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

A continued rise in leafy green-linked outbreaks of disease caused by pathogenic Escherichia coli or Salmonella, 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 E. coli (DEC) and Salmonella isolates obtained from leafy greens from rural and urban areas of India. Of the collected samples (830), 14.1 and 6.5% yielded 117 E. coli (40 DEC and 77 non-DEC) and 54 Salmonella isolates, respectively. Among the DEC pathotypes, enteroaggregative E. coli was the most prevalent (10.2 %), followed by enteropathogenic E. coli (9.4 %), enteroinvasive E. coli (7.6 %) and enterohemorrhagic E. coli (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 Salmonella 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 Salmonella strains in the rural or urban areas of India.