title: Occurrence, antibiotic resistance and molecular characterization of Listeria monocytogenes in the beef chain in the Republic of Ireland.
abstract: This study investigated the occurrence, concentration and key characteristics of Listeria monocytogenes in beef chain samples (n=1100) over a 2-year period (July 2007-June 2009). Listeria monocytogenes was isolated from bovine hides (27%), pre-chill carcasses (14%) and ground beef (29%), but not from ready-to-eat (RTE) beef. The concentration of the pathogen in the majority (95%) of contaminated samples was low and detected by enrichment only. The highest concentrations recovered (100-200 CFU/g) were in ground beef samples. The most commonly isolated serotype group was 1/2a (58%) followed by 4b (12%), 1/2b (10%) and 1/2c (6%). A small portion (<5%) isolates had demonstrated resistance to key anti-microbials including ampicillin, vancomycin and gentamycin which are recommended treatment options for listeriosis. Pulsed-field gel electrophoresis showed indistinguishable profiles for a number of isolates recovered from the hide and carcass (after slaughter and dressing) of the same animals, highlighting the role of hides as a source of contamination. Equally, indistinguishable pulsotypes for isolates recovered at different stages and time points (up to 6 months apart) in the beef chain demonstrated the persistence of specific clones in the factory, process and distribution environments. Overall, the study demonstrated a high prevalence of clinically significant L. monocytogenes entering and progressing along the beef chain and highlights the needs to control cross-contamination during beef processing and distribution and the need for thorough cooking of raw beef products.
authors: Teagasc Food Research Centre, Dublin, Ireland; School of Health Sciences, University of Ulster, Jordanstown, UK.
authors: B K
authors: BK
authors: Khen
authors: O A
authors: OA
authors: Lynch
authors: J
authors: J
authors: Carroll
authors: D A
authors: DA
authors: McDowell
authors: G
authors: G
authors: Duffy
mesh_terms: D000003:Abattoirs; D000818:Animals; D002417:Cattle / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D008089:Listeria monocytogenes / Q000187:drug effects / Q000302:isolation & purification; D008088:Listeriosis / Q000453:epidemiology; D008460:Meat / Q000382:microbiology*; D016133:Polymerase Chain Reaction
keywords: Listeria monocytogenes; beef; carcass; ground meat; hide