Characterization of strains of Mycoplasma mycoides subsp mycoides small colony type isolated from recent outbreaks of contagious bovine pleuropneumonia in Botswana and Tanzania: Evidence for a new biotype
Jb. March et al., Characterization of strains of Mycoplasma mycoides subsp mycoides small colony type isolated from recent outbreaks of contagious bovine pleuropneumonia in Botswana and Tanzania: Evidence for a new biotype, J CLIN MICR, 38(4), 2000, pp. 1419-1425
Four strains of Mycoplasma mycoides subsp, mycoides small colony type (MmmS
C) isolated from recent outbreaks of contagious bovine pleuropneumonia (CBP
P) in Africa have been investigated. One Botswanan strain, M375, displayed
numerous and significant phenotypic differences from both contemporary fiel
d isolates and older field and vaccine strains (African, Australian, and Eu
ropean strains dating back to 1936). Differences include altered morphology
, reduced capsular polysaccharide production, high sensitivity to MmmSC rab
bit hyperimmune antisera in vitro, and unique polymorphisms following immun
oblotting. While insertion sequence analysis using IS1634 clearly indicates
a close evolutionary relationship to west African strains, hybridization w
ith IS1296 shows the absence of a band present in all other strains of MmmS
C examined. The data suggest that a deletion has occurred in strain M375, w
hich may explain its altered phenotype, including poor growth in vitro and
a relative inability to cause septicemia in mice. These characteristics are
also exhibited by Il Mycoplasma capricolum subsp, capripneumoniae (causal
agent of contagious caprine pleuropneumonia [CCPP]), against which M375 ant
iserum exhibited some activity in vitro (unique among the various MmmSC ant
isera tested). These findings may have evolutionary implications, since CCP
P is believed to be lung specific and without a septicemic phase (unlike CB
PP). Since M375 was isolated from a clinical case of CBPP, this novel bioty
pe may be fairly widespread but not normally isolated due to difficulty of
culture and/or a potentially altered disease syndrome. Bovine convalescent
antisera (obtained from contemporary naturally infected cattle in Botswana)
were active against strain M375 in an in vitro growth inhibition test but
not against any other strains of MmmSC tested. There exists the possibility
therefore, that strain M375 may possess a set of protective antigens diffe
rent from those of other strains of MmmSC (including vaccine strains), Thes
e findings have implications for the control of the current CBPP epidemic i
n Africa.