Drug resistance patterns of bacteria isolated from patients with nosocomial pneumonia at Tehran hospitals during 2009-2011

INTRODUCTION: Nosocomial pneumonia remains an important cause of mortality and morbidity worldwide. Surveillance programs play an important role in the identification of common etiologic agents and local patterns of antimicrobial resistance. METHODOLOGY: In this study we determined the frequency and antimicrobial susceptibility of pathogens isolated from patients with nosocomial pneumonia during 2009 to 2011. RESULTS: A total of 642 bacteria were isolated from 516 suspected samples. Acinetobacter baumannii (21.1%, n = 136), was the commonest isolated pathogen followed by Pseudomonas aeruginosa (17.4%, n = 112), Staphylococcus aureus (15.8%, n = 102) and enterococci (8.4% n = 54). The most effective therapeutic agents against A. baumannii were polymyxin B (95.5% susceptible), ceftriaxone/tazobactam (72% susceptible) and levofloxacin (52.9% susceptible). Polymixin B (89.2% susceptible), ceftriaxone/tazobactam (89.2% susceptible) and piperacillin-tazobactam (80.3% susceptible) were found to be the most active agents against P. aeruginosa. Extended-spectrum beta-lactamases were detected among isolates of K. pneumoniae (45.4%) and E. coli (20.3%). Overall, the prevalence of methicillin-resistant S. aureus and vancomycin resistant enterococci were 80.4% and 40.7% respectively. Linezolid was found to be the most active antibiotic against these pathogens. The etiology of 50% of the nosocomial infection cases was polymicrobial. CONCLUSIONS: The combination of ceftriaxone/tazobactam seems to be beneficial agent against multidrug-resistant Gram-negative bacilli isolated form respiratory tract infections. The results of our study can be used for guiding appropriate empiric therapy in this geographic region.