Mycoplasma

• What are mycoplasmas?


  Mycoplasmas are the smallest free-living organisms.
• What is a key characteristic of mycoplasmas regarding their structure?

  Mycoplasmas are pleomorphic organisms that do not possess a cell wall.
• How do mycoplasmas differ from bacterial L-forms?

  The absence of a cell wall in mycoplasmas is a permanent characteristic, unlike bacterial L-forms where it is a temporary environmental change.
• What unique component is found in the bacterial membrane of mycoplasmas?

  Mycoplasmas are the only bacteria that contain cholesterol, a sterol usually found in eukaryotic cell membranes.
• What are the two main species of mycoplasmas mentioned?

  The two main species are M. pneumoniae and M. hominis.
• What disease does M. pneumoniae cause?

  M. pneumoniae causes "atypical" pneumonia and bronchitis.
• How is M. pneumoniae transmitted?

  M. pneumoniae is transmitted by respiratory droplets.
• Who is most at risk for clinical disease caused by M. pneumoniae?

  Groups at risk include closed-in populations such as prisoners, college students, and military personnel.
• What is the typical incubation period for M. pneumoniae infections?

  The incubation period usually lasts 2 to 3 weeks.
• What are some early nonspecific symptoms of M. pneumoniae infection?

  Early nonspecific symptoms include headache, low-grade fever, malaise, and anorexia.
• What are some accompanying symptoms of M. pneumoniae infection?

  Accompanying symptoms include sore throat, dry cough, and earache.
• What are extrapulmonary complications of M. pneumoniae infection?

  Extrapulmonary complications can include cardiovascular, CNS, dermatologic, and GIT problems, but are rare occurrences.
• How long does the disease caused by M. pneumoniae typically last?

  The disease resolves spontaneously in 10 to 14 days.
• What type of infections is M. hominis associated with?

  M. hominis is associated with infections of the urogenital tract and may cause pelvic inflammatory disease.
• How are mycoplasmas classified in terms of pathogenicity?

  Mycoplasmas are considered opportunistic pathogens.
• Why is Gram-staining not useful for laboratory diagnosis of mycoplasmas?

  Gram-staining is not useful because mycoplasmas lack a cell wall.
• What laboratory technique can be used to diagnose mycoplasma infections?

  Polymerase chain reaction (PCR) can be used for diagnosis.
• What does serology demonstrate in the context of mycoplasma infections?

  Serology shows a fourfold rise in titer in acute and convalescent sera.
• What is a critical consideration for handling mycoplasma specimens?

  Due to the lack of a cell wall, all mycoplasmas are extremely sensitive to drying and heat.
• How should mycoplasma specimens be handled for laboratory analysis?

  Specimens should be inoculated at bedside or delivered immediately to the laboratory in a transport medium.
• Can mycoplasmas be grown in the laboratory?

  Yes, mycoplasmas can be grown in the laboratory on artificial media, but they have complex nutritional requirements.
• How long does it typically take for mycoplasmas to form a visible colony in the laboratory?

  Mycoplasmas require at least 1 week to form a visible colony.
• What is the characteristic appearance of mycoplasma colonies?

  The colony has a characteristic "fried-egg" appearance, with a raised center and a thinner outer edge.
• What is the treatment of choice for mycoplasma infections?

  The treatment of choice is either a macrolide, such as erythromycin/azithromycin, or a tetracycline, such as doxycycline.
• Which fluoroquinolone is effective against mycoplasma infections?

  Levofloxacin is an effective fluoroquinolone for treating mycoplasma infections.
• Why are penicillins and cephalosporins inactive against mycoplasmas?

  Penicillins and cephalosporins are inactive because the organism has no cell wall.