Mycoplasma Infections in Humans: More Than a Bad Cold

Mycoplasma pneumoniae is a bacterium like organism that exclusively affects humans, usually causing only mild symptoms. Yet Talkington and Waites, authors of a 2004 overview of research, argued that "it does not always receive the attention it merits considering the number of illnesses it causes and the degree of morbidity associated with it". Though this species is the most studied of all the mycoplasmas, the absence of quick and easy tests to detect it means that it is under-diagnosed.

What is M. pneumoniae?

The mycoplasmas are the smallest known free-living organisms. Classified as mollicutes, they are primitive bacteria that, unusually, lack a cell wall. Mycoplasma pneumoniae favours the mucus membranes of the respiratory tract, where it produces the familiar symptoms of respiratory infection: cough, sore throat, earache and malaise.

Infection typically causes mild, or even no, symptoms -- hence the colloquial name 'walking pneumonia' -- but can be more serious in children, the elderly and those with a poorly functioning immune system. Even if symptoms are mild, one of the infection's features is its tendency to cause lingering after-effects, particularly joint and muscle pain, with full recovery potentially taking months. Epidemics of M. pneumoniae are well known in conditions where close contact occurs, such as schools, military bases and institutions.

Complications of M. pneumoniae infection

Apart from respiratory infections, M. pneumoniae has been implicated in a host of other health problems. Some attribute the symptoms of Gulf War Syndrome to mycoplasma infection, but firm evidence to support this claim is lacking.

It seems that complications arising from M. pneumoniae infection may be due to the immune system response in some individuals, rather than the bug itself. Researchers have proposed that M. pneumoniae may be implicated in rheumatoid arthritis, an autoimmune disease. It is possible that it plays a role in chronic asthma. Skin problems, such as rashes, are commonly experienced complications. It may also affect cardiac function in various ways.

Effects on the nervous system are relatively well-documented. Facial paralysis, as in Bell's Palsy, is one condition that has been attributed to M. pneumoniae. Suspicion has fallen on the organism's role in other neurological diseases, including encephalitis, aseptic meningitis, Guillain-Barré syndrome and optic nerve inflammation. (Some of these neurological problems may be indirect consequences of infection, developing as a result of the body's autoimmune response.)

Prognosis and treatment

Fortunately, the infection is treatable with antibiotics. Most people recover completely and, except in very rare cases of chronic infection, antibodies form so that it is unlikely that sufferers will contract it more than once.

Sources:

1. Archana Chatterjee. Mycoplasma Infections. Emedicine, updated August 2007. www.emedicine.com/ped/TOPIC1524.HTM
2. Deborah Talkington and Ken Waites. 2004. Mycoplasma pneumoniae and Its Role as a Human Pathogen. Clinical Microbiology Reviews, Vol. 17, No. 4,
p. 697-728.