Mycoplasma

Bacteriology MYCOPLASMA GENERAL CHARACTERISTICS 1. Smallest and simplest procaryotes that self-replicate 2. Belong to class Mollicutes, small procaryotes containing single trilaminar membrane a. Mycoplasmataceae require cholesterol for cell membranes b. Two genera of medical importance in humans ("pleuropneumonia-like organisms" is synonym) i. MYCOPLASMA ii. UREAPLASMA MORPHOLOGY, PHYSIOLOGY 1 . Lacks cell wall 2. Morphology may vary 3. Has gliding motility on liquid-covered surfaces 4. Circular double-stranded DNA 5. Require cholesterol, and purine acid pyrimidines for growth 6. Resembles "fried eggs" when grown in solid media 7. Doubling time 1-6 hours; may require 3 weeks to visualize colonies 8. Facultative anaerobes MYCOPLASMA PNEUMONIAE infection 1. Epidemiology a. Throughout the world, usually in colder months b. Transmission from aerosol droplets of infected persons c. Illness more likely in ages 5-20; however, found in all age groups. 2. Clinical manifestations a. 2-3 week incubation period b. Fever, nonproductive cough, headache c. Chest x-ray appearance worse than pulmonary examination d. lasts about 3 weeks untreated e. Cold agglutinins found in convalescent sera; may be associated with i. Hemolytic anemia ii. Acrocyanosis f. less common manifestations i. Otitis media, bullous myringitis ii. Meningoencephalitis iii. Myocarditis iv. Stevens-Johnson syndrome 3. Diagnosis a. Culture in enriched medium with serum and yeast extracts b. Rising titer of cold agglutinins c. Complement-fixation test 4. Treatment a. Erythromycin and tetracycline reduce disease severity b. Penicillins are ineffective