Curcumin and restoration of ciprofloxacin susceptibility to clinical isolates of Pseudomonas aeruginosa with mutated genes involved in ciprofloxacin resistance

Pseudomonas aeruginosa is an opportunistic nosocomial infection implicated in bacteremia in patients with compromised host defenses. Resistance to ciprofloxacin and imipenem, which are considered as suitable therapeutic options, is increasing in P. aeruginosa. Curcumin is a diferuloylmethane with antimicrobial properties. The present study was conducted to find the molecular effects of curcumin on clinical isolates with mutated genes involved in ciprofloxacin resistance. Fifty-two clinical isolates of P. aeruginosa were obtained from several hospitals and laboratories in Guilan province, northern Iran. Susceptibility to five antibiotics was evaluated by disc diffusion and broth dilution (MIC) methods. Furthermore, PCR-sequencing was carried out to evaluate mutations in topoisomerase subunits, five negative regulators of efflux pumps and oprD gene in these isolates. The effects of curcumin on the expression of mexB and mexY were evaluated using Q-RT-PCR. Of 52 P. aeruginosa isolated strains, 32-44% resistance to amikacin, ciprofloxacin, imipenem and gentamicin was observed. All isolates had mutation in gyrA. Some isolates had mutation in other topoisomerase subunits, some negative regulator genes and oprD gene. Curcumin (400μg/ml) along with ciprofloxacin (subMIC) increased ciprofloxacin susceptibility in four isolates. In these isolates, the expression of MexB and MexY efflux pump genes were downregulated. It seems that among P. aeruginosa isolates with various mutations in important genes in antibiotic resistant pathways, curcumin can intelligently sensitize isolates to these drugs.