Mycoplasma

Question 1

Major features of Mycoplasma.

Answer 1

• Mycoplasma are the smallest free-living organisms that are still capable of self-replication (they are smaller than some large viruses!)
• these LACK a peptidoglycan cell wall (and therefore lack a specific shape); this makes them immune to many antibiotics (penicillins and cephalosporins)

Question 2

What are the two pathogenic species of Mycoplasma? What diseases does each causes?

Answer 2

• Mycoplasma pneumoniae: causes a mild self-limiting bronchitis and pneumonia
• Ureaplasma urealyticum: causes urethritis

Question 3

Mycoplasma pneumoniae is the number one cause of bacterial bronchitis and pneumonia in which population of patients? What is this type of pneumonia also known as? Why?

Answer 3

• number 1 cause of bacterial bronchitis and pneumonia in teens and young adults
• it is also known as “walking pneumonia” because patients don’t feel very sick (compared to other cases of pneumonia); they have a gradual onset of fever, sore throat, malaise, and a dry hacking cough
• this is a type of atypical pneumonia

Question 4

Which organisms are responsible for atypical pneumonia? How do we treat atypical pneumonia?

Answer 4

• atypical pneumonia is caused by viruses, Legionella, Mycoplasma pneumoniae, and Chlamydophila species
• most cases of Mycoplasma induced pneumonia don’t require treatment
• atypical coverage: macrolides, tetracyclines, and quinolones

Question 5

7% of patients infected with Mycoplasma pneumoniae will develop which complications?

Answer 5

• 7% will develop erythema multiforme or Stevens-Johnson syndrome

Question 6

How do we diagnose walking pneumonia (pneumonia due to Mycoplasma pneumoniae)?

Answer 6

• cold agglutinins: some patients develop IgM Abs against a modified RBC antigen that is present during the infection and the resulting Ab-antigen complex agglutinates in cold temperatures
• complement fixation test
• sputum culture
• Mycoplasma DNA probe

Question 7

What are the major characteristics of Ureaplasma urealyticum? What disease does it cause? How do patients present?

Answer 7

• this organism is found in urine and produces urease to convert urea into ammonia and CO2
• it produces very tiny colonies
• it causes urethritis (along with N. gonorrhoeae and C. trachomatis)
• patients present with dysuria and a yellow mucoid discharge from the urethra