Mycoplasma pneumoniae is among the smallest of free-living organisms. In humans, it is usually found in the throat and lungs and is susceptible to antimicrobial agents that inhibit protein synthesis. The spread of mycoplasmal infections depends on close and prolonged contact between people, as it is transmitted by means of droplet nuclei from the respiratory tract.

Mycoplasmal infection may be asymptomatic, or may produce upper respiratory tract disease, or atypical pneumonia. The pneumonia is difficult to differentiate from viral diseases by clinical means alone. Laboratory tests such as isolation, complement fixation serology and ELISA serology are helpful as aids in the diagnosis of Mycoplasma pneumoniae infection.