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Table 3 Fractional inhibitory concentration index (FICI) of essential oils plus itraconazole

From: Use of Pinus sylvestris L. (Pinaceae), Origanum vulgare L. (Lamiaceae), and Thymus vulgaris L. (Lamiaceae) essential oils and their main components to enhance itraconazole activity against azole susceptible/not-susceptible Cryptococcus neoformans strains

Antifungal agents

C. neoformans ADS 37 (azole susceptible strain)

C. neoformans ADS 006 (azole not-susceptible strain)

ITC

MIC (μg/ml) alone

0.5

2

Origanum vulgare

MIC (mg/ml) alone

0.3

0.3

FIC of oregano oil

0.125

0.5

FIC of ITC

0.25

0.125

FICI

0.375

0.625

Interpretation

SYN

ADD

Pinus sylvestris

MIC (mg/ml) alone

0.14

0.54

FIC of pine oil

0.25

1

FIC of ITC

0.125

0.125

FICI

0.375

1.125

Interpretation

SYN

IND

Thymus vulgaris

MIC (mg/ml) alone

0.56

1.12

FIC of thyme red oil

0.125

0.25

FIC of ITC

0.25

0.125

FICI

0.375

0.375

Interpretation

SYN

SYN

(+)-α-pinene

MIC (mg/ml) alone

0.54

1.07

FIC of α-pinene

0.125

0.5

FIC of ITC

0.5

0.125

FICI

0.625

0.625

Interpretation

ADD

ADD

Carvacrol

MIC (mg/ml) alone

0.6

0.6

FIC of carvacrol

0.125

0.25

FIC of ITC

0.125

0.125

FICI

0.25

0.375

Interpretation

SYN

SYN

Thymol

MIC (mg/ml) alone

0.04

0.08

FIC of thymol

1

1

FIC of ITC

1

0.125

FICI

2

1.125

Interpretation

IND

IND

  1. FIC of ITC = MIC of ITC in combination with EO/MIC of ITC alone. FIC of EO = MIC of EO in combination with ITC/MIC of EO alone
  2. FICI (FIC Index) = FIC of ITC + FIC of EO. IND: indifferent; ADD: additive; SYN: synergy