Leafy greens as a potential source of multidrug-resistant diarrhoeagenic Escherichia coli and Salmonella

Abstract

A continued rise in leafy green-linked outbreaks of disease caused by pathogenic <i>Escherichia coli</i> or <i>Salmonella</i>, particularly strains exhibiting multidrug resistance (MDR), has emerged as a major threat to human health and food safety worldwide. Thus, the present study was conducted to examine antimicrobial resistance, including MDR, in diarrhoeagenic <i>E. coli</i> (DEC) and <i>Salmonella</i> isolates obtained from leafy greens from rural and urban areas of India. Of the collected samples (830), 14.1 and 6.5% yielded 117 <i>E. coli</i> (40 DEC and 77 non-DEC) and 54 <i>Salmonella</i> isolates, respectively. Among the DEC pathotypes, enteroaggregative <i>E. coli</i> was the most prevalent (10.2 %), followed by enteropathogenic <i>E. coli</i> (9.4 %), enteroinvasive <i>E. coli</i> (7.6 %) and enterohemorrhagic <i>E. coli</i> (6.8 %). Antimicrobial susceptibility testing of all bacterial isolates with respect to drugs categorized as critically or highly important in both human and veterinary medicine revealed moderate to high (30-90%) resistance for amoxicillin/clavulanic acid, ampicillin, gentamycin and colistin, but relatively low resistance (>30 %) for ciprofloxacin, trimethoprim/sulfamethoxazole and fosfomycin. Notably, all DEC and more than 90% non-DEC or <i>Salmonella</i> isolates were found to be multidrug-resistant to drugs of both human and animal importance. Overall, the results of the present study suggest that leafy greens are potential reservoirs or sources of multidrug-resistant DEC and <i>Salmonella</i> strains in the rural or urban areas of India.