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

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 in calves is necessary for animal and human health.

METHODS AND RESULTS

A total of 54 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 I 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  2a serotypes were resistant to cephalosporin and/or fluoroquinolones. The genes , , and were detected in 19 cephalosporin-resistant 2a isolates. Among 14 fluoroquinolone-resistant isolates, the ' gene was largely present in each strain, followed by (5). Only one ciprofloxacin-resistant isolate harbored the gene. Sequencing the quinolone resistance determining regions (QRDRs) of the fluoroquinolone-resistant isolates revealed two point mutations in (S83 L, D87N/Y) and a single point mutation in (S80I). Interestingly, two (D87N/Y) strains were resistant to ciprofloxacin.

CONCLUSIONS

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