Changes in antibiotic susceptibility in staphylococci habituated to sub-lethal concentrations of tea tree oil (Melaleuca alternifolia).

Isolates of methicillin-resistant ? -sensitive Staphylococcus aureus (MRSA and MSSA) and coagulase-negative staphylococci (CoNS) were habituated to sub-lethal concentrations of tea tree oil TTO (72 h). Habituated MRSA?MSSA cultures had higher MIC values than control cultures for the examined antibiotics. Habituated MRSA?MSSA cultures also displayed decreased susceptibility to TTO. MIC of habituated MRSA?MSSA for the examined antibiotics reverted to control values after subsequent culture in the absence of TTO, but the increased MIC against TTO were maintained. Habituated CoNS cultures had higher MIC values against three-fifths of the antibiotics examined; no changes in TTO MIC were observed. Letters in Applied Microbiology. 2008;47:263-8.