Treatment of streptococcal pharyngitis: Influence of penicillinase-producing staphylococci

Abstract

A study was undertaken to determine the influence, if any, of penicillinase-producing staphylococci in the upper respiratory tract on penicillin treatment of streptococcal pharyngitis. Cultures were obtained, during a 5 month period, from the nose and throat of patients with evidence of an upper respiratory infection who were seen in a private pediatric group practice. In those patients exhibiting Group A streptococci, follow-up cultures were obtained from 10 days to 30 days later. Streptococcal isolates were grouped and typed and staphylococcal isolates were tested for coagulase and penicillinase activity. Cultures were obtained from a total of 1,231 children. Group A streptococci were isolated from 315 children and adequate follow-up studies were obtained from 163. Ninety per cent of these children were treated with a single intramuscular injection of benzathine penicillin G, 1.2 million units; the remainder received oral penicillin or some other antibiotic for 10 days. Penicillinase-producing staphylococci were isolated concomitantly with streptococci on initial culture in 54 of the 163 children (33 per cent). Streptococci were isolated on a subsequent culture from 5 of these 54 children (9 per cent) and from 14 of the 109 children (13 per cent) without penicillinase-producing staphylococci on initial culture. After therapy, penicillinase-producing staphylococci were isolated from 69 of the 163 children (42 per cent). Streptococci were isolated on subsequent culture from 8 of these 69 children (11.5 per cent) and from 11 of the 94 children without penicilIin-producing staphylococci after therapy (11.6 per cent). As an indirect quantitative measurement of penicillinase, the growth of staphylococcal strains in various concentrations of penicillin was determined. Eleven per cent of strains isolated from the initial cultures of children who continued to exhibit Group A streptococci on follow-up cultures grew in a concentration of 400 units of penicillin. Fifteen per cent of staphylococcal strains isolated from children in whom streptococci were eradicated grew in this concentration of penicillin. These data indicate that peniciIlinase-producing staphylococci in the upper respiratory tract probably do not influence the effectiveness of benzathine penicillin treatment for streptococcal pharyngitis.