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Background and purpose: Increasing resistance to Quinolones in Escherichia coli and Klebsiella pneumonia in Sari, has caused many problems in treatment. Mutation in gyrA gene lead to changes in amino acids and resistance against Fluoroquinolones in E. coli and K. pneumonia. This study aimed at identifying remarkable mutations in E. coli and K. pneumonia isolates using PCR-SSCP analysis.

Materials and methods: Antibiotic sensitivity test (ciprofloxacin, nalidixic acid) was performed using Agar Disk Diffusion method. Resistance to fluoroquinolones was confirmed by E-test.(MIC experiment). We used PCR-SSCP method to detect mutation in gyrA (ser83–asp 87) genes. Then, the PCR products were randomly sequenced.

Results: From 103 isolates, 65 (63.2%) were E. coli and 38 (36.8%) were K. pneumoniae. In all E. coli isolates resistant to Ciprofloxacin, at least one mutation was observed. Also, in all K. pneumoniae samples resistant to Ciprofloxacin, at least one mutation was seen and in 14 samples two mutation points were observed, but in 5 samples that were sensitive to Ciprofloxacin no mutation was observed.

Conclusion: This study showed that the mutation in gyrA genes is closely related to quinolones resistance. High prevalence of quinolones resistance in E. coli and K. pneumoniae isolates requires more appropriate infection control programs.