Expansion of Typhi Clonal Lineages with Ampicillin Resistance and Reduced Ciprofloxacin Susceptibility in Eastern China
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Purpose: This study was aimed to investigate the dynamics of antimicrobial resistance expansion among different lineages and isolates of . Typhi.
Materials And Methods: The . Typhi isolates were collected from the patients clinically suspected of typhoid fever in Eastern China during 2005-2017. All isolates were tested retrospectively for susceptibility to eight antimicrobials and the genes related to quinolone and ampicillin resistance, including and . The isolates were subtyped by PFGE.
Results: Of 140 isolates, all were susceptible to ciprofloxacin, cefotaxime, chloramphenicol, and trimethoprim-sulfamethoxazole, 95 (68%) were nalidixic acid resistant, and 74 (53%) were ampicillin resistant. The resistance to ampicillin and nalidixic acid was first observed in 2006. Among the 95 nalidixic acid-resistant . Typhi isolates, 62 possessed S83F mutation in and 25 possessed D87Y mutation. All ampicillin-resistant isolates harbored gene . PFGE generated 47 distinguishable clonal lineages. Overall, 64% (89/140) belonged to seven prevalent lineages of clustering isolates. PFGE results illustrated the prevalence of nalidixic acid-resistant lineages increased steadily from 19% during 2005-2012 to 50% during 2013-2014, and thereafter to 74% during 2015-2017 and similar development of ampicillin-resistant lineages increased from 6% to 38%, and also to 39%.
Conclusion: The present study indicated the clonal expansion of . Typhi with ampicillin resistance and reduced ciprofloxacin susceptibility. The findings also suggested that the differential development of antimicrobial resistance to various antimicrobial agents in . Typhi, showing the rapid increase in ampicillin resistance and reduced ciprofloxacin susceptibility, and the high susceptibility to other traditional antimicrobial agents.
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