Prevalence of antimicrobial-resistant Escherichia coli from raw vegetables in Lebanon

Abstract

Introduction: Fresh produce has been implicated in a number of documented outbreaks of foodborne illness caused by bacteria, viruses, and parasites. Shiga toxin-producing Escherichia coli (STEC) have been detected on vegetables, raising concerns about the prevalence of E. coli contamination in produce, which can take place at various points from farm to fork. This study aimed to detect the presence of STEC and multidrug-resistant (MDR) E. coli on fresh vegetables and water from different sources along the fresh produce supply chain in Lebanon.

Methodology: E. coli isolates (n = 60) were group serotyped using trivalent antisera (trivalent 1 [O111+O55+O26], trivalent 2 [O86+O119+O127], trivalent 3 [O125; O126; O128], and trivalent 4 [O114+O124+O142]) and tested for stx1 and stx2 genes by polymerase chain reaction (PCR) assay. Resistance to antimicrobial agents was determined using the disk diffusion method.

Results: The virulence genes stx1 and stx2 were not detected in any of the isolates. However, 60% of the isolates were MDR and predominantly observed in trivalent 2 (32%). It is postulated that the inadequate post-harvest washing contributed to transmission of antimicrobial-resistant E. coli at wholesale and retail levels. Fresh vegetables harbor MDR E. coli and their consumption poses risks of increasing the reservoir of antimicrobial resistance in the intestines of the Lebanese population.

Conclusions: Greater emphasis should be placed on vigilant sanitation measures at the consumption level, and effective national risk mitigation strategies are crucial to minimize fecal contamination in the early stages of production, particularly in the post-harvest washing processes.