic-resistant organisms in the study area.
Conclusion: Most of the food samples investigated was contaminated in varying degrees with pathogenic, opportunistic pathogenic bacteria and other bacterial indicators of contamination. There was an overall high rate of resistance to antibiotics with equally high rate of multiple antibiotic resistance (MAR) among the bacterial contaminants. This portent high risks of further spread of antibiotic resistance in the community and environment. Further study will hopefully help to determine the presence of resistance genes and or mode of resistance among the MAR organisms.