title: Reemergence of gram-negative health care-associated bloodstream infections.
abstract: BACKGROUND
  Primary health care-associated bloodstream infections (PHA-BSIs) affect as many as 350 000 patients in the United States annually. Whereas gram-negative organisms were the leading cause before the 1970s, gram-positive organisms have been the predominant microbial isolates since then.
  
  
  METHODS
  We identified all PHA-BSIs among adult inpatients in a 625-bed quaternary care hospital from January 1, 1996, through December 31, 2003, and evaluated trends in the microbial etiology, geographic distribution within the institution, and antimicrobial susceptibilities.
  
  
  RESULTS
  A total of 3662 PHA-BSIs caused by 4349 bacterial and fungal isolates were identified. From 1999 to 2003, the proportion of PHA-BSIs due to gram-negative organisms increased from 15.9% to 24.1% (P<.001 for trend). This trend was not significantly different across various units of the hospital, and no specific gram-negative species contributed disproportionately to the increase. With few exceptions, there were no significant increases in antimicrobial resistance. The increase in gram-negative organisms was accompanied by a decline in the proportion of PHA-BSIs from coagulase-negative staphylococci (from 33.5% in 1999 to 29.9% in 2003, P = .007) and from Staphylococcus aureus (from 18.8% in 1999 to 11.8% in 2003, P = .004). The proportion of PHA-BSIs from Candida species almost doubled from 5.8% in 1999 to 11.3% in 2003 (P = .002).
  
  
  CONCLUSIONS
  To our knowledge, this is the first US study to report a reemergence of gram-negative organisms as a cause of PHA-BSIs. This finding does not seem to be related to changes in specific gram-negative organisms or to antimicrobial resistance. If this trend continues, it will have important implications for the management of bloodstream infections.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, 423 Guardian Drive, Philadelphia, PA 19104, USA.
authors.forename: Svenja J
authors.initials: SJ
authors.lastname: Albrecht
authors.forename: Neil O
authors.initials: NO
authors.lastname: Fishman
authors.forename: Jennifer
authors.initials: J
authors.lastname: Kitchen
authors.forename: Irving
authors.initials: I
authors.lastname: Nachamkin
authors.forename: Warren B
authors.initials: WB
authors.lastname: Bilker
authors.forename: Cindy
authors.initials: C
authors.lastname: Hoegg
authors.forename: Carol
authors.initials: C
authors.lastname: Samel
authors.forename: Stephanie
authors.initials: S
authors.lastname: Barbagallo
authors.forename: Judy
authors.initials: J
authors.lastname: Arentzen
authors.forename: Ebbing
authors.initials: E
authors.lastname: Lautenbach
mesh_terms: D000328:Adult; D016470:Bacteremia / Q000453:epidemiology* / Q000382:microbiology; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D006090:Gram-Negative Bacteria / Q000302:isolation & purification; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology; D006785:Hospitals, University / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D010414:Pennsylvania / Q000453:epidemiology; D011320:Primary Health Care; D012189:Retrospective Studies