Reemergence of gram-negative health care-associated bloodstream infections.
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.
Albrecht
Svenja J
SJ
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.
Fishman
Neil O
NO
Kitchen
Jennifer
J
Nachamkin
Irving
I
Bilker
Warren B
WB
Hoegg
Cindy
C
Samel
Carol
C
Barbagallo
Stephanie
S
Arentzen
Judy
J
Lautenbach
Ebbing
E
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