Abstract:
The availability of whole genome sequences in public databases permits genome-wide
comparative studies of various bacterial species. Whole genome sequence-single nucleotide polymorphisms
(WGS-SNP) analysis has been used in recent studies and allows the discrimination of
various Brucella species and strains. In the present study, 13 Brucella spp. strains from cattle of various
locations in provinces of South Africa were typed and discriminated. WGS-SNP analysis indicated a
maximum pairwise distance ranging from 4 to 77 single nucleotide polymorphisms (SNPs) between
the South African Brucella abortus virulent field strains. Moreover, it was shown that the South African
B. abortus strains grouped closely to B. abortus strains from Mozambique and Zimbabwe, as well as
other Eurasian countries, such as Portugal and India. WGS-SNP analysis of South African B. abortus
strains demonstrated that the same genotype circulated in one farm (Farm 1), whereas another farm
(Farm 2) in the same province had two different genotypes. This indicated that brucellosis in South
Africa spreads within the herd on some farms, whereas the introduction of infected animals is the
mode of transmission on other farms. Three B. abortus vaccine S19 strains isolated from tissue and
aborted material were identical, even though they originated from different herds and regions of
South Africa. This might be due to the incorrect vaccination of animals older than the recommended
age of 4–8 months or might be a problem associated with vaccine production.
Description:
SUPPLEMENTARY TABLES: Table S1: Sample order used in Bruce-ladder (A) and AMOS (B) multiplex PCR assays and the descriptive information of the gel images, Table S2: Clean unique variants of the South African strains (refer to Table 2 for the sample names (in column 1) and sample ID (in column 2)).
