Staphylococcus aureus bacteremia after median sternotomy: clinical utility of blood culture results in the identification of postoperative mediastinitis.
BACKGROUND
Mediastinitis is a complication of coronary artery bypass graft surgery (CABG) that can be difficult to diagnose. This study evaluated the utility of blood culture results in identifying patients with mediastinitis.


RESULTS
All unique patients undergoing CABG at our institution over a 60-month study period (n=5500) and all blood cultures performed on these patients <or=90 days after CABG were identified. Mediastinitis was identified by prospective active infection control surveillance. Eight hundred fifty-five (15.5%) patients had >or=1 blood culture drawn within 90 days of CABG. Mediastinitis occurred in 46 of 60 (76.7%) patients with blood cultures positive for Staphylococcus aureus, 15 of 126 (11.9%) patients with blood cultures positive for other pathogens, 37 of 669 (5.5%) patients with blood cultures with no growth, and 44 of 4645 (0.9%) patients with no blood cultures obtained. The isolation of S aureus from even 1 blood culture drawn after <or=90 days of CABG was strongly associated with mediastinitis (likelihood ratio [LR], 25; 95% CI, 14.7 to 44.4). Bacteremia attributable to other organisms did not alter pretest suspicion for mediastinitis (LR, 1.0; 95% CI, 0.6 to 1.7). Patients with negative blood cultures were less likely to have mediastinitis (LR, 0.45; 95% CI, 0.35 to 0.58). The association between S aureus bacteremia and mediastinitis remained highly significant when all unique patients undergoing CABG were analyzed in a logistic regression model and when a case-control analysis was used to evaluate patients with >or=1 blood culture obtained after CABG.


CONCLUSIONS
Among patients with blood cultures drawn after CABG, S aureus bacteremia strongly suggests the presence of mediastinitis.
Fowler
Vance G
VG
Division of Infectious Diseases, Duke University Medical Center, Durham, NC 27710, USA. fowle003@mc.duke.edu
Kaye
Keith S
KS
Simel
David L
DL
Cabell
Christopher H
CH
McClachlan
Douglas
D
Smith
Peter K
PK
Levin
Scott
S
Sexton
Daniel J
DJ
Reller
L Barth
LB
Corey
G Ralph
GR
Oddone
Eugene Z
EZ
D000046:Academic Medical Centers; D000368:Aged; D016470:Bacteremia / Q000175:diagnosis / Q000382:microbiology*; D001431:Bacteriological Techniques; D016022:Case-Control Studies; D015331:Cohort Studies; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D003428:Cross Infection / Q000175:diagnosis / Q000382:microbiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D017053:Infection Control; D016013:Likelihood Functions; D016015:Logistic Models; D008297:Male; D008480:Mediastinitis / Q000175:diagnosis / Q000382:microbiology*; D009657:North Carolina; D011183:Postoperative Complications / Q000175:diagnosis / Q000382:microbiology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D018401:Sample Size; D013211:Staphylococcus aureus / Q000302:isolation & purification*; D013249:Sternum / Q000601:surgery*