Study of Imipenem Resistant Pseudomonas aeruginosa and Associated Predisposing Risk Factors in a Rural Tertiary Care Hospital

Imipenem resistance is an emerging threat in nosocomial infections caused by Pseudomonas aeruginosa. Imipenem resistant Pseudomonas aeruginosa (IR-PA) with a increased mortality and morbidity worsen the situation by virtue of their multi-drug resistance and thus limit therapeutic options. Very limited data available on IR-PA nosocomial infections and associated predisposing risk factors necessitated the present study. Of the 523 patients presenting with R aeruginosa, 110 isolates from nosocomial infections (as per CDC definitions) were analyzed by Kirby-Bauer's disc diffusion method of antimicrobial susceptibility testing for the detection of IR-PA. Predisposing risk factors were analyzed by student "t" test, and "z" test for proportions, using SPSS for windows, version 13.0. Incidence of Imipenem resistant Pseudomonas aeruginosa infections was 21.82% with eight distinct antibiogram types circulating in the hospital. Overall mortality in P aeruginosa infections was 13.63% (15/110). Increased mortality was observed in IR-PA than in IS-PA (33.3% Vs 8.14% P value=0.01 S) with a mean duration of stay in ICU till death of 3.16 +/- 0.98 days indicating the severity of the infections. Majority of deaths among IR-PA infections were due to VAP as an underlying disease. Previous Imipenem therapy was significantly associated with IR-PA infections (P value <0.001 HS) resulting in emergence and/or acquisition of IR-PA. Other predisposing risk factors were significantly associated with IR-PA infections. IR-PA infections results in significantly higher mortality than IS-PA. VAP is the underlying disease in majority of deaths due to IR-PA infections. Attributable mortality in IR-PA infections, is partially mediated by Imipenem resistance, severity of underlying disease, predisposing risk factors, Multidrug resistance and Pan drug resistance, making IR-PA isolate, a successful and difficult to treat pathogen. Patients in whom Imipenem is selected as antipseudomonal antibiotic, the potential for emergence of IR-PA strains should be anticipated, and in appropriate circumstance, routine culture and sensitivity should be performed to detect the emergence of IR-PA strains. These findings can be generalized to other tertiary care hospitals with similar conditions.