High-level resistance to fluoroquinolones and cephalosporins in Burkholderia pseudomallei and closely related species.

The molecular mechanisms involved in the development of a high level of resistance to a wide range of antimicrobials in Burkholderia pseudomallei and closely related species have not been sufficiently investigated. In the present study, the properties of B. pseudomallei, B. mallei and B. thailandensis mutants with increased resistance to fluoroquinolones and cephalosporins were analysed. Resistance to pefloxacin, ofloxacin and ceftazidime in B. pseudomallei and B. thailandensis was accompanied by an increased resistance to aminoglycosides, beta-lactams, macrolides and chloramphenicol, whereas mutants of B. mallei were characterized by a narrower spectrum of resistance. With the use of the differential display technique, we demonstrated that multiple resistant variants of B. pseudomallei, B. mallei and B. thailandensis had an increased expression of putative efflux transporters belonging to the resistance-nodulation division superfamily and the major facilitator superfamily. With the application of PCR-single-stranded conformational polymorphism (PCR-SSCP) and sequencing, point mutations in gyrA quinolone-resistance determining region were detected in the part of multiple resistant B. pseudomallei and B. mallei mutants. These results indicate that various molecular mechanisms are involved in the development of multiple drug resistance in pathogenic Burkholderia and may be useful for further studying the adaptability of this microorganism and optimization of treatment.