Etiology of community-onset monomicrobial bacteremic pneumonia and its clinical presentation and outcome: Klebsiella and Pseudomonas matters

To describe the difference of the clinical features, bacteremia severity, and outcome of patient with community-onset bacteremic pneumonia between Pseudomonas, Klebsiella, and other causative microorganisms, the total 278 adults with community-onset monomicrobial bacteremic pneumonia were studied in a retrospective cohort. Klebsiella (61 patients, 21.9%) and Pseudomonas (22, 7.9%) species was the leading and the fifth common pathogen, respectively. More patients having initial presentation with critical illness (a Pitt bacteremia score ≥ 4) and a fatal comorbidity (McCabe classification) as well as a higher short- (30-day) or long-term (90-day) mortality rate was evidenced in patients infected with Klebsiella or Pseudomonas species, compared to other causative microorganisms. Compared to patients in the Klebsiella group, more frequencies of recent chemotherapy and an initial presentation of febrile neutropenia, and less proportions of diabetes mellitus were disclosed among those in the Pseudomonas group. Of importance, a significantly differential survival curve between Klebsiella or Pseudomonas species and other species during 30-day or 90-day period after bacteremia onset but a similarity of Pseudomonas and Klebsiella species was evidenced, using the Cox-regression after adjusting the independent predictors of 30-day mortality. Conclusively, of pathogens causing community-onset bacteremic pneumonia, Klebsiella and Pseudomonas species should be recognized as the highly virulent pathogens and resulted in poor short- and long-term prognoses.