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PRODUCE AS A VECTOR FOR CAMPYLOBACTERIOSIS
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The Organism, Its Disease and Habitat:

Campylobacter jejuni is a zoonotic organism present in the gastrointestinal tract of a large number of warm-blooded animals. Campylobacter jejuni and C. coli cause an estimated 2.4 million cases of human illness per year, of which 80% are foodborne, making it the leading cause of bacterial foodborne illness, even surpassing Salmonella as a diarrhea-causing pathogen (1, 11). Potential reservoirs of the organism include poultry, wild birds, cows, swine, sheep, horses, rabbits, rodents and domestic pets (12,15).  As a fecal organism, C. jejuni is present in sewage (14), sewage effluents (8) and untreated waters (17).  Soil, through which Campylobacter-contaminated water has passed, can also contain the organism. In a study of the survival of pathogens during mesophilic anaerobic digestion of animal manure (i.e. prior to sewage treatment), Kearney et al. (9) found that C. jejuni was remarkably resistant to treatment.  The organism was approximately 13-times more resistant to anaerobic digestion than Salmonella typhimurium.  Thus, C. jejuni represents a paradox (15).  In spite of its "fragility", the organism can be found in the environment, particularly in water, and while it may not grow, it can survive.  More information about the paradoxical behavior of C. jejuni can be found in an article authored by Solomon and Hoover (15).

Its Fragile Nature 

C. jejuni is widely thought of as an environmentally-fragile organism, indicating that it would not persist for long periods of time on fruits and vegetables.  It is sensitive to drying, acidity, freezing, salting, osmotic stress, oxygen (>5%), chemical rinses and disinfectants.  C. jejuni does not grow below 30?C, is a poor competitor and is very sensitive to heat (D55C=1 min).  Therefore, this susceptibility to a number of environmental conditions would suggest its survival in properly stored and processed foods is unlikely (12,15).

A Relatively Rare Contaminant of Produce

While the literature is sparse, it appears that C. jejuni may be a rare contaminant of produce.  A recent review surveying pathogenic microorganisms associated with fresh produce indicates that C. jejuni was isolated only from retail mushrooms.  Out of 200 mushroom samples, three (1.5%) were positive for C. jejuni (5,7).  An United Kingdom study (11) indicated that imported unprepared whole lettuce (n = 151) obtained from retail outlets were free from Campylobacter, as well as being free of Salmonella and Escherichia coli O157:H7.  In a study comparing the presence of C. jejuni on raw vegetables obtained from farmers' outdoor markets (n = 533) or supermarkets (n = 1031), only vegetables from the farmers' markets were positive, whereas supermarket samples were Campylobacter-free. The incidence of Campylobacter-contaminated vegetables averaged 1.7% (13). Vegetables from farmers' markets are more likely to be produced and stored under less sanitary conditions than vegetables obtained from supermarkets. To minimize microbial hazards, vegetables, especially those from farmers' markets, should be thoroughly washed and rinsed before eating.

Produce - An Uncommon Vehicle for Infection

Produce is not a common vehicle for Campylobacter enteritis, since few incidents in which vegetables have been involved have been reported. An outbreak of campylobacteriosis was shown to be due to ingestion of a cabbage-beef stew by school children in Germany.  Since the stew was cooked, cross-contamination with C. jejuni was probably a major contributing factor to the outbreak (16).  Similarly, cross-contamination of salad lettuce by raw chicken led to a small outbreak of campylobacteriosis in an Oklahoma restaurant in 1996 (2).  Harris et al. (7) analyzed a number of dietary histories of individuals who had campylobacteriosis and determined that out of a number of vegetable items, only mushrooms were significantly associated with C. jejuni enteritis cases.  A single outbreak of Campylobacter enteritis due to contaminated fruits or vegetables was reported for the period 1973-1987 (4) and another outbreak due to fruits or vegetables contaminated with Campylobacter was reported during 1989 (3). Details of these two outbreaks were not given.

Leafy vegetables and root crops irrigated with untreated water or grown in soils contaminated with Campylobacter would be expected to contain C. jejuni. The use of C. jejuni-contaminated water to wash produce or fruit may lead to depositing the organism on the surface of the product.  Thus, the facts that waterborne outbreaks of campylobacteriosis occur (17) and that C. jejuni is present in sewage and water indicate that produce or fruit irrigated or washed with C. jejuni-contaminated water will allow the entrance of the organism into the food chain.

Microbial Food Safety Research Unit

The Microbial Food Safety Research Unit (MFSRU) within the USDA/ARS Eastern Regional Research Center maintains a commitment to high quality basic and applied research on pathogenic bacteria to ensure a safe food supply.  As part of this research program, the MFSRU addresses strategies to control and detect Campylobacter jejuni in food.  Examples of research include:

References:

  1. Altekruse, S. F., N. J. Stern, P. I. Fields and D. L. Swerdlow 1999  Campylobacter jejuni an emerging foodborne pathogen. Emerg. Infect. Dis. 5: 28-35.
  2. Anon. 1998 Outbreak of Campylobacter enteritis associated with cross-contamination of food Oklahoma, 1996. MMWR 47: 129-131.
  3. Bean, N. H., J. S. Goulding, C. Lao and F. J. Angulo 1996 Surveillance for foodborne-disease outbreaks United States, 1988-1992. MMWR 45, #SS-6.
  4. Bean, N. H. and P. M. Griffin 1990 Foodborne disease outbreaks in the United States, 1973-1987: pathogens, vehicles, and trends. J. Food Prot. 53: 804-817.
  5. Beauchat, L. R. 1996 Pathogenic microorganisms associated with fresh produce. J. Food Prot. 59: 204-216.
  6. Doyle, M. P. and J. L. Schoeni 1986 Isolation of Campylobacter jejuni from retail mushrooms. Appl. Environ. Microbiol. 51: 449-450.
  7. Harris, N. V., T. Kimball, N. S. Weiss and C. Nolan 1986 Dairy products, produce and other non-meat foods as possible sources of Campylobacter jejuni enteritis. J. Food Prot. 49: 347-351.
  8. Hudson, J. A., C. Nicol, J. Wright, R. Whyte and S. K. Hasell 1999 Seasonal variation of Campylobacter types from human cases, veterinary cases, raw chicken, milk and water. J. Appl. Microbiol. 87: 115-124.
  9. Kearney, T. E., M. J. Larkin, J. P. Frost and P. N. Levett 1993 Survival of pathogenic bacteria during mesophilic anaerobic digestion of animal waste. J. Appl. Bacteriol. 75: 215-219.
  10. Little, C., D. Roberts, E. Youngs and J. de Louvois 1999 Microbiological quality of retail imported unprepared whole lettuce: a PHL Food Working Group study. J. Food Prot. 62: 325-328.
  11. Mead, P.S., L. Slutsker, V. Dietz, L.E. McCraig, J.S. Bresee, C. Shapiro, P.M. Griffin, and R.V. Tauxe. 1999. Food-related illness and death in the United States. Emerg. Infect. Dis. 5: 607-625.
  12. Nachamkin, I. 1997 Campylobacter jejuni, p. 159-170.  In M. P. Doyle, L. R. Beuchat and T. J. Montville (eds.), Food Microbiology: Fundamentals and Frontiers, ASM Press, Washington, DC, USA.
  13. Park, C. E. and G. W. Sanders 1992 Occurrence of thermotolerant campylobacters in fresh vegetables sold at farmers' outdoor markets and supermarkets. Can. J. Microbiol. 38: 313-316.
  14. Park, R. W. A., P. L. Griffiths and G. S. Moreno 1991 Sources and survival of campylobacters: relevance to enteritis and the food industry. J. Appl Bacteriol. 70 (Suppl.): 97S-106S.
  15. Solomon, E. B. and D. G. Hoover 1999 Campylobacter jejuni: a bacterial paradox. J. Food Safety 19: 121-136.
  16. Steffen, W., H. Mochmann, I. Kontny, U. Richter, U. Werner and O. el Naeem 1986 A food-borne infection caused by Campylobacter jejuni serotype Lauwers 19. Zentralbl. Bakteriol. Mikrobiol. Hyg. [B] 183: 28-35. Abstract.
  17. Thomas, C., H. Gibson, D. J. Hill and M. Mabey 1999 Campylobacter epidemiology: an aquatic perspective. J. Appl. MIcrobiol. (Suppl.) 85: 158S-177S.

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Author: James L. Smith, Ph.D. (James.Smith@ars.usda.gov)
Editor: Mark L. Tamplin, Ph.D.