H. influenzae type b, GBS, N. meningitidis, herpes simplex virus [HSV], enteroviruses), bacterial diarrhea (Salmonella, Shigella, E. coli), and osteomyelitis or septic arthritis (S. aureus or GBS).
Differentiation between viral and bacterial infections in young infants is difficult. Febrile infants <3 months of age who appear ill, especially if follow-up is uncertain, and all febrile infants <4 weeks of age should be admitted to the hospital for empirical antibiotics pending culture results. After blood, urine, and cerebrospinal fluid cultures are obtained, broad-spectrum parenteral antibiotics (typically ampicillin with cefotaxime or gentamicin) are administered. The choice of antibiotics depends on the pathogens suggested by localizing findings. The possibility of neonatal HSV should also be considered in febrile children <4 weeks old, and empirical acyclovir begun in those in whom neonatal HSV is a concern. Well-appearing febrile infants ≥4 weeks of age without an identifiable focus and with certainty of follow-up are at a low risk of developing a serious bacterial infection (0.8% develop bacteremia, and 2% develop a serious localized bacterial infection). Specific criteria identifying these low-risk infants include age older than 1 month, well-appearing without a focus of infection, no history of prematurity or prior antimicrobial therapy, a white blood cell (WBC) count of 5000 to 15,000/μL, and urine with less than 10 WBCs/high-power field. Fecal leukocyte testing and chest radiograph can be considered in infants with diarrhea or respiratory signs. Low-risk infants may be followed as outpatients without empirical antibiotic treatment, or, alternatively, may be treated with intramuscular ceftriaxone. Regardless of antibiotic treatment, close follow-up for at least 72 hours, including re-evaluation in 24 hours or immediately with any clinical change, is essential.
A common problem is the evaluation of a febrile but well-appearing child younger than 3 years of age without localizing signs of infection. Although most of these children have self-limited viral infections, some have occult bacteremia (bacteremia without identifiable focus) or UTIs, and a few have severe and potentially life-threatening illnesses. It is difficult, even for experienced clinicians, to differentiate patients with bacteremia from those with benign illnesses.
Observational assessment is a key part of the evaluation. Descriptions of normal appearance and alertness include child looking at the observer and looking around the room, with eyes that are shiny or bright. Descriptions that indicate severe impairment include glassy eyes and stares vacantly into space. Observations such as sitting, moving arms and legs on table or lap, and sits without support reflect normal motor ability, whereas no movement in mother’s arms and lies limply on tableindicate severe impairment. Normal behaviors, such as vocalizing spontaneously, playing with objects, reaching for objects, smiling, and crying with noxious stimuli, reflect playfulness; abnormal behaviors reflect irritability. Normally, crying children are consolable and stop crying when held by the parent, whereas severe impairment is indicated by continual cry despite being held and comforted.