Serious Bacterial Infections in Febrile Infants Younger Than 90 Days of Age:
The Importance of Ampicillin-Resistant Pathogens
Carrie L. Byington, MD*,, Kristine
K. Rittichier, MD, Kathlene E. Bassett, MD, Heidi
Castillo, MD*, Tiffany S. Glasgow, MD*,
Judy Daly, PhD¶ and Andrew T. Pavia, MD
* University of Utah Divisions of General Pediatrics
Pediatric Infectious Diseases
Pediatric Emergency Medicine ¶ PCMC Microbiology Laboratory, Salt Lake City, Utah
Background. Intrapartum antibiotic prophylaxis against groupB Streptococcus (GBS) has reduced the occurrence of seriousbacterial infections (SBI) in young infants caused by GBS. Recommendationsfor initial antibiotic therapy for the febrile infant 1 to 90
days old were developed when infections with GBS were commonand
antibiotic resistance was rare.
Objective. To document the pathogens responsible for SBI in
recent years in febrile infants 1 to 90 days old and the antibiotic
susceptibility of these organisms.
Methods. The results of bacterial cultures from infants 1 to90 days old evaluated for fever at Primary ChildrensMedical
Center in Salt Lake City, Utah, between July 1999 andApril 2002 were
analyzed. Antibiotic susceptibility profileswere collected and
patient records were reviewed to determineif initial antibiotic
therapy was changed following the identificationof the organism.
Results. Of 1298 febrile infants enrolled from the Primary ChildrensMedical Center emergency department, 105 (8%) had SBI. The mean
age of the infants with SBI was 39 days (range 282 days)and 2 (2%)
were <7 days. SBI included urinary tract infection(UTI; 67%),
bacteremia (16%), bacteremia and UTI (6%), bacteremiaand meningitis
(5%), meningitis (2%), abscess (2%), meningitisand UTI (1%), and
meningitis and gastroenteritis (1%). Eighty-three(79%) of 105
episodes of SBI were caused by Gram-negative bacteria,including 92%
of UTI, 54% of bacteremia, and 44% of meningitiscases. The most
common pathogen was Escherichia coli (61%).Other
Gram-negative pathogens were responsible for 19% of SBI.
Staphylococcus aureus was the most common Gram-positive pathogen,
causing 8% of SBI. GBS accounted for 6% of SBI.
Of the 105 pathogens, 56 (53%) were resistant to ampicillin.Of
the pathogens causing meningitis, UTI, and bacteremia, 78%,53%, and
50%, respectively, were resistant to ampicillin. Antibiotictherapy
was changed in 54% of cases of SBI following identificationof the
organism.
Conclusions. In Utah, ampicillin-resistant Gram-negative bacteriaare the most common cause of SBI in febrile infants <90 days
old. This finding impacts antibiotic selection, especially incases
of meningitis. Local surveillance of pathogens and antibiotic
susceptibility patterns is critical to determine appropriate
antibiotic therapy.
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