Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii Isolates Among Intensive Care Unit Patients and Environment

Objective: Critical patients in intensive care unit (ICU) are highly susceptible to acquiring carbapenem-resistant Acinetobacter baumannii (CRAB) infection. To investigate the relationship between nosocomial infections and environmental health, we studied the distribution and homology of CRAB isolates from patients and environment and evaluated the effectiveness of infection control measures. Methods: In the 4-month study, we conducted a monthly CRAB screening of the ICU environment prior to disinfection in a Chinese teaching hospital. The ICU underwent routine disinfection procedures twice a day. We collected samples from the environment around the patients before disinfection. Clinical specimens from patients were also screened. The samples obtained were studied for phenotype and homology via antibiotic susceptibility testing, pulsed-field gel electrophoresis (PFGE), and whole-genome sequencing (WGS). Results: Ten specimens were sampled from ICU environments. Five were obtained in May 2020, and sputums from patient a in bed A at this time were cultured for CRAB isolates; in June 2020 another 5 environmental specimens were obtained from the same bed unit for CRAB, and sputums from patient b in bed A at this time were also cultured for CRAB isolates. Following intensive infection control measures, environmental sampling was negative in July and August. These 18 CRAB isolates all carried OXA-66 and OXA-23 genes and showed a similar resistance phenotype. WGS showed a close relationship among specimens from patients' sputum and their surroundings, but no homology between patients. Conclusion: The analysis of cgMLST and SNPs is more accurate for strain homology analysis. Our data confirm that CRAB isolates spread from patient to environment in ICU; however, contact isolation and disinfection measures are effective in avoiding transmis-sion, highlighting the importance of continued education and surveillance of CRAB. WGS could provide rich information on antimicrobial resistance, which is of great value in scientific research and clinical diagnosis.