Detection of gyr A gene mutations in quinolone-resistant clinical isolates of Pseudomonas aeruginosa

Abstract number: 1135_38

El Gharbawy M., El Mofty M., Abd El Hady H., El Shenity M., Moursi A.

Objectives:  

To investigate the frequency of resistance of P. aeruginosa to fluoroquinolones and to detect gyrA gene mutations in quinolone-resistant P. aeruginosa isolates obtained from discharge of sinuses, middle or external ears of patients.

Methods:  

The 126 isolated strains were tested for susceptibility to various antibiotics and those resistant to ofloxacin were tested for point mutations in the gyr A gene using single strand conformational polymorphism analysis ( SSCP, and by sequencing in 2 selected strains.

Results:  

Twenty-eight (22.2%) out of the 126 isolates were resistant to ofloxacin. Point mutation in gyrA gene was not detected in any of the 28 quinolone resistant strains by SSCP. However, by direct sequencing of the PCR- amplified gyrA fragment from two clinical isolates, single mutation in which, threonine at position 83 was substituted by an isoleucine, was detected in both cases.

Conclusion:  

SSCP was not a perfect method in the detection of gyrA gene mutation (s) in clinical isolates of P. aeruginosa. Confirmation of SSCP by direct sequencing, or modification of the usual SSCP analysis ought to be considered in future studies.