A bulletin for the Australian Food Industry November 2001
Contents: Food allergies and food sensitivities | Pathogens in fresh fruit and vegetables | Decontamination of fresh fruit and vegetables | Preservation of vegetables in oil and vinegar
Pathogens in fresh fruit and vegetables
A recent outbreak of Salmonella bovismorbificans infection in Queensland confirms that foodborne infections are being associated with a wider range of foods.
In this outbreak reported in ProMED-mail, 31 August 2001, total of 41 cases of this particular serotype were notified to Queensland Health between May and June of this year. A case control study identified a significant association between illness and having eaten a particular takeaway food product from a takeaway business.
Subsequently, S. bovismorbificans was cultured from a swab of food residue taken from behind the blade of a shredder used for slicing iceberg lettuce only. The shredded lettuce was the primary component used in the production of a salad mix. The salad mix was one of the ingredients for the takeaway food product implicated in the epidemiological study. The source of contamination of the lettuce was not identified but no further cases were reported when the food product was withdrawn from sale.
We have discussed foodborne illness and fresh produce previously (Food Safety & Hygiene September 2001, May 2000, November 1999) and although documented cases in Australia are few, reports coming from the USA and UK indicate a growing problem.
In England, this year, nine cases of infection with S. newport with a link to a salad item were identified as part of a survey of retail prepared pre-packed salad vegetables (ProMED-mail 29 June 2001).
Last year an outbreak of S. typhimurium DT104 infection linked to consumption of lettuce from catering outlets affected 361 people and a similar Europe-wide outbreak was reported (Microbiology Newsletter June 2001).
The same picture emerges from the USA. California Department of Health services records indicate that in the past decade an increasing number of foodborne outbreaks (36 per cent) were associated with fresh fruit and vegetables (California Agriculture 54 (5) 2000 3). On the national level, 164 foodborne outbreaks due to fresh produce, excluding salads, were reported from 1973 to 1997. In addition to outbreaks associated with specific fruit and vegetable items, there were 202 outbreaks associated with salads (California Agriculture 54 (5) 2000 54-61). Two-thirds of those were caused by unknown agents with Norwalk-like viruses suspected as a major cause. This implies contamination of the salad by a food handler although the source could be as far back in the production chain as the growing area.
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