Isolation and identification of β-lactamase producing Pseudomonas spp. in ready-to-eat raw vegetables

Contamination of antibiotic-resistant bacterial pathogens in raw food is becoming an increased health risk in numerous countries, including Vietnam where raw herbs and vegetables are used daily in many dishes as a flavor enhancer and a source of vitamin and nutrients. However, raw vegetables can also be a reservoir of various foodborne pathogens such as Pseudomonas spp. and Enterobacteriaceae. In this study, we evaluated the extent of Pseudomonas spp. contamination in 180 ready-to-eat (RTE) vegetables samples from restaurants in Hanoi, examined their antibiotic susceptibility profiles and determined the ability to produce β-lactamase enzymes of Pseudomonas spp. strains. Our results showed that 21.67 % (n = 39) of ready-to-eat vegetables samples in Hanoi were contaminated with Pseudomonas spp.. Of those, sixteen samples were determined to be β-lactamase producing strains including Pseudomonas putida, P. mendocina and P. aeruginosa. Further analysis revealed six strains (37.50 %) producing extended spectrum β-lactamase (ESBL) enzyme, five strains (31.25 %) producing ampC β-lactamase enzyme and five strain (31.25 %) producing both ESBL and ampC β-lactamases. It can be concluded that ready-to-eat vegetables in Hanoi would be a source of contamination of β-lactamase producing Pseudomonas spp. that could pose a threat to public health in the community.