Quantitative cultures of aerobic bacteria and their antibiotic susceptibility patterns from endotracheal aspirates of patients with ventilator associated pneumonia. A one year cross-sectional study

Abstract

Background: Ventilator-associated pneumonia ( VAP ) is an important intensive care unit ( ICU ) infection in mechanically ventilated patients. VAP occurs approximately in 9-27% of all intubated patients. Samples collected by invasive bronchoscopic methods have been shown to be highly specific in diagnosing VAP. However, bronchoscopy is not accessible in many settings and because of the invasive nature, cost of the bronchoscopy and need of a bronchoscopist for the procedure; samples obtained by non bronchoscopic methods may be useful alternative to bronchoscopy in the diagnosis of VAP. Aim of the Study: The present study was undertaken 1. To isolate and identify aerobic organisms associated with ventilator- associated pneumonia. 2. To study the antibiotic susceptibility pattern of the isolates by Kirby Bauer disc diffusion method. 3. To detect metallo-beta lactamase producing Pseudomonas aeruginosa isolates. Materials and Methods: The present study was undertaken at the Department of Microbiology, J.N. Medical College, Belgaum during the period from 01-01-09 to 01- 01-10. Endotracheal aspirates ( ETA ) were collected from patients with suspected VAP, and direct gram’s stain criteria was used to accept the sample. Quantitative cultures of ETA were performed with the threshold for microbiological diagnosis of VAP taken as ≥10 5 colony forming units ( cfu ) /ml. Isolates showing reduced susceptibility to Imipenem were selected for detection of MBLs enzymes by Imipenem-EDTA combined disk method. IV Results: Out of 53 cases, 2 ( 3.77% ) were polymicrobial. Acinetobacter baumannii 49.09% ( 27/55) and Pseudomonas aeruginosa 30.91% ( 17/55) were the most common pathogens isolated. Most of the organisms were highly resistant to the commonly used antibiotics. Piperacillin-tazobactam and doxycycline were found to be most effective against Acinetobacter baumannii. MBL was produced by 47.06% ( 8/17) of Pseudomonas aeruginosa. Conclusion: The bacteriological approach for the management of VAP helps the clinicians in choosing the appropriate antibiotics. This study showed that quantitative cultures of endotracheal aspirate at a cut off point of 10 diagnostic method in clinically suspected ventilator associated pneumonia.