Antimicrobial and antibiofilm potentials of cinnamon oil and silver nanoparticles against Streptococcus agalactiae isolated from bovine mastitis: new avenues for countering resistance

Table 3 In vitro antibacterial activities of cinnamon oil, silver nanoparticles and their combination against S. agalactiae isolated from clinical bovine mastitis

Isolate No.	Zone diameters for the agar well diffusion method (mm)*						MIC (μg/mL)**			ΣFIC	Interactive category
	Cinnamon oil (%)			Silver nanoparticles (%)			Cinnamon oil	Silver nanoparticles	Cinnamon oil/ Silver nanoparticles
	100	50	25	100	50	25	Cinnamon oil	Silver nanoparticles	Cinnamon oil/ Silver nanoparticles
1	38	29	20	31	24	18	0.063	8	0.00012/0.125	0.02	Synergistic
2	40	31	23	29	22	17	0.004	8	0.0005/0.250	0.16	Synergistic
3	40	30	22	30	23	16	0.016	8	0.0005/0.250	0.06	Synergistic
4	39	28	19	28	25	19	0.016	16	0.002/0.125	0.13	Synergistic
5	36	27	18	30	21	17	0.008	16	0.002/0.125	0.26	Synergistic
6	36	26	18	28	21	15	0.031	16	0.0005/0.250	0.03	Synergistic
7	40	33	21	29	23	18	0.063	8	0.0005/0.250	0.04	Synergistic
8	36	28	21	30	21	17	0.016	8	0.002/0.125	0.14	Synergistic
9	40	32	23	30	22	16	0.004	8	0.0005/0.250	0.16	Synergistic
10	40	30	22	28	22	16	0.063	16	0.00012/0.125	0.01	Synergistic
11	39	30	21	31	23	18	0.016	8	0.002/0.125	0.02	Synergistic
12	36	28	19	28	25	19	0.016	16	0.0005/0.250	0.05	Synergistic
13	36	26	18	29	22	17	0.031	8	0.0005/0.250	0.05	Synergistic
14	40	34	23	27	20	15	0.008	16	0.002/0.125	0.3	Synergistic
Mean ± SE	38.29 ± 0.50^a	29.43 ± 0.66^b	20.57 ± 0.51^c	29.14 ± 0.33^a	22.43 ± 0.40^b	17.00 ± 0.35^c	0.01± 0.01^a	11.43± 1.10^a	0.0010 ± 0.0002^b/0.19 ± 0.02^b	–	–

MIC minimum inhibitory concentration, ΣFIC fractional inhibitory concentration index; SE, standard error
* Means ± standard errors of the inhibition zones` diameters for different concentrations (25, 50 and 100%) of cinnamon oil or silver nanoparticles carrying different superscripts are highly significant (P < 0.0001)
** Means ± standard errors of the MIC values of cinnamon oil or silver nanoparticles (serial dilutions were done for each antibacterial agent starting from 1024 μg/mL and downwards) and their combination carrying different superscripts are highly significant (P < 0.0001)