ABSTRACT
Aim: The aim of this study was to determine etiology and drug resistance pattern of most frequency isolates of microorganisms responsible for VAP in an Iranian 1000-bed tertiary care hospital in Tehran Iran. Place and Duration: This study was conducted in microbiology laboratory of Milad Hospital in Tehran, Iran from November 2010 to December 2011. Methodology: Ventilator Associated Pneumonia (VAP) was defined as any lower respiratory tract infection that developed 48 hours after mechanical ventilation. Tracheal aspirate specimens were collected and processed according standard microbiological procedures. Bacterial identification and susceptibility testing were performed using disk diffusion standard procedures as recommended by CLSI. Results: One hundred and one patients developed at least one episode of nosocomial pneumonia were subject of our study. Of 101 patients 61 patients were male and 40 female patients. The mean time for hospitalization in ICUs and ventilation duration were 16 and 9, 5 days respectively. Old age, History of previous use of antibiotics and duration of ventilation times were the most important risk factors for VAP. In total 126 microorganisms were isolated from VAP cases. Acinetobacer baumannii with 46 (36.5%) isolates was the predominant organism followed by Staphylococcus aureus with 31 (24. 60% and Pseudomonas aeruginosa with 19 (15%) isolates. Other isolated organisms included Klebsiella pneumoniae and E. coli. The majority isolated organism included Acinetobacter baumannii and Pseudomonas aeruginosa were resistant to many antibiotics including the third generation of cephalosporins and nearly 50% isolates were resistant to amikacin. Colistin was the most effective antibiotic against multidurug resistant (MDR) isolates. We found a high rate of methicillin resistant Staphylococcus aureus (93.54%). All isolates of S. aureus were susceptible to vancomycin. Conclusion: Our study revealed that A. baumannii, S. aureus and P. aeruginosa were the major etiological agents of VAP in our hospital. The majority isolates were resistant to routinely used antibiotics including the third generation of cephalosporins. We also observed a high rate of MRSA among our isolates.