Increased carriage of resistant non-pneumococcal alpha-hemolytic streptococci after antibiotic therapy.
OBJECTIVE
We compared colonization and resistance rates of non-pneumococcal alpha-hemolytic streptococci (AHS) and Streptococcus pneumoniae in children receiving antibiotic therapy for acute otitis media.


METHODS
Between December 1997 and September 1998, children 6 months to 6 years of age, diagnosed with acute otitis media were randomly assigned to receive amoxicillin/clavulanate (Augmentin) 45 mg/kg/d in 2 divided doses for 10 days or azithromycin (Zithromax), 10 mg/kg, once on the first day, followed by 5 mg/kg daily for 4 days. Nasopharyngeal swabs for culture were obtained before and at 2 weeks and 2 months after the start of therapy. Streptococci were identified by species, and antibiotic susceptibility was determined by the epsilometric test.


RESULTS
One hundred six children completed the 2-week follow-up and 2-month follow-up, respectively. The nasopharyngeal carriage rate of non-pneumococcal AHS increased from 14% before treatment to 32% at the 2-week follow-up (P =.02) and was similar in both treatment groups. In contrast, the carriage of S pneumoniae decreased from 51% before therapy to 27% at the 2-week follow-up (P =.002). The carriage of penicillin-resistant AHS strains (minimum inhibitory concentration > 1 microg/mL) increased from 9% before treatment to 26% at 2 weeks and 36% at 2 months.


CONCLUSIONS
Amoxicillin/clavulanate and azithromycin therapy resulted in increased isolation of nasopharyngeal non-pneumococcal AHS, many of which were multidrug-resistant, in contrast to a decrease in pneumococcal carriage. This suggests that the competitive balance between these 2 groups of organisms was disturbed as a result of differential antibiotic susceptibility. The importance of drug-resistant AHS as a reservoir for resistance genes for S pneumoniae warrants further investigation.
Ghaffar
F
F
Department of Pediatrics, Division of Infectious Disease, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9063, USA.
Friedland
I R
IR
Katz
K
K
Muniz
L S
LS
Smith
J L
JL
Davis
P
P
Reynolds
J
J
McCracken
G H
GH
D019980:Amoxicillin-Potassium Clavulanate Combination / Q000627:therapeutic use; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D017963:Azithromycin / Q000627:therapeutic use; D002675:Child, Preschool; D018432:Drug Resistance, Multiple; D004359:Drug Therapy, Combination / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D010033:Otitis Media / Q000188:drug therapy; D013291:Streptococcus / Q000187:drug effects* / Q000302:isolation & purification; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000302:isolation & purification; D018440:beta-Lactam Resistance
D000900:Anti-Bacterial Agents; D019980:Amoxicillin-Potassium Clavulanate Combination; D017963:Azithromycin