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Table 3 Fractional Inhibitory Concentration (FIC) and FICI of combination of Alkaloid compounds with Ampicillin

From: Antibacterial activity against β- lactamase producing Methicillin and Ampicillin-resistants Staphylococcus aureus: fractional Inhibitory Concentration Index (FICI) determination

Microorganisms

MIC(μg/ml)/Ampicillin

FICa

FICb

FICI

Effect

MRSA/ARSA-1

>400

0.50

≤0.03

≤0.53

Synergistic

MRSA/ARSA-5

>400

0.50

≤0.03

≤0.53

Synergistic

MRSA/ARSA-10

>400

0.50

≤0.03

≤0.53

Synergistic

MRSA/ARSA-12

>400

0.50

≤0.03

≤0.53

Synergistic

MRSA/ARSA-14

>400

0.50

≤0.03

≤0.53

Synergistic

  1. FIC a = MIC of the combination/MICa alone; FIC b = MIC of the combination/MICb alone and FICI = FICa + FICb.
  2. a = Alkaloid fractions; b = Ampicillin.
  3. The FICI was interpreted as follows: (1) a synergistic effect when FICI ≤0.5; (2) an additive or indifferent effect when FICI >0.5 and <1 and (3) an antagonistic effect when FICI >1.