[Significance of normal oropharyngeal flora in the development of streptococcal pharyngitis and outcome of penicillin therapy].

Pharyngitis is one of the most frequent diseases in children. The most important of the bacterial infections is due to Streptococcus pyogenes. For many years, penicillin is considered to be the drug of choice for streptococcal pharyngitis, although failure rates of up to 20% have been reported. One of possible explanations for penicillin treatment failure is presence of other species of bacteria in the normal oropharyngeal flora that can interfere with colonization and growth of Streptococcus pyogenes and influence the development of pharyngitis. A wide variety of microorganisms, including alpha-haemolytic streptococci and anaerobic bacteria, are present within the oropharynx (table 1). The strain of alpha-haemolytic streptococci is in interference with Streptococcus pyogenes. By producing bacteriocins, they inhibit colonization and growth of Streptococcus pyogenes and assist in its eradication. Anaerobic bacteria may play a direct or indirect role in development of pharyngitis. They may be directly responsible for specific forms of pharyngitis or contribute indirectly with possibility of synergy between them and Streptococcus pyogenes. Beta-lactamase-producing aerobic and anaerobic organisms may contribute to penicillin treatment failure. By producing beta-lactamase within the tonsillar tissue, they destroy penicillin and protect streptococci from the antibacterial effect of penicillin. Pharyngeal bacterial flora may vary according to the state of the patient (Figure 1). During an acute infection and in the cases of treatment failure and recurrent pharyngitis the number of alpha-haemolytic streptococci declines, while there is an increase in the number of anaerobic and beta-lactamase-producing organisms. After successful treatment the number and type of bacteria is similar to those found within normal tissue. Knowing the distribution and changes in pharyngeal bacterial flora is important for choosing the optimal drug for treatment of streptococcal pharyngitis. Although penicillin reduces the number of interfering beta-haemolytic streptococci, because of its advantages, if remains the drug of choice for the treatment of streptococcal pharyngitis. In cases of treatment failure and recurrent infections cephalosporins and macrolides may be a useful alternative to penicillin because they possess relatively poor activity against alpha-haemolytic streptococci, resistance to beta-lactamase and because of better penetration into tonsilar tissue.