Exposure to carbapenem and carboxypenicillin or ureidopenicillin during the week before onset of ventilator-associated pneumonia (VAP) and severity of disease with regard to respiratory and hematologic failures were independent risk factors for the occurrence of Stenotrophomonas maltophilia-related VAP, according to study results published in the Journal of Infection. Furthermore, adequate antimicrobial therapy did not improve the prognosis of Smaltophilia VAP.

Researchers conducted a matched case-control study based on prospectively collected multicenter data using the French OUTCOMERA database. They designed 2 matched cohort analyses to identify risk factors for S maltophilia VAP and evaluate the outcome of patients. In one group, 92 patients with at least 1 episode of S maltophilia VAP were matched with 375 patients with VAP caused by other pathogens. In the other group, 84 patients with at least 1 episode of S maltophilia VAP were matched with 237 patients with Pseudomonas aeruginosa VAP.

The matching criteria for both groups were  same intensive care unit (ICU), same predicted hospital mortality assessed by Simplified Acute Physiology Score II (±10%), and same time interval between ICU admission and VAP onset, taking into account the time of VAP occurrence.

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In the multivariate analysis, patients with S maltophilia VAP were more frequently women, who also demonstrated respiratory and coagulation components of Sequential Organ Failure Assessment (SOFA) score >2 before onset of VAP and had more frequent exposure to carbapenem and carboxypenicillin or ureidopenicillin, such as piperacillin-tazobactam, within the week before VAP.

Adequate therapy was not associated with improvement of prognosis (P =.42 log rank test) regardless of the coinfection. In addition, age and chronic cardiac failure were the only variables associated with S maltophilia VAP 30-day mortality.

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After matching on previous duration of ICU stay, there was no difference in ICU and 30-day mortality in the 2 case-control analyses. However, the 60-day mortality was higher among patients with S maltophilia VAP compared with the matched group whose VAP was caused by other pathogens, but not when compared with the matched group with VAP caused by P aeruginosa.

“Attributable mortality of [S maltophilia] VAP is still unclear, but the presence of [S maltophilia] in the lungs seems to have a deleterious effect on outcome in ICU patients,” noted the researchers.


Ibn Saied W, Merceron S, Schwebel C, et al. Ventilator-associated pneumonia due to Stenotrophomonas maltophilia: risk factors and outcome [published online November 2, 2019]. J Infect. doi:10.1016/j.jinf.2019.10.021