Mycoplasmas isolated from the respiratory tract of horses

Abstract

SUMMARYTen mycoplasmas were isolated from 130 nasopharyngeal swabs from thoroughbred horses with acute respiratory disease and three from 198 apparently normal horses. Two mycoplasmas were isolated from 21 tracheal swabs taken at necropsy. These mycoplasmas, together with six isolated from the equine respiratory tract by other workers, were subjected to biochemical and serological tests. Other properties examined in certain representative strains were appearance under the electron microscope, ability to adsorb or agglutinate the erythrocytes of various animal species and the electrophoretic pattern of the cell proteins.On the basis of these tests, mycoplasmas from the equine respiratory tract were divided into seven species. Three species belonged to the genusAcholeplasma, members of which do not require sterol for growth, and were identified asA. laidlawii, A. oculi(formerlyA. oculusi) originally isolated from the eyes of goats, and a recently named speciesA. equifoetale, previously isolated from aborted equine fetuses.Of the four sterol-dependentMycoplasmaspecies, one was identified asM. pulmonis, a common rodent pathogen. Another cross-reacted serologically withM. felisand should probably be classified as that species. The other two species probably represent new species peculiar to the horse. One of these, represented by the strains N3 and N11, ferments glucose and is serologically distinct from 19 recognized species of glucose-utilizing mycoplasmas and from two species which do not metabolize either glucose or arginine. The other species, represented by four strains, hydrolyses arginine and, because it is serologically distinct from all the named arginine-hydrolysingMycoplasmaspecies, the nameM. equirhinissp.nov. is proposed for it.Of the seven species, onlyM. pulmonisand the glucose-utilizing species represented by N3 and N11 were found exclusively in horses with acute respiratory disease.A. oculiwas isolated from an apparently normal horse. The other four species were found in normal horses as well as those with respiratory disease, although three out of the four strains ofM. equirhiniswere from sick horses.