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. 2017 Sep 6:6:92.
doi: 10.1186/s13756-017-0252-6. eCollection 2017.

Epidemic characterization and molecular genotyping of Shigella flexneri isolated from calves with diarrhea in Northwest China

Zhen Zhu #  1 , Mingze Cao #  1 , Xuzheng Zhou  1 , Bing Li  1 , Jiyu Zhang  1
Affiliations

Epidemic characterization and molecular genotyping of Shigella flexneri isolated from calves with diarrhea in Northwest China

Zhen Zhu et al. Antimicrob Resist Infect Control. .

Abstract

Background: The widespread presence of antibiotics resistance genes in pathogenic bacteria can cause enormous problems. Food animals are one of the main reservoirs of intestinal pathogens that pose a potential risk to human. Analyzing the epidemiological characteristics and resistance patterns of Shigella flexneri in calves is necessary for animal and human health.

Methods and results: A total of 54 Shigella flexneri isolates, including six serotypes (1a, 2a, 2b, 4a, 6 and Xv), were collected from 837 fecal samples obtained from 2014 to 2016. We performed pulsed-field gel electrophoresis (PFGE) and applied the restriction enzyme NotI to analyze the genetic relatedness among the 54 isolates and to categorize them into 31 reproducible and unique PFGE patterns. According to the results of antimicrobial susceptibility tests, all 26 Shigella flexneri 2a serotypes were resistant to cephalosporin and/or fluoroquinolones. The genes blaTEM-1 , blaOXA-1 , and blaCTX-M-14 were detected in 19 cephalosporin-resistant S. flexneri 2a isolates. Among 14 fluoroquinolone-resistant isolates, the aac(6')-Ib-cr gene was largely present in each strain, followed by qnrS (5). Only one ciprofloxacin-resistant isolate harbored the qepA gene. Sequencing the quinolone resistance determining regions (QRDRs) of the fluoroquinolone-resistant isolates revealed two point mutations in gyrA (S83 L, D87N/Y) and a single point mutation in parC (S80I). Interestingly, two gyrA (D87N/Y) strains were resistant to ciprofloxacin.

Conclusions: The current study enhances our knowledge of Shigella in cattle, although continual surveillance is necessary for the control of shigellosis. The high level of cephalosporin and/or fluoroquinolone resistance in Shigella warns us of a potential risk to human and animal health.

Keywords: Antimicrobial susceptibility; Resistant; Shigella flexneri.

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Conflict of interest statement

Ethics approval and consent to participate

Permission to work in specific locations, information regarding the number of samples harvested, and an associated permit number for calves were not required, and no endangered or protected species were involved or harmed during this study.

Consent for publication

All authors agreed on the publication of the paper.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
S. flexneri serotypes collected from 2014 to 2016
Fig. 2
Fig. 2
Number of S. flexneri isolated from different quarters
Fig. 3
Fig. 3
PFGE dendrogram and antibiotic susceptibility profile of 54 NotI-digested S. flexneri. B = Beef cattle; Y = Yak. R = Resistance; N = Sensitive and Intermediary
See this image and copyright information in PMC

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