Microbiological contamination of herbal medicinal products marketed in Kenya for chronic diseases: A case study of Nairobi metropolis

Abstract Herbal medicines’ use is steadily increasing globally, thus creating a compelling need for quality assurance. The present study assessed the microbial contamination of 86 herbal preparations marketed in the Nairobi metropolis used in the management of chronic diseases. Aqueous suspensions of each herbal product were inoculated into agar and evaluated for bacterial and fungal growth. Discrete colonies were transferred to selective media by streak-plate technique for differential analysis. Twenty-eight (32.6 %) products failed to comply with the British Pharmacopoeia (2019) specifications for microbial load. Twenty-six (30.2 %) herbal products, were contaminated with bile-tolerant Enterobacteriaceae. A total of 41 bacterial isolates, including 14 (34.1 %) E. coli, 10 (24.4 %) Salmonella spp. and 17 (41.5 %) undetermined bile-tolerant Enterobacteriaceae, were identified from the 26 herbal products. Overall, 41 (47.7 %) products were non-compliant with pharmacopoeial specifications for microbiological quality. Results of this study imply herbal medicines are heavily contaminated with pathogenic microbes thus underscoring the need for stringent quality assurance policies to safeguard the public from low quality and contaminated herbal medicines.