TABLE 3.

Distribution of resistance genes among 244 genetically distinct GAS isolatesa

Macrolide susceptibility or resistanceNo. of isolates
Susceptible to tetracyclinetet(M)tet(O)Tetracycline resistant, gene unknownTotal
Susceptible to erythromycin128 51 3 2 184
erm(A) 12 9 1 1 23
erm(B) 4 12 1 017
mef(A) 8 7 2 017
erm(A) + erm(B)0 1 001
Macrolide resistant, gene unknown0 1 1 02
Total1528183244
  • a Thirty-six isolates are doubly resistant to both drugs (boldfaced), 56 are resistant to tetracycline but susceptible to erythromycin (underlined), 24 are resistant to erythromycin but susceptible to tetracycline (italicized), and 128 are susceptible to both (P < 0.001 by Fisher's exact test).