Bacterial and Clinical Characteristics of Health Care- and Community-Acquired Bloodstream Infections Due to Pseudomonas aeruginosa

Abstract

f Health care-associated infections, including Pseudomonas aeruginosa bloodstream infection, have been linked to delays in appropriate antibiotic therapy and an increased mortality rate. The objective of this study was to evaluate intrinsic virulence, bacterial resistance, and clinical outcomes of health care-associated bloodstream infections (HCABSIs) in comparison with those of community-acquired bloodstream infections (CABSIs) caused by P. aeruginosa. We conducted a retrospective multicenter study of consecutive P. aeruginosa bacteremia patients at two university-affiliated hospitals. Demographic, clinical, and treatment data were collected. Microbiologic analyses included in vitro susceptibility profiles and type III secretory (TTS) phenotypes. Sixty CABSI and 90 HCABSI episodes were analyzed. Patients with HCABSIs had more organ dysfunction at the time of bacteremia (P ‫؍‬ 0.05) and were more likely to have been exposed to antimicrobial therapy (P < 0.001) than those with CABSIs. Ninety-two percent of the carbapenem-resistant P. aeruginosa infections were characterized as HCABSIs. The 30-day mortality rate for CABSIs was 26% versus 36% for HCABSIs (P ‫؍‬ 0.38). The sequential organ failure assessment score at the time of bacteremia (hazard ratio [HR], 1.2; 95% confidence interval [CI], 1.1 to 1.3) and the TTS phenotype (HR 2.1; 95% CI, 1.1 to 3.9) were found to be independent predictors of the 30-day mortality rate. No mortality rate difference was observed between CABSIs and HCABSIs caused by P. aeruginosa. Severity of illness and expression of TTS proteins were the strongest predictors of the 30-day mortality rate due to P. aeruginosa bacteremia. Future P. aeruginosa bacteremia trials designed to neutralize TTS proteins are warranted. Bloodstream infections (BSIs) are serious clinical events with life-threatening consequences. The total number of deaths resulting from nosocomial BSIs is difficult to estimate and varies greatly, depending on the etiology. However, the attributable mortality rate may be as high as 80% among patients in intensive care units (1). Pseudomonas aeruginosa accounts for 3 to 7% of all BSIs and 23 to 26% of Gram-negative bacteremias (2, 3). Pneumonia, pancreaticobiliary tract infection, indwelling catheters, and urinary tract infection have all been implicated as potential sources of infection (1, 4). Despite recent advances in critical-care management, mortality rates due to P. aeruginosa BSI remain high, ranging between 27 and 48% (1, 5).Poor outcomes of P. aeruginosa BSIs have been associated with both microbial and host factors. Neutropenia, a respiratory source of bacteremia, shock, renal failure, and metastatic foci of infection are among the host factors implicated in increased mortality rates (4, 6). Bacterial attributes include a high degree of intrinsic virulence (7, 8) and widespread antibiotic resistance. P. aeruginosa is intrinsically resistant to many structurally unrelated antimicrobial agents (9) because of the low permeability of its outer membrane, the constitutiv...

Prevalence and risk factors for antibiotic-resistant community-associated bloodstream infections

“…Hattemer et al [14] examined differences between patients with carbapenem-resistant versus carbapenem-sensitive P. aeruginosa CA-BSI and reported no significant differences by age, sex, or Charlson comorbidity index but did find that prior antibiotic therapy was highly predictive of resistance—a factor that we were not able to assess in this analysis. We did find a positive, though not statistically significant, association between malignancy and antibiotic resistance among patients with enterococcal infections, but this finding was not consistent across all of the organisms we evaluated.…”

Multidrug-Resistant Bacteria in the Community

“…In a cohort of 60 patients with community-acquired bloodstream infections with P. aeruginosa , 100% of isolates were meropenem susceptible, and 95% were susceptible to piperacillin/tazobactam and ceftazidime 49 . A case report from Turkey describes a young man without healthcare exposure who presented with a pyogenic liver abscess caused by a P. aeruginosa strain that was only susceptible to imipenem, amikacin, and colistin 50 .…”

Spatial Mapping of Pyocyanin inPseudomonas AeruginosaBacterial Communities Using Surface Enhanced Raman Scattering

“…1 The success of P. aeruginosa as a pathogen depends partly on the production and secretion of an arsenal of virulence factors which include the phenazines – a class of redox-active heterocyclic small-molecule metabolites. 2 Phenazines have also been implicated in several functions critical to the survival of the bacteria, such as biofilm formation and growth.…”