P20. From colonization to infection: assessing the BSI potential in patients with KPC, NDM, VRE, and CRAB rectal colonization

Although rectal colonization by multidrug-resistant microorganisms (MDRO) is a known risk factor for subsequent bloodstream infection (BSI) development, the predisposing factors of this transition remain poorly defined. Therefore, we designed this study to investigate the progression to BSI from different MDRO rectal colonization.

This retrospective study includes patients admitted to clinical, surgical, and intensive care (ICU) departments of the IRCCS Policlinico di Pavia, Northern Italy, with rectal colonisation by Klebsiella pneumoniae carbapenemase (KPC)-producing and New Delhi metallo-β-lactamase (NDM)-producing Klebsiella pneumoniae, vancomycin-resistant Enterococcus faecium (VRE) or carbapenem-resistant Acinetobacter baumannii (CRAB). Chi-square test was used to assess the association between MDRO and progression to BSI. Nested logistic regression models was used to assess the association between demographic, clinical and ward factors and the probability of BSI. A stepwise model-building approach was applied for parameter selection and final model was selected through 4-fold cross-validation.

A total of 1556 patients with rectal colonization by MDRO were included in the study, with a median age of 65 years (55–74) and predominantly male (66.2%). Since patients could be colonized by more than one MDRO, the total number of rectal colonization was 2284. BSI developed in 12.6% of KPC carriers, 10.4% of NDM carriers, 4.2% of VRE carriers, and 20% of CRAB carriers (P < 0.0001) (Table 1). We found that the ward is strongly associated with BSI in KPC and NDM carriers, with patients in ICU at higher risk compared to those in other departments (OR 3.1 and 10.8 respectively, P-value < 0.05). Hematological diseases were associated with BSI in VRE and KPC carriers (OR 3.9 and 3.1, P-value <0.01) while solid organ transplants were associated with BSI in CRAB carriers (OR 11.5, P-value <0.05).

Assessing the likelihood of progression from colonization to BSI is very difficult: demographic and clinical characteristics showed no significant association, except for hematological diseases in VRE and KPC carriers and solid organ transplant in CRAB cases. ICU stay and the type of MDRO are significantly associated with progression to BSI. These findings are important for guiding the choice of appropriate empirical treatment in MDRO colonized patients.

Table 1.

Development of BSI based on the different colonizing MDRO

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