Mycoplasmas are a genus of bacteria that includes pathogens of importance in poultry.
Photomicrograph (subgross view) showing the classic Mycoplasma colonies (red arrows) with dark centers surrounded by the typical circular periphery ("fried egg" appearance) on modified Frey's agar. Notice the size variability is mostly in the periphery of the colony, whereas the centers remain relatively constant in size. Also notice that some colonies are merging (black arrows). Scale bar = 249 mcm; 4X objective lens.
Courtesy of Dr. Mohamed El-Gazzar.
More than 20 Mycoplasma spp have been isolated from avian hosts; however, only four species are considered pathogenic in poultry. M gallisepticum and M synoviae are pathogenic for chicken, turkey, and other species, whereas M meleagridis and M iowae are pathogenic primarily in turkeys. M meleagridis has been eradicated from commercial turkeys, but the other 3 mycoplasma species still have economic importance. Each of these species has distinctive epidemiological and pathological characteristics.
Mycoplasmas lack a cell wall. They are small in size, measuring approximately 0.2–0.3 mcm, and have the smallest genome among all independently replicating forms of life.
Because of their small genome and the lack of many metabolic pathways, they are fastidious microorganisms. Therefore, isolation requires complex nutritional supplements that allow Mycoplasma to grow on specialized artificial media. Growth in broth and on agar media is slow (5–21 days).
The small (0.1–1 mm diameter) colony morphology typically has a "fried egg" appearance under low magnification (see ).
Mycoplasmas do not survive for more than a few days outside the host and are vulnerable to common disinfectants.
For More Information
Ferguson-Noel N, Armour NK, Noormohammadi AH, El-Gazzar M, Bradbury JM. Mycoplasmosis. In: Swayne DE, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez DL, associate eds. Diseases of Poultry. 14th ed. Wiley Blackwell; 2020:907-911. doi:10.1002/9781119371199.ch21
