Watermelon poisoning

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.

Phenotypic and virulence traits of Escherichia coli and Salmonella strains isolated from vegetables and fruits from India

AIMS

The present study was designed to assess the phenotypic traits and virulence determinants of vegetable-/fruit-origin Escherichia coli and Salmonella strains.

METHODS AND RESULTS

A total of 520 fresh vegetables/fruits samples were analysed for the presence of E. coli, including Shiga toxin-producing E. coli (STEC), and Salmonella. The vegetable-/fruit-origin E. coli and Salmonella strains were further assessed for antimicrobial resistance, biofilm formation, extracellular matrix production and in vitro invasion/intracellular survivability assays. A total of 73 E. coli, including four STEC, and 26 Salmonella strains were recovered from vegetables/fruits in the present study. Most of the E. coli and Salmonella isolates were able to form biofilm with higher production of cellulose/curli-fimbriae. Furthermore, more resistance was observed in E. coli isolates (61·6%) than in Salmonella isolates (38·5%) against tested antimicrobials. Additionally, invasion/intracellular survival results showed that majority of the E. coli and Salmonella isolates were able to efficiently invade/replicate intracellularly in the human epithelial cells.

CONCLUSIONS

Our results demonstrate that vegetable-/fruit-origin E. coli and Salmonella significantly exhibited distinct phenotypic/virulence traits which could be linked to their plant-associated lifestyle with food safety issues.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study provides valuable baseline information that E. coli and Salmonella may use plants as an alternative host with significant clinical importance.