[A case of group B streptococcal occult bacteremia]

We reported an infant with occult bacteremia caused by group B Streptococcus (GBS). An 8-week-old girl, who was uneventfully born to an 18-year-old mother, was hospitalized because of a 4-hour history of fever. On admission, she appeared nontoxic, and the temperature was 39.0 degrees C, and the pulse and respiratory rates were 162/min and 42/min, respectively. Laboratory findings showed a total white blood count of 5,200/microliter with 44% neutrophils and C-reactive protein of 0.7 mg/dl. Cerebrospinal fluid and urine examinations did not disclosed any abnormalities. After a complete evaluation of sepsis including cultures from blood, cerebrospinal fluid, urine, stool, and throat swab, intravenous cefotaxime was administered at 100 mg/kg/day in three fractions. Nine hours after the start of the culture, GBS was isolated from blood, and thereafter from the throat, but not from other culture sites obtained on admission. However, at that time she fed well and her temperature was subsiding. Forty-eight hours after admission, she became afebrile and cefotaxime administration was continued for 7 days. Based on the examinations of minimal inhibitory concentrations of various antibiotics, serotype analysis, and restriction-digestion patterns of genomic DNA, the 3 GBS strains isolated from the patient's blood and throat and the maternal anus were identical, suggesting that the infant was infected by her mother. This is the first report in Japan describing the clinical course of GBS occult bacteremia. According to a case series published in the English literature and our case, there are few clinical and laboratory markers predictive for GBS occult bacteremia, but this condition may develop focal invasive infections. A high index of suspicion is required for correct diagnosis. Further accumulation of such patients is warranted to establish the appropriate treatment.