ABSTRACT
OBJECTIVES: Stenotrophomonas maltophilia has emerged as an important opportunistic nosocomial pathogen due to its intrinsic and acquired resistance to a wide range of antimicrobial agents. The present study aimed to investigate the occurrence of antibiotic resistance and resistance mechanisms among clinical isolates of S. maltophilia from Iranian patients. MATERIALS AND METHODS: This cross-sectional study was performed on 44 S. maltophilia isolates that were recovered from different clinical specimens in 2015 and 2016. Conventional microbiologic methods were used for primary identification of isolates and confirmed by specific polymerase chain reaction (PCR) primers. Minimum inhibitory concentrations (MICs) were determined by the E-test. PCR was applied to determine antibiotic resistance genes. RESULTS: All of S. maltophilia isolates were susceptible to trimethoprim/sulfamethoxazole (TMP/SMX) and colistin. Moreover, the susceptibility rates of isolates toward ceftazidime and ciprofloxacin were 93.2%, and 84.1%, respectively. Class 1 integrons was detected in 24 (54.5%) isolates by the presence of int1 gene. Moreover, the prevalence of antibiotic resistance genes sul1, sul2, and Smqnr were found in 16 (36.4%), 15 (34.1%), and 29 (65.9%) isolates, respectively. CONCLUSION: In summary, the prevalence of sul and Smqnr genes in integrons-contained isolates point out the significant risk of sulfonamides and fluoroquinolones resistance among clinical isolates of S. maltophilia in our region.
ABSTRACT
The emergence of multiple drug-resistant (MDR) Acinetobacter baumannii strains has become a global problem. This study aimed to evaluate the occurrence of antibiotic resistance and to investigate the presence of antibiotic resistance determinants among A. baumannii isolates obtained from hospitalized patients in Iran. This cross-sectional study was performed on 92 A. baumannii isolates in the years 2015-2016. Antimicrobial susceptibility testing was carried out by the disk diffusion method. The presence of antibiotic resistance determinants was detected by the PCR method. All the A. baumannii isolates were resistant to tested carbapenems, fluoroquinolones and sulfonamide agents, and susceptible to polymixins. Of the isolates 92.4% were extensive drug-resistant (XDR) and 7.6% were MDR. PCR screening for the presence of integron genes revealed that class 1 integron presented in 46.7% of isolates and class 2 in 18.5% isolates. Of the investigated antibiotic resistance genes, bla vim, bla imp, bla spm, sul1 and sul2 were positive in 75%, 12%, 12%, 47.8%, and 67.4% of isolates, respectively. The high prevalence of metallo-beta-lactamase (MBL) and sul genes in our results may indicate the importance of these genes in the dissemination of carbapenem- and sulfonamide-resistant A. baumannii isolates. Rational and restricted prescription of carbapenems may be an effective way to minimize the emergence and spread of MBL-harboring strains.
