Molecular epidemiology and patient outcome of carbapenem-resistant Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii in Japan: a multicenter study from MultiDrug-Resistant organisms clinical research network

Background and objectives: Carbapenem-resistant Gram-negative bacilli (CRGNB), especially Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii, are critical pathogens associated with excess morbidity and mortality. To elucidate their molecular epidemiology and clinical outcomes in Japan, patients with CRGNB were enrolled in the MDR organisms clinical research network (MDRnet) consisting of eight tertiary care facilities. Methods: Between 2019 and 2022, 246 unique patients with carbapenem-resistant Enterobacterales (CRE), carbapenem-resistant P. aeruginosa (CRPA) and carbapenem-resistant A. baumannii (CRAB) isolates were prospectively enrolled. Results: A total of 246 isolates were collected from 246 patients, including 78 (31.7%) CRE, 167 (67.9%) CRPA and 1 (0.4%) CRAB. For CRE, 74.4% of the isolates carried carbapenemase genes with predominance of bla_IMP (64.1%). Only 2.4% of CRPA had carbapenemase genes, which was lower than CRE. Among the infected patients, 20.0% and 12.5% died of CRE and CRPA within 30 days, respectively. In patients with CRE, the mortality rate within 30 days for those without carbapenemase-producing Enterobacterales (CPE) was higher compared with those with CPE (22.2% compared with 18.8%). Conclusions: Our study highlights the unique molecular epidemiology and clinical outcomes of CRGNB in Japan.