New Algorithm Identifies Risks in Nosocomial Pneumonia

A hospital patient
A hospital patient
A new algorithm can search administrative data for individuals with HAP and VAP, who are at significant risk for carbapenem-resistant infection.

A new administrative data-driven algorithm can identify individuals who are at an increased risk for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), and describe characteristics of carbapenem resistance in this population, according to a study published in Chest. Results of this study suggested that infection with carbapenem-resistant organisms significantly contributed to increased hospital costs and length of stay.

This retrospective cohort study included 8969 individuals with HAP (50.8%) and VAP (48.2%) from the Premier Research database (2009-2016). Inclusion criteria were: testing positive for gram negative organism (Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Acinetobacter bamannii, or Enterobacteriaceae) via blood and/or respiratory culture, and no diagnosis of pneumonia on admission.

The study’s primary outcome was hospital death related to carbapenem resistance. Logistic regression was used to investigate associations between carbapenem resistance and inappropriate empiric therapy, as well as between mortality and 30-day readmission. Generalized linear modeling was used to examine carbapenem resistance/inappropriate empiric therapy and cost/length of stay associations.

Carbapenem resistance was found in 11.8% of participants. Compared with participants whose samples showed carbapenem-susceptible organisms, carbapenem resistance was associated with patients who were admitted from an extended-care facility (7.2% vs 4.6%, respectively; P=.014), female (41.4% vs 33.2%; P<.001), and who had a higher comorbidity burden (Charlson Comorbidity Index 3 vs 2; interquartile range 1 to 4, for each measure; P <.001).

The most common gram negative bacteria causing both HAP and VAP was P aeruginosa (21.1%); however, this pathogen accounted for 16.8% in cases of carbapenem resistance. The most commonly identified organism in carbapenem-resistant infection was S maltophilia (38.7%). Inappropriate empiric therapy was more likely to occur in participants with carbapenem resistance compared with those with a carbapenem-susceptible organism infection (25.8% vs 10.0%; P <.001). Mortality and 30-day readmission risk postinfection were not shown to be affected by carbapenem resistance or carbapenem susceptible infections. However, hospital costs were significantly higher for patients with a carbapenem-resistant infection ($8921 [95% CI, $3864-$13,977). In addition, patients with carbapenem-resistant infection were associated with a 3-day longer stay in the hospital, compared with patients with carbapenem-susceptible infection.

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Limitations to this study included the use of a novel algorithm in an administrative set of data, potential misclassification due to a lack of radiographic data, potential selection bias, and the potential of positive cultures to have been a result of colonization, rather than infection.

The researchers concluded that “Our algorithm opens the possibility of using large administrative data to ask questions that require high generalizability and power in order to understand better various aspects of care in HAP and VAP.”

This study was funded by Melinta Therapeutics. Multiple authors declare affiliations with the pharmaceutical industry. Please refer to the reference for a full list of the authors’ disclosures.


Zilberberg MD, Nathanson BH, Sulham K, Fan W, Shorr AF. A novel algorithm to analyze epidemiology and outcomes of carbapenem resistance among patients with hospital-acquired and ventilator-associated pneumonia: a retrospective cohort study [published online January 24, 2019]. Chest. doi: 10.1016/j.chest.2018.12.024