In Vitro Antimicrobial Efficacy of Aloe vera Gel Against Oral and Skin Pathogens: A Cross-Sectional Laboratory Study

Abstract

Background: The accelerating global crisis of antimicrobial resistance (AMR) has renewed interest in botanical antimicrobials as low-cost adjuncts for the management of common oral and skin infections. Aloe vera (L.) Burm.f. is one of the most widely cultivated and traditionally used medicinal plants of South India, yet quantitative comparative screening of its gel against clinically relevant oral and cutaneous pathogens remains limited.

Objective: To evaluate the concentration-dependent in vitro antimicrobial efficacy of Aloe vera leaf gel against five oral and skin pathogens and to determine its bactericidal potential.

Methods: In this cross-sectional in vitro laboratory comparative study, Aloe vera gel was tested against Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa using agar well diffusion at 25, 50, 75 and 100% v/v in triplicate, alongside a standard-antibiotic positive control and a vehicle negative control. Minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations were determined by broth dilution. The gel was physicochemical and phytochemicals characterized (pH, viscosity, total phenolic and flavonoid content, dry matter). Data were summarized as mean ± SD; the 100% gel was compared with the negative control using independent-samples t-tests with Cohen's d (p < 0.05).

Results: Aloe vera gel produced concentration-dependent inhibition against all five pathogens. At 100% v/v, zones ranged from 19.57 ± 0.67 mm (S. aureus) to 13.27 ± 0.45 mm (P. aeruginosa). Gram-positive organisms were most susceptible and P. aeruginosa least. Activity was bactericidal (MBC:MIC ≤ 2) at achievable concentrations, with MIC values of 25–75% v/v. All 100%-versus-control comparisons were highly significant (p < 0.001) with very large effect sizes (Cohen's d 21.00–78.30). The gel was mildly acidic (pH 4.64) and rich in phenolics (37.75 mg GAE/g) and flavonoids (19.52 mg QE/g).

Conclusion: Aloe vera gel demonstrated bactericidal, dose-dependent antimicrobial activity against oral and skin pathogens, below the standard antibiotic but far exceeding the vehicle.