The mutation of mar gene in clinical isolated Escherichia coli resistant to fluoroquinolones / 中华传染病杂志

ABSTRACT

Objective To study the antibiotic resistance mediated by the mar mechanism in clinical isolated Escherichia coli. Methods To analyse the antibiotic resistance pattern and the out membrane protein spectrum of clinical isolated E. coli . The plasmid pNJR3 2 carrying the wild type gyr A gene was transferred into clinical multiple resistant strain LC 1. The resistant pattern and plasmid pattern of LC 1 before and after plasmid transferring were compared. The mar OR of clinical strain LC 1 was cloned and sequenced through PCR. The nucleotides of mar gene were compared with the wild type issued by GenBank. Results Of all the 49 clinical strains , six strains express Mrp5, a mar specific out membrane protein. No changes were detected on susceptibility to fluoroquinolone of clinical strain LC 1 after pNJR3 2 transferred suggesting that gyr A was not the main reason contributing to fluoroquinolone resistance. Sequence analysis showed three mutant spots in mar OR of clinical strain LC 1. Conclusion There does exist mar mechanism in clinical isolated Escherichia coli resistant to fluoroquinolone. The mutation in mar OR may contribute to the mar phenotype of LC 1.