Abstract
BackgroundMembers of the genus Shigella are intestinal pathogens and a major cause of seasonal outbreaks of bacterial diarrhea worldwide. Although humans are the conventional hosts of Shigella species, expansion of the Shigella host range to certain animals was recently reported. To investigate the prevalence of Shigella sonnei (S. sonnei) in yaks and perform molecular characterization, we analyzed 1132 fresh yak diarrheal stool samples and collected a total of 44 S. sonnei isolates.ResultsWe performed multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) with XbaI-digested DNA to study genetic relatedness among the 44 isolates, which were differentiated into 4 sequence types (STs) and 32 PFGE types (PTs). All isolates harbored virulence genes, and 87.36% tested positive for invasion plasmid antigen H (ipaH), invasion associated locus (ial) and the Shigella enterotoxin gene sen. According to the results of antimicrobial susceptibility tests, 45.45% (20/44) were resistant to fluoroquinolones and/or cephalosporin. By sequencing the quinolone resistance determining region (QRDR) genes, we identified double mutations in gyrA (Ser83-Leu and Asp87-Asn) and a single mutation in parC (Ser80-Ile). All 12 fluoroquinolone-resistant S. sonnei isolates tested positive for the aac(6′)-Ib-cr gene but negative for qepA. Three isolates harbored qnr genes, including two with qnrS and one with qnrB. In addition, three types of β-lactamase genes, blaTEM-1, blaOXA-1 and blaCTX-M-14/79, were detected in cephalosporin-resistant isolates.ConclusionsThe findings of this study have enriched our knowledge of fluoroquinolone- and/or cephalosporin-resistant S. sonnei isolates from yaks, which has important public health significance.
Highlights
Members of the genus Shigella are intestinal pathogens and a major cause of seasonal outbreaks of bacterial diarrhea worldwide
Identification of S. sonnei isolates A total of 44 S. sonnei isolates were collected from 1132 fresh diarrheal stool samples from yaks in three Chinese provinces, Gansu, Qinghai and Tibet, from 2014 to 2016
Based on the results of biochemical characterization assays, we observed that all 44 S. sonnei isolates possessed the typical biochemical features of Shigella species and demonstrated the ability to ferment I-D-galactopyranoside (ONPG), glucose (GLU), mannitol (MAN), melibiose (MEL) and arabinose (ARA)
Summary
Members of the genus Shigella are intestinal pathogens and a major cause of seasonal outbreaks of bacterial diarrhea worldwide. Bacteria of the genus Shigella are important members of the Enterobacteriaceae family and cause acute diarrhea in humans and animals [1,2,3]. This pathogen has been historically divided into 4 subgroups based on biochemical properties and group-specific O antigens in the outer membrane, subgroups A (S. dysenteriae), B (S. flexneri), C (S. boydii) and D (S. sonnei). The specific pathogenicity of a given Shigella isolate is derived from the expression of diverse virulence genes that are associated with colonization, invasion/penetration and toxin-mediated disease [8]. An investigation of the virulence determinant genes in Shigella would help us
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