Mycoplasma Notes

NOTES NOTES MYCOPLASMA MICROBE OVERVIEW ▪ Smallest free living organisms ▪ Prokaryotic with absence of cell wall, presence of flexible cell membrane containing cholesterol ▫ Pleomorphic ▫ Not visible on Gram stain ▫ Resistant to beta lactam, glycopeptide antibiotics ▪ Limited metabolic activity → not culturable on standard culture media, require specialized medium (e.g. Eaton’s agar) with sterols, nutrients provided by natural animal protein (e.g. blood serum) ▪ Can grow under aerobic, anaerobic conditions MYCOPLASMA PNEUMONIAE osms.it/mycoplasma-pneumoniae PATHOLOGY & CAUSES ▪ Species of mycoplasma; primarily affects respiratory tract; usually causes upper respiratory tract infections; can also cause atypical pneumonia ▪ Transmitted through respiratory droplets after close contact with infected individual → attaches to respiratory epithelium with P1 surface protein → hydrogen peroxide, superoxide radicals synthesized by mycoplasma interact with endogenous toxic molecules synthesized by host cells → oxidative stress in respiratory epithelial cells ▪ Macrophages migrate to site of infection → activation and phagocytosis → initiate inflammatory response → T, B lymphocyte proliferation → antibody production, release of inflammatory cytokines → control infection/initiate immune-mediated lung injury ▪ Extrapulmonary disease (rare) ▫ Due to immune mediated injury/cross reactive antibody mechanism/direct invasion 434 OSMOSIS.ORG ▪ Central nervous system (CNS), joints, skin, blood, heart, liver, pancreas affected ▫ CNS is the most common extrapulmonary site; usually encephalitis ▪ Can develop cold agglutinin response (60%) ▫ Autoimmune hemolytic anemia ▫ Coombs positive ▫ Cold (active below 37°C/98.6°F) IgM antibodies against erythrocyte surface antigen due to cross reaction of antigen with mycoplasma antigens → can agglutinate/lyse erythrocytes RISK FACTORS ▪ Common in children, young adults ▪ Immunocompromised status, smoking, close community living (e.g. nursing homes, dorms) COMPLICATIONS ▪ Asthma exacerbations ▪ Respiratory failure ▪ CNS involvement

Chapter 81 Mycoplasma ▫ Encephalitis with high mortality rate ▪ Heart involvement ▫ Rhythm disorders, heart failure SIGNS & SYMPTOMS ▪ Can be asymptomatic ▪ Gradual onset ▫ General fatigue, myalgias, headache, low grade fever, sore throat, cough (worsening, frequent, non-productive), chills ▪ Less common ▫ Sinus/ear pain, wheezing ▪ Chest auscultation ▫ Scattered rales, wheezes, rhonchi, crackles ▪ Sinus tenderness ▪ Erythema of tympanic membrane ▪ Pharyngeal erythema ▪ Pulse-temperature dissociation: normal pulse despite fever indicative of atypical pneumonia DIAGNOSIS LAB RESULTS ▪ Molecular testing with polymerase chain reaction (PCR); most accurate ▪ Serological tests ▫ ≥ four-fold rise in IgM antibodies titers of acute, convalescent sera 2–3 weeks apart using enzyme immunoassay ▫ High titer of IgM antibodies ▫ Cold agglutinins titer ▪ Isolation with culture ▫ Limited use due to slow growth (2–3 weeks), need for specialized media DIAGNOSTIC IMAGING Chest X-ray/CT scan/high resolution CT scan ▪ Diffuse reticulonodular pattern indicative of interstitial pneumonia ▪ Areas of airspace consolidation (esp. lower lobes) ▪ Thickening of bronchovascular bundle OTHER DIAGNOSTICS ▪ Histopathology ▫ Inflammation in trachea, bronchioles, peribronchial tissues ▫ Airspaces filled with purulent exudate with polymorphonuclear cells ▪ Physical examination ▫ Vague symptoms (e.g. fatigue) indicative of atypical/“walking” pneumonia TREATMENT ▪ Most cases mild, self-limited MEDICATIONS ▪ Atypical pneumonia ▫ Macrolides (e.g, erythromycin, azithromycin); tetracyclines (e.g. doxycycline); fluoroquinolones (e.g., levofloxacin, moxifloxacin) OSMOSIS.ORG 435