Identification of Yersinia enterocolitica isolates from humans, pigs and wild boars by MALDI TOF MS

Kamila Korzekwa,Agnieszka Korzeniowska-Kowal,Jacek Bania,Katarzyna Guz-Regner,Katarzyna Morka,Gabriela Bugla-Płoskońska,Jarosław Bystroń

doi:10.1186/s12866-018-1228-2

Abstract

BackgroundYersinia enterocolitica is widespread within the humans, pigs and wild boars. The low isolation rate of Y. enterocolitica from food or environmental and clinical samples may be caused by limited sensitivity of culture methods. The main goal of present study was identification of presumptive Y. enterocolitica isolates using MALDI TOF MS. The identification of isolates may be difficult due to variability of bacterial strains in terms of biochemical characteristics. This work emphasizes the necessity of use of multiple methods for zoonotic Y. enterocolitica identification.ResultsIdentification of Y. enterocolitica isolates was based on MALDI TOF MS, and verified by VITEK® 2 Compact and PCR. There were no discrepancies in identification of all human’ and pig’ isolates using MALDI TOF MS and VITEK® 2 Compact. However three isolates from wild boars were not decisively confirmed as Y. enterocolitica. MALDI TOF MS has identified the wild boar’ isolates designated as 3dz, 4dz, 8dz as Y. enterocolitica with a high score of matching with the reference spectra of MALDI Biotyper. In turn, VITEK® 2 Compact identified 3dz and 8dz as Y. kristensenii, and isolate 4dz as Y. enterocolitica. The PCR for Y. enterocolitica 16S rDNA for these three isolates was negative, but the 16S rDNA sequence analysis identified these isolates as Y. kristensenii (3dz, 4dz) and Y. pekkanenii (8dz). The wild boar’ isolates 3dz, 4dz and 8dz could not be classified using biotyping. The main bioserotype present within pigs and human faeces was 4/O:3. It has been shown that Y. enterocolitica 1B/O:8 can be isolated from human faeces using ITC/CIN culturing.ConclusionThe results of our study indicate wild boars as a reservoir of new and atypical strains of Yersinia, for which protein and biochemical profiles are not included in the MALDI Biotyper or VITEK® 2 Compact databases. Pigs in the south-west Poland are the reservoir for pathogenic Y. enterocolitica strains. Four biochemical features included in VITEK® 2 Compact known to be common with Wauters scheme were shown to produce incompatible results, thus VITEK® 2 Compact cannot be applied in biotyping of Y. enterocolitica.

Highlights

Yersinia enterocolitica is widespread within the humans, pigs and wild boars
All 650 isolates growing on cefsulodin-irgasan-novobiocin Agar (CIN) Agar as mannitol fermenting colonies and presenting the “red bull’s eye” morphology were subjected to further MALDI TOF MS analysis
MALDI TOF MS can be successfully used for Yersinia sp. identifiaction from human’ and pig’ samples, but identification of wild boar’ isolates needs additional tests

Summary

Introduction

Yersinia enterocolitica is widespread within the humans, pigs and wild boars. The low isolation rate of Y. enterocolitica from food or environmental and clinical samples may be caused by limited sensitivity of culture methods. The main goal of present study was identification of presumptive Y. enterocolitica isolates using MALDI TOF MS. A causative agent of yersiniosis is widespread in an environment and animals [1]. Yersiniosis was the third most frequently reported zoonosis in the European Union in 2015, with the notification rate of 2.20 cases per 100,000 population which was 6.8% higher than in 2014 [2]. Studies on the prevalence of Y. enterocolitica in wild boars can be considered important from the point of view of public health. The research undertaken by BancerzKisiel et al [9] indicated the isolation of Y. enterocolitica from the half of 20 wild boar carcasses

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Conclusion