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Abstract

Introduction: Colistin resistant bacteria induce a high mortality in intensive care units (ICU) patients. Colistin is used for the management of infections due to multidrug-resistant (MDR) Gram-negative bacteria (GNB) and had acceptable effectiveness and considerably less toxicity. Colistin is a rapidly bactericidal antimicrobial agent that possesses a significant postantibiotic effect against MDR Gram-negative pathogens, such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae. Increased use of colistin to treat MDR has led to the development of colistin-resistant strains. However, exact estimation of incidence and outcome based on both in vitro and in vivo data is to be clarified in ICU. Methods: Critically ill patients with sepsis caused by GNB resistant to all antibiotics (MDR) were treated with colistin. Diagnosis of infection including sepsis or ventilator associated pneumonia (VAP) was based on clinical and criteria. Using Broncho-alveolar lavage (BAL) samples for bacteria were obtained and tested with respect to their susceptibility to colistin by E-test. Clinical response to colistin ad survival rate was evaluated. Results: 150 patients with sepsis or VAP enrolled in the study and BAL samples were obtained from all patients. 102 (68%) of the 150 GNB isolates were resistant to Colistin by E-test. Clinical response was observed for 86 (56.6%) of the treatments and survival at 30 days was 59 (57.8%) in colistin resistant group (E-test colistin resistance). The prevalence of Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae was 48%, 33%, and 19%, respectively in colistin resistance. Conclusions: overall MDR GNB was found to have high level of colistin resistant in ICU patients by E-test (in vitro). However, MDR GNB showed less colistin resistant clinically (in vivo) and survival rate was much better than expected.