Isolation of Yersinia enterocolitica and Listeria monocytogenes from fresh vegetables in Saudi Arabia and their growth behaviour in some vegetable juices.

Abstract

The occurrence of Yersinia enterocolitica and Listeria monocytogenes in fresh market vegetables in Saudi Arabia was investigated. The two organisms were isolated from cabbage, carrot, cucumber, lettuce, potato, and radish. The incidence of Y. enterocolitica on each of these vegetables was higher than that of L. monocytogenes. The isolation rate of both genera was higher on underground crops than on the other crops. The Y. enterocolitica isolates were sensitive to chloramphenicol, streptomycin and tetracycline but resistant to erythromycin, ampicillin, penicillin, and vancomycin, whereas the L. monocytogenes isolates were sensitive to all of the above antibiotics with the exception of tetracycline to which it experienced some resistance. The ability of the above two organisms to survive and/or grow in raw juices of potato, carrot and lettuce and in potassium phosphate buffer was investigated. The viable counts were always higher in samples incubated at 26°C than at 4°C. Y. enterocolitica was able to grow both in the buffer and juices; best growth occurred in lettuce juice and poorest growth occurred in carrot jfiice. L. monocytogenes grew in lettuce juice and to a lesser degree in potato juice but its number decreased in carrot juice and in the buffer.