Fried egg colonies are characteristic of which organism?

• A. Ehrlichia chaffeensis
• B. Mycoplasma genitalium
• C. Mycoplasma hominis
• D. Ureaplasma urealyticum

Answer: (C)

Fried-egg colonies are a classic appearance of Mycoplasma species growing on cholesterol-containing, cell-free media. These organisms lack a cell wall, so they require specialized culture conditions and form colonies with a dense central region and a lighter peripheral zone that resembles a fried egg under the microscope. Mycoplasma hominis is a representative organism that shows this pattern. Ehrlichia chaffeensis is an intracellular bacterium and does not form colonies on standard agar, while other Mycoplasma genus members like Mycoplasma genitalium and Ureaplasma urealyticum also grow on specialized media, but the fried-egg morphology is a hallmark commonly associated with Mycoplasma species, including M. hominis.