Observation of a new pattern of mutations in gyrA and parC within Escherichia coli exhibiting fluroquinolone resistance

Therapeutic options with quinolones are severely compromised in infections caused by members of Enterobacteriaceae family. Mutations in chromosomal region are one of the major reasons for bacterial resistance towards this group of antibiotic. The aim of the study is to detect the mutations in gyr A and par C responsible for quinolone resistance among clinical isolates of Escherichia coli. A total of 96 quinolone-resistant clinical isolates of E. coli were collected from a tertiary care hospital of North-east India during March 2015 to August 2015. All the quinolone-resistant E. coli strains were investigated for mutations in the topoisomerases genes gyrA and parC by amplifying and sequencing the quinolone resistance determining regions. Among the 96 E. coli isolates, 83.3% were resistant to nalidixic acid and 80.2%, 66.6%, 23.9% and 50% to ciprofloxacin, norfloxacin, levofloxacin and ofloxacin, respectively. Several alterations were detected in gyrA and parC genes. Three new patterns of amino acid substitution are reported in E. coli isolates. The findings of this study warrant a review in quinolone-based therapy in this region of the world to stop or slow down the irrational use this drug.

Utility of a Mycobacterium tuberculosis GC-rich repetitive sequence in the diagnosis of tuberculous pleural effusion by PCR.

A GC-rich repetitive sequence (GCRS) of Mycobacterium tuberculosis was identified in our laboratory which displayed a high homology with GC-rich sequences of M. tuberculosis and M. bovis. A PCR assay based on the amplification of the proximal 150 bp of GCRS and its detection by non-radioactive hybridization was developed. The accuracy of the GCRS-based PCR assay was evaluated in a clinical setting for the detection of mycobacterial DNA in pleural fluids for the diagnosis of tuberculosis (TB) using clinical criteria and pleural biopsy histology as gold standard. In a blind study, a total of 67 pleural fluid samples (38 tuberculous and 29 nontuberculous) were analysed by PCR and the results were compared with pleural biopsy, Ziehl-Neelsen staining and culture. Mycobacteria could not be detected by either smear or culture techniques in any of the pleural fluids samples. Out of 38 tuberculous pleural effusions, 24 were positive by PCR (63.2% sensitivity). When PCR results were compared with pleural biopsy histology, an increased sensitivity of 73.3% was obtained. Out of the 29 nontuberculous pleural effusions, 2 false positive results were obtained accounting for an overall specificity of 93.1%. The GCRS-based PCR assay thus has a definite role in the diagnosis of tuberculous pleural effusion in contrast to smear and/or culture techniques.