Properties

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment & Prevention

Mycoplasma pneumoniae

Small, wall-less organisms.

Smallest free-living organism.

Absence of a cell wall.

Stains poorly with Gram’s stain.

Pathogen only for humans; transmitted by respiratory droplets.

Respiratory mucosa is not invaded, but ciliary motion is inhibited & necrosis of epithelium occurs.

Only one serotype.

Immunity is incomplete & a second episode of disease can occur.

During infection, autoantibodies are produced against red cells (cold agglutinins), brain, lung & liver cells.

Accounts for about 5-10% of all community-acquired pneumonia.

Most common type of atypical pneumonia (causative bacteria cannot be isolated or disease does not resemble pneumococcal pneumonia).

The other atypical pneumonias are:

- Legionnaires’ disease

- psittacosis

- Q fever

- viral pneumonia such as influenza.

Onset of pneumonia is gradual, beginning with a nonproductive cough, sore throat or earache.

Small amounts of whitish, nonbloody sputum are produced.

Other symptoms: fever, headache, malaise & myalgias.

Children may suffer paroxysmal cough, causing confusion with whooping cough.

Very severe infection may occur in immunocompromised patients & those with sickle cell disease: infection of joints & these infections are hard to treat.

Complications:

- Stevens-Johnson syndrome, or other rashes.

- joint pains

- encephalitis or meningitis

- hemolytic anemia

- myocarditis or pericarditis

Serologic testing is mainstay of diagnosis.

A cold-agglutinin titer of 1:128 or higher is indicative of recent infection.

About 50% of patients produce ‘cold agglutinins’: antibodies which react with I antigen present on all human red cells, detectable at 4 but not 37 degrees.

Specific serology using mycoplasma antigen is more sensitive: 4-fold or greater rise in specific antibody titer in complement fixation test.

Erythromycin or tetracycline for up to 3 weeks.

Penicillins & cephalosporins are inactive as the organism has no cell wall.

Mycoplasma hominis

Pelvic inflammatory disease

Urinary tract infection & renal stones.

Bacterial vaginosis predisposes to late miscarriage & preterm labor: may cause post-abortion & post-partum fever.

Premature infants may develop meningitis.

Ureaplasma urealyticum

Non-gonococcal urethritis

Urinary tract infection & renal stones.

Bacterial vaginosis predisposes to late miscarriage & preterm labor: may cause post-abortion & post-partum fever.

Premature infants may develop meningitis.