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Received 12 April 2004; returned 13 June 2004; revised 2 August 2004; accepted 10 August 2004Objectives: The aim of the present study was to determine the clonal relationships of ciprofloxacin-resistant Shigella dysenteriae type 1 strains isolated from south Asia, and S. dysenteriae 1 strainsassociated with epidemics in 1978, 1984 and 1994.Methods: The antimicrobial susceptibilities were examined by NCCLS methods. Molecular epidemio-logical characterization was performed by plasmid profiling, pulsed-field gel electrophoresis (PFGE)and mutation analysis of the quinolone resistance-determining region (QRDR) of gyrA by sequencing.Results: Plasmid patterns of the current ciprofloxacin-resistant strains from India, Nepal andBangladesh were very similar to those of the 1978, 1984 and 1994 epidemic isolates of S. dysenteriae1, except for the presence of a new plasmid of 2.6MDa, which was found in one recent ciprofloxacin-resistant strain isolated in Bangladesh. PFGE analysis showed that the ciprofloxacin-resistant strainsisolated in Bangladesh, India and Nepal belonged to a PFGE type (type A), which was possibly relatedto that of the 1984 and 1994 clone of S. dysenteriae 1, but different from 1978 epidemic strains. Thecurrent ciprofloxacin-resistant strains belong to five subtypes (A3–A7), all of which were found inIndia, but in Bangladesh and Nepal, only A3 existed. Mutation analysis of the QRDR of gyrA revealedthat amino acid substitutions at positions 83 and 87 of ciprofloxacin-resistant strains isolated inBangladesh were similar to those of the strains isolated in Nepal, but different (at position 87) fromciprofloxacin-resistant strains isolated in India.Conclusions: PFGE and mutation analysis of gyrA showed differences between the current ciprofloxa-cin-resistant S. dysenteriae 1 strains isolated in south Asia and those associated with epidemics in1978, 1984 and 1994.Keywords: pulsed-field gel electrophoresis, gyrA, QRDRs, epidemics

Although ciprofloxacin is one of the recommended drugs of choice for the treatment of gonorrhea, in vitro resistance to this drug has been observed in surveillance studies and case reports from many parts of the world, including Bangladesh. However, to our knowledge, there have been no prospective studies of the correlation between in vitro response to the drug and treatment outcome. Therefore, a prospective study of 217 female sex workers in Dhaka, Bangladesh, was conducted to examine the correlation between the in vitro response of Neisseria gonorrhoeae and the outcome of ciprofloxacin treatment. Overall, 37.8% of the gonococcal isolates recovered from female sex workers were resistant to ciprofloxacin, and there was a good correlation between in vitro resistance and treatment failure. These findings suggest that in vitro resistance to ciprofloxacin is predictive of clinical treatment failure in patients with gonorrhea.