Beta-lactamase production in the upper respiratory tract flora in relation to antibiotic consumption: a study in children attending day nurseries.

The occurrence of beta-lactamase production in Haemophilus influenzae, Branhamella catarrhalis and Moraxella nonliquefaciens was compared in 191 healthy children attending day nurseries in 2 municipalities differing with regard to the prescription rate of beta-lactam antibiotics. A significantly higher frequency of beta-lactamase production was recorded in M. nonliquefaciens isolated in the municipality with the higher prescription rate. A corresponding difference was not recorded for H. influenzae or B. catarrhalis. Approximately 75% of the nasopharyngeal pathogens H. influenzae, B. catarrhalis and Streptococcus pneumoniae, as well as the commensal M. nonliquefaciens, were eliminated and often replaced by other strains of either species over a period of one month. Although none of the children were on antibiotics a substantial proportion of the acquired strains produced beta-lactamase. This suggested that the carrier rate of beta-lactamase producing strains of the respiratory tract is not only related to the effect of recent antibiotic treatment but also to the prevalence of such strains in the population.