Original Research

Investigating selective media for optimal isolation of Brucella spp. in South Africa

Maphuti B. Ledwaba, Okechukwu C. Ndumnego, Itumeleng Matle, Awoke K. Gelaw, Henriette van Heerden
Onderstepoort Journal of Veterinary Research | Vol 87, No 1 | a1792 | DOI: https://doi.org/10.4102/ojvr.v87i1.1792 | © 2020 Maphuti B. Ledwaba, Okechukwu C. Ndumnego, Itumeleng Matle, Awoke K. Gelaw, Henriette van Heerden | This work is licensed under CC Attribution-NoDerivatives 4.0
Submitted: 21 May 2019 | Published: 04 March 2020

About the author(s)

Maphuti B. Ledwaba, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
Okechukwu C. Ndumnego, Africa Health Research Institute, Durban, South Africa
Itumeleng Matle, Department of Bacteriology, Agricultural Research Council – Onderstepoort Veterinary Research Institute, Onderstepoort, South Africa
Awoke K. Gelaw, Department of Bacteriology, Agricultural Research Council – Onderstepoort Veterinary Research Institute, Onderstepoort, South Africa
Henriette van Heerden, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa


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Abstract

Bovine brucellosis in South Africa is caused mainly by Brucella abortus biovar (bv.) 1 and less frequently by B. abortus bv. 2. Bacterial isolation is regarded as the gold standard for diagnosis of Brucella species; however, it is not very sensitive. The aim of this study was to determine the selective medium with optimum antibiotic composition that will allow the growth of Brucella species (spp.) while inhibiting moulds, yeast and most, if not all, Gram-negative contaminants in South Africa. In the controlled experiment, modified Agrifood Research and Technology Center of Aragon (CITA) medium (mCITA) seemed to be the optimum selective medium for isolation of Brucella spp. as compared with Farrell’s medium (FM) and modified Thayer Martin (mTM), while FM inhibited the growth of most fungal and bacterial contaminants. Mean comparison between the three media used to culture B. abortus resulted in lower mean difference ranging from 0 to 2.33. In case of Brucella ovis, high mean difference was obtained when comparing FM with mCITA (10.33) and mTM (12). However, the mean differences of 0.67 and 1.67 were obtained when comparing mCITA and mTM media used to, respectively, culture pasteurised and raw milk spiked with B. ovis. Further optimisation at the Agricultural Research Council – Onderstepoort Veterinary Research Institute resulted in a comparable performance between FM and mCITA; however, mCITA allowed optimal growth of the fastidious B. ovis, which is generally inhibited on FM. Generally, mCITA seemed to be the optimum selective medium for isolation of Brucella spp., while FM inhibits the growth of most fungal and bacterial contaminants. Thus, veterinary laboratories can use mCITA and/or FM but should take into consideration the detection of factious Brucella isolated in the country or region.

Keywords

Bovine brucellosis; selective media; Bacterial isolation

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