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The Changing Epidemiology of Serious Bacterial Infections in Young Infants

Greenhow, Tara L. MD*; Hung, Yun-Yi PhD; Herz, Arnd M. MD; Losada, Elizabeth MD§; Pantell, Robert H. MD

Pediatric Infectious Disease Journal:
doi: 10.1097/INF.0000000000000225
Original Studies

Background: Management of febrile young infants suspected of having serious bacterial infections has been a challenge for decades. The impact of changes in prenatal screening for Group B Streptococcus and of infant immunizations has received little attention in population-based studies.

Methods: This study analyzed all cultures of blood, urine and cerebrospinal fluid obtained from full-term infants 1 week to 3 months of age, who presented for care at Kaiser Permanente Northern California during a 7-year period utilizing electronic medical records.

Results: A total of 224,553 full-term infants were born during the study period. Of 5396 blood cultures, 129 bacteremic infants were identified (2%). Of 4599 urine cultures, 823 episodes of urinary tract infection (UTI) were documented in 778 infants (17%). Of 1796 CSF cultures, 16 infants had bacterial meningitis (0.9%). The incidence rate of serious bacterial infections (bacteremia, UTI and meningitis) and febrile serious bacterial infections was 3.75 and 3.1/1000 full-term births, respectively. Escherichia coli was the leading cause of bacteremia (78), UTI (719) and bacterial meningitis (7). There were 23 infants with Group B Streptococcus bacteremia including 6 cases of meningitis and no cases of Listeria infection. Nine percentage of infants had multiple sites of infection; 10% of UTIs were associated with bacteremia and 52% of bacteremia was associated with UTI.

Conclusions: Compared with earlier studies, UTIs now are found significantly more often than bacteremia and meningitis with 92% of occult infections associated with UTIs. These data emphasize the importance of an urinalysis in febrile infants.

Author Information

From the *Division of Infectious Diseases, Department of Pediatrics, Kaiser Permanente Northern California, San Francisco; Division of Research, Kaiser Permanente Northern California, Oakland; Division of Infectious Diseases, Department of Pediatrics, Kaiser Permanente Northern California, Hayward; §Department of Pediatrics, Kaiser Permanente Northern California, Oakland; and Department of Pediatrics, Division of General Pediatrics, University of California, San Francisco, CA.

Accepted for publication November 25, 2013.

Funding for Drs. Greenhow and Hung was provided Kaiser Permanente Northern California Community Benefit Grant. The authors have no funding or conflicts of interest to disclose.

Address for correspondence: Tara L Greenhow, MD, Division of Infectious Diseases, Department of Pediatrics, Kaiser Permanente Northern California, 2200 O’Farrell St San Francisco, CA 94115. E-mail:

© 2014 by Lippincott Williams & Wilkins, Inc.