E. Carino

The Effectiveness of Processed Grapefruit-Seed Extract as An Antibacterial Agent: II. Mechanism of Action and In Vitro Toxicity

OBJECTIVES Recent testimonials report grapefruit-seed extract, or GSE (Citricidal) to be effective against more than 800 bacterial and viral strains, 100 strains of fungus, and a large number of single and multicelled parasites. This study investigated GSE for antibacterial activity at varying time intervals and concentration levels and tissue toxicity at varying concentrations in an effort to determine if a concentration existed that was both microbicidal and nontoxic and in what period of time. DESIGN Gram-negative and gram-positive isolates were introduced into graduated dilutions of GSE (twofold concentrations ranging from 1:1, through 1:512) for determination of bacterial activity. In vitro assays with human skin fibroblast cells were also performed at the same dilutions to determine toxicity. RESULTS These tests indicated that from the 1:1 through the 1:128 concentrations, GSE remained toxic as well as bactericidal. However, test results indicated that at the 1:512 dilution, GSE remained bactericidal, but completely nontoxic. CONCLUSIONS The initial data shows GSE to have antimicrobial properties against a wide range of gram-negative and gram-positive organisms at dilutions found to be safe. With the aid of scanning transmission electron microscopy (STEM), the mechanism of GSEs antibacterial activity was revealed. It was evident that GSE disrupts the bacterial membrane and liberates the cytoplasmic contents within 15 minutes after contact even at more dilute concentrations.

The effectiveness of processed grapefruit-seed extract as an antibacterial agent: I. An in vitro agar assay.

OBJECTIVES Grapefruit-seed extract (GSE) Citricidal has, in recent reports, been reported to be successful in combating a variety of common infectious agents. In our study, drops of concentrated grapefruit-seed extract were tested for antibacterial properties against a number of gram-positive and gram-negative organisms. DESIGN Sixty-seven (67) distinct biotypes were tested for their susceptibilities to the GSE as well as to 5 other topical antibacterials (Silvadene, Sulfamylon, Bactroban, Nitrofurazone, and Silvadene, Nystatin). Wells were punched into Mueller-Hinton agar plates, which were then inoculated with the organism to be tested; each well was then inoculated with one of the antibacterial agents. After an overnight incubation period, the plates were checked for zones of bacterial susceptibility around the individual wells, with a measured susceptibility zone diameter of 10 mm or more considered a positive result. RESULTS The GSE was consistently antibacterial against all of the biotypes tested, with susceptibility zone diameters equal to or greater than 15 mm in each case. CONCLUSIONS Our preliminary data thus suggest an antibacterial characteristic to GSE that is comparable to that of proven topical antibacterials. Although the GSE appeared to have a somewhat greater inhibitory effect on gram-positive organisms than on gram-negative organisms, its comparative effectiveness against a wide range of bacterial biotypes is significant.

The efficacy of Polysporin First Aid Antibiotic Spray (polymyxin B sulfate and bacitracin zinc) against clinical burn wound isolates.

Polysporin First Aid Antibiotic Spray (Burroughs Wellcome Co., Research Triangle Park, N.C.) is a dry spray containing 200,000 units Aerosporin (polymyxin B sulfate) and 10,000 units bacitracin zinc, along with a propellant. Each 1-second spray delivers approximately 2300 units of polymyxin B sulfate and 115 units of bacitracin zinc. This study was designed to evaluate the efficacy of Polysporin Spray against various clinical isolates. Blood agar plates were inoculated with a pure culture of each isolate. Polysporin was then sprayed in an area approximately 30 mm in diameter. The area of inhibition was measured and recorded after 18 to 24 hours of incubation. A clear zone at least 20 mm in diameter with surrounding edges of growth indicated sensitivity. A zone less than 20 mm in diameter or growth over the whole plate indicated resistance. Three hundred fifty-three clinical isolates (202 gram positive and 151 gram negative) were tested. The results show that Polysporin inhibits the growth of all the gram-positive organisms, including methicillin-resistant strains of Staphylococcus. The gram-negative organisms were also sensitive to Polysporin Spray, with the exception of Serratia marcescens, Morganella morganii, and Proteus mirabilis. This study suggests that Polysporin First Aid Antibiotic Spray may be effective for wounds contaminated with gram-positive and some gram-negative organisms.