09006775

Mycoplasma pneumoniae

general features

it is the mager cause of community acquired Pneumonia - production of fluid in the inter-membrane space of the lungs. the optimum growing temperature is 37°c, due to its evolutionary adaptations to surviving within a human host, this makes it a mesophyle. Mycoplasma are unusual in that they do not have a cell wall, making them resistant to antibiotics such as penicillin and other β lactam ring antibiotics, which target cell wall synthesis. However it is susceptible to tetracyclines and erythromycin. As a result of having no cell wall the cell would normally be more unstable and likely to die of osmotic lysis. Instead they use hopanoids, structures much like cholesterol in eukaryotic cells which strengthens the plasma membrane. However this does give the cell the advantage of being pleomorphic.

Mycopasmas are the smallest known bacteria, in both dimensions and genome size making them the smallest known free living organisms i.e. excluding viruses. Cells of Mycoplasma Pneumonia are 1–2 mm in length and 0.1–0.2 mm in width.

fig 1. artistic image of Mycoplasma Pneumoniae
Pneumonia bacteria-89
Pneumonia bacteria-89
(medicalRF.com, 2011)

History
1. 1898 first isolated in cattle
2. 1938 first case in man
3. further described as primary atypical pneumonia after 7 further cases, typical pneumonia associated with being too cold
4. 1943 accidental discovery of cold agglutinin
5. 1944 discovery of the "agent" Eaton's agent
6. 1961 viral theory disproved after identification as a mycoplama

Pathophysiology

M. pneumoniae is able to imbed itself in epithelial linings casing inhibition of cilia. The body attempts to compensate by coffing. As part of the cells biochemistry the bacteria produces hydrogen peroxide, causing much of the disruption to hosts. Host maturity not virulence factors contribute to the severity of disease, thus younger people are more likely to catch, and present with, the disease. It is uncertain as to whether the immune response helps to reduce infection or causes further complications through immunologic lesion development.

Mycoplasma pneumoniae has been associated with an increasing array of illnesses, such as acute hepatitis, immune thrombocytopenic purpura, severe autoimmune haemolytic anaemia, Stevens-Johnson syndrome, arthritis, and transverse myelitis. Pneumonia does not necessarily follow infection and a long latent period can be observed. Protective immunity only develops if pneumonia develops. bronchitis is often a milder observed manifestation.

Due to their small genome they are very fastidious and as such must live as pathogens. This adds to the problems of identifying them as they are difficult to culture, this means that a person with suspected pneumonia must wait weeks for a confirmed diagnosis.

fig 2. x ray imaga og a lung infected with pnumonia
Treatment For Pneumonia
Treatment For Pneumonia
(N.N., N.D.)

Epidemiology

Epidemics usually occur every 4 to 5 years. However the last epidemic occurred in 1997 and continued till 1999 however incidence has not risen to epidemic levels since. Epidemics usually last for 12 - 15 months. Epidemics can develop in closed or semi closed environments such as military bases hospitals and schools. Due to the long latent period and often asymptomatic manifestations several people can become infected. Outbreaks in temperate climates show seasonality, usually occurring in summer or early autumn when other respiratory infections are usually low, it suggests that it has an arthropod vector. The imunocompromised and those in low income areas, where close contact is comon are predictably high risk areas of the community.

M. pneumoniae is usually transmitted form person to person through coffing. Schools appear to be a common place for transition due to the large number of people in contact with each other. Increased numbers of children under the age of 5 are now being reported as having M. pneumoniae this is probably due to the fact that there are now a larger number of children attending day-care. children also represent an asymptomatic pool for outbreaks amongst families. M. pneumoniae causes up to 40% of the community acquired pneumonia in children and around 18% of these require hospitalisation. The bacteria does have animal hosts making it impossible to totally irradiate, the best we can do is control it..

diagnosis and treatments

diagnosis is by x-ray (see image above) and by culturing sputum sample to confirm the microorganism. Most antibacterial treatments can be taken at home and symptoms start to ease after only 2 days. Many people recover after only a few weeks however symptoms may continue after the cause to treatment is finished. if serious treatment may be required in hospital.

complications

pneumonia may be a complication of previous infection or more serious condition. It rarely causes pnumonial meningitis. It may require hospitalisation in the very old and very young.

references

http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Mycoplasma/
http://www.nlm.nih.gov/medlineplus/ency/article/000082.htm
http://emedicine.medscape.com/article/807927-overview
http://onlinelibrary.wiley.com/doi/10.1002/ppul.10346/pdf
http://www.nhs.uk/Conditions/Pneumonia/Pages/Complications.aspx
http://www.nhs.uk/Conditions/Pneumonia/Pages/Treatment.aspx

list of figs

fig 1: http://www.medicalrf.com/Pneumonia-bacteria-89-image_RF000004180.html
fig 2: http://treatmentforpneumonia.com/