Isolation and Genetic Characterization of Gram-negative Bacteria from Different Fresh Retail Vegetables in Nigeria

Abstract

Aim: The proportion of food borne disease outbreaks as a result of contaminated products has increased over the years. In this study, the genetic characteristics of antibiotic resistant Gram-negative bacteria from different fresh retail vegetables in Okada, Edo state Nigeria was investigated. Place and Duration of Study: In April-May 2021, the study was carried out in the Department of Pharmaceutical Microbiology, Igbinedion University Okada Edo state Nigeria. Methodology: One hundred and eight isolates were isolated from sixteen different retail leafy and salad vegetable samples. Recovered isolates from samples were identified using standard microbiological techniques. Species identification for ten randomly selected isolates was performed by Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and ribosomal multilocus sequence typing (rMLST). Antimicrobial susceptibility testing was performed using the Kirby-Bauer method for 15 antibiotics. Isolates were characterized by whole genome sequencing (WGS). Results: Species identification using MALDI-TOF-MS and ribosomal MLST assigned the 10 randomly selected isolates to four different species. Identified isolates include Proteus mirabilis, Proteus vulgaris, Acinetobacter baumanii and Klebsiella quasipneumoniae. Out of the 10 randomly selected isolates, 60% (6/10) were antibiotic resistant in the antibiotic susceptibility test. WGS data confirmed the identities of the isolates except Proteus vulgaris identified as P. terrae. More than one resistant determinant was detected on the draft genome sequence of 80% (8/10) of the randomly selected isolates especially the regulatory system modulating antibiotic efflux CRP and the plasmid mediated quinolone resistant determinant qnrD1. Significantly, one Proteus mirabilis isolate was sensitive to the antibiotics in the phenotypic testing but had resistance determinants present. Conclusion: This study provides genomic characterization of antibiotic resistant isolates from retail leafy and salad vegetables from Nigeria. Further study is important to understand the public health importance of such resistance and the amount of risk posed to human health by these resistant organisms.