Mycoplasma pneumoniae

These bacteria do not have a cell wall. Hence, they cannot be stained by the Gram stain and are not killed by cell wall active antibiotics like penicillins and cephalosporins. They are the only bacteria that have cholesterol in the cell membrane. Morphologically they are pleomorphic and may show a “gliding” motility.

It is the most common cause of atypical pneumonia. It presents as fever, headache, sore throat, cough etc. It has been associated with the development of SJS (Stevens Johnson Syndrome), GBS and cardiac arrhythmias.

This image depicted two chest x-rays, which revealed pathologic changes in a patient’s lung fields due to a condition known as mycoplasma pneumonia, caused by a Mycoplasma pneumoniae bacterial infection. Note on the anteroposterior (AP) view on the left, the generalized infiltrate permeating both lung fields, and consolidation in the region of the right lower lobe, as well as bilateral hilar adenopathy. In the left lateral view on the right, you can see that the consolidation occupied more of the posterior aspect of the lung fields, almost obliterating a view of the spinal column.

The cold agglutinin test is positive in Mycoplasma infections. It is an IgM antibody that agglutinates human “O” blood group antigens at 4 degree C. Complement fixation test, indirect haemagglutination test or enzyme immunoassay are more specific for diagnosis. PCR for DNA detection can be done. Antigen can also be detected by immunofluorescence, CIEP, enzyme immunoassay or immunoblot tests. Mycoplasma need sterols in the culture medium to grow. They produce “fried egg” colonies on Mycoplasma agar which are stained blue by Dienes stain which is poured over the colony.