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
CC424200301CA, CT, GA, NY, OR, TN
MUP120120109CA, GA, NY, OR
CC + MUP5550005CA, GA, OR
GM + TMP-SMZ3003303CA, TN
GM + MUP4044104GA, PA, TN
MUP + TMP-SMZ1010001OR
CC + TMP-SMZ1100100OR
CC + DOX2200021GA, OR
CC + MUP + DOX1110011TN
  • 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.