Oval cells and cystic structures in multiplication of M leprae

Ten preserved biopsy suspensions from leprosy patients were inoculated in biphasic medium and incubated alternatively in refrigerator and at 37 °C. The cultures were observed every week for 3 months. The typical actinomycetoid growth appeared within 3-5 days. Microscopically, two types of cysts (unstained and dark) were seen along with oval cells. Dark cysts showed developement of irregular septae or cracks breaking the mass into irregular quadrangular pieces. Granular acid-fast material could be made out inside the cracks and around the cysts. Oval cells were seen either independently or organised around pink homogeneous material. The oval cells were stained blue or pink. Some of them showed both blue and pink shades.