Serious Bacterial Infections in Hospitalized Febrile Infants in the First and Second Months of Life.

OBJECTIVE: Most protocols evaluating serious bacterial infection (SBI) risk in febrile infants classify neonates <30 days of age as high risk (HR), while other protocols do not distinguish between infants <30 and 30-60 days of age. We compared SBI rates in febrile infants at the first and the second months of life.

METHODS: This was a retrospective, population-based, cohort study. All febrile infants ≤60 days of age hospitalized in southern Israel, January 2013 through May 2014, were included. SBI risk assessment included medical history, physical examination, blood count and dipstick urine analysis.

RESULTS: Overall, 623 infants were identified; 142 HR infants <30 days of age, 95 low-risk (LR) infants <30 days of age, 232 HR infants 30-60 days of age and 154 LR infants 30-60 days of age. Urinary tract infection comprised 84.7% (133/157) of all SBIs. Among HR infants, higher SBI rates were observed in <30 versus 30-60 days (45.0% vs. 29.3%; P = 0.003), while respective rates were similar among LR infants (8.4% vs. 11.0%; P = 0.66). SBI rates in HR infants 0-14 versus 15-60 days of age were 45.3% versus 33.6% (P = 0.12), and 19.2% versus 8.9% (P = 0.15) in LR infants. Among HR infants, SBI rates were 52.8% and 39.5% in infants <30 days of age with temperature ≥39°C and <39°C, respectively, while in infants ≥30 days of age, respective rates were 31.2% and 26.7% (P = 0.005, comparing the 4 groups). Among LR infants, rates were not affected by temperature degree. Thrombocytopenia was associated with higher SBI rates in HR, but not in LR.

CONCLUSIONS: In HR infants, higher SBI rates were associated with younger age, higher body temperature and thrombocytopenia. In contrast, SBI (mostly urinary tract infection) rates among LR infants (approximately 10%) were not associated with these factors.