Sir.—We read with interest the letter of Drs Gentry and Burns (Journal 1980;134:801) reporting their experience in Pensacola, Fla, with erythromycin-resistant group A β-hemolytic streptococcal (GABHS) isolations. Since erythromycin is the usual choice for treating GABHS infections in penicillin-sensitive patients, we wish to contrast the results of our studies with those of Drs Gentry and Burns.
Methods.—Prompted by the report of Maruyama et al1 and a GABHS isolate from a 9-year-old girl who had persistent clinical illness and persistently positive cultures after erythromycinethylsuccinate therapy with good compliance, we studied 69 isolates from her area (Ft Dix, NJ) and 133 isolates from the greater Washington, DC, area for erythromycin resistance.
Minimal inhibitory concentrations (MICs) for erythromycin were screened for all isolates by an agar dilution method2 modified by enrichment of Mueller-Hinton medium with 5% sheep RBCs. All isolates were identified as GABHS using bacitracin and sulfamethoxazole and