In vitro antibacterial activity of "Nira" garlic extracts (Allium tuberosum Rottler ex-Spreng.)

Abstract

To demonstrate the influence of seasoning on the Predictive Validity of Negative Results in the diagnosis of bacteria transmissible through food, the intensity of bacterial inhibition activity (IINIB) and the intensity of bacterial inactivation activity (IINAB) were determined in vitro for three sources of Allium tuberosum Rottler ex Spreng. - Liliaceae ("Nira" Garlic) from the metropolitan area of Porto Alegre, Rio Grande do Sul State, Brazil. The 50% ethanol extract of those different sources (alcoholature obtained with the evaporation of ethanol in rotavapor system with aseptic hydric-reconstitution) was assessed through dilution tests in multiple tube series against standardized inocula of Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 19.433), Salmonella enteritidis (ATCC 11.076) and Escherichia coli (ATCC 11.229). Tests revealed selective antibacterial activity against the different Gram-negative inocula, which reached maximum and permanent inhibition and inactivation for Salmonella after 48 hours and for Escherichia coli after 72 hours of exposition. The Gram-negative bacteria, Staphylococcus and Enterococcus, presented total resistance to the ethanol extracts. There were no significant differences among activity times for Salmonella and Escherichia, as well as between presence and absence of bacterial non-inhibitors. However, there were significant differences among "Nira" garlic sources.