Effect of Eugenol against Streptococcus agalactiae and Synergistic Interaction with Biologically Produced Silver Nanoparticles

Table 1

Phenotypic and genotypic characteristics and antibacterial susceptibility profile of eugenol for planktonic and sessile cells of Streptococcus agalactiae.

GBS; strains	MLVA genotypes^a	Capsular types^a	E (µg/mL)	DA (µg/mL)	Antimicrobial resistance genes^a	Eugenol (%)
			MIC^b			MIC^b/MBC^c
50	8	Ia	0.25	0.25	—	0.5	0.25	0.09
72	5	III	0.125	0.25	—	0.125	0.25	0.06
80	6	V	0.25	0.125	—	0.25	0.125	0.05
89	13	Ia	0.25	0.125	—	0.25	0.25	0.09
115	7	V	>1024	1024	ermB	0.125	0.5	0.02
121	8	Ia	16	0.125	mefA/E	0.125	0.5	0.25
ATCC 13813	—	—	0.125	0.125	—	0.25	0.06	0.04

^aThe genetic diversity, the capsular type, and the resistance genes were previously determined by Otaguiri et al. [11]. ^bMinimum inhibitory concentration (MIC) of the compound which resulted in total inhibition of visible planktonic cell growth defined according to CLSI (2012) [31] guidelines by broth microdilution assays. ^cMinimum bactericidal concentration (MBC) of the eugenol. ^dSessile MIC (SMIC) of the eugenol which resulted in total reduction in metabolic activity of sessile cells during biofilm formation, using the XTT-reduction assay, after 24 h. ^eSMIC of the eugenol which resulted in 50% of reduction in metabolic activity of sessile cells from mature biofilm (24 h), using the XTT-reduction assay. MLVA: multiple locus variable number of tandem repeat analysis; E: erythromycin; DA: clindamycin.