Screening methods used to determine the anti-microbial properties of Aloe vera inner gel

The emergence of antibiotic resistant bacterial strains is a growing problem and is an important concern for patients, physicians, healthcare managers, and policymakers as it results in poorer health and economic outcomes. This has led to an urgent global call for new antimicrobial drugs, particularly from natural resources. We have been studying the antimicrobial properties of the inner leaf gel component of Aloe barbadensis Miller and have used a number of different, simple in vitro assays to establish a scientific basis for the potential use of Aloe vera on a range of clinically relevant bacteria. The bacteria used include Shigella flexneri, Methicillin-Resistant Staphylococcus aureus (MRSA), Enterobacter cloacae and Enterococcus bovis. In this paper, we compare standard methods recommended by the Clinical and Laboratory Standards Institute (CLSI) with a microtitre assay using a metabolic colour indicator Alamar blue. All the techniques described have shown that Aloe vera has an antimicrobial effect, however, the microtitre assay enables high throughput screening, under similar conditions and is less wasteful of plant material.