Assessment of the Microbial Quality and Antimicrobial Activities of Some Herbal Formulations Marketed in Awka Metropolis, Awka, Nigeria

Abstract

Background: The microbiological quality and antimicrobial performance of commercially available herbal formulations are important considerations because contaminated or ineffective preparations may present avoidable risks to consumers. Aim: This study assessed the microbial quality and in vitro antimicrobial activity of selected liquid herbal formulations marketed in Awka metropolis, Nigeria. Methods: Ten aqueous herbal formulations, comprising five registered and five unregistered products, were obtained from different sales outlets. Total heterotrophic bacterial, mould and yeast, and coliform counts were determined using culture-based methods. Bacterial and fungal isolates recovered from the products were characterised phenotypically. Antimicrobial activity of the formulations was evaluated by agar-well diffusion against Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Proteus mirabilis, Candida albicans, and Aspergillus niger, using appropriate positive and negative controls. Results: Total heterotrophic bacterial counts ranged from 4.48 to 5.00 log CFU/mL, while mould and yeast counts ranged from 3.30 to 4.00 log CFU/mL. Six of the ten formulations contained detectable coliforms, with counts ranging from 3.00 to 3.67 log CFU/mL. Phenotypic examination indicated the presence of several bacterial and fungal species, including Escherichia coli, Salmonella sp., and Aspergillus flavus. None of the ten formulations produced measurable inhibition against the six test organisms at either stock concentration or two-fold dilution, whereas the positive controls produced measurable inhibition zones. Conclusion: The findings indicate substantial microbial contamination among the sampled formulations and no detectable antimicrobial activity under the experimental conditions used. Improved microbiological quality control and laboratory-based evaluation of marketed herbal formulations are therefore warranted.