LOW-DOSAGE AND LONG TREATMENT DURATION OF BETA-LACTAM - RISK-FACTORS FOR CARRIAGE OF PENICILLIN-RESISTANT STREPTOCOCCUS-PNEUMONIAE

Context.-The spread of drug-resistant Streptococcus pneumoniae in the community is a public health problem in developed and developing natio ns, but whether antibiotic use is responsible for the increase in drug resistance is not known. Objective.-To analyze the relationship betwe en penicillin-resistant S pneumoniae (PRSp) pharyngeal carriage and ch aracteristics of beta-lactam use. Design.-Observational study of child ren attending 20 randomly sampled schools.Setting.-The Loiret, in the center of France. Participants.-A total of 941 children, 3 to 6 years old. Main Outcome Measure(s).-Pharyngeal carriage of S pneumoniae, ant ibiotic use, and medical events during the preceding 30 days. Pneumoco ccal penicillin G sodium minimal inhibitory concentrations and serotyp ing were performed. Results.-Medical illnesses and the use of antibiot ics were not associated with PRSp carriage. However, oral beta-lactam use was associated with an increased risk of PRSp carriage (odds ratio [OR], 3.0; 95% confidence interval [CI], 1.1-8.3; P=.03). Children tr eated by low daily doses of an oral beta-lactam (defined as lower than clinical recommendations) had an increased risk of PR,Sp carriage, as compared with children who did not (OR, 5.9; 95% CI, 2.1-16.7; P=.002 ). A treatment of long duration (>5 days) with a beta-lactam was assoc iated with an increased risk of PRSp carriage (OR, 3.5; 95% CI, 1.3-9. 8; P=.02). Conclusions.-Our results suggest that a low daily dose and a long duration of treatment with an oral beta-lactam contribute to th e selective pressure in promoting pharyngeal carriage of PRSp.