Serious bacterial infections in hospitalized febrile infants aged 90 days or younger: The traditional combination of ampicillin and gentamicin is still appropriate

Background: A change in the bacterial epidemiology of infantile serious bacterial infection (SBI) has raised concerns regarding the appropriate empirical antibiotic therapy. Objective: To describe the epidemiological features of SBI in febrile infants in order to elucidate the appropriate empirical regimens. Methods: From 2005 to 2009, clinical and laboratory data were prospectively collected for all infants aged ≤90 days who were hospitalized for fever. Results: Of the 1584 febrile infants who met the study criteria, 149 (9.4%) had a culture-proven SBI: urinary tract infection in 128 (86%), urinary tract infection with bacteraemia in 11 (7%), bacteraemia in 7 (5%), enteritis with bacteraemia in 2 (1.3%), and meningitis in 1 (0.7%). Ninety-one percent of cases were caused by Gram-negative bacteria, mostly Escherichia coli (72%). Among the causative Gram-positive bacteria were Enterococcus spp. (4%) and group B Streptococcus (0.7%); no cases of Listeria monocytogenes infection were identified. Sixty-one percent of the causative bacteria were resistant to ampicillin. According to in vitro susceptibility testing, the combination of ampicillin and gentamicin provided appropriate antibiotic coverage. Conclusions: Despite changes in the epidemiology of infantile SBI, the traditional combination of ampicillin and gentamicin is still appropriate for empirical treatment of febrile infants aged ≤90 days.