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.
