A comparative study of some cultural methods in the isolation of avian mycoplasma from field material

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Abstract
Comparison was made between direct plating onto mycoplasma agar and culture in overlay or broth in the recovery of mycoplasma from poultry, wild and exotic birds. The value of an atmosphere of increase CO2, provided by 5% CO2 in N2 or by candle jar, and of restreaking was also investigated. From a total of 1784 tissues examined in 4 experiments mycoplasma were recovered from 463 involving 509 strains. Of these strains, 73% were grown by direct plating, 82% by a combination of subcultures from overlay and fewer by the individual overlay subcultures. A proportion of recoveries was made by each method alone. Recovery of mycoplasma through culture in broth was markedly inferior to direct plating or overlay culture. There was no apparent advantage in incubating mycoplasma plates in an atmosphere of increased CO2. Restreaking increased recoveries by only a small number. The mycoplasma recovered included the following recognized avian species or serotypes:- Mycoplasma gallisepticum, M. gallinarum, serotype D, M. iners, serotype F, M. meleagridis, serotype I, M. synoviae, M. anatis, Acholeplasma laidlawii and a number of untyped strains especially from exotic birds. Combinations of 2 or more serotypes were also isolated from approimately 10% of the tissues from domestic poultry. Although most serotypes were isolated by direct plating and overlay methods, the recovery of serotype I and M. meleagridis seemed to be favored by direct plating while M. gallisepticum and a number of untyped organisms were more frequently isolated after culture in overlay. The only organism recovered by 1 method alone was serotype D (from overlay) but only 3 recoveries were made. For maximum recovery of avian mycoplasma direct plating together with subcultures from overlay is recommended. Incubation of plates in additional CO2 seems unnecessary and restreaking is of limited value.

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