Resistance of Mycoplasma hyopneumoniae to chlortetracycline.
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Animals↗
Biomedical subjects
G S Cottew
Publications and source records attributed to G S Cottew.
Pathogenicity of the subspecies mycoides of Mycoplasma mycoides for cattle, sheep and goats.
Recent work has shown that strains classified as M. mycoides subsp. mycoides may be separated into 2 types according to their growth rate and their behaviour in certain biochemical tests. The large colony (LC) types, most of which are from goats, are pathogenic for sheep and goats but apparently not for cattle. The small colony (SC) types include the classical contagious bovine pleuropneumonia (CBPP) strains from cattle and four strains from goats. These SC types are potentially pathogenic for cattle, sheep and goats. Strains of M. mycoides subsp. mycoides from CBPP differ in their virulence in cattle. The degree of virulence is correlated with the quantity of galactan produced in cultures of the organism, suggesting an important role for galactan in pathogenicity. This is consistent with the production by galactan of physiological effects in calves and in the enhancement of infection in cattle given galactan at the same time as cultures of the organism. Contagious caprine pleuropneumonia (CCPP) can be produced experimentally in goats using cultures of M. mycoides subsp. capri. Whether the glucan produced in such cultures is a factor in pathogenicity of this organism has not been determined. Hydrogen peroxide demonstrated in tracheal organ cultures of M. mycoides subsp. capri may contribute to its pathogenicity.
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Isolation of Mycoplasma hyopneumoniae from lesions in experimentally infected pigs.
Pigs aged 6 to 9 weeks from enzootic pneumonia-free herds were inoculated intranasally with a suspension of pneumonic lung containing Mycoplasma hyopneumoniae or were placed in contact with such inoculated pigs. All the inoculated pigs had gross lesions of enzootic pneumonia when killed 27 to 42 days after inoculation. The culture methods described enabled M. hyopneumoniae to be isolated from all 29 inoculated pigs. Of 45 pigs in contact with inoculated pigs 35 had gross lesions of enzootic pneumonia when killed 28 to 71 days later and M. hyopneumoniae was isolated from 33. Another 9 had lesions, detected only microscopically, and M. hyopneumoniae was recovered from 3 of these when killed 75 to 98 days after contact began. In a separate experiment M. hyopneumoniae isolated from experimentally infected pigs, and adapted to the culture medium after 6 passages, caused gross lesions of enzootic pneumonia in 1 of 4 pigs inoculated intranasally.
Animals↗
Subdivision of Mycoplasma mycoides subsp. mycoides from cattle and goats into two types.
Some strains of Mycoplasma mycoides subsp. mycoides, mostly isolated from goats, grow to greater turbidity in broth and form larger colonies on solid medium than does the type strain, PG1. These strains also digest casein, liquefy inspissated serum actively and survive longer at 45 degrees C and are referred to as LC (large colony) strains. Strains more closely resembling PG1 have been called SC (small colony) strains. The SC strains comprise those from contagious bovine pleuropneumonia (CBPP) and some from goats. One LC strain was isolated from a steer; all others have come from goats. Differentiation of M. mycoides subsp. mycoides into 2 types on the basis of the characteristics described may be relevant to their role in CBPP.
Animals↗
The isolation and identification of Mycoplasma mycoides subsp. capri from goats in Australia.
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Animals↗
Atypical mycoplasmas from sheep in Great Britain and Australia identified as Mycoplasma ovipneumoniae.
Representative strains of "lacy-colony" mycoplasmas isolated from sheep in Great Britain and Victoria (Australia) were classified as M ovipneumoniae following comparison with strain Y98 of this species. The taxonomic description of M ovipneumoniae is extended and Y98 is proposed as the type strain. A brief description is given of the isolation of M ovipneumoniae from sheep in East Anglia.
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Studies on the origin of false positive reactions to the complement-fixation test for contagious bovine pleuropneumonia.
Serums of cattle free from contagious bovine pleuropneumonia (CBPP) were tested in complement fixation (CF) tests using 3 antigens; these were the standard antigen (SA) used to test to CBPP in Australia, an ethanol extract antigen (EA) also prepared from Mycoplasma mycoides subsp. mycoides (M. mycoides) and an antigen prepared from a Group 7 bovine mycoplasma isolated from arthritis (AA). The serums included 146 which fixed complement with SA. Eighty percent of these false-positive serums reacted with AA but not with EA; the other 20% were positive at low titre with EA but gave no reaction with AA. Attempts were made to produce false-positive serums experimentally by inoculating 3 Group 7 mycoplasmas and 2 Mycoplasma bovigenitalium strains into cattle. Serums from 3 of 9 cattle inoculated with strain L2917 (Group 7) reacted with SA but differed from the false-positive serums of field cattle by reacting with all 3 antigens. Tests with serums from cattle experimentally infected with CBPP gave similar titres with SA and EA, but the results with AA were mostly negative or less than 10% of the titres obtained with SA and EA. The results of CF tests on serums from the experimental cattle, after absorptions with suspensions of the mycoplasmas, showed that there was a one-way serological relationship between strain L2917 and M. mycoides and between this Group 7 strain and M. bovigenitalium. The CF tests with 3 antigens have assisted in demonstrating the false-positive nature of the reacting field serums encountered in the course of routine CF tests for CBPP in cattle in Australia.
Absorption↗
An indirect haemolysis test (IHLT) for bovine brucellosis.
A simple indirect haemolysis test (IHLT) was developed to avoid the problem of prozones in the complement fixation test (CFT) for bovine brucellosis. It makes use of a sheep or bovine erythrocytes, treated with a crude lipopolysaccharide fraction of Br. abortus, which are lysed by specific antibody in the presence of excess complement (C'). A number of bovine serum which gave large prozones in the warm CFT, and some in which C'-fixation was completely blocked, were found to react to high titre, without prozones, in the IHLT. Following primary vaccination with Br. abortus strain 19, fewer animals gave positive reactions in the IHLT than in the CFT. Following two doses of 45/20 vaccine, however, positive reactions were more frequent in the IHLT than in the CFT. Preliminary studies of serums from animals known to be infected indicate that the IHLT may be of diagnostic value. The test is easy to carry out, especially when bovine erythrocytes are used, since very few bovine serums require preliminary absorption.
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