Amoxicillin-clavulanate therapy increases childhood nasal colonization by methicillin-susceptible Staphylococcus aureus strains producing high levels of penicillinase.

Author(s): Guillemot D, Bonacorsi S, Blanchard JS, Weber P, Simon S, Guesnon B, Bingen E, Carbon C

Affiliation(s): Institut Pasteur, Paris 15, France. guillemo@pasteur.fr

Publication date & source: 2004-12, Antimicrob Agents Chemother., 48(12):4618-23.

Publication type: Clinical Trial; Randomized Controlled Trial

We examined factors associated with penicillinase production by nasal carriage Staphylococcus aureus strains in 648 children aged 3 to 6 years attending 20 randomly sampled playschools. The children were prospectively monitored for drug use and medical events for 6 months and were then screened for S. aureus carriage. Isolates were tested for their susceptibility to penicillin G and methicillin, and penicillinase production by methicillin-susceptible, penicillin-resistant strains was quantified. S. aureus was isolated from 166 children (25.6%). Exposure to amoxicillin-clavulanate during the previous 3 months was associated with higher penicillinase production by penicillin-resistant, methicillin-susceptible strains (odds ratio, 3.6; P = 0.03). These results suggest that use of the amoxicillin-clavulanate combination could induce a herd selection process of S. aureus strains producing higher levels of penicillinase.