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Mycoplasma Pneumoniae

Summary

Mycoplasma pneumoniae is a pleomorphic free-living organism that belongs to the Mycoplasmataceae family [1]. It is also sometimes referred to as the Eaton agent, named so after the name of the researcher who initially isolated the organism [2].

Mycoplasma pneumoniae is a pleomorphic free-living organism that belongs to the Mycoplasmataceae family [1]. It is also sometimes referred to as the Eaton agent, named so after the name of the researcher who initially isolated the organism [2].

Virulence and microbiologic features:   

  • The peptidoglycan-containing cell wall is absent in mycoplasma pneumoniae, rendering it resistant to antibiotics that target cell wall synthesis, such as penicillin and cephalosporins [1].
  • It has a sterols-containing cell membrane [1].
  • The organism is motile and depends on the presence of cholesterol for its membrane synthesis [3].
  • It exhibits strict aerobic respiration [4] and can thrive and reproduce outside the host cell [3].
  • A clinically important virulence factor of mycoplasma pneumoniae is the P1 protein, which facilitates bacterial attachment with target cells of the respiratory tract [3].
  • It does not produce toxins [3].
  • Recruitment of inflammatory cells and cytokine release in response to the bacterium contribute to bacterial elimination and disease manifestation [4].

Transmission: 

  • Transmission is through respiratory route [1]

Disease and complications: 

  • Tracheobronchitis [5]
  • Atypical pneumonia or walking pneumonia: The patient can present with a nonproductive cough and fever. Imaging studies such as X-rays will confirm streaky infiltrate and imaging findings appear worse than observed physical signs and reported symptoms. [1,5]

Two chest x-rays in the case by Centers for Disease Control and Prevention is marked with CC0 1.0.

  • Some other conditions that can develop in some patients infected with mycoplasma pneumoniae include Steven-Johnson syndrome and erythema multiforme [1].

Diagnostic Testing:   

  • Cold agglutinins: These are monoclonal IgM antibodies aginst I antigen of RBCs. These antibodies cause RBC agglutination at lower temperature, i.e., at 4°C. [1]

File:Red blood cell agglutination due to cold agglutinin.jpg by Spicy is licensed under CC BY-SA 4.0.

  • Culture of the sputum specimen will show colonies with a mulberry appearance. [1]
  • Complement fixation test can also detect rising antibody titers [1].
  • Rapid detection is possible through mycoplasma DNA probe and PCR [1].

 References:

  1. CMMRS edition 6, 2016-17 (page no: 156)
  2. Medical Microbiology by Patrick R. Murray Ph.D., Ken Rosenthal Ph.D., Michael A. Pfaller MD, 8th edition (page no: 334)
  3. CMMRS edition 6, 2016-17 (page no: 158)
  4. Medical Microbiology by Patrick R. Murray Ph.D., Ken Rosenthal Ph.D., Michael A. Pfaller MD, 8th edition (page no: 335
  5. CMMRS edition 6, 2016-17 (page no: 159)
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