Assessment of susceptibilities of a range of antibiotic-resistant clinical isolates to Aloe vera inner gel

Abstract number: 1734_66

Habeeb F.M., Dashti A.A., Morrison D., Gray A.I., Ferro V.A.

Since the discovery of penicillin in 1928, by Alexander Fleming, the emergence of antibiotic resistant bacterial strains has been a growing problem. This has led to an urgent global call for new antimicrobial drugs, particularly from natural resources. We investigated the therapeutic potential of Aloe vera, a plant known anecdotally for its anti-microbial properties. Aloe vera, has widespread use in health and beauty products, toiletries and disinfectants, however, we wished to determine if there was a scientific basis for its anti-microbial usage and whether this could be exploited for use against antibiotic resistant bacteria.

Objectives: To determine the effect of Aloe vera on a range of clinical isolates identified as antibiotic resistant, including Gram positive (Methicillin-Resistant Staphylococcus aureus, [MRSA] and Enterococcus bovis) and Gram negative (Enterobactercloacae) strains.

Methods: A standard broth tube dilution method, as recommended by NCCLS was used to calculate the minimum inhibitory concentrations (MIC) of a preservative free Aloe vera inner gel powder (Aloe vera of America, Inc). The MIC is read as the lowest concentration of antimicrobial agent, which inhibited bacterial growth. Minimal bactericidal concentrations (MBC) were determined by inoculating 10 microlitres from each MIC broth tube without visible growth, on a Nutrient agar plate. Plates were then incubated in an inverted position at 37°C. Following overnight incubation, the plates were examined for colony growth. Lack of growth indicates that the tested drug was bactericidal at that dilution and this was reported as MBC. Growth indicates that the drug was bacteriostatic at that dilution.

Results: The results showed that the MIC of Aloe vera on MRSA 9, MRSA 6, E. cloacae, and E. bovis was 25, 25, 25 and 12.5 mg/mL respectively. The MBC of Aloe vera on MRSA 9, MRSA 6, E. cloacae, and E. bovis was 62.5, 125, 62.5 and 125 mg/mL respectively.

Conclusion:Aloe vera has antimicrobial activity and it could be used in healthcare settings. If a product contains 250 mg/mL of Aloe vera this will result in 10×MIC for MRSA 9, MRSA 6, E. cloacae, 20×MIC for E. bovis, 4×MBC for MRSA 9 and E. cloacae and 2×MBC for MRSA 6 and E. bovis. This indicates that Aloe vera is active against these clinical isolates and has the potential to be a source for new antimicrobials.