Abstract:
As a result of the high lability and slow growth of Campylobacter fetus subspecies, the laboratory
diagnosis of bovine genital campylobacteriosis has always been difficult. This is especially
true under South African conditions, where farms are far apart, laboratories are only present
in major centres and there are high ambient temperatures. In order to overcome the shortcomings
associated with traditional diagnostic methods, the implementation of a molecular
assay was sought. This work describes how a previously published PCR assay (MG3F/
MG4R primers) was adapted, optimised and applied in the diagnostic laboratory to test
preputial samples directly for the presence of Campylobacter fetus. Field evaluation of the
assay revealed an analytical sensitivity and specificity of 85.7 % and 99 %, respectively.
Subsequent genotyping and phenotyping of a diverse collection of South African field
isolates revealed that South Africa has an unexpected and previously unreported high
incidence of Campylobacter fetus subsp. venerealis biovar intermedius strains. These strains
were not identified correctly by the subspecies-specific primer set evaluated. Until such
time that cost- effective genotyping methods are available to diagnostic laboratories in
South Africa, and other countries with these atypical Campylobacter fetus subsp. venerealis
strains, the need for bacterial culture will persist. Identification to subspecies level of isolates
at present remains dependent upon a single phenotypic criterion, namely tolerance to
1 % glycine.
