Antimicrobial‐Resistance Genetic Markers Among Multidrug‐Resistant Enterobacteriaceae and <i>Acinetobacter</i> spp. From Vegetable Market Chains in Ethiopia

Abstract

Occurrence of antimicrobial resistance (AMR) and antimicrobial resistance genes (ARGs) in Enterobacteriaceae and <i>Acinetobacter</i> spp. within agricultural environments represents a growing global health concern. Vegetables have been increasingly recognized as reservoirs of multidrug-resistant (MDR) pathogens. The study aimed to detect ARGs in Enterobacteriaceae and <i>Acinetobacter</i> spp. from vegetable market chains and assess the clonal relationship of isolates. Antimicrobial susceptibility testing was conducted for a total of 170 isolates obtained from vegetables, irrigation water, and soil samples, and ARGs were detected by polymerase chain reaction (PCR). Conjugation assay was conducted, and genetic relatedness among bacterial isolates was assessed by ERIC-PCR at a 70% similarity cut-off. High resistance rate was observed to sulfamethoxazole/trimethoprim (34.0%) and cefepime (28.8%). Phenotypically, 23.5% (40/170) of isolates were extended spectrum <i>β</i>-lactamase (ESBL) producers and from meropenem resistance isolates 60% (6/10) were carbapenemase producers. Genes encoding for broad-spectrum <i>β</i>-lactamases were detected in 30% (12/40) tested isolates, including those from irrigation water (50%; 3/6), vegetables (30.7%; 8/26) and soil (12.5%; 1/8) samples. Carbapenemase genes were detected in carbapenem resistant isolates from irrigation water (80%; 4/5) and vegetable (40%; 2/5) samples. The most prevalent <i>β</i>-lactamase genes identified were <i>bla</i>CTX-M and AmpC (<i>n</i> = 5 each), <i>bla</i>SHV (<i>n</i> = 2), and <i>bla</i>TEM (<i>n</i> = 1). Among carbapenemase genes <i>bla</i>NDM (<i>n</i> = 6) was frequently detected, and <i>bla</i>KPC and <i>bla</i>VIM in a single isolate each. A <i>sul1</i> gene was identified in 33.3% of isolates from vegetable and 15.3% of those from irrigation water. Four transconjugants were detected and successfully transferred resistance genes with conjugation frequency ranging from 1.48 × 10^-5 to 3.3 × 10^-6 out of 15 tested. ERIC-PCR revealed diverse clonal lineages, although <i>K. pneumoniae</i>, <i>K. aerogenes</i> and <i>E. coli</i> isolates from vegetables and irrigation water displayed close genetic similarity (100%, 70%, and 78%), respectively. This study provided the first evidence of diverse <i>β</i>-lactamases and carbapenemase-producing Enterobacteriaceae in Ethiopian vegetable market chains. These findings highlight the need for continued surveillance and improved food safety measures to mitigate potential public health risks posed by antimicrobial-resistant pathogens in the food supply chain.