Development of in vitro resistance to fluoroquinolones in Pseudomonas aeruginosa

In this study, we investigated the dynamics of different resistance mechanisms inP. aeruginosa populations that have evolved under fluoroquinolone pressure, as well as the interactions between these mechanisms in evolutionary trajectories. Bacteria of strain ATCC27853 were selected under different concentrations of ciprofloxacin and levofloxacin for six parallel lineages, followed by amplification of four target genes in the quinolone-resistance determining region (QRDR) and Sanger sequencing to identify the mutations. The expression of four efflux pump proteins was evaluated by real-time polymerase chain reaction using the relative quantitation method, with the ATCC27853 strain used as a control. We found that ciprofloxacin killedP. aeruginosa sooner than did levofloxacin. Further, we identified five different mutations in three subunits of QRDRs, withgyrA as the main mutated gene associated with conferring fluoroquinolone resistance. Additionally, we found a larger number of mutations appearing at 2  mg/L and 4 mg/L of ciprofloxacin and levofloxacin, respectively. Moreover, we identified the main efflux pump being expressed as MexCD-OprJ, with initial overexpression observed at 0.25 mg/L and 0.5 mg/L of ciprofloxacin and levofloxacin, respectively. These results demonstratedgyrA83 mutation and MexCD-OprJ overexpression as the primary mechanism conferring ciprofloxacin and levofloxacin resistance inP. aeruginosa. In addition, we also show that ciprofloxacin exhibited...
Source: Antimicrobial Resistance and Infection Control - Category: Infectious Diseases Source Type: research