The Incubation Period Necessary for Detection of Bacteremia in Immunocompetent Children with Fever: Implications for the Clinician

The authors determined the time required for blood cultures to be detected as positive for the common bacterial pathogens in immunocompetent infants and children with fever who had no apparent source of infection. Records of the bacteriology laboratory were reviewed retrospectively from 1981 to 1984 for blood cultures that were positive for Haemophilus influenzae type b, Streptococcus pneumoniae, Neisseria meningitidis Salmonella species, and group B streptococcus. Blood culturing by a conventional technique and a radiometric method were compared sequentially. Only four (1.5%) of 268 specimens were detected as positive after the second day of incubation; in each case that detection of bacteremia was delayed there was an identified source of infection. For H. influenzae but not S. pneumoniae significantly more bacteremias were detected earlier by the radiometric method. Discontinuation of empiric antibiotic therapy in immunocompetent children with suspected bacteremia and without focal infection appears warranted when blood cultures have been sterile for at least 48 hours.