Detection and antibiotic susceptibility of coliform bacteria in fresh vegetables

We have determined the presence of coliform bacteria, as well as their antibiotic susceptibilities, in fresh vegetables. Ten samples of six different fresh vegetables (two kinds of tomato, three of lettuce, and one of carrot) purchased from supermarkets and greengrocer’s shops in Valencia city (Spain) were analyzed. Coliforms were isolated in 50% out of the 60 samples. The identified isolates (n: 45) included mainly species belonging to Klebsiella (n: 15) , Enterobacter (n: 20), and other genera, and only one was identified as Escherichia coli. Most isolates were resistant to ampicillin, and to amoxicillin/clavulanic acid; although resistances to other chemoterapeutic agents were sporadic, seven isolates showed multiresistance to three/four/five agents. Therefore, microbial contamination of these products with opportunistic pathogens can be considered as a food safety concern, as consumption of fresh vegetables may represent a potential risk for the consumer health, particularly in debilitated or immunocompromised individuals.