Mycoplasma pneumoniae

[Mr. Nine]

Clinical Features
Majority with upper respiratory tract infections with fever, cough,
malaise, and headache. May lead to tracheobronchitis with fever and
nonproductive cough: radiologically confirmed pneumonia develops in
5-10% of cases; rare extrapulmonary syndromes, including cardiologic,
neurologic, and dermatologic findings.

Etiologic Agent
Mycoplasma pneumoniae, a small bacterium.

Incidence
Each year an estimated 2 million cases and 100,000 pneumonia-related
hospitalizations occur in the United States.

Sequelae
Persistent cough is common during convalescence; other sequelae are
rare. Fatal cases are reported occasionally, primarily among the
elderly and persons with sickle-cell disease.

Transmission
Person-to-person transmission by respiratory secretions.

Risk Groups
All ages at risk, but most common in school-age children. In the
United States, about 50% of adults have evidence of past infection by
age 20. Reinfection throughout life appears to be common.

Surveillance
No national or state surveillance exists.

Trends
Unknown. Improved diagnostic testing may lead to improved recognition
of infection.

Challenges
There is a lack of standardized diagnostic methods. Isolation of the
etiologic agent is difficult, so antibody tests using paired acute-
and convalescent-phase sera have been used for diagnosis. There are no
known methods to prevent possible sequelae. The role of C. pneumoniae
in atherosclerotic vascular disease needs further definition

Source: Centers for Disease control & Prevention
http://www.cdc.gov

[mr. pearl]

can i ask u some questions,dr?
first,why does it cause extrapulmonary syndromes?(immune-mediated or other mechanisms)
is it Gram-positive or negative,aerobic or anaerobic?(for antibiotic choice)
How can we diagnose it?(u say improved diagnostic testing may lead to improved recognition of infection but which has difficult standardized method and high prevalence)

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[Mr. Nine]

Thank u doctor for ur discussion. Sorry for my late reply, because I
didn't reach online last week.

Extrapulmonary syndromes are caused by immune mediated mechanisms.
Mycoplasmas can activate macrophages and stimulate cytokine production
and lymphocyte activation. M. pneumoniae acts as a superantigen
(macrophage activation, cytokine induction) and stimulates
inflammation. Extrapulmonary manifestations include otitis media,
myocarditis, pericarditis, erythema multiforme (Stevens-Johnson
syndrome), hemolytic anemia, and neurological complications.

It is Gram-negative bacteria with irregular shape ( including round,
pear shaped and even filamentous) due to lack of cell wall. They are
the smallest free-living bacteria. They range from 0.2 - 0.8
micrometers and thus can pass through some filters used to remove
bacteria. They have the smallest genome size.
The mycoplasmas are facultative anaerobes, except for Mycoplasma
Pneumoniae, which is a strict aerobe.

Mycoplasmas are lack of cell wall, so they are resistant against
antibiotics which interfere the cell wall synthesis such as
penicillins, cephalosporins, vancomycin. Mycoplasmal RNA polymerase is
resistant to rifampin.
Choice of antibiotics is Macrolides (erythromycin, azithromycin,
clarithromycin, dirithromycin) for 1st line and Fluoroquinolones
(levofloxacin, ciprofloxacin) for 2nd line. And may use Doxycycline as
alternatives.
Macrolides & doxycycline have bacteriostatic activity and quinolones
have bacteriocidal action.

The specific diagnosis mainly based on serology tests to detect
mycoplasma antibodies by Complement fixation test, Cold agglutinins,
WB, ELISA, ICC/IF etc.
Sputum Culture (usually scant) or throat washings must be sent to the
laboratory in special transport medium. It may take 2 -3 weeks to get
a positive identification. Culture is essential for a definitive
diagnosis.
Tests using diagnostic DNA probes and PCR are being developed.

Additional studies for the disease may be done, include:
* Complete blood count (CBC)
* Blood cultures
* Bronchoscopy
* Open lung biopsy (only done in very serious illnesses when the
diagnosis cannot be made from other sources).




regards,

[mr. pearl]

thank a millon
i feel a heartfelt gratitude for fulfilling my curiosity
it doesn't matter when u reply,as i know the difficulties and hinderances to reply
wishing u happy,healthy and wise
and more so, able to discuss more!!!!