The Drug-Specific Propensity Regarding the Acquisition of Fluoroquinolone Resistance in Escherichia coli: An in vitro Challenge and DNA Mutation Analysis

Abstract

Objective

Many fluoroquinolones, such as ciprofloxacin, are used clinically. We investigated the relationship between resistance acquisition and exposure duration in each drug through the exposure of fluoroquinolone to Escherichia coli clinical isolates in vitro.

Methods

Eleven E. coli clinical isolates were exposed to each fluoroquinolone, ie, ciprofloxacin, levofloxacin, sitafloxacin, garenoxacin, and lascufloxacin, with the concentration of the mutant selection window for 5 days; these procedures were repeated 5-times. In addition, the DNA sequence in the quinolone-resistance determining region (QRDR) and the expression level in the drug efflux pump acrA were analyzed to determine the resistance mechanism.

Results

Although resistant strains were not detected after 5 to 10 days of exposure to fluoroquinolone, after 25 days of exposure to ciprofloxacin and levofloxacin, 100% and 45% of isolates acquired resistance, respectively. Due to 25 days of exposure to sitafloxacin, garenoxacin, and lascufloxacin, MIC measurement was elevated 2- to 4096-fold for those of the parental strain, and the cross-resistance rate to levofloxacin was 72%, 54%, and 27%, respectively. In strains with high fluoroquinolone resistance, acrA overexpression was observed in addition to QRDR mutation.

Conclusion

In our findings, fluoroquinolone resistance was not observed in the E. coli strain after 5- to 10-days of exposure. However, resistance acquisition was detected frequently after 15- to 25-days of exposure. Among fluoroquinolones, lascufloxacn had the least impact on the resistance acquisition in E. coli.

Plain Language Summary

The need to combat quinolone-resistant E. coli is urgent. The resistance acquisition tendency of E. coli varies according to the drug used. After 25 days of exposure, 45% of E. coli showed levofloxacin resistance. Lascufloxacin may have the lowest influence on resistance acquisition to regular E. coli.

Keywords:

• Escherichia coli
• respiratory quinolone
• mutant selection window
• quinolone-resistance determining region
• efflux pump

Ethical Approval

Not required, according to the Research Ethics Statement of the Ministry of Health, Labour and Welfare of Japan, because this study is basic research that used bacterial isolates only. Following this statement, this study is exempt from ethical approval. Clinical isolates that were used in this study were collected and stocked by the Tohoku Infectious Diseases Society; therefore, we cannot access patient information.

Acknowledgments

We thank Dr. Akira Watanabe of Tohoku Infectious Disease Society, for he gifted E. coli clinical isolates. We also thank M. Yagi for technical assistance.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis, and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

There is no funding to report.