In vitro study on the anticandidal activity of Melaleuca alternifolia (tea tree) essential oil combined with chitosan

The in vitro activities of commercial Melaleuca alternifolia essential oil (tea tree oil; TTO) and chitosan
were investigated against Candida albicans, both alone and in combination, to assess their potential synergistic action;
their anticandidal properties were assessed using standard microbiological techniques, such as MIC evaluation and a
‘time–kill’ test. Our results demonstrated that both TTO and chitosan possess remarkable activity against Candida: TTO
inhibited C. albicans at 0.5 % v/v and was able to kill yeast cells in 120min at 1% and in 300 min at 0.5–0.25%; as far as
chitosan was concerned, 0.5 mg/ml were required to inhibit Candida growth in liquid medium, whereas 0.5–2 mg/ml chitosan
required 24 h to kill them in the ‘time–kill’ test; this effect was pH-dependent, being present at pH 5.0 and disappearing
at pH 2.0. When TTO and chitosan were tested together, the polymer reduced the MIC of TTO but did not enhance the
activity of the oil as evaluated in the ‘time–kill’ test.