Changing epidemiology of serious bacterial infections in febrile infants without localizing signs

Abstract

Objective: Historically, management of infants with fever without localizing signs (FWLS) has generated much controversy, with attempts to risk stratify based on several criteria. Advances in medical practice may have altered the epidemiology of serious bacterial infections (SBIs) in this population. We conducted this study to test the hypothesis that the rate of SBIs in this patient population has changed over time.

Patients and methods: We performed a retrospective review of all infants meeting FWLS criteria at our institution from 1997-2006. We examined all clinical and outcome data and performed statistical analysis of SBI rates and ampicillin resistance rates.

Results: 668 infants met criteria for FWLS. The overall rate of SBIs was 10.8%, with a significant increase from 2002-2006 (52/361, 14.4%) compared to 1997-2001 (20/307, 6.5%) (p = 0.001). This increase was driven by an increase in E. coli urinary tract infections (UTI), particularly in older infants (31-90 days).

Conclusions: We observed a significant increase in E. coli UTI among FWLS infants with high rates of ampicillin resistance. The reasons are likely to be multifactorial, but the results themselves emphasize the need to examine urine in all febrile infants <90 days and consider local resistance patterns when choosing empiric antibiotics.

Figure 1. Analysis of Raw Data and Trends in SBIs among FWLS Infants, 1997–2006.

A) Raw numbers of FWLS infants as well as SBIs and % SBI. B) Data in Figure 1a is graphed by %SBI on the y axis and year on the x axis (blue line). Also presented: overall mean %SBI (green line) and linear regression (red line). Statistical data on linear regression line is included.

Figure 2. Bayesian Analysis of SBIs among FWLS Infants, 1997–2001 and 2002–2006.

The graph represents the probability of SBI based on data from the early and later periods of this study compared with the Rochester data as well as data on FWLS infants from Utah , . The probability curve from the data from the later period centers at approximately 14.4% whereas the other three curves all overlap between 5–10% probabilities.