Background & Objectives: Staphylococci are among common causes of community acquired and nosocomial infections around the world. Over the last decade, the resistance of these bacteria in hospital environments is increasing to various antibiotics such as vancomycin. The aim of present study was to determine the antimicrobial resistance pattern and Minimum Inhibitory Concentration (MIC) values among a clinical collection of staphylococci isolated from hospitalized children in Tabriz.

  Methods: In this prospective and descriptive study, 88 staphylococcal isolates including 53 S. aureus and 35 coagulase-negative staphylococcus species were recovered from various clinical specimens referred to microbiology laboratory of Children Hospital during study period (April 2011 to March 2012). Susceptibility of the isolates against 15 different antimicrobial agents and MIC values of vancomycin was tested using standard disk diffusion and E-test methods respectively.

  Results: According to the results of drug susceptibility testing, vancomycin and rifampin were the most effective but clindamycin and penicillin were the least effective drugs against tested isolates. Accordingly, the prevalence of methicillin resistant Staphylococcus aureus (MRSA) strains was determined more than 80%. According to MIC values, 13.2% of S. aureus and 3.3% of coagulase-negative staphylococcus isolates showed intermediate resistance to vancomycin. None of the isolates was fully resistant to vancomycin isolates in this study.

  Conclusion: Although fully vancomycin resistant staphylococci was not found among tested isolates in this study, there was VISA strains. Since there are reports on the emergence of VRSA strains from Iran and other countries, it is necessary for the clinician to care in prescription of vancomycin as a selective drug against staphylococcal infections. Moreover, the necessity of MIC measurement in determining of vancomycin susceptibility is more apparent.

  Background & Objectives : Acinetobacter baumannii is an opportunistic Gram-negative pathogen with increasing relevance in a variety of hospital-acquired infections especially among intensive care unit patients. A. baumannii is mostly a cause of septicemia, pneumonia and urinary tract infection following hospitalization of patients. In this study antibiotic susceptibility pattern of A.baumannii isolates and molecular typing among isolates resistant by REP-PCR were determined.

  Methods : During study, the A. baumannii, were isolated from hospitals in Tehran. The isolates were identified using standard biochemical tests and antibiotic susceptibility was determined by the disk diffusion method. Extraction of DNA and molecular typing of isolates performed using CTAB method and REP-PCR, respectively.

  Results : In this study 75 A. baumannii isolates separated from patients with an average age of 51 ± 18.45 years . The highest resistance rate was against azteronam (97%), ceftazidim (93%), cefepime (93%), piperacillin-tazobactam (93%), ciprofloxacin (93%) and ticarcillin (93%) while the lowest resistance rate was against tigecycline (n= 51, 68%), followed by tobramycin (n=24, 32%), ampicillin-sulbactam (n=21, 28%), amikacin (n=16, 21%), and carbapenems (n=11, 15%). The REP-PCR in resistant of A. baumannii isolates showed that the genotypes of A, B and C are the predominant genotypes in the resistant antibiotics.

  Conclusion: This study showed a high percentage of resistance to antimicrobial agents among genotypes A, B, and C of the A. baumannii isolates therefore strategies to control the spread of A. baumannii isolates must be designed and evaluated.

Background & objectives: Fluoroquinolones have important role in treatment of P. aeruginosa infections. The main mechanism of fluoroquinolones resistance in P. aeruginosa is mutations in the quinolone-resistance-determining region (QRDR) of gyrA and parC genes. The aim of this study was to investigate the role of these mutations in ciprofloxacin resistance in different clinical isolates of P. aeruginosa.

Methods: A total of 75 clinical P. aeruginosa isolates were collected from different university-affiliated hospitals in Tabriz. Minimum inhibitory concentrations (MICs) of ciprofloxacin were evaluated by Etest assay. DNA sequences of the QRDR of gyrA and parC were determined by dideoxy chain termination method.

Results: From 75 isolates, 77.33% were resistant to ciprofloxacin. No amino acid changes were detected in gyrA or parC genes of the ciprofloxacin susceptible isolates. Thr-83→Ile substitution in gyrA was observed in all ciprofloxacin resistant isolates. About 90% of them had Ser-87→Leu substitution in parC. Geometric mean MICs of ciprofloxacin were different for various clinical isolates of P. aeruginosa which had the same situation in type and location of gyrA and parC mutations. Moreover, the geometric mean MIC in isolates from urine was significantly (p<0.05) higher than isolates from tracheal aspirates.

Conclusion: Mutations in gyrA and parC genes are the major mechanisms for ciprofloxacin resistance in clinical isolates of P. aeruginosa. Moreover, the role of different effective factors in fluoroquinolone resistance can be different in various clinical isolates of P. aeruginosa.