MYCOPLASMA PNEUMONIA

Introduction• Mycoplasma species are the smallest free-living

organisms. (150-250 nm)• Pleomorphic organism

• unlike bacteria, lacks a cell wall, • unlike viruses, does not need a host cell for replication.

• Prokaryotes - lack a cell wall - Lack of a reaction to Gram stain and lack of susceptibility to many antimicrobial agents

• Usually associated with mucosal surfaces, residing extracellularly in the respiratory and urogenital tracts.

• Mycoplasma pneumoniae, Mycoplasma hominis, Mycoplasma genitalium, and Ureaplasma species.

Pathophysiology• The Mycoplasma organism produces a protein that allows

attachment to a receptor on the respiratory epithelium.• Gliding motility and specialized filamentous tips - burrow

between cilia within the respiratory epithelium• Inhibition of ciliary movement• Sloughing of the respiratory epithelial cells• M.pneumoniae Pathogenesis in respiratory tract is due to

• Selective affinity for respiratory epithelial cells• Ability to produce hydrogen peroxide

Epidemiology• One of the common causes of acquired pneumonias in

healthy patients. < 40 years.• Common in all age groups• Rare in <5 yeas old children• Highest rates are seen in 5-20 year age group.• The incubation period is 1-3 weeks.• They are spread by large particles by aerosol to close

contacts.

Presentation• Disease of gradual and insidious onset of several days to

weeks.• Fever• Malaise• Persistent, slowly worsening dry cough• Headache• Chills, not rigors• Scratchy sore throat• Sore chest and tracheal tenderness (result of the

protracted cough)

Presentation• Less common symptoms include:

• Ear pain• Muscle aches• Pleuritic chest pain (rare)

• Extrapulmonary symptoms are thought to be autoimmune induced • rashes• Stevens Johnson Syndrome• meningoencephalitis • arthritis, gastrointestinal symptoms

Examination• A nontoxic general appearance• Normal lung findings with early infection but rhonchi,

rales, and/or wheezes several days later• Erythematous tympanic membranes - an uncommon but

unique sign

Investigations• Laboratory tests are generally of limited benefit• Elevated ESR• Normal or elevated WBC• Sputum Gram stains and cultures not helpful

• M pneumoniae lacks a cell wall and cannot be stained• difficult to culture and requires 7-21 days to grow

• Polymerase chain reaction (PCR) - accurately diagnose atypical pneumonia• used for epidemiologic studies • not used in clinical practice

Radiographic findings • Multifocal, bilateral diffuse infiltrates most frequent• occasionally have lobar pneumonia picture.• Pleural effusions are not rare• The x-ray often looks worse than the clinical picture. 

Treatment• Suggested to teat for 7-10 days.• Empiric antimicrobial therapy must be comprehensive and

should cover all likely pathogens in the context of the clinical setting.

• Antimicrobials against M pneumoniae are bacteriostatic-not bactericidal

• Erythromycin - Will also be effective against other community acquired infections such as pneumococcal pneumonia.

• Clarithromycin and Azithromycin• Tetracylcines in patients > 10 years old (Doxycycline)• Levofloxacin

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