English: The disk diffusion test performed with six strains of Staphylococcus aureus illustrates resistance of this bacterium to commonly used anti-staphylococcal antibiotics. Resistance of S. aureus to antibiotics in general varies considerably with the highest resistance to penicillin (B, D, E, F), erythromycin (C, D, E, F) and clindamycin (F).

In images C, E you can see inducible resistance to clindamycin. Flattening of the clindamycin zone of inhibition in the area between the clindamycin and erythromycin disks to resemble the letter "D" indicates inducible resistance and infections caused by these strains should not be treated with clindamycin. Notice that inducible resistance to clindamycin is not present in strain D.

S. aureus strains reveal varying susceptibility to cefoxitin and tetracycline but some MRSA strains remain susceptible to these antibiotics (MRSA strains E, F).