95 - Contaminant Organism Growth in Febrile Infants at Low-Risk for Invasive Bacterial Infection

Poster Number: 95
Publication Number: 95.1422

Background: Although blood cultures continue to be recommended universally for febrile infants ≤60 days old evaluated in the emergency department (ED), newly released guidelines recommend against urine cultures in infants with normal urinalyses and against cerebrospinal fluid (CSF) cultures in low-risk infants. False-positive culture results often require additional resource utilization while awaiting confirmation of contamination.

Objective: We aimed to describe the proportion of contaminated blood, urine, and CSF cultures in a multicenter sample of low-risk febrile infants. For infants discharged from the initial ED visit, we aimed to describe the proportion of infants with and without contaminated cultures who had repeat ED visits and hospital admission within 72 hours.

Design/Methods: We conducted a secondary analysis of a cross-sectional, 34-site study of well-appearing low-risk febrile infants 29 to 60 days old seen in the ED in 2018-2019. Infants were included if they had a fever ≥38C and were low-risk for invasive bacterial infection based on history, physical exam, and results of screening blood and urine testing. Our primary outcome was contaminant organism growth in blood, urine, and CSF cultures obtained at the index ED visit, determined using standard definitions. We calculated frequencies and proportions for categorial variables. We calculated chi-square statistics for comparisons between dichotomous variables.

Results: Of 4042 infants meeting inclusion criteria, 3645 (90.2%) had a blood culture obtained, 179 (4.9%) had a contaminated blood culture (range 0 – 42.9% by site, Figure 1a). Infants with contaminant growth in blood culture were more likely to have a repeat ED visit within 72 hours of discharge from the index ED visit (73.9% vs 7.8%, p < 0.001, Table 1). Of 3850 (95.2%) infants who underwent urine testing, 36 (1.0%) had likely contaminant growth and 184 (5.0%) had definite contaminate growth (range 0 – 33.3% by site, Figure 1b). There was no difference in ED revisits between discharged infants with contaminated and negative urine cultures (Table 1). In total, 669 infants (16.6%) had a non-indicated lumbar puncture attempted, of whom 601 (89.8%) had CSF obtained and 11 (1.8%) had a contaminated CSF culture.

Conclusion(s): Nearly 10% of the low-risk febrile infants 29 to 60 days old in this multicenter sample had a contaminated culture obtained during their evaluation for fever. Our findings have important implications for efforts to reduce unnecessary cultures and improve sterile technique when obtaining cultures.