The in-vitro activities of co-amoxiclav and other oral antibiotics against Streptococcus pneumoniae isolates exhibiting intermediate susceptibility to penicillin

Impact of antimicrobial therapy on nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, and Branhamella catarrhalis in children with respiratory tract infections

We conducted a multicenter prospective study to document changes in nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, and Branhamella catarrhalis during antibiotic therapy. A cohort of 629 children with respiratory tract infections underwent nasopharyngeal sampling before and after antibiotic treatment. Susceptibility testing, serotyping, arbitrarily primed polymerase chain reaction, and pulsed-field gel electrophoresis were used to compare pretreatment and posttreatment strains of S. pneumoniae. A significant decrease in carriage of all 3 species (especially S. pneumoniae and B. catarrhalis) was recorded. The increase in the proportion of penicillin-resistant pneumococci (PRP; 66% vs. 44%) was due to the decreased carriage of penicillin-susceptible pneumococci (71 of 629 vs. 176 of 629). The risk of PRP carriage in a given child did not increase. None of the children was found to harbor genetically related strains with increased minimum inhibitory concentrations. Given the multiple resistance of PRP, beta-lactam antibiotic therapy also increased the incidence of macrolide-resistant strains, whereas macrolides selected both macrolide- and penicillin-resistant strains.