Comparison of Efflux Pump Involvement in Antibiotic Resistance Among Pseudomonas aeruginosa Isolates of Burn and Non-Burn Patients

Pseudomonas aeruginosa is an important cause of hospital-acquired infections that can create serious problem for patients and physicians. Many factors are associated with the antibiotic resistance of P. aeruginosa, such as efflux pumps.
The aim of this study was the phenotypic and molecular detection of efflux pumps in our clinical P. aeruginosa isolates in a comparison between burn and non-burn specimens.
In this study, clinical strains of P. aeruginosa were collected from burn and non-burn specimens from April - July 2013. Antibiotic susceptibility testing of the isolates was performed after biochemical and molecular identification. The minimum inhibitory concentration (MIC) of imipenem, cefepime, gentamycin, and ciprofloxacin, with and without carbonyl cyanide 3-chlorophenylhydrazone (CCCP), was determined for phenotypic detection of efflux pumps.
Our results confirmed 203 and 60 P. aeruginosa isolates from burn and non-burn specimens, respectively. The most antibiotic resistance was observed against tobramycin in both group of specimens, and no resistance was seen to colistin. Phenotypic detection of efflux pumps was determined to correlate to a > 4-fold decrease in the MICs of the tested antibiotics with CCCP compared to without CCCP in 57 strains.
High-level antibiotic resistance can occur as a result of multidrug efflux pumps combined with other mechanisms of resistance. However, the association between over-expression of these genes and highly resistant clinical isolates cannot be ignored.