Emergence of beta-lactamase-producing aerobic and anaerobic bacteria in the oropharynx of children following penicillin chemotherapy.

The acquisition of beta-lactamase-producing aerobic and anaerobic bacteria was investigated in 21 children treated with penicillin for otitis media or pharyngitis and in 18 untreated control children. Beta-lactamase-producers were isolated in three children before and in ten children after treatment (p = 0.04). Although the variety of bacterial species isolated did not change following treatment, beta-lactamase-producing Bacteroides melaninogenicus, B. oralis, and Branhamella catarrhalis were encountered only after therapy, while some beta-lactamase-producing Staphylococcus aureus and Hemophilus influenzae were found before treatment. The incidence of beta-lactamase-producers did not increase in the control children. Spread of beta-lactamase-producers to household contacts by 12 treated and 13 normal control children also was studied. Ten of the treated children and 15 of 33 of the household contacts harbored beta-lactamase-producers, while none were found in normal control children and only two were found in 27 of their household contacts (comparison of the two household contacts, p less than 0.01).