Value of the Pitt bacteremia score in predicting the outcome of nonbacteremic patients with infections caused by multidrug-resistant organisms.

OBJECTIVES: Infections caused by multidrug-resistant organisms (MDROs) are increasingly associated with significant morbidity and mortality. Early identification of high-risk patients is essential. The Pitt Bacteremia Score (PBS) is validated in bloodstream infections, but its role in nonbacteremic infections remains unclear. The aim of this study is to evaluate the performance of the PBS in predicting mortality among patients with nonbacteremic MDRO infections and compare it with the quick Sequential Organ Failure Assessment (qSOFA) score and the Charlson Comorbidity Index (CCI).

METHODS: We conducted a 5-year retrospective study at a tertiary care center including adults (>18 years) admitted between December 2018 and December 2023 with confirmed nonbacteremic MDRO infections. Organisms included methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), carbapenem-resistant Pseudomonas aeruginosa (CRPA), carbapenem-resistant Enterobacterales (CRE), and carbapenem-resistant Acinetobacter baumannii (CRAB). Patients with bloodstream infection, colonization, ICU stay >48 h, severe COVID-19, or terminal illness were excluded. Separate multivariable logistic regression models were constructed for PBS, qSOFA, and CCI. Discriminatory performance was assessed using receiver operating characteristic (ROC) curve analysis.

RESULTS: Among 202 patients (mean age 62.1 ± 18.3 years; 67.8% male), in-hospital mortality was 21.3%. In multivariable analyzes, PBS (aOR 1.75, 95% CI 1.49-2.05; P < 0.001) and qSOFA (aOR 11.46, 95% CI 5.37-24.47; P < 0.001) remained independently associated with mortality, whereas CCI did not retain statistical significance after adjustment. Age remained an independent predictor in all models, while time to effective antimicrobial therapy was independently associated with mortality in the CCI model (aOR 0.62, 95% CI 0.47-0.81; P < 0.001). PBS demonstrated excellent discriminatory performance (AUC 0.939, 95% CI 0.897-0.968), outperforming qSOFA (AUC 0.883) and CCI (AUC 0.696).

CONCLUSION: PBS is a strong predictor of in-hospital mortality in patients with nonbacteremic MDRO infections and demonstrated superior discriminatory performance compared with qSOFA and CCI. These findings support its use as an early risk-stratification tool in this high-risk population.