Bloodstream infections caused by ST2 Acinetobacter baumannii over 6 years in China: risk factors, antibiotic regimens and virulence

Background Acinetobacter baumannii (Ab) is an important pathogen of medical-related infections, A.baumannii sequence type 2 (ST2) has spread all over the world. To the best of our knowledge, this is the first study to analyze the clinical and microbiological characteristics of patients with bloodstream infection (BSI) due to ST2 A.baumannii. Methods A retrospective study was conducted in a large tertiary hospital in China. From January 2013 to December 2018, the clinical and microbiological data of all consecutive hospitalized patients with bacteremia due to multidrug-resistant A.baumannii (MDR-AB) were included and analyzed comprehensively. Results A total of 108 episodes of BSI due to MDR-AB cases were enrolled during the study period. Overall, 30-day mortality was 69.4% (75/108). The use of mechanical ventilation, intensive care unit (ICU) stay and thrombocytopenia may cause higher mortality (P = 0.048, P < 0.001, and P < 0.001, respectively). Change antimicrobial within 48 h after isolating from blood, use of antibacterial combination and more inpatient days were significantly associated with survival (P < 0.001, P = 0.037, and P = 0.007, respectively). All MDR isolates belong to ST2, and have strong biofilm formation ability and high pathogenicity. Conclusions BSI caused by ST2 A.baumannii represents a difficult challenge for physicians, considering the high mortality associated with this infection. The combination of cefoperazone/sulbactam and tigecycline may be a meaningful treatment option.