Listeria monocytogenes at chicken slaughterhouse: Occurrence, genetic relationship among isolates and evaluation of antimicrobial susceptibility

The aims of this study were to verify the occurrence of Listeria monocytogenes in chicken at industrial slaughterhouse, the presence of virulence genes and genetic relationship among isolates, and evaluate the antimicrobial susceptibility. A total of 195 samples distributed in 36 carcasses after evisceration, 36 after chilling and 36 after packing, 43 carcasses cutting and 44 cuts after packaging, were collected. L. monocytogenes was found in 35 (17.9%) samples, especially in meat cuts, and samples collected after packing were the ones with higher rate of contamination (8.3%). Serotyping revealed the presence of three serovars: 1/2a (87%), 1/2c (8%) and 1/2b (5%). Macrorestriction profile with Apal at Pulsed-field gel electrophoresis (PFGE) showed 12 pulsotypes, and isolates from carcass and drumettes after packing and breast filet from cuts section showed high pulsotypes diversity. Regarding the profile of antimicrobial susceptibility, 100% of the isolates were sensitive to most antibiotics tested, except for clindamycin; 42% had intermediate resistance and 5% resistance. Isolation of L. monocytogenes in high levels in the chicken slaughtering line, as found in this study points to a potential risk associated, because the pathogen remains viable in the food throughout the cold chain that is used to commercialization. Still, the antimicrobial susceptibility monitoring is of interest of public health and our result shows that the isolates were susceptible to almost all antibiotics tested, indicating that treatment commonly used to control listeriosis infection is adequate.