The prevalence of aminoglycoside-modifying enzyme genes among Pseudomonas aeruginosa strains isolated from burn patients

Abstract

Background: The prevalence of resistance to aminoglycosides among P. aeruginosa isolates has increased all around the world. The resistance is caused through different mechanisms. One of these mechanisms is the use of enzymes such as phosphoryltransferases, acetyltransferases, and nucleotidyltransferases. Objectives: The present study was conducted to determine the prevalence of Aph (3′)-Ib, Aph(6′)-VI, rmtA, aac (6′)-IIa, aadA, aadB, and armA genes among P. aeruginosa strains isolated from burn patients located in Tehran, Iran. Methods: This descriptive study was performed on patients hospitalized at the Shahid Motahari burn hospital during August 2014 to July 2015. Antibiotic susceptibility tests were performed by disc diffusion and minimum inhibitory concentration methods. Aph (3′)-Ib, Aph (6′)-VI, rmtA, aac (6′)-IIa, aadA, aadB, and armA genes were detected by PCR. Results: 6′ isolates were evaluated for antimicrobial susceptibility testing. The resistance of P. aeruginosa isolates to the tested antibiotics was as follows: 56 (94%) to ciprofloxacin, 57 (95%) to gentamicin, 57 (95%) to Imipenem, 57 (95%) to meropenem, 56 (94%) to doripenem, 49 (82%) to piperacillintazobactam, 58 (97.2%) to amikacin, 45 (75%) to ceftazidime, 59(98%) to Ticarcillin, 56 (93%) to Cefepime, 54 (90%) to piperacillin, 54 (90%) to Aztreonam, and 0 (0%) to colistin. Minimum inhibitory concentration (MIC) for amikacin and Gentamicin was determined according to the guidelines of CLSI. The highest resistance rate according to the MIC method was observed for Gentamicin and amikacin in 128 (40%) and 256 (92%) of the isolates, respectively. In this study, 94% of the isolates were multiple drug resistance (MDR). The prevalence of Aph (3′)-Ib, Aph (6′)-VI, rmtA, aac (6′)-IIa, aadA, aadB, and armA genes were 60%, 85%, 45%, 10%, 87.5%, and 55% according to the PCR, method respectively. Conclusions: This study detected multiple drug resistance (MDR) in P. aeruginosa including aminoglycosides. Therefore, identification of drug resistance patterns in P. aeruginosa is of great importance in prevention and control of infections in burn patient centers.