Comparison of survival of Campylobacter jejuni in the phyllosphere with that in the rhizosphere of spinach and radish plants

Campylobacter jejuni has been isolated previously from market produce and has caused gastroenteritis outbreaks linked to produce. We have tested the ability of this human pathogen to utilize organic compounds that are present in leaf and root exudates and to survive in the plant environment under various conditions. Carbon utilization profiles revealed that C. jejuni can utilize many organic acids and amino acids available on leaves and roots. Despite the presence of suitable substrates in the phyllosphere and the rhizosphere, C.jejuni was unable to grow on lettuce and spinach leaves and on spinach and radish roots of plants incubated at 33degreesC, a temperature that is conducive to its growth in vitro. However, C.jejuni was cultured from radish roots and from the spinach rhizosphere for at least 23 and 28 days, respectively, at 10degreesC. This enteric pathogen also persisted in the rhizosphere of spinach for prolonged periods of time at 16degreesC, a temperature at which many cool-season crops are grown. The decline rate constants of C. jejuni populations in the spinach and radish rhizosphere were 10- and 6-fold lower, respectively, than on healthy spinach leaves at 10degreesC. The enhanced survival of C. jejuni in soil and in the rhizosphere may be a significant factor in its contamination cycle in the environment and may be associated with the sporadic C. jejuni incidence and campylobacteriosis outbreaks linked to produce.