Abstract
To identify predictors of bloodstream infections (BSI) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) among patients with colonization by the same organism.
Observational, prospective study including consecutive patients admitted to intensive care unit (ICU) with colonization by CRAB (June 2020–June 2023). According to internal protocols, all patients underwent routine microbiological surveillance (rectal swab, urine cultures, endotracheal aspirate cultures) on admission and then twice weekly. Burn patients underwent also skin cultures. The primary outcome measure was CRAB-BSI. A predictive score was developed using multivariable regression. Regression coefficients were used to calculate the score. Discrimination was evaluated using the area under the receiver operating characteristic curve (AUC). Risk groups based on quartiles of the score were derived. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated in each risk group.
During the study period, we identified 283 patients colonized by CRAB. Of them, 49.1% had a multi-site colonization. The most common site of colonization was rectal (228/283, 80.6%), followed by respiratory tract (148/283, 52.3%), skin (44/283, 15.5%) and urinary tract (31/283, 11%). A total of 103/283 (36.4%) colonized patients developed a CRAB-BSI. On multivariable analysis, burns (OR 8.219, 95% CI 3.591–18.812, P < 0.001), respiratory tract colonization (OR 4.285, 95% CI 2.179–8.426, P < 0.001), number of colonization sites (risk per each site) (OR 2.197, 95% CI 1.363–3.541, P = 0.001) and cardiovascular disease (OR 1.940, 95% 1.068–3.524, P = 0.029) were independently associated with increased risk for CRAB-BSI (Figure 1, Panel a). In our study population, the score ranged from 1 to 9 and showed a good discrimination (AUC 0.817, 95% CI 0.764–0.869, P < 0.001) (Figure 1, Panel b). The risk of CRAB-BSI ranged from 9.5% if the score was <2 (sensitivity 94.2%, specificity 31.7%, PPV 44.1%, NPV 90.5%) to 83.8% if the score was >5 (sensitivity 30.1%, specificity 96.7%, PPV 83.8%, NPV 70.7%) (Figure 1, Panel c).
Risk score points and Odds Ratios (Panel a). ROC curve analysis (Panel b). BSI-rates across different risk groups of the score (the risk groups were calculated according to the percentiles of the score); 1 represents low probability of BSI, 2 represents low-intermediate probability of BSI, 3 represents low-high probability of BSI, and 4 represents high probability of BSI (Panel c).
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