Recent evaluation of antimicrobial resistance in beta-hemolytic streptococci.

Although antimicrobial resistance among bacteria continues to increase and to be a clinical problem, the beta-hemolytic streptococci have remained remarkably susceptible to most antibiotics. For example, there has not been a single documented instance of a clinical isolate of a penicillin-resistant group A streptococcus. Moreover, available data indicate that the minimal inhibitory concentrations (MICs) of penicillin for group A streptococci have not changed during the past 4, decades. In one study, the MIC90 for more than 300 strains of group A streptococci was only 0.012 microgram/mL. Resistance to the macrolide antibiotics, the tetracyclines, and the sulfa drugs remains more clinically important. Outbreaks of macrolide resistance have been documented in several parts of the world, but macrolide resistance in most countries of the world remains at < 5% among group A streptococci. Despite the fact that clinically significant antibiotic resistance has not emerged, careful surveillance is required.