Antibiotic susceptibility of escherichia coli O157:H7 and Salmonella sp. in water, sediment and irrigated vegetables from rivers in Ilorin metropolis, Nigeria

Abstract

The assessment of the incidence of Escherichia coli and Salmonella sp. in irrigated fresh fruits and vegetables, and its nexus with the irrigation water is essential to prevent transfer of pathogens to humans. This study aimed at the detection and antibiogram profiling of E. coli O157:H7 and Salmonella sp. in the three prominent rivers (Asa, Oyun and Afon) in Ilorin metropolis. Ninety samples of water, sediment, and irrigated vegetables were collected over a period of 12 weeks and analyzed for total heterotrophic bacteria, E. coli and Salmonella/Shigella populations. Antibiotic susceptibility profiling of E. coli O157:H7 and Salmonella sp. was carried out using the disc diffusion method. The heterotrophic bacteria populations were mostly higher in sediments (3.90 x 105 ± 1.15 x 105 – 2.35 x 106 ± 8.75 x 105 cfu/g) than in waters (5.60 x 104 ± 7.00 x 103 – 2.16 x 105 ± 2.00 x 104 cfu/ml) obtained from the same point. The high counts of E. coli (0 – 1.53 x 103 ± 5.65 x 102 cfu/g) and Salmonella/Shigella sp. (0 – 1.59 x 103 ± 6.95 x 102 cfu/g) on the irrigated vegetables may be due to the observed direct contamination from polluted water. All E. coli O157:H7 isolates showed extensive drug-resistance while Salmonella sp. exhibited a combination of extensive and pan-drug resistance to standard antibiotics belonging to penicillins, aminoglycosides, macrolides, and fluoroquinolones. The occurrence of extensively drug-resistant strains of these pathogens in the environment portend a great risk to public health and can increase the chances of an outbreak of fatal infections among the human population.