Prevalence and Persistence of Multidrug-Resistant Yersinia enterocolitica 4/O:3 in Tonsils of Slaughter Pigs from Different Housing Systems in Croatia.

Yersinia enterocolitica is one of the priority biological hazards in pork inspection. Persistence of the pathogen, including strains resistant to antimicrobials, should be evaluated in pigs from different housing systems for risk ranking of farms. In this 2019 study, tonsils were collected from 234 pigs, of which 69 (29.5%) were fattened on 3 big integrated farms, 130 (55.5%) on 10 medium-sized farms, and 35 (15%) on 13 small family farms. In addition, 92 pork cuts and minced meat samples from the same farms were tested for the presence of Y. enterocolitica using the culture method. Phenotypic and genetic characteristics of the isolates were compared with previously collected isolates from 2014. The overall prevalence of Y. enterocolitica in pig tonsils was 43% [95% CI 36.7−49.7]. In pigs from big integrated, medium-sized, and small family farms, the prevalence was 29%, 52%, and 40%, respectively. All retail samples of portioned and minced pork tested negative for pathogenic Y. enterocolitica, likely due to high hygienic standards in slaughterhouses/cutting meat or low sensitivity of culture methods in these matrices. The highest recovery rate of the pathogen from tonsils was found when alkali-treated PSB and CIN agar were combined. The biosecurity category of integrated and medium farms did not affect the differences in prevalence of Y. enterocolitica (p > 0.05), in contrast to family farms. Pathogenic ail-positive Y. enterocolitica biotype 4 serotype O:3 persisted in the tonsils of pigs regardless of the type of farm, slaughterhouse, and year of isolation 2014 and 2019. PFGE typing revealed the high genetic concordance (80.6 to 100%) of all the Y. enterocolitica 4/O:3 isolates. A statistically significant higher prevalence of multidrug-resistant Y. enterocolitica 4/O:3 isolates was detected in the tonsils of pigs from big integrated farms compared to the other farm types (p < 0.05), with predominant and increasing resistance to nalidixic acid, chloramphenicol, and streptomycin. This study demonstrated multidrug resistance of the pathogen in pigs likely due to more antimicrobial pressure on big farms, with intriguing resistance to some clinically relevant antimicrobials used in the treatment of yersiniosis in humans.

Tracing of Listeria monocytogenes Contamination Routes in Fermented Sausage Production Chain by Pulsed-Field Gel Electrophoresis Typing.

In this study, the presence of Listeria monocytogenes was assessed along the production process of fermented sausages in a small-scale facility. Following the isolation of the pathogen from the final product (ISO 11290-1), retrospective sampling was performed during the production of a new batch of sausages, including raw materials, casings, additives, sausage mixtures, sausages during fermentation, and environmental samples. L. monocytogenes was recovered from the following sampling points: the defrosting room and the cuttering, mixing, stuffing, and fermentation phases. Ten strains were isolated, molecularly confirmed as L. monocytogenes by means of a molecular detection system, and subjected to pulsed-field gel electrophoresis (PFGE) typing. On the basis of an unweighted pair group method with arithmetic mean (UPGMA) dendrogram from Ascl pulsotypes, the strains were indistinguishable (no band difference). The same pulsotypes of strains present in both batches of sausages, as well as in environmental samples, indicated the persistence of L. monocytogenes in the sausage production unit.