For most infants ≤60 days old evaluated in a pediatric emergency department for suspected invasive bacterial infection, the combination of ampicillin plus either gentamicin or a third-generation cephalosporin is an appropriate empiric antimicrobial treatment regimen. Of the pathogens isolated from infants with invasive bacterial infection, 11% were resistant to third-generation cephalosporins alone.

Objective To determine factors associated with adverse outcomes among febrile young infants with invasive bacterial infections (IBI), i.e., bacteremia and/or bacterial meningitis. Study design Multicenter, retrospective cohort study (July 2011 – June 2016) of febrile infants ≤60 days of age with pathogenic bacterial growth in blood and/or cerebrospinal fluid. Subjects were identified by query of local microbiology laboratory and/or electronic medical record systems, and clinical data were extracted by medical record review. Mixed-effect logistic regression was employed to determine clinical factors associated with 30-day adverse outcomes, which were defined as death, neurologic sequelae, mechanical ventilation, or vasoactive medication receipt. Results 350 infants met inclusion criteria; 279 (79.7%) with bacteremia without meningitis and 71(20.3%) with bacterial meningitis. Forty-two (12.0%) infants had a 30-day adverse outcome: 29/71 (40.8%) with bacterial meningitis vs. 13/279 (4.7%) with bacteremia without meningitis (36.2% difference, 95% CI 25.1% to 48.0%; P < .001). On adjusted analysis, bacterial meningitis (adjusted odds ratio [aOR] 16.3, 95% CI 6.5 to 41.0; P<0.001), prematurity (aOR 7.1, 95% CI2.6 to 19.7; P<0.001), and ill appearance (aOR 3.8, 95% CI 1.6 to 9.1; P=0.002) were associated with adverse outcomes. Among infants who were born at term, not ill appearing, and had bacteremia without meningitis, only 2/184 (1.1%) had adverse outcomes, and there were no deaths. Conclusions Among febrile infants ≤60 days old with IBI, prematurity, ill appearance, and bacterial meningitis (vs bacteremia without meningitis) were associated with adverse outcomes. These factors can inform clinical decision-making for febrile young infants with IBI.

Empirical antibiotic use differed across regionally diverse US children's hospitals in infants <90 days old with UTI, bacteremia, or meningitis. Antimicrobial susceptibility to common antibiotic regimens was similar across hospitals, and adding ampicillin to a third-generation cephalosporin minimally improves coverage. Our findings support incorporating empirical antibiotic recommendations into national guidelines for infants with suspected bacterial infection.