Prevalence of usual USA300 antimicrobial resistance phenotypes that were not further evaluated

Phenotypic resistanceaNo. (%) of isolatesbExpected resistance mechanism(s)c
OXA30 (3.6)mec
OXA, ERY345 (42)mec, mrsA
OXA, LEV16 (2)mec, gyrase gene mutations
OXA, ERY, LEV355 (43)mec, msrA, gyrase gene mutations
OXA, TET (± ERY, ± LEV)d69 (8.4)mec, tetK
  • a OXA, oxacillin; ERY, erythromycin; LEV, levofloxacin; TET, tetracycline.

  • b The total number of isolates was 746 (90.6% of the isolates in this study).

  • c The expected mechanisms are based on previous reports (11, 17, 18, 35).

  • d TET-resistant, doxycycline-susceptible isolates were resistant to ERY and/or LEV and were included in the total 746-isolate count.