Tan, Lai Kuan (2014) Isolation and characterization of Yersinia Enterocoliticafrom food and swine / Tan Lai Kuan. Masters thesis, University of Malaya.
Abstract
Yersinia enterocolitica is an important foodborne enteric pathogen that causes gastroenteritis. There are limited studies on Y. enterocolitica in Malaysia, hence the potential complication due to yersiniosis in the country remains unknown. The objectives of this study were: (i) to determine the prevalence of Y. enterocolitica from raw food and pigs in Malaysia; (ii) to characterize the Malaysian Y. enterocolitica by using phenotypic and genotypic methods and; (iii) to study the genetic relatedness of Malaysian Y. enterocolitica strains from different food sources and pigs in Malaysia; and (iv) to improve the isolation of rate of Y. enterocolitica by modifying the composition of Cefsulodin-Irgasan-Novobiocin(CIN) agar. Between years 2010 to 2011, 106 raw food samples (58 pork products and 48 non-porcine food) and 495 swine specimens (from 165 pigs) were analysed for the presence of Y. enterocolitica. The pathogen was isolated in 7/58(12.1%) raw pork products, in which pork (whole meat) had the highest prevalence 5/21(23.8%), followed by liver 1/5(20.0%) and intestine 1/8(12.5%). Y. enterocolitica was not isolated from raw non-porcine food. Of 165 pigs, 3(1.8%) were carriers (asymptomatic pigs) for Y. enterocolitica. Bioserotyping showed that the isolates were of bioserotypes 3 variant/O:3(n=92), 1B/O:8(n=3), and 1A/O:5(n=3). The 3 variant/O:3 was the most prevalent bioserotype (present in pork products and pigs) and is probably the common bioserotype in Malaysia (warm climate region). Thirty-two Y. enterocolitica isolates were further subtyped by using pulsed-field gel electrophoresis (PFGE) and the antimicrobial profiles and carriage of virulence markers were evaluated. Isolates of three different bioserotypes were distinguished into three clusters (D value = 0.87, 90% similarity) by using PFGE. However, isolates were highly clonal within each bioserotype and exhibited minor variation. Of 29 ABSTRACT iv antimicrobials tested, the 1B/O:8 isolates were only resistant to clindamycin and the 1A/O:5, resistant to ampicillin, ticarcillin, amoxicillin, and clindamycin. Majority of the 3 variant/O:3 isolates were resistant to nalidixic acid, clindamycin, ampicillin, ticarcillin, tetracycline and amoxicillin. About 90% were multidrug-resistant(MDR) with multiple antibiotic resistance(MAR) index for isolates of bioserotype 3 variant/O:3 the highest, 0.183, followed by 1A/O:5 and 1B/O:8 with MAR indices at 0.121 and 0.103, respectively. Isolates were examined for the presence of pYV plasmid and 15 virulence genes. Four reproducible virulence genes patterns obverved and each virulotype belonged to a particular bioserotype. The pYV plasmid was only present in the 3 variant/O:3 isolates. To improve the isolation of Y. enterocolitica, the composition of CIN agar was modified. Based on the evaluation on the plating efficiency, detection limit and recovery strength for both CIN and modified CIN media, modified CIN provided a better discrimination of Y. enterocolitica from five bacteria exhibiting Yersinia-like colonies on CIN than the original CIN while retaining similar detection limit and culture capability for Y. enterocolitica. In conclusion, the occurrence of virulent strains of Y. enterocolitica in pigs and raw pork products indicated that pigs are important reservoir of Y. enterocolitica. The high incidence of multidrug resistant Y. enterocolitica is of public health concern and possibly reflects the abuse of antimicrobial agents in the animal husbandry. The modified CIN might be useful for routine surveillance for Y. enterocolitica.
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