Use of incubation time to detection in BACTEC 9240 to distinguish coagulase-negative staphylococcal contamination from infection in pediatric blood cultures.
BACKGROUND
Growth of coagulase-negative staphylococci (CoNS) in a blood culture indicates infection or contamination. Differentiation may be difficult in pediatric patients from whom only a single blood culture is commonly obtained.


METHODS
We evaluated the use of the incubation time to detection of growth [time to positive (TTP)] of CoNS in a continuously monitored blood culture system (BACTEC Peds/F bottles in BACTEC 9240) to differentiate infection from contamination. Three groups of febrile pediatric patients with blood cultures growing CoNS were identified: Group 1, children with vascular catheter-associated bloodstream infection; Group 2, previously healthy children with a contaminant; Group 3, chronically ill children with a contaminant.


RESULTS
The median TTP for blood cultures from the 17 infection episodes, 11 h [mean, 13.2 h; 95% confidence interval (CI), 11.4 to 17.7], was significantly shorter than either the 30 episodes in the previously healthy group with contaminant, median 19 h (mean, 22.7 h; 95% CI 19.5 to 26.2; P < 0.0001) or the 12 episodes in the chronically ill group with contaminant, median 24 h (mean, 35.2 h; 95% CI 17.2 to 53.1; P < 0.0001). A TTP of < or =15 h had a positive predictive value of 84% for diagnosis of infection. A TTP of > or =22 h had a positive predictive value of 87% for diagnosis of contaminant.


CONCLUSIONS
In our experience the TTP was a useful adjunctive test to determine the clinical significance of isolation of CoNS from a blood culture from a pediatric patient.
Haimi-Cohen
Yishai
Y
Division of Infectious Diseases, Department of Pediatrics, Schneider Children's Hospital, Long Island Jewish Medical Center, North Shore/Long Island Jewish Health System, New Hyde Park, NY, USA.
Shafinoori
Shideh
S
Tucci
Victor
V
Rubin
Lorry G
LG
D016470:Bacteremia / Q000175:diagnosis*; D001431:Bacteriological Techniques; D003030:Coagulase / Q000378:metabolism; D003428:Cross Infection / Q000175:diagnosis; D003470:Culture Media; D004866:Equipment Contamination; D006801:Humans; D010372:Pediatrics; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000175:diagnosis*; D013210:Staphylococcus / Q000201:enzymology / Q000302:isolation & purification*; D018709:Statistics, Nonparametric
D003030:Coagulase; D003470:Culture Media