Interpretive criteria to differentiate low- and high-level mupirocin resistance in Staphylococcus aureus

Abstract

Meticillin-resistant Staphylococcus aureus isolates were classified into three mupirocin susceptibility groups by the disc diffusion method using 5 and 200 μg mupirocin discs. The zone diameter observed for a 5 μg disc distinguished Mup^S from the resistant strains (either Mup^RL or Mup^RH). On the other hand, a 200 μg disc distinguished the high-resistance Mup^RH strains from the other two (Mup^S or Mup^RL). Thus, the concomitant use of 5 and 200 μg mupirocin discs allowed the clear distinction among the three mupirocin susceptibility groups, Mup^S, Mup^RL or Mup^RH.