DEMONSTRATION OF A CAPSULE ON MYCOPLASMA-OVIPNEUMONIAE

Objective-To examine Mycoplasma ovipneumoniae for presence of a capsul e and its potential role in adherence. Sample Population-17 isolates o f M ovipneumoniae and 2 isolates of M arginini, recovered from sheep w ith respiratory tract disease. Procedure-Mycoplasmas were cultured in modified Friis broth medium, ovine fetal lung cells, or ovine tracheal ring explants. Pelleted mycoplasmas or ring cultures infected with my coplasmas were treated with ruthenium red or polycationic ferritin and visualized by transmission electron microscopy. Reactivity of several lectins with the mycoplasmas was studied by use of a microtitration p late agglutination test. Results-Electron microscopy revealed a large number of M ovipneumoniae cells covered with an electron dense-stained amorphous material suggesting that it was a capsule. Multiple passage s of the microorganisms in modified Friis broth medium decreased thick ness of the capsule, but not percentage of cells encapsulated. Marked differences were observed when M ovipneumoniae isolates grown in modif ied Friis broth medium or co-cultured with ovine fetal lung cells were compared for capsular thickness or percentage of encapsulation. in th in sections of ruthenium red-stained tracheal ring cultures, the mycop lasmas appeared to be in close contact with cilia through their capsul e. All isolates of NI ovipneumoniae reacted strongly with wheat germ a gglutinin lectin. Conclusions-Mycoplasma ovipneumoniae produces a poly saccharide capsule with variable thickness that is dependent on cultur e conditions and strain. Morphologic observations suggest that this ca psule facilitates adherence of the organism to ciliated epithelium.