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Abstract

Introduction: The purpose of this study was to evaluate outcomes between patients with third-generation cephalosporin-resistant (3GCR) and carbapenem-resistant (CR) Klebsiella pneumoniae bloodstream infections (BSIs). Hypothesis: Differences in outcomes may exist between patients with CR Klebsiella pneumoniae BSIs and those with 3GCR isolates that remain carbapenem susceptible. Methods: This was a retrospective, cohort study. Patients were identified via the microbiology laboratory’s electronic record system and included if they had a positive blood culture for K. pneumoniae and were > 18 years old. Patients without clinical evidence of infection were excluded. Data on baseline characteristics, clinical and microbiologic success, and mortality was collected. Results: A total of 464 patients were identified with blood cultures positive for K. pneumoniae from 2006-2011. 152 patients were included in the study; 108 in the 3GCR group and 44 in the CR group. The groups were similar in terms of the age of the patients, proportion of male patients, and whether the patients were immunocompromised. Patients with CR BSIs were more likely to be in the ICU at the time of BSI (77.3% versus 59.3%, p=0.03), but otherwise had similar Charlson indices (mean 2.93 vs. 3.43, p=0.69) and APACHE II scores (mean 18.7. vs. 17.3, p=0.28). Patients in the CR group were less likely to have polymicrobial blood cultures (18.2% versus 41.8%, p=0.005). Median time to active antibiotics did not differ significantly between groups (51.6 versus 56.6 hours, p=0.67). Microbiological success was significantly more common among 3GCR BSIs (92.5% versus 61.2%, p<0.001); clinical success (61.1% versus 46.5%, p=0.11) and 30-day survival trended in favor of 3GCR patients (70.4% versus 55.5%, p=0.06). On multivariate analysis, CR was strongly associated with less microbiologic success (adjusted odds ratio [aOR] 0.07, 95% CI 0.02 – 0.26), though not clinical success (aOR 0.55, [95% CI 0.23-1.32]), or 30-day survival (aOR 1.74, 95% CI 0.76 -3.96). Conclusions: Patients with CR Klebsiella BSIs had less microbiologic clearance than those with 3GCR isolates that remained carbapenem-susceptible.