Predicting resistant etiology in hospitalized patients with blood cultures positive for Gram-negative bacilli

Published:February 06, 2018DOI:


      • It is very important to ensure an adequate empirical therapy in patients with bacteremia due to Gram-negative bacilli
      • We assessed the independent risk factors for bacteremia caused by a resistant strain.
      • We developed a score for a bedside estimation of the risk of multidrug-resistant etiology.
      • The score is an easy instrument to guide the decision of the most appropriate initial antibiotic therapy strain in septic patients.



      To develop a risk-scoring tool to predict multidrug-resistant (MDR) etiology in patients with bloodstream infections (BSI) caused by Gram-negative bacilli (GNB).


      A prospective multicenter study analyzed patients with BSI hospitalized in 31 Internal Medicine wards in Italy from March 2012 to December 2012. Patients with BSI caused by MDR-GNB (non-susceptible to at least one agent in three antimicrobial categories) were compared to those with BSI due to susceptible GNB. A logistic regression to identify predictive factors of MDR-GNB was performed and the odds ratio (OR) were calculated. A score to predict the risk of MDR was developed.


      Of 533 BSI episodes, 253 (47.5%) were caused by GNB. Among GNB-BSI, 122 (48.2%) were caused by MDR-GNB while 131 (51.8%) by non-MDR GNB. At multivariate analysis transfer from long-term care facility (OR 9.013, 95% CI 1.089–74.579, p = 0.041), hospitalization in the last 3 months (OR 2.882, 95% CI 1.580–5.259, p = 0.001), urinary catheter (OR 2.315, 95% CI 1.202–4.459, p = 0.012), antibiotic therapy in the last 3 months (OR 1.882, 95% CI 1.041–3.405, p = 0.036), age ≥ 75 years (OR 1.866, 95% CI 1.076–3.237, p = 0.026) were factors independently associated with MDR etiology. A score ranging from 0 to 10 was useful to recognize patients at lowest risk (0 points: Negative Likelihood Ratio 0.10) and those at highest risk (>6 points, Positive Likelihood Ratio 11.8) of GNB bacteremia due to a MDR strain.


      Specific predictors of MDR etiology are useful to calculate probabilities of MDR etiology among hospitalized patients with blood cultures positive for GNB.


      BSI (bloodstream infections), CDC (Centers for Disease Control and Prevention), COPD (chronic obstructive pulmonary disease), CRE (carbapenem-resistant Enterobacteriaceae), ESBL (extended-spectrum β-lactamases), GFR (glomerular filtration rate), GNB (Gram-negative bacilli), IQR (interquartile ranges), LTCF (long-term care facility), K/DOQI (Kidney Disease Outcomes Quality Initiative), LR (likelihood ratios), MDR (multidrug-resistant), OR (odds ratio), ROC (receiver operating characteristic), SD (standard deviation)


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