The response of each microorganism to coffee samples might be influenced by a number of factors. Firstly, structural differences between Gram-negative and Gram-positive bacteria, specifically in the outer membrane, have been associated with resistance patterns. Secondly, the differences in the antimicrobial activity could also be affected by the variation of the concentrations of the phytochemicals among coffee samples (Table 1). Our data suggest that Gram-positive bacteria appear to be more susceptible to phenolic acids, coinciding with that which was reported by Del Castillo et al. (2007). Several authors have proposed that the hydroxycinnamic acids, and specifically the hydroxyl groups on chlorogenic acids, are responsible for the antimicrobial activity, probably due to their capability