Guiding Antimicrobial Therapy using Gram Stain in Patients with Ventilator Associated Pneumonia- An Effective Preliminary Diagnostic Tool

Abstract

Introduction: Empirical antimicrobial therapy is the mainstay of antimicrobial stewardship. The gram stain can be used to guide initial empiric antimicrobial therapy in cases where culture report is not available. This rapid test can therefore be helpful in preventing the initiation of inappropriate therapy and its adverse outcomes. Aim: To determine the effectiveness of gram stain of tracheal aspirate samples in order to predict the causative microorganism and starting appropriate initial antimicrobial therapy. Materials and Methods: This cross-sectional study was done for 208 tracheal aspirate samples that were sent to Department of Microbiology, Lady Hardinge Medical College, New Delhi, India, with a request for bacterial culture and Antibiotic Susceptibility Testing (AST) from January 2019 to June 2019. Each sample was inoculated on 5% Sheep blood agar, Chocolate agar and MacConkey agar followed by gram stain preparation and smears. The culture plates were checked after 24 hours for any bacterial growth and further identification was done by gram stain, motility and biochemical tests. The AST was performed as per Clinical and Laboratory Standards Institute (CLSI) 2019 guidelines. All data entry was done on MS excel software and appropriate statistical tests were applied. Results: Out of total 208 samples significant gram stain findings were seen in 90 cases (43.2%). Out of 208 samples 132 (63.5%) cases grew significant pathogens on culture. Out of these 90 cases, 68 (75.5%) of gram stain finding matched with culture results. The correlation between gram stain and culture was found to be 75.5%. Conclusion: Gram stain is not only a quick and cost-effective method but also easily available in most laboratories and is highly reproducible. Gram stain, a rapid diagnostic tool, can thus be very useful in antimicrobial stewardship especially for the critically ill patients.