Treatment of S. pyogenes infections by antibiotics varies depend-ing upon the clinical conditions. Penicillin is highly effective againstS. pyogenes. As of now, no penicillin-resistant strains of S. pyogenes have been documented in clinical practice. Penicillin,therefore, remains the drug of choice, except in penicillin-aller-gic individuals (with pharyngeal infections) and in complicated or invasive diseases.
Failures of penicillin therapy: In uncomplicated cases, peni-cillin is given orally in a dosage of 250–500 mg twice daily for at least 10 days. Noncompliance is the most common reason for the failure to respond to therapy. The drug is often discontinued before the 10-day course is completed, because children usually appear to have recovered in 3–4 days. And the presence of beta-lactamase-producing flora (particularly organisms, such as mouth anaerobes), which could inactivate penicillin, has also been proposed. However, this theory is yet to be proved conclusively.
Most of the failures of penicillin therapy have been thought to occur in patients where streptococcal pharyngitis has not been well defined and some of these patients may in fact be streptococcal carriers who actually had viral pharyngitis.
· Erythromycin and clindamycin are given to patients aller-gic to penicillins. Recently, strains resistant to erythromycin have been reported.
· Sulfonamides and tetracycline are not used for streptococcal infections.