Antimicrobial susceptibility and genotyping of microorganisms isolated from sputum culture of children with cystic fibrosis in an Iranian referral children's hospital.

Background: Chronic bacterial infections of the airways are present in most patients with cystic fibrosis (CF). Although most pathogens are acquired from the environment, there is great evidence of patient-to-patient transmission. Therefore, evaluating the genetic variation of strains isolated from CF patients is recommended for the purpose of examining hospital infection.

Aim: The aim of this study was to determine the antibiotic susceptibility pattern and genotyping of Staphylococcus aureus and Pseudomonas aeruginosa strains isolated from sputum samples of children with CF referred to a single pediatric CF center in Tehran, Iran.

Methods: In this cross-sectional study, the antimicrobial susceptibility profiles of strains isolated from patients with CF during 1 year were determined. Pseudomonas aeruginosa and S. aureus isolates were genotyped using the random amplified polymorphic DNA polymerase chain reaction method and were analyzed using GelCompar II software.

Results: Of 534 patients with CF, 384 had negative sputum cultures (72%), and 94 strains of P. aeruginosa (18%) and 53 strains of S. aureus (10%) were isolated. The mean age of the patients was 8.22 ± 5.7 years (range, 2 months to 18 years). The P. aeruginosa strains showed high sensitivity to ceftazidime (96%), piperacillin/tazobactam (96%), and imipenem (94%). All strains of S. aureus were susceptible to vancomycin, and 13% of the strains were methicillin-resistant S. aureus. High resistance to penicillin (92%) and erythromycin (88.5%) were reported. The results of P. aeruginosa genotyping revealed that there were six major clusters in this hospital. Also, based on the analysis of genotyping results, S. aureus strains were obtained from five clusters, most of which were located in cluster B1 (34 isolates, 64%).

Conclusion: The results of this study show the possibility of strains being transferred from one part of the hospital to another (especially from the respiratory ward to other areas). Hence, high attention should be paid to the basic methods of preventing infection.