Evaluation of the antibiotic resistance profiles of bacterial isolates from wet and dry grinding machines in Benin city, Nigeria

Abstract

The contamination of grinding machines with microbes can enable transmission of food pathogens especially in the open markets where the standards of hygiene are minimal. This study aimed to assess the bacteriological quality and antibiotic resistance of the wet and dry grinding machines in selected markets in Benin City, Nigeria. Swab samples of the machines were obtained aseptically and subjected to standard microbiological methods. The total heterotrophic bacterial count ranged from 3.17 ± 0.28 x 10 cfu/cm² and 5.10 ± 0.04 x 10 cfu/cm² for the dry and wet grinding machines. The highest bacteria count was obtained in the wet grinding machine in Uselu market. The total coliform count varied between 1.16 ± 0.08 x 10 cfu/cm and 1.64 ± 0.20 x 10 CFU/cm. A total of five bacterial genera were isolated they include Bacillus spp., Klebsiella spp., Staphylococcus aureus, Enterobacter spp. and Citrobacter spp., with percentages of 26.47%, 23.52%, 20.60%, 17.65% and 11.76%, respectively. Phenotypic virulence test of the bacteria isolates indicated that Klebsiella spp., Citrobacter spp., Staphylococcus aureus and Enterobacter spp. had DNase activity. Lipase activity was observed in all isolates except Enterobacter spp. The isolated bacteria showed resistance to colistin, cephalexin and tetracycline but sensitive to ciprofloxacin, gentamycin and clindamycin. The multiple antibiotic resistance of the pathogens ranged from 0.50-0.87 CFU/cm². These findings demonstrate that grinding machines serves as reservoir for the transfer of pathogenic and multi-drugs resistance bacteria isolates, emphasizing the need for routine microbial monitoring to reduce the risk of foodborne disease.