Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2004
Publication Date: 5/12/2004
Citation: Byrne, C.M., Call, J.E., Wallace, F.M., Plumblee, J., Adams, E.S., Rossman, M.L., Cray, P.J., Luchansky, J.B. 2004. Incidence and characterization of Listeria monocytogenes in beef processing plants in the United States. Meeting Abstract. P.18. Interpretive Summary:
Technical Abstract: The aim of this study was to determine the incidence and types of Listeria monocytogenes in beef processing environments in the United States. Five thousand carcass and environmental samples were collected from two geographically distinct beef processing plants between April and October of 2002 and analysed for the presence of the pathogen. All isolates were subsequently characterized by pulsed field gel electrophoresis (PFGE) and antibiotic susceptibility testing. We established a 3% prevalence of L. monocytogenes in environmental and animal-related (hide and carcass) samples (141/5000) in the two beef processing plants. There was a marked geographical difference in the prevalence of the pathogen, with 96% of L. monocytogenes-positive samples being isolated from one plant. Niches for L. monocytogenes within the two beef processing environments were identified, with the pathogen predominantly isolated from hides (69%) and product contact surfaces, such as belts (17%). Analyses of the L. monocytogenes samples by PFGE revealed 59 distinct profiles. Typically, each positive sample contained only one strain of L. monocytogenes. However, in some samples, there were several strains of the pathogen, as indicated by different PFGE profiles. In most instances, a specific L. monocytogenes strain was only isolated at one particular time period and was not recovered thereafter. In some cases, the same strain was found across several months of sampling, demonstrating the persistence of the pathogen in the processing environment. With the exception of clindamycin and tetracycline, isolates were sensitive to all other antimicrobial agents tested, including ampicillin, gentamicin, trimethoprim/sulfamethoxazole, erythromycin, vancomycin and ciprofloxacin, which are the antimicrobials commonly used to treat listeriosis. The present study aids our understanding of the ecology of L. monocytogenes by identifying the prevalence, sources, clonality and antimicrobial susceptibility of the pathogen within the beef processing environment. Based on this information, modifications to the environment may be made to reduce the prevalence of the pathogen, which will ultimately decrease the likelihood of food-borne illnesses.