Studies on Mycoplasma ovipneumoniae in New Zealand sheep : epidemiology and comparison of isolates : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Microbiology at Massey University, New Zealand
As part of a larger study to examine the role of
M. ovipneumoniae in chronic non-progressive pneumonia
(CNP) of sheep, the colonisation of the respiratory tract
by mycoplasmas was examined in two flocks of lambs over .
a nine month period.
In both farms M. ovipneumoniae was detected in the ewes
at the time of first swabbing of the lambs. The two
flocks of lambs differed in the time when the nasal cavity
first became colonised by M. ovipneumoniae: thus in
Flock 2 M. ovipneumoniae was detected in the nasal cavity
relatively early and also became disseminated throughout
the flock some months earlier than occurred in Flock
1. Nevertheless, M. ovipneumoniae was widespread in both
flocks of lambs by March i.e. at• or before peak
seasonal prevalence of CNP. At slaughter in May, Flock
2 (colonised early) had a much higher prevalence of CNP
than Flock 1.
These findings are consistant with the hypothesis that
M. ovipneumoniae colonises the nasal tract of lambs and
subsequently invades the
lung possibly in response to
the stress of exposure to hot dry weather.
The second part of this thesis is concerned with the
adaptation of Sodium dodecyl sulfate-polyacrylamide gel
electrophoresis (SDS-PAGE) to distinguish strains of
M. ovipneumoniae with the ultimate objective of comparing
M. ovipneumoniae strains isolated from pneumonic lungs
to nasal isolates and isolates from apparently normal
Isolates from different sources were heterogeneous when
examined by SDS-PAGE, but comparisons were made difficult
because of the excessive number of protein bands. In
response to this problem fractions of M. ovipneumoniae
were examined. Membrane preparations conserved the unique
protein bands which in principle allow discrimination
between strains, but because the number of protein bands
was still excessive we examined surface proteins by labelling
intact cells with Fluorescein isothiocyanate (FITC).
This approach still gave gels with too many protein bands
for convenient comparisons to be made, but had the advantage
of allowing the identification of surface proteins,
some of which were unique to individual isolates.
This encouraged us to combine SDS-PAGE with a classic
immunological approach to strain identification i.e.
we investigated the possibility of excising protein bands
from gels for subsequent use as immunising antigens.
One common protein band was excised, it was found to
be antigenic and the antisera crossreacted with a single
line of identity in gel precipititin tests with all the
strains tested. While within the time limit available
we have examined only one common protein band, the result
suggests that the excision of individual strain-specific
protein bands from SDS-PAGE for use as immunising antigens
will provide strain-specific antisera which should allow
the development of a simple approach to strain identification.