IX. IDENTIFICATION OF MYCOPLASMAS
3s5
The inhibitory activity is demonstrated by the prevention of a change
of p H (a decrease in the case of glucose-fermenting organisms and an
increase with organisms hydrolysing arginine or urea), or by the absence of
the change to a red colour resulting from the reduction of tetrazolium. The
M I test may occasionally be performed even on the basis of a metabolic
activity whose exact nature is not yet known. Thus, the acidity produced
during the growth of M. bovigenitalium and M. bovis has been utilised for
determining the metabolism inhibitory activity of antisera against these
organisms, although it is not a result of glucose degradation and its origin
is obscure.
Although there is no consistent correlation between the G I and M I
titres of an antiserum, convincing evidence is available to support the
view that the MI test is essentially a growth inliibition technique carried
out in liquid medium (Purcell et al., 1967; Taylor-Robinson and Berry,
1969; Woode and McMartin, 1973). The specific inhibitory activity of
antiserum is believed to be related to the adsorption of antibody to the
mycoplasma cell membrane with a consequent depression of cell metabolism and growth (Woode and McMartin, 1973), possibly associated under
appropriate conditions with a mycoplasmacidal process.
T h e specificity and sensitivity of the M I test are both a t a very high
level. Cross-reactions between different species are seen only occasionally
and a t rather low titres. Homologous titres of hyperimmune sera exceeding
1 : 20 000 are by no means unusual. It should be pointed out that a great
deal of care and experience is required in performing the test. The time of
reading the test is often particularly critical, and for that and other reasons
a proper standardisation of the M I tcst is difficult. I n consequence, MI
titrations of one and the same serum carried out in different laboratories
may well result in titres differing by a factor of ten.
It follows from this brief review of the M I test that this method is
extremely useful for taxonomic studies, for which purpose the time and
special precautions needed for its performance are justified. It may be
found less suitable, on the other hand, for the routine identification of
mycoplasma isolates. I n certain situations, however, the M I test may be
used with advantage in the identification procedure, for example, where an
identification ohtained by the immunofluorescence test cannot be confirmed
by the G I test.
(c) Immunojuorescence. The fluorescent antibody technique was introduced
in mycoplasmology by Liu (1957) for localisation of the important human
pathogen, M . pneumoniae (the “Eaton agent”) in chick embryos and was
used also for demonstration or identification of this organism by Clyde
(1961), Goodburn and Marmion (1962) and Chanock et al. (1962). As
3s5
The inhibitory activity is demonstrated by the prevention of a change
of p H (a decrease in the case of glucose-fermenting organisms and an
increase with organisms hydrolysing arginine or urea), or by the absence of
the change to a red colour resulting from the reduction of tetrazolium. The
M I test may occasionally be performed even on the basis of a metabolic
activity whose exact nature is not yet known. Thus, the acidity produced
during the growth of M. bovigenitalium and M. bovis has been utilised for
determining the metabolism inhibitory activity of antisera against these
organisms, although it is not a result of glucose degradation and its origin
is obscure.
Although there is no consistent correlation between the G I and M I
titres of an antiserum, convincing evidence is available to support the
view that the MI test is essentially a growth inliibition technique carried
out in liquid medium (Purcell et al., 1967; Taylor-Robinson and Berry,
1969; Woode and McMartin, 1973). The specific inhibitory activity of
antiserum is believed to be related to the adsorption of antibody to the
mycoplasma cell membrane with a consequent depression of cell metabolism and growth (Woode and McMartin, 1973), possibly associated under
appropriate conditions with a mycoplasmacidal process.
T h e specificity and sensitivity of the M I test are both a t a very high
level. Cross-reactions between different species are seen only occasionally
and a t rather low titres. Homologous titres of hyperimmune sera exceeding
1 : 20 000 are by no means unusual. It should be pointed out that a great
deal of care and experience is required in performing the test. The time of
reading the test is often particularly critical, and for that and other reasons
a proper standardisation of the M I tcst is difficult. I n consequence, MI
titrations of one and the same serum carried out in different laboratories
may well result in titres differing by a factor of ten.
It follows from this brief review of the M I test that this method is
extremely useful for taxonomic studies, for which purpose the time and
special precautions needed for its performance are justified. It may be
found less suitable, on the other hand, for the routine identification of
mycoplasma isolates. I n certain situations, however, the M I test may be
used with advantage in the identification procedure, for example, where an
identification ohtained by the immunofluorescence test cannot be confirmed
by the G I test.
(c) Immunojuorescence. The fluorescent antibody technique was introduced
in mycoplasmology by Liu (1957) for localisation of the important human
pathogen, M . pneumoniae (the “Eaton agent”) in chick embryos and was
used also for demonstration or identification of this organism by Clyde
(1961), Goodburn and Marmion (1962) and Chanock et al. (1962). As