Distribution of CRISPR Types in Fluoroquinolone-Resistant Isolates.

To aid development of phage therapy against , we investigated the distribution of the clustered regularly interspaced short palindromic repeats (CRISPR) systems in fluoroquinolone (FQ)-resistant . A total of 100 FQ-resistant strains from different sources were analyzed by PCR and DNA sequencing to determine resistance-conferring mutation in the gene and the presence of various CRISPR systems. All but one isolate harbored 1-5 point mutations in and the most common mutation was the Thr86Ile change. Ninety-five isolates were positive with the CRISPR PCR, and spacer sequences were found in 86 of them. Among the 292 spacer sequences identified in this study, 204 shared 93-100% nucleotide homology to phage D10, 44 showed 100% homology to phage CP39, and 3 had 100% homology with phage CJIE4-5. The remaining 41 spacer sequences did not match with any phages in the database. Based on the results, it was inferred that the FQ-resistant isolates analyzed in this study were potentially resistant to phages D10, CP39, and CJIE4-5 as well as some unidentified phages. These phages should be excluded from cocktails of phages that may be utilized to treat FQ-resistant .