In Reply.—Drs Conde-Glez and Calderon are uncertain about the number of MRPS pneumococci isolated at daycare centers. Twenty strains of multiply resistant pneumococci were isolated (from 7.9% of the children). Minimum inhibitory concentrations were determined for penicillin, tetracycline, erythromycin, clindamycin, and the combination product of trimethoprim and sulfamethoxazole against all these strains.
Fifteen strains were tested against ten additional antibiotics, and these data were presented in Table 3 of our report. Minimum inhibitory concentrations of penicillin were thus performed for all 20 isolates, not just 15 strains as suggested by Drs Conde-Glez and Calderon. Table 2 gives data for three strains that showed penicillin resistance. These were among the 20 multiply resistant strains isolated but were not MRPS pneumococci by definition. These strains were identified as penicillin resistant by MICs and because their methicillin disk zone sizes were less than 25 mm. The false susceptibility rate of 20% (three
KLUGMAN KP, KOORNHOF HJ, KUHNLE V. Unusual Multiply Resistant Pneumococci-Reply. Am J Dis Child. 1988;142(3):254. doi:10.1001/archpedi.1988.02150030019009