Distribution, Diversity And Persistence Of Listeria Monocytogenes In Swine Slaughterhouses And Their Association With Food And Human Listeriosis Strains

Listeria monocytogenesis the etiological agent of listeriosis, a major foodborne disease and an important public health concern. Contamination of meat withL.monocytogenesoccurs frequently at the slaughterhouse. Our aims were; 1) to investigate the distribution ofL.monocytogenesin the processing areas of four swine slaughterhouses; 2) to describe the diversity ofL.monocytogenesstrains by pulsed-field gel electrophoresis; 3) to identify persistentL.monocytogenesstrains and describe their distribution; 4) to investigate the associations between persistence of strains and their following characteristics: detection in food isolates, detection in human clinical isolates, and the presence of benzalkonium chloride (BAC) resistance genes. Various operation areas within the four swine slaughterhouses were sampled on four occasions. A total of 2496 samples were analyzed, andL.monocytogeneswas successfully isolated from 243 samples. The proportion of positive samples ranged from 32 to 58% in each slaughterhouse and from 24 to 68% in each operation area. Fifty-eight different pulsotypes were identified and eight pulsotypes, present in samples collected during 4 visits, were considered persistent. The persistent pulsotypes were significantly more likely to be detected in food (P< 0.01, exact chi(2)) and human clinical cases (P< 0.01, exact chi(2)), respectively. Among pulsotypes harboring the BACbcrABCresistance cassette or theemrEmultidrug transporter gene, 42.8% were persistent compared to 4.5% for pulsotypes without these resistance genes (P< 0.01, exact chi(2)). Our study highlights the importance of persistentL.monocytogenesstrains in the environmental contamination of slaughterhouses, which may lead to repeated contamination of meat products. It also shows that the presence of disinfectants resistance genes is an important contributing factor.