Multilocus Variable-Number Tandem-Repeat Analysis, Pulsed-Field Gel Electrophoresis, and Antimicrobial Susceptibility Patterns in Discrimination of Sporadic and Outbreak-Related Strains of Yersinia enterocolitica

Abstract

BackgroundWe assessed the potential of multilocus variable-number tandem-repeat analysis (MLVA), pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing for discriminating 104 sporadic and outbreak-related Yersinia enterocolitica (YE) bio/serotype 3-4/O:3 and 2/O:9 isolates. MLVA using six VNTR markers was performed in two separate multiplex PCRs, and the fluorescently labeled PCR products were accurately sized on an automated DNA sequencer.ResultsMLVA discriminated 82 sporadic YE 3-4/O:3 and 2/O:9 strains into 77 types, whereas PFGE with the restriction enzyme NotI discriminated the strains into 23 different PFGE pulsotypes. The discriminatory index for a sporadic strain was 0.862 for PFGE and 0.999 for MLVA. MLVA confirmed that a foodborne outbreak in the city of Kotka, Finland in 2003 had been caused by a multiresistant YE 4/O:3 strain that was distinctly different from those of epidemiologically unrelated strains with an identical PFGE pulsotype. The multiresistance of Y. enterocolitica strains (19% of the sporadic strains) correlated significantly (p = 0.002) with travel abroad. All of the multiresistant Y. enterocolitica strains belonged to four PFGE pulsotypes that did not contain any susceptible strains. Resistance to nalidixic acid was related to changes in codons 83 or 87 that stemmed from mutations in the gyrA gene. The conjugation experiments demonstrated that resistance to CHL, STR, and SUL was carried by a conjugative plasmid.ConclusionsMLVA using six loci had better discriminatory power than PFGE with the NotI enzyme. MLVA was also a less labor-intensive method than PFGE and the results were easier to analyze. The conjugation experiments demonstrated that a resistance plasmid can easily be transferred between Y. enterocolitica strains. Antimicrobial multiresistance of Y. enterocolitica strains was significantly associated with travel abroad.

Virulence-associated gene pattern of porcine and human Yersinia enterocolitica biotype 4 isolates

“…This intrinsic antibiotic resistance is based on 2 well-known chromosomal betalactamase genes, blaA and blaB (Fàbrega and Vila, 2012). The occurrence of multiresistant human pathogenic Y. enterocolitica strains and a high proportion of antibiotic resistance to chloramphenicol, streptomycin and sulfonamides in porcine strains in Italy have recently been described (Sihvonen et al, 2011b;Bonardi et al, 2014). These findings raise questions about the current situation in Swiss isolates.…”

“…Recent studies in Europe have reported increasing antibiotic resistance of both human and porcine Y. enterocolitica isolates (Sihvonen et al, 2011b;Bonardi et al, 2014). Low level of antibiotic resistance found in Swiss human strains from 2001-to 2003 underline the increasing tendency in human strains, whereas the rate of acquired antibiotic resistance in recently isolated predominant Swiss porcine Y. enterocolitica BT 4 strains is currently very low.…”

“…In contrast, the 2 chloramphenicol-resistant strains showed an elevated MIC of > 128 mg/L, which indicated that they are resistant to streptomycin as well. The origin of this antibiotic resistance pattern (chloramphenicol, streptomycin and sulfonamide) is most likely a conjugative plasmid, as Sihvonen et al (2011b) have indicated. The 2 chloramphenicol-resistant strains also possessed antibiotic resistance to nalidixic acid.…”

“…One strain was also resistant to sulfamethoxazole.. Y. enterocolitica antibiotic resistance to chloramphenicol is rarely described in the literature, but Bonardi et al (2014) recently found BT 4 strains resistant to chloramphenicol. Additionally, Sihvonen et al (2011b) detected antibiotic resistance to chloramphenicol in human Y. enterocolitica strains. For streptomycin, the human and the porcine tonsil strains showed an MIC50 of 8 mg/L and an MIC90 of 16 mg/L.…”

Multiple-Locus Variable-Number Tandem-Repeat Analysis in Genotyping Yersinia enterocolitica Strains from Human and Porcine Origins

“…Of these, bioserotype 4/O:3 strains have been responsible for yersiniosis cases in Europe, the United States, Canada, and Japan (3)(4)(5)(6). Recently, bioserotype 2/O:9 infections have been on the rise (7)(8)(9). Besides humans, bioserotype 4/O:3 frequently is isolated from samples of pig origin (2,(10)(11)(12)(13).…”