title: Gram-negative bacteremia induces greater magnitude of inflammatory response than Gram-positive bacteremia.
abstract: BACKGROUND
  Bacteremia is recognized as a critical condition that influences the outcome of sepsis. Although large-scale surveillance studies of bacterial species causing bacteremia have been published, the pathophysiological differences in bacteremias with different causative bacterial species remain unclear. The objective of the present study is to investigate the differences in pathophysiology and the clinical course of bacteremia caused by different bacterial species.
  
  
  METHODS
  We reviewed the medical records of all consecutive patients admitted to the general intensive care unit (ICU) of a university teaching hospital during the eight-year period since introduction of a rapid assay for interleukin (IL)-6 blood level to routine ICU practice in May 2000. White blood cell count, C-reactive protein (CRP), IL-6 blood level, and clinical course were compared among different pathogenic bacterial species.
  
  
  RESULTS
  The 259 eligible patients, as well as 515 eligible culture-positive blood samples collected from them, were included in this study. CRP, IL-6 blood level, and mortality were significantly higher in the septic shock group (n = 57) than in the sepsis group (n = 127) (P < 0.001). The 515 eligible culture-positive blood samples harbored a total of 593 isolates of microorganisms (Gram-positive, 407; Gram-negative, 176; fungi, 10). The incidence of Gram-negative bacteremia was significantly higher in the septic shock group than in the sepsis group (P < 0.001) and in the severe sepsis group (n = 75, P < 0.01). CRP and IL-6 blood level were significantly higher in Gram-negative bacteremia (n = 176) than in Gram-positive bacteremia (n = 407) (P < 0.001, <0.0005, respectively).
  
  
  CONCLUSIONS
  The incidence of Gram-negative bacteremia was significantly higher in bacteremic ICU patients with septic shock than in those with sepsis or severe sepsis. Furthermore, CRP and IL-6 levels were significantly higher in Gram-negative bacteremia than in Gram-positive bacteremia. These findings suggest that differences in host responses and virulence mechanisms of different pathogenic microorganisms should be considered in treatment of bacteremic patients, and that new countermeasures beyond conventional antimicrobial medications are urgently needed.
authors.affiliation: Department of Emergency and Critical Care Medicine, Chiba University Graduate School of Medicine, Inohana Chuo, Chiba, Japan. ryuzo@pf6.so-net.ne.jp
authors.forename: Ryuzo
authors.initials: R
authors.lastname: Abe
authors.forename: Shigeto
authors.initials: S
authors.lastname: Oda
authors.forename: Tomohito
authors.initials: T
authors.lastname: Sadahiro
authors.forename: Masataka
authors.initials: M
authors.lastname: Nakamura
authors.forename: Yo
authors.initials: Y
authors.lastname: Hirayama
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Tateishi
authors.forename: Koichiro
authors.initials: K
authors.lastname: Shinozaki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hirasawa
mesh_terms: D000368:Aged; D016470:Bacteremia / Q000276:immunology* / Q000382:microbiology; D005260:Female; D006090:Gram-Negative Bacteria / Q000276:immunology*; D016905:Gram-Negative Bacterial Infections / Q000276:immunology; D006094:Gram-Positive Bacteria / Q000276:immunology*; D016908:Gram-Positive Bacterial Infections / Q000276:immunology; D006785:Hospitals, University; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008485:Medical Audit; D008875:Middle Aged; D012720:Severity of Illness Index; D018746:Systemic Inflammatory Response Syndrome / Q000097:blood / Q000209:etiology* / Q000503:physiopathology