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Abstract

Objective

To examine Mycoplasma ovipneumoniae for presence of a capsule and its potential role in adherence.

Sample Population

17 isolates of M ovipneumoniae and 2 isolates of M arginini, recovered from sheep with 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 mycoplasmas 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 plate 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 passages of the microorganisms in modified Friis broth medium decreased thickness of the capsule, but not percentage of cells encapsulated. Marked differences were observed when M ovipneumoniae isolates grown in modified Friis broth medium or co-cultured with ovine fetal lung cells were compared for capsular thickness or percentage of encapsulation. In thin sections of ruthenium red-stained tracheal ring cultures, the mycoplasmas appeared to be in close contact with cilia through their capsule. All isolates of M ovipneumoniae reacted strongly with wheat germ agglutinin lectin.

Conclusions

Mycoplasma ovipneumoniae produces a polysaccharide capsule with variable thickness that is dependent on culture conditions and strain. Morphologic observations suggest that this capsule facilitates adherence of the organism to ciliated epithelium. (Am J Vet Res 1998;59:557–562)

Free access
in American Journal of Veterinary Research

Summary

The influence of recombinant bovine interferon gamma (rBoIFN-gamma) treatment on resistance of clinically normal and dexamethasone-treated calves to Haemophilus somnus infection was evaluated. Four groups of 6 calves each were treated with saline solution (controls), dexamethasone (0.04 mg/kg of body weight/for 3 days), rBoIFN-gamma (2 μg/kg for 2 days), or dexamethasone and rBoIFN-gamma (aforementioned dosages). All treatments were started 24 hours before intrabronchial challenge exposure with 5 × 109 colony-forming units of H somnus. Rectal temperature and WBC count were monitored daily. Two of the dexamethasone-treated calves died of pneumonia 4 days after challenge exposure and were necropsied. All other calves were euthanatized and necropsied 7 days after challenge exposure. All calves had pneumonia of variable intensity. Dexamethasone-treated calves had increased volume of pneumonic lung (P < 0.05) and increased severity of pneumonia, compared with control calves. Recombinant bovine interferon gamma treatment resulted in reduction in pneumonic lung volume and severity of pneumonia in dexamethasone-treated calves (P < 0.05), although it did not influence severity of pneumonia in nondexamethasone-treated calves.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate a multiplex polymerase chain reaction (PCR) to distinguish Campylobacter jejuni from C coll as causes of reproductive failure.

Procedure

Review of clinical cases of reproductive failure attributed to C jejuni or C coli.

Results

A case of swine abortion was attributable to infection with C coli. The porcine abortion isolates were verified as C coli by restriction fragment length polymorphism and multiplex PCR. Cases of endometritis in a fox and in mink caused by C jejuni were reviewed, and isolates were confirmed as C jejuni by results of the multiplex PCR.

Conclusion

Multiplex PCR was useful in identifying C coli and C jejuni recovered from atypical cases of reproductive failure. Multiplex PCR in conjunction with conventional assays may be useful for verifying other unusual instances of campylobacteriosis. (Am J Vet Res 1997;58:1070–1075)

Free access
in American Journal of Veterinary Research