antimicrobial activity of coriandrum sativum and pinus spp. extracts, alone and in combination, against streptococcus iniae

Streptococcus iniae (s. iniae) is recognized as one of the most significant bacterial pathogens in aquaculture, responsible for severe infections that lead to substantial economic losses annually. given the growing concerns surrounding antibiotic resistance and its implications for both aquaculture and public health, there is an urgent need to explore alternative antimicrobial agents. this study was conducted to evaluate the antimicrobial potential of coriandrum sativum (coriander) and pinus (pine) extracts, both individually and in combination, against this bacterium. hydroalcoholic extracts of coriander and pine were obtained using the soxhlet extraction method. antibacterial effects were quantified by measuring the minimal concentrations required for inhibition (mic) and killing (mbc) of bacterial growth. in addition, the combined effect of the extracts was assessed through the determination of the fractional inhibitory concentration (fic) index. the findings demonstrated that the coriander extract exhibited a significantly stronger inhibitory effect against s. iniae, with an mic value of 15.625 μg/ml, compared to the pine extract, which had an mic of 250 μg/ml. however, neither extract showed strong bactericidal activity at concentrations below 500 μg/ml. the evaluation of the combined extracts revealed an antagonistic effect with a fic index of 17. these results confirm the superior efficacy of the coriander extract in inhibiting the growth of s. iniae. however, the combination with pine extract not only did not lead to synergistic effects, but also resulted in a lower antimicrobial activity. these results emphasize the need for a more thorough investigation of phytochemical interactions prior to their combined use in therapeutic protocols.