Biochemical Characterization of Clinical Strains of Staphylococcus spp. and Their Sensitivity to Polyphenols-Rich Extracts from Pistachio (Pistacia vera L.)

We characterized a number of clinical strains of Staphylococcus spp. and investigated their sensitivity against polyphenols-rich extracts from natural raw and roasted pistachios (NPRE and RPRE, respectively). Out of 31 clinical isolates of Staphylococcus spp., 23 were coagulase-positive and identified as S. aureus, of which 21 were MRSA. Polyphenols-rich extracts from natural pistachios and roasted pistachios were prepared: the total phenols content, expressed as gallic acid equivalent (GAE)/100 g fresh weight (FW), was higher in natural pistachios (359.04 ± 8.124 mg) than roasted pistachios (225.18 ± 5.055 mg). The higher total phenols content in natural pistachios also correlated to the higher free-radical scavenging activity found by DPPH assay: NPRE and RPRE showed IC50 values of 0.85 (C.L. 0.725⁻0.976 mg mL-1) and 1.15 (C.L. 0.920⁻1.275 mg mL-1), respectively. Both NPRE and RPRE were active against S. aureus 6538P and Staph. spp. clinical isolates, with RPRE being the most active (MIC values ranging between 31.25 and 2000 μg mL-1). The antimicrobial potential of pistachios could be used to identify novel treatments for S. aureus skin infections.