In Vitro Antistaphylococcal Effects of Embelia schimperi Extracts and Their Component Embelin with Oxacillin and Tetracycline
Table 3
In vitro inhibitory activity of embelin in combination with tetracycline against S. aureus.
MICs (μg/mL)
MICs of tetracycline in combination with listed embelin concentrations (μg/mL)
S. aureus strain
Emb
Tet
+Emb 4 g/mL
+Emb 2 μg/mL
+Emb 1 μg/mL
+Emb 0.5 μg/mL
+Emb 0.25 μg/mL
MIC
ΣFIC
MIC
ΣFIC
MIC
ΣFIC
MIC
ΣFIC
MIC
ΣFIC
ATCC 29213
32
0.33
0.33
1.125
0.33
1.063
0.33
1.031
0.33
1.016
x
x
ATCC 43300
10.67
0.33
0.04
0.496
0.07
0.400
0.17
0.609
0.33
1.047
0.33
1.023
EMRSA15
10.67
0.67
0.14
0.584
0.5
0.934
0.5
0.840
0.58
0.913
0.58
0.889
MRSA1
8
0.25
0.04
0.660
0.13
0.770
0.25
1.125
0.25
1.063
0.25
1.031
MdRSA2
10.67
21.33
10.67
0.875
21.33
1.187
21.33
1.094
21.33
1.047
21.33
1.023
MdRSA3
8
21.33
3
0.641
14
0.906
18.67
1.000
18.67
0.938
18.67
0.907
MRSA4
8
0.25
0.01
0.540
0.04
0.410
0.21
0.965
0.21
0.903
0.21
0.871
TRSA1
8
16
2.33
0.646
9.33
0.833
10.67
0.792
13.33
0.896
13.33
0.864
TRSA2
10.67
16
1.17
0.448
8
0.687
8
0.594
10.67
0.714
10.67
0.690
MIC: minimum inhibitory concentration expressed as an average from three independent experiments, each performed in triplicate; Emb: embelin; Tet: tetracycline; ATCC: American type culture collection; MRSA: methicillin-resistant S. aureus; EMRSA: epidemic MRSA; TRSA: tetracycline-resistant S. aureus; MdRSA: multidrug-resistant S. aureus; x: not tested; ΣFIC: sum of fractional inhibitory concentrations: the combinatory effect is evaluated as follows: synergy if ΣFIC ≤0.5; additive if ΣFIC >0.5 and ≤1; indifferent if ΣFIC >1 and <2; antagonism if ΣFIC ≥2.
