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Occurrence, Antibiotic Resistance and Molecular Characterization of Listeria monocytogenes in the Beef Chain in the Republic of Ireland
Author(s) -
Khen B. K.,
Lynch O. A.,
Carroll J.,
McDowell D. A.,
Duffy G.
Publication year - 2015
Publication title -
zoonoses and public health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.87
H-Index - 65
eISSN - 1863-2378
pISSN - 1863-1959
DOI - 10.1111/zph.12106
Subject(s) - listeria monocytogenes , serotype , listeria , ampicillin , biology , food science , food contaminant , contamination , antibiotic resistance , raw meat , veterinary medicine , antibiotics , microbiology and biotechnology , bacteria , medicine , ecology , genetics
Summary 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.