A paper published yesterday in The Lancet Regional Health—Western Pacific describes the introduction and spread of carbapenem-resistant Acinetobacter baumannii (CRAB) in a Chinese intensive care unit (ICU), with more than half of samples collected from patient rooms and 28% of patients testing positive.
In the cross-sectional study, a team of researchers from China and the United Kingdom collected and conducted whole-genome sequencing on 5,068 swab and clinical samples from the hospital environment (3,985), patients (964), and staff (119) at a 28-bed ICU in Hangzhou. Their aim was to assess the prevalence of CRAB, a World Health Organization priority pathogen that persists for prolonged periods on hospital surfaces and medical equipment and can colonize patients within 48 hours of admission. They also investigated population structure, dynamics of strain movement and dissemination, and horizontal gene transfer events.
Extensive spread in the ICU
Overall, CRAB was isolated from 532 (10.5%) samples, including 432/3,985 (10.8%) environmental samples and 100/964 (10.4%) patient samples, and was isolated more frequently from bed units (183/335, 54.6%) than from patients (72/299, 24.1%). Within the bed units (patients' rooms), samples from ventilators (80/287, 27.9%) and dispensing trolleys (10/39, 25.6%) were most likely to yield CRAB. Almost a third of patients screened (35/254, 28.0%) during the study were CRAB-positive, with 14 acquiring CRAB during their stay. The acquired clusters were frequently found in the patient's environment.
All isolates were resistant to imipenem, meropenem, and ciprofloxacin, and 274 (49.7%) were resistant to amikacin.
WGS showed that the CRAB population was dominated by OXA-23–producing global clone 2 isolates (99.3%) that could be divided into 20 distinct clusters, 17 of which were introduced separately or circulating independently in the ICU during the study period. Three horizontal gene transfer events involving three different plasmids were observed between CRAB strains.
The study authors note that the endemicity of CRAB observed in the study is in stark contrast to monoclonal CRAB hospital outbreaks that have been documented in high-income countries, which typically occur after breaches in infection prevention and control and involve a single cluster of patients infected or colonized with CRAB.
"The quantity of CRAB found in this ICU highlights the urgent need for targeted infection prevention and control measures in healthcare facilities where such large accumulations of the bacteria are likely, so that we can stem the global spread of this pathogen," study co-author Alan McNally, PhD, of the University of Birmingham, said in a university press release.
McNally and his colleagues suggest such measures could include regular deep cleaning of surfaces touched by patients and staff, isolation of CRAB-positive patients, minimal relocation of patients between beds, and enhanced staff hand washing.
The quantity of CRAB found in this ICU highlights the urgent need for targeted infection prevention and control measures in healthcare facilities where such large accumulations of the bacteria are likely, so that we can stem the global spread of this pathogen.