135. Clinical and Microbiologic Analysis of Risk Factors for Mortality in Patients with Carbapenem-Resistant Acinetobacter baumannii Bacteremia

Abstract Background Carbapenem-resistant Acinetobacter baumannii (CRAB) infection is an emerging clinical issue and shows high mortality rates. There are a few studies that have evaluated the microbiologic risk factors for mortality in CRAB bacteremia. Aim of this study is to identify the clinical and microbiologic risk factors for mortality in CRAB bacteremia. Methods Adult patients with monomicrobial CRAB bacteremia at a 2,700-bed tertiary hospital between December 2012 and December 2018 were retrospectively enrolled in the study. Risk factors for 30-day mortality were evaluated through a detailed clinical and microbiological analysis of study patients. All isolates collected on the first day of bacteremia were subjected to colistin susceptibility testing by broth microdilution and genotyping by multilocus sequence typing (MLST). Results A total of 164 patients were enrolled and 90 (55%) died within 30 days. Of the 164 patients, 111 (68%) were male and median age was 66.5 years. The most common MLST genotype was ST191 (80 isolates, 49%), followed by ST451 (14%) and ST784 (13%), and 12 (7%) isolates were resistant to colistin (MIC ≥4 mg/L). Deceased patients were more likely to have hematologic malignancy, neutropenia, pneumonia, and primary bacteremia; less likely to have solid tumor, catheter-related infection, and biliary tract infection; more likely to have a high Pitt bacteremia score; and less likely to receive appropriate antibiotic treatment, colistin, and combination therapy with colistin and tigecycline, compared with surviving patients (Table 1). Genotype, colistin MIC, and colistin resistance were not associated with mortality (Figure 1 and 2). In multivariable analysis, neutropenia (aOR, 3.25; 95% CI, 1.18–8.95), catheter-related infection (aOR, 0.33; 95% CI, 0.11–0.99), biliary tract infection (aOR, 0.20; 95% CI, 0.04–0.99), a high Pitt bacteremia score (aOR,1.42; 95% CI, 1.20–1.67), and combination therapy with colistin and tigecycline (aOR, 0.36; 95% CI, 0.14–0.92) were independent risk factors for mortality (Table 2). Conclusion Clinical factors such as the site of infection, severity of bacteremia, and specific combination therapy rather than microbiologic factors contributed to mortality in CRAB bacteremia. Appropriate combination therapy may help improving outcomes in CRAB bacteremia. Disclosures All authors: No reported disclosures.