TABLE 2.

Antibiotic susceptibility of USA300 isolates

Antibiotic classAntibioticMIC (μg/ml)aCLSI standard range (μg/ml)b
188051880618807188081880918810188111881319321LACFPR3757SIR
AminoglycosideGentamicin0.510.50.520.5110.528<48>16
Kanamycin >64 >64 >64 >64 >64 >64 >64 >64 >64 >64 >64 <1632>64
Tobramycin2121211220.52<48>16
AnsamycinRifampin<0.125<0.125<0.125<0.125<0.125<0.125<0.1250.250.50.25<0.125<12>4
FluoroquinoneCiprofloxacin 32 8 64 0.50.1250.5 >64 0.5 64 >64 64 <12>4
Levofloxacin 32 1 32 0.250.250.25 8 0.52 16 16 <12>4
Gatifloxacin20.5411120.5142
GlycopeptideVancomycin220.2521120.5212<24-8>16
Teicoplanin0.250.250.250.250.250.250.250.25<0.125<0.1250.25<816>32
LincosamideClindamycin0.5<0.1250.125<0.1251<0.125<0.125<0.125 >64 1 >64 <0.51-2>4
MacrolideErythromycin 64 64 64 64 >64 64 64 8 64 >64 >64 <0.51-4>8
OxazolidinoneLinezolid24444444444<4
PenicillinOxacillin 16 16 16 16 32 16 32 32 32 32 32 <2>4
PhenicolChloramphenicol48888816 32 16 32 16<816>32
Pseudomonic acidMupirocin212111110.50.5 >64
SteroidFusidic acid<0.1250.250.250.25<0.1250.250.250.250.250.50.25<0.51>2c
TetracyclineTetracycline10.50.50.5140.25<0.1250.50.5 64 <48>16
Minocycline0.5<0.1250.250.250.250.250.250.250.250.250.5<48>16
Doxycycline0.5<0.1250.50.250.250.250.250.250.250.254<48>16
  • a All of the USA300 isolates exhibited susceptibility to the antibiotics used in the antibiotic disc assays: the folate pathway inhibitor trimethoprim-sulfamethoxazole, the streptogramins quinupristin-dalfopristin, and the glycylglycine tigecycline. None of the isolates exhibited erythromycin-inducible clindamycin resistance. Values in boldface indicate antibiotic resistance.

  • b S, susceptible; I, intermediate; R, resistant.

  • c Standards in the United Kingdom, Canada, and Australia. Fusidic acid is not approved by the FDA.