Detection of Listeria in crawfish processing plants and in raw, whole crawfish and processed crawfish (Procambarus spp.)

The foodborne pathogen Listeria monocytogenes represents a major concern to the food industry and particularly to producers of ready-to-eat (RTE) foods because of the severity of human listeriosis infections and because of the ubiquitous nature of this organism. Although several studies on the prevalence and sources of L. monocytogenes in various RTE seafoods have been conducted, limited information is available on the presence and potential sources of this organism in RTE crawfish products. We thus monitored the presence of L. monocytogenes and other Listeria spp. in the processing environment, in raw, whole crawfish, and in cooked crawfish meat from two processing plants. Samples were collected from the two plants throughout one crawfish season (April to June 2001) at 5 and 8 separate visits, respectively. At each visit, 6 raw, whole crawfish, 6 finished product samples (crawfish meat), and 14 mid- or end-of-processing environmental sponge samples were collected and tested for L. monocytogenes and Listeria spp. Of the 337 samples tested, 31 contained Listeria spp. Although Listeria innocua was the predominant Listeria spp. found (20 samples), four samples were positive for L. monocytogenes. L. monocytogenes was detected in three raw material samples and in one environmental sample. Listeria spp. were found in 29.5% of raw, whole crawfish (n = 78) and in 4.4% of environmental samples (n = 181) but in none of the finished product samples. Among the environmental samples, Listeria spp. were found in 15.4% of the drains (n = 39) and in 5.1% of the employee contact surfaces (gloves and aprons) (n = 39) but in none of the samples from food contact surfaces. Even though a high prevalence of Listeria spp. was detected on raw materials, it appears that the heat treatment during the processing of crawfish and the practices preventing postprocessing recontamination can significantly reduce Listeria contamination of RTE crawfish meat.