Mycoplasma infections

Mycoplasma are the smallest of the free-living organisms; unlike viruses, mycoplasma can reproduce outside of living cells. Many species within the genusMycoplasma thrive as parasites in human, bird, and animal hosts. Somespecies can cause disease in humans.

Mycoplasma are found most often on the surfaces of mucous membranes. They cancause chronic inflammatory diseases of the respiratory system, urogenital tract, and joints. The most common human illnesses caused by mycoplasma are dueto infection with M. pneumoniae, which is responsible for 10-20% of all pneumonias.

Pneumonia caused by mycoplasma is also called atypical pneumonia, walking pneumonia, or community-acquired pneumonia. Infection moves easily among peoplein close contact because it is spread primarily when infected droplets from the respiratory system circulate in the air due to coughing, spitting, or sneezing.

Atypical pneumonias can affect otherwise healthy people who have close contact with one another. Pneumonia caused by M.pneumoniae may start out with symptoms of an upper respiratory infection, probably a sore throat, progressing to a dry cough within a few days. Gradually, fever, fatigue, muscle aches, and a cough that produces thin sputum (spit or phlegm) will emerge. Non-respiratory symptoms may occur too: abdominal pain, headache, and diarrhea. About 20% of patients may have ear pain.

Another mycoplasma species, M. hominis, is common in the mucous membranes of the genital area and can cause infection in both males and females. Its presence does not always cause symptoms.

Usually, mycoplasma pneumonia will be identified after other common diagnoseshave been eliminated. For example, a common antibiotic might be prescribed for a respiratory infection producing fever and cough. If symptoms do not improve in 3-5 days, the organism causing the disease is not a typical one and not susceptible to this antibiotic.

If a Gram's stain (a common test done on sputum) does not indicate a gram-positive pathogen, the doctor will suspect a gram-negative organism, such as mycoplasma. The actual underlying organism may not be identified (it isn't in almost 50% of cases of atypical pneumonia). Although it is rare, a rash may appear along with pneumonia symptoms. This should trigger suspicion of mycoplasma pneumonia, even if laboratory tests are inconclusive.

Standard x rays may reveal a patchy material that has entered the lung tissue; this can be evident for months. Highly sophisticated and specific polymerase chain reaction methods (PCR) have been developed for many respiratory pathogens, including M. pneumoniae. They are not readily available and arevery expensive.

A 2-3 week course of certain antibiotics (erythromycin, azithromycin, clarithromycin, dirithromycin, or doxycycline) is generally prescribed for atypicalpneumonia. This disease is infectious for weeks, even after the patient starts antibiotics. A persistent cough may linger for 6 weeks.

Mycoplasma pneumonia may be involved in the onset of asthma in adults. Otherrare complications include meningoencephalitis, Guillain-Barré syndrome, mononeuritis multiplex, myocarditis, or pericarditis. This may increase the risk of acute heart arrhythmias leading to sudden cardiac death. However, with proper treatment and rest, recovery should be complete.

At this time, there are no vaccines for mycoplasma infection. It is difficultto control its spread, especially in a group setting. The best measures arestill the simplest ones. Avoid exposure to people with respiratory infectionswhenever possible, wash hands frequently, and cover the moth while coughingor sneezing.

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