Changing trend of antimicrobial resistance among gram-negative bacilli isolated from lower respiratory tract of ICU patients: A 5-year study

Background: Lower respiratory tract infections (LRTIs) are the most frequent infections among patients in intensive care units (ICUs). Aim: To track the resistance rate among the causative agents causing LRTI in the ICU patients. Design and Settings: This is a retrospective study done in a tertiary care hospital. Materials and Methods: Transtracheal or bronchial aspirates from 2776 patients admitted to the ICU were cultured and identified, and antibiotic sensitivity was performed by standard methods. Results: Of 2776 specimens, 1233 (44.41%) isolates were recovered, of which 1123 (91.07%) were gram-negative bacilli (GNB) and 110 (8.92%) were gram-positive organisms. From 2004 to 2009, Pseudomonas aeruginosa remained the most common pathogen. In phase I, high level of resistance (79-98%) was observed against all GNB. During phase II increasing trend in resistance to cephalosporins and declining trend in resistance to aminoglycosides against most GNB were observed. Multidrug resistance (resistance to three or more than three drugs) was observed in 83% of total isolates. Conclusions: Gram-negative organisms are the predominant pathogens causing LRTI in ICU. The increasing trend of resistance to cephalosporins and carbapenems in gram-negative organisms is very disturbing. Judicious use of antimicrobial agents is essential to prevent the emergence of multidrug-resistant bacteria in the ICU