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

Abstract

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.

Prevalence, Genetic Homogeneity, and Antibiotic Resistance of Pathogenic Yersinia enterocolitica Strains Isolated from Slaughtered Pigs in Bulgaria

“…In 2 out of the 43 isolated Y. enterocolitica strains, we detected resistance also to tetracycline, nalidixic acid, and chloramphenicol, and only in 1 (out of 43) to streptomycin, trimethoprim/sulfamethoxazole, levofloxacin, and doxycycline. Unlike our data, resistance to sulfamethoxazole and streptomycin of Y. enterocolitica isolated from pigs and humans is continuously reported [ 10 , 17 , 20 ]. In line with our findings, resistance to chloramphenicol has not been frequently found [ 35 ], which contradicts other reports on the high rate of Y. enterocolitica resistance to chloramphenicol among slaughtered pigs in Northern Italy and Croatia [ 17 , 20 , 36 ], and among Y. enterocolitica clinical isolates that appeared during the time of the Swedish outbreaks [ 37 ].…”

“…The estimated 6.7% prevalence of pathogenic Y . enterocolitica in healthy slaughtered pigs in this study is relatively lower compared to other European countries, such as Serbia (10.4%) [ 8 ], Italy (14% and 27.4%) [ 19 , 20 ], Belgium (23.5%) [ 9 ], Latvia and Lithuania (35%) [ 7 ], Croatia (43%) [ 17 ], Finland (60%) [ 21 ], Switzerland (85%) [ 12 ], and Spain (93%) [ 22 ]. The high prevalence in some countries could be explained by the different isolation methods, different age of the pigs, technical parameters, etc.…”

“…Here, we combined microbiological, biochemical, and PCR methods with enrichment step in Peptone Sorbitol Bile Broth (PSB broth) to ensure the most successful possible isolation and detection of pathogenic Y. enterocolitica strains. To enhance recovery of pathogenic Y. enterocolitica, the enrichment period was reduced from five to two days, and isolation was performed on selective agar after alkali treatment of PSB broth [ 17 , 25 ]. Although we believe that the choice of farm type can also affect the detection of pathogenic Y. enterocolitica, specific types of farms that could be responsible for the occurrence of Y. enterocolitica among pigs were not explored herein and remain to be further researched.…”

“…Heterogeneity of the antimicrobial resistance profile is shown to depend on the bioserotype and geographic distribution [ 16 ]. Multidrug-resistant Y. enterocolitica bioserotype 4/O:3 isolates from pigs have increased lately [ 17 ]. Their transmission highlights the importance of monitoring the resistance of circulating strains.…”

Systematic Review and Meta-Analysis of the Efficacy of Interventions Applied during Primary Processing to Reduce Microbial Contamination on Pig Carcasses

“…Lairage time and direct or indirect contact of groups of pigs during lairaging prior to slaughter influence the bacterial load of carcasses or the occurrence of pathogens in lymphoid tissues [ 45 , 46 ]. For example, a higher prevalence of Y. enterocolitica was found in the tonsils of pigs slaughtered in the slaughterhouses where pigs were held in the lairage pens separated by a fence that allowed contact between the pigs (40% and 52%), than in the tonsils of pigs slaughtered in the slaughterhouse that had a solid wall between lairage pens thus preventing contact between pigs (29%) [ 47 ]. Moreover, in one study, a higher prevalence of Salmonella was found in pigs in the lairage than in the farm of origin [ 6 ].…”