Occurrence and plasmid profiles of multidrug-resistant Enterobacteriaceae isolated from hawked soymilk samples in the Polytechnic of Ibadan Community, Nigeria

This study was conducted to determine the occurrence, antibiotic susceptibility pattern, and plasmid profile of multidrug-resistant (MDR) Enterobacteriaceae isolated from soymilk hawked in the Ibadan Polytechnic Community, Nigeria. Bacterial isolation and identification were performed using a culture-dependent method and biochemical characterization, respectively, while antibiotic susceptibility was tested using the disk diffusion method. Plasmid analysis and curing were performed using standard procedures. The results revealed the following occurrence rate of bacterial species in soymilk samples collected from all axes (South, North, East, West, and Central) of Ibadan Polytechnic: Citrobacter spp., 64%; Klebsiella spp., 7%; Enterobacter spp., Escherichia coli, and Serratia spp., 6% each; Proteus spp., 5%; and Salmonella spp. and Shigella spp., 3% each. The highest heterotrophic bacterial count of 9.3 × 10(3) CFU/ml was recorded at Ibadan Polytechnic North and South, while the least count (3.2 × 10(7) CFU/ml) was recorded at Ibadan Polytechnic Central. The highest enteric bacterial count of 1.3 × 10(3) CFU/ml was recorded in soymilk samples from Ibadan Polytechnic Central, while the least count of 1.7 × 10(7) CFU/ml was recorded in soymilk samples from Ibadan Polytechnic North. A total of 26% of the isolates showed resistance to cefpodoxime, while 88% of the isolates were susceptible to trimethoprim-sulfamethoxazole. Four of the MDR isolates possessed plasmid bands ranging from 6 to 1 with molecular weights from 2.7 to 17.2 kbp. Enterobacteriaceae such as isolates O14 (Klebsiella spp.) and B10 (E. coli ) retained their resistance to antibiotics even after removal of plasmids, while isolates S13 (Citrobacter spp.) and O4 (Shigella spp.) were susceptible to some antibiotics after curing. Conclusively, soymilk sold in the sampled areas was highly contaminated with Enterobacteriaceae, thereby indicating poor hygiene standards of soymilk production.