Listeria monocytogenes in poultry: Detection and strain characterization along an integrated production chain in Italy

In this study, thirteen batches of broiler chicken from an integrated Italian poultry company were investigated for the detection of Listeria monocytogenes. The prevalence was evaluated in faeces samples at farm level and after transport, caecal contents and carcass neck skin from 2 slaughterhouses (M1 and M2), for a total of 2080 samples, throughout a 27-month period. No positive results were recorded in faeces, while the overall prevalence of contamination in carcass neck skin was 26.7%. Then, 123 isolates out of 139 positive skin samples, with the prevalent serotypes 4b (76%) and 1/2b (94%) from slaughterhouses M1 and M2 respectively, were PFGE characterized, showing the presence of 18 different pulsotypes and 8 genetic clusters. The same pulsotypes were found in carcasses from different farms, but slaughtered in the same abattoir, highlighting the environmental origin of contamination. The persistence of the pathogen over long time seemed to be very likely, considering that undistinguishable pulsotypes were found in carcasses slaughtered in the same slaughterhouse after periods up to 18 months long. The implementation of cleaning and sanitation at slaughterhouse level could represent the main factor for the control of such pathogen in the poultry meat processing line. •Faeces and carcass neck skin samples analyzed for Listeria monocytogenes.•Detected strains belonged to serogroups IIc, IVb and IIa.•Persistence confirmed by the same pulsotypes found in different sampling sessions.•Contamination linked to the environment at slaughterhouse level.