Among patients infected with carbapenem-resistant Acinetobacter baumanii (CRAB) and carbapenem-resistant Pseudomonas aeruginosa (CRPA), the risk of mortality was increased among those with a higher Charlson comorbidity index score and those diagnosed via blood cultures, according to results of a national retrospective cohort study published in BMC Infectious Diseases.

Investigators assessed data captured from veterans who tested positive for CRAB or CRPA via culture analysis between 2013 and 2018. The analysis comprised 2 patient groups, including inpatients and outpatients receiving long-term care (LTC). Multivariable cluster adjusted regression models were used compare the postculture length of hospitalization (LOH) among inpatients vs LTC patients. The investigators also assessed factors associated with 90- and 365-day mortality between the 2 groups.

There were 1849 CRAB cultures from 1048 patients and 17,073 CRPA cultures from 8204 patients included in the analysis. Among patients in the CRAB and CRPA groups, the mean age was 68  and 70 years, 62.5% and 78.2% were White, 49.1% and 41.4% were located in the Southern US, and the mean Charlson comorbidity score was 5.0 and 4.6, respectively.

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The investigators found that the rate of mortality at 90 and 365 days was 30.3% and 46.5% among patients in the CRAB and CRPA groups, respectively. Factors associated with an increased risk of 90-mortality among patients in CRAB vs CRPA groups included inpatient care (adjusted odds ratio [aOR]; 1.59 vs 2.95), older age (aOR, 7.41 vs 2.96), and a higher Charlson comorbidity score (aOR, 1.11 vs 1.13). For both inpatients and LTC patients exposed to antibiotics within the past 90 days, the risk of 90-day mortality was decreased among those in the CRAB (aOR, 0.66) and CRPA (aOR, 0.58) groups.

Findings were similar in regard to the risk of 365-day mortality, with the exception of a decreased risk among patients in the CRAB group from the Midwest, and an increased risk among LTC patients in the CRPA group.

Further analysis was performed to assess the postculture LOH between the patient groups. Among patients in the CRAB and CRPA groups, the median postculture LOH was 20 and 16 days for inpatients, respectively, compared with 96 and 70 days for LTC patients, respectively.

Diagnosis via cultures obtained from blood specimens was associated with a significantly increased risk of 90-day mortality among patients in both the CRAB (aOR, 6.98; 95% CI, 3.55-13.73) and CRPA (aOR, 2.82; 95% CI, 2.04-3.90) groups.

This study was limited as the investigators did not assess factors associated with carbapenem resistance or the effect of different types of treatment on patients’ outcomes.

“It is important for clinicians to recognize these factors in patients infected with [CRAB and CRPA] and to appropriately treat these patients in a timely manner to cease the transmission and improve outcomes of patients infected with these pathogens,” the investigators concluded.


Vivo A, Fitzpatrick MA, Suda K, et al. Epidemiology and outcomes associated with carbapenem-resistant Acinetobacter baumanii and carbapenem-resistant Pseudomonas aeruginosa: a retrospective cohort study. BMC Infect Dis. Published online May 24, 2022. doi:10.1186/s12879-022-07436-w