African Journal of Immunology Research

African Journal of Immunology Research ISSN 2756-3375 Vol. 10 (6), pp. 001-011, June, 2024. Available online at www.internationalscholarsjournals.org © International Scholars Journals

Full Length Research Paper

Response of Flavobacterium Species Isolates Associated with Fish to Cinnamaldehyde, Vanillin, and Extracts from Kigelia africana Fruits

Hafizah Y. Chenia* and Sarisha Singh

Microbiology (Westville Campus), School of Life Sciences, University of KwaZulu-Natal, Private Bag X54001, KwaZulu-Natal, 4001, South Africa.

Accepted 18 May, 2024

Abstract

Phytochemicals are being explored as therapeutic alternatives in aquaculture since they have de-stressing, growth-promoting, appetite-increasing, immune-stimulating, and antimicrobial properties. The susceptibility of 28 Flavobacterium johnsoniae-like isolates and nine selected Flavobacterium spp. isolates to three phytochemicals, viz.: cinnamaldehyde (10 - 250 µg/ml), vanillin (5 - 500 µg/ml) and four crude Kigelia africana extracts (4 – 10 mg/ml ethyl acetate, dichloromethane, methanol and hexane), were assessed using disk diffusion assays and compared to standard antimicrobial agents, ampicillin and tetracycline using activity indices. Cinnamaldehyde (250 µg/ml) was more effective than 250 µg/ml vanillin, which was ineffective even at higher concentrations. K. africana extract (4 mg/ml) antibacterial efficacy decreased in the following order: Ethyl acetate, methanol, dichloromethane and hexane. The 10 mg/ml methanolic K. africana extract was most effective, with 100% of isolates displaying susceptibility, irrespective of the isolation source. Methanolic extract (10 mg/ml) activity indices ≥ 1 were obtained for 67.9 and 71.4% of isolates, respectively, relative to AMP10 and TE30. Cinnamaldehyde and the K. africana methanol extract are promising candidates to be tested for their efficacy in the treatment of Flavobacterium-associated fish infections. These phytochemicals might be environmentally-friendly, cost-effective alternatives to antimicrobial agent use in aquaculture, with a lesser potential of resistance development.

Key words: Aquaculture, Flavobacterium, phytotherapy.