TABLE 3.

Unusuala antimicrobial resistance phenotypes and resistance genes identified in USA300 isolates

Resistance phenotype (drug or drug combination)bNo. of isolatescNo. of isolates with the following genetic determinant detected by PCR:Source(s) of isolates
ermCmupAaac2′-aph6"dfrAtetMpSK41d
CC424200301CA, CT, GA, NY, OR, TN
MUP120120109CA, GA, NY, OR
CC + MUP5550005CA, GA, OR
GM1001100CA
GM + TMP-SMZ3003303CA, TN
GM + MUP4044104GA, PA, TN
MUP + TMP-SMZ1010001OR
CC + TMP-SMZ1100100OR
CC + DOX2200021GA, OR
CC + MUP + DOX1110011TN
Total725123810325
  • a Likely plasmid-mediated resistance to clindamycin, mupirocin, gentamicin, trimethoprim-sulfamethoxazole, and/or doxycycline.

  • b CC, clindamycin resistance (10 isolates had inducible resistance, and 41 had constitutive resistance); MUP, high-level mupirocin resistance; GM, gentamicin resistance; DOX, doxycycline resistance.

  • c The total number of isolates was 72 (8.7% of the isolates in this study).

  • d The presence of pSK41 was identified by positive PCR for traE, traI, and repA.