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Survey for psychrotrophic bacterial pathogens in minimally processed lettuce
E A Szabo1, K J Scurrah, J M Burrows
1Food Science Australia, North Ryde Laboratory, New South Wales and The Cooperative Research Centre for International Food Manufacture and Packaging Science, Hawthorn, Victoria, Australia. lisa.szabo@foodscience.afisc.csiro.au
Letters in Applied Microbiology
|June 10, 2000
Summary
Minimally processed lettuce frequently harbors bacteria. While Listeria monocytogenes was found in some samples, most Yersinia enterocolitica and Aeromonas isolates showed low pathogenic potential.
Area of Science:
- Food Microbiology
- Food Safety
- Public Health
Background:
- Minimally processed foods, like packaged lettuce, are susceptible to microbial contamination.
- Ensuring the safety of ready-to-eat produce is crucial for public health.
Purpose of the Study:
- To assess the microbiological quality of packaged lettuce.
- To identify and characterize potentially pathogenic bacteria, including Listeria, Aeromonas, and Yersinia species, in these products.
Main Methods:
- Collected 120 packaged lettuce samples over 8 months.
- Performed total aerobic plate counts.
- Screened for Listeria, Aeromonas, and Yersinia species.
- Assessed the virulence potential of Yersinia enterocolitica isolates using various genetic and biochemical markers.
Main Results:
- Aerobic plate counts ranged from 10^3 to 10^9 colony forming units (cfu)/g.
- Listeria monocytogenes was detected in 3 samples.
- Yersinia enterocolitica (71 samples) and Aeromonas species (66 samples) were frequently isolated.
- Most Y. enterocolitica isolates lacked key virulence markers.
Conclusions:
- Packaged lettuce can harbor significant bacterial loads.
- While common pathogens were detected, most Yersinia enterocolitica isolates from lettuce appear to have limited pathogenic potential.
- The public health risk associated with Aeromonas species in lettuce requires further investigation.