Carbapenem-resistant Acinetobacter baumannii complex in the United States – an epidemiological and molecular description of isolates collected through the Emerging Infections Program, 2019

Abstract

Background: Understanding the epidemiology of carbapenem-resistant A. baumannii complex (CRAB) and the patients impacted is an important step towards informing better infection prevention and control practices and improving public health response. Methods: Active, population-based surveillance was conducted for CRAB in 9 U.S. sites from January 1-December 31, 2019. Medical records were reviewed, isolates were collected and characterized including antimicrobial susceptibility testing and whole genome sequencing. Results: Among 136 incident cases in 2019, 66 isolates were collected and characterized; 56.5% were from cases who were male, 54.5% were from persons of Black or African American race with non-Hispanic ethnicity, and the median age was 63.5 years. Most isolates, 77.2%, were isolated from urine, and 50.0% were collected in the outpatient setting; 72.7% of isolates harbored an acquired carbapenemase gene (aCP), predominantly blaₒₓₐ₋₂₃ or blaₒₓₐ₋₂₄/₄₀; however, an isolate with blaₙᴅₘ was identified. The antimicrobial agent with the most in vitro activity was cefiderocol (96.9% of isolates were susceptible). Conclusions: Our surveillance found that CRAB isolates in the U.S. commonly harbor an aCP, have an antimicrobial susceptibility profile that is defined as difficult-to-treat resistance, and epidemiologically are similar regardless of the presence of an aCP.