Prediction of imipenem-resistant microorganisms among the nosocomial critically ill patients with Gram-negative bacilli septicemia: a simple risk score

Objectives: The increasing number of reports on infections due to carbapenem-resistant Gram-negative bacilli (GNB) has raised concerns, because they have complicated empiric or guided antibiotic therapy for critically ill patients. We aimed to develop a scoring system to predict nosocomial imipenem-resistant GNB (IR-GNB) septicemia among the critically ill patients. Materials and methods: The study included critically ill adult patients with nosocomial GNB septicemia at Kaohsiung Chang Gung Memorial Hospital (CGMH) in 2013-2015, and the scoring system for predicting IR-GNB septicemia was developed, followed by prospective validation conducted among patients at Linkou CGMH and Kaohsiung CGMH between January and June, 2016. Results: In the development of the scoring system, 748 patients were included. The independent factors associated with IR-GNB septicemia were prior exposure (days) to carbapenems (adjusted odds ratio [ aOR] per 1-day increase, 1.1; 1-3 days: 2 points, 4-6 days: 5 points, 7-9 days: 8 points, and >= 10 days: 13 points), use of mechanical ventilation (aOR 3.7; 5 points), prior colonization with IR-GNB strains (aOR 3.5; 5 points) within 30 days before the onset of GNB septicemia, and comorbid condition with chronic kidney disease (aOR 2.1; 3 points). The internal validation showed an area under the receiver operating characteristic curve (ROC) of 0.75; and an external validation among 314 patients showed similarly good performance (ROC 0.77). Youden's index indicated the score of >= 6 as the best cutoff value with sensitivity of 75% and specificity of 79%. Conclusion: This scoring system might help clinicians stratify the risk for developing IR-GNB septicemia among critically ill patients and combined antibiotics may be used until antimicrobial de-escalation/adjustment is clearly indicated by the subsequently identified GNB and its susceptibility profile.