Emergence of colistin resistant Pseudomonas aeruginosa at Tabriz hospitals, Iran.
OBJECTIVE
The prevalence of multidrug resistant Pseudomonas aeruginosa is the main reason of new drugs resurgence such as colistin. The main objectives of this study were to determine the antibiotic resistance pattern and the rate of colistin resistance along with its correlation with overexpression of MexAB-OprM and MexXY-OprM efflux pumps among P. aeruginosa isolates.


METHODS
Hundred clinical isolates were collected from 100 patients during 6 months in 2014. Susceptibility to the eight antibiotics was investigated using Kirby-Bauer and agar dilution methods. The Quantitative Real-time PCR was used to determine the expression levels of efflux genes.


RESULTS
Resistance rates to various antibiotics were as follows: ticarcillin (73%), ciprofloxacin (65%), aztreonam (60%), ceftazidime (55%), gentamicin (55%), imipenem (49%), piperacillin/tazobactam (34%) and colistin (2%). In disk diffusion method, only two isolates were non susceptible to colistin, however in agar dilution method the two isolates were confirmed as resistant and two others were intermediate resistant. Sixty eight (68%) isolates were multi-drug resistant and 10 isolates were susceptible to all tested antibiotics. Both colistin resistant isolates showed overexpression of both efflux pumps, but two intermediate resistant isolates exhibited reduction of efflux genes expression.


CONCLUSIONS
Emergence of colistin resistance is increasing in P. aeruginosa indicating great challenge in the treatment of infections caused by MDR strains of this organism in Iran. ParRS may promote either induced or constitutive resistance to colistin through the activation of distinct mechanisms such as MDR efflux pumps, and LPS modification.
Drug Applied Research Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Medical Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Hamid Reza
HR
Goli
Drug Applied Research Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Medical Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Mohammad Reza
MR
Nahaei
Infectious Diseases and Tropical Medicine Research Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Medical Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Mohammad
M
Ahangarzadeh Rezaee
Infectious Diseases and Tropical Medicine Research Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Medical Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Alka
A
Hasani
Drug Applied Research Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Medical Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Hossein
H
Samadi Kafil
Drug Applied Research Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Medical Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Mohammad
M
Aghazadeh
Colistin; MexAB-OprM; MexXY-OprM; Multi drug resistant; Pseudomonas aeruginosa