Table 2.

Antibacterial potential of caffeic acid (CA) alone and in antibiotic-phytochemical combination against Staphylococcus aureus. The combined effect of CA and antibiotics was evaluated using plates with MHA enriched with the subinhibitory concentration of CA.

Straina	CAb MICc (µg/mL)	Ed	E+CA	-Δ%e	DAf	DA+CA	-Δ%	FOXg	FOX+CA	-Δ%	VAh	VA+CA	-Δ%
S. aureus ATCC 25923	256	0.38	0.38	0	0.064	0.047	-27	1	1	0	0.75	0.75	0
S. aureus ATCC 43300	256	256	256	0	256	256	0	12	8	-33	0.38	0.50	-32
S. aureus ATCC 6538	256	0.064	0.125	95	0.023	<0.016	-30	2	1	-50	0.50	0.50	0
S. aureus 1	1024	0.50	0.25	-50	0.064	0.032	-50	2	1.5	-25	0.75	0.50	-33
S. aureus 2	512	0.50	0.38	-24	0.064	0.064	0	0.75	0.75	0	0.38	0.75	97
S. aureus 3	512	256	0.19	<-99.99	0.023	<0.016	-30	1.5	0.38	-75	0.50	0.50	0
S. aureus 4	512	0.38	0.19	-50	0.064	0.047	-27	2	1	-50	0.50	0.50	0
S. aureus 5	512	256	4	-98	0.094	0.064	-32	256	24	-91	0.75	0.50	-33
S. aureus 6	512	0.50	0.125	-75	0.064	<0.016	-75	1.5	1.5	0	0.38	0.50	32
S. aureus 7	256	0.38	0.19	-50	0.032	0.032	0	1	1	0	0.50	0.38	-24
S. aureus 8	1024	0.19	0.19	0	0.032	<0.016	-50	1.5	0.50	-67	0.38	0.38	0
S. aureus 9	512	0.38	0.19	-50	0.064	<0.016	-75	1	1	0	0.38	0.38	0
S. aureus 10	512	32	3	-91	0.047	<0.016	-66	2	0.75	-63	0.38	0.38	0
S. aureus 11	1024	0.38	0.19	-50	0.047	0.032	-32	1.5	0.75	-50	0.38	0.19	-50
S. aureus 12	512	256	256	0	256	256	0	256	256	0	0.75	0.75	0
S. aureus 13	512	256	0.125	<-99.99	256	0.094	<-99.99	32	12	-63	0.75	0.50	-33
S. aureus 14	1024	256	<0.016	<-99.99	256	<0.016	<-99.99	256	<0.016	<-99.99	0.75	<0.016	-98
S. aureus 15	1024	0.25	0.19	-24	0.064	0.023	-64	8	1.5	-81	0.38	0.38	0
S. aureus 16	1024	256	256	0	256	256	0	256	32	-88	0.50	0.50	0
S. aureus 17	512	256	<0.016	<-99.99	256	<0.016	<-99.99	256	<0.016	<-99.99	0.38	<0.016	-96
S. aureus 18	512	0.38	0.094	-75	0.047	<0.016	-66	6	0.75	-88	0.50	0.50	0
S. aureus 19	1024	256	256	0	256	256	0	256	64	-75	0.50	0.50	0
S. aureus 20	256	256	<0.016	<-99.99	256	<0.016	<-99.99	12	<0.016	<-99.99	0.38	<0.016	-96
Median	512	0.5	0.19	-50	0.064	0.032	-32	2	1	-63	0.50	0.5	0
p i		0.0004			0.0003			0.0003			0.091

^a Staphylococcus aureus 1 ÷ 20: strains from intractable surgical wounds.

^bCA: caffeic acid.

^cMIC: minimum inhibitory concentration.

^dE: erythromycin.

^eMICs changes according to the formula [(MIC of antibiotic - MIC of antibiotic with CA) / MIC of antibiotic] x 100%.

^fDA: clindamycin.

^gFOX: cefoxitin.

^hVA: vancomycin.

ⁱWilcoxon Signed-Rank Test.