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21 Cards in this Set

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What are the human mycoplasma pathogens
Mycoplasma pneumoniae- respiratory infections
Mycoplasma hominis- genital infections
Mycoplasma genitalium- genital infections
What does Ureaplasma urealyticum cause
Genital infections
What is the structure of the Mycoplasma
Smallest free-living organism
Lacks cell wall. Resistant to cell-wall active antibiotics
Can pass through filter due to lack of cell wall rigidity (pleomorphic)
What are the nutritional characteristics of Mycoplasma
Can grow on cell-free media
Require sterols
Osmotically stable medium
Grow slowly
How do Mycoplasma reproduce
Binary fission. They also have very small DNA genomes
What are the clinical manifestations of Mycoplasma pneumoniae infections
Primary atypical pneumonia
Otitis media, erythema multiforme, hemolytic anemia, myocarditis, pericarditis
Asthma
What is primary atypical pneumonia
A general term applied to an acute infectious pulmonary disease caused by Mycoplasma pneumoniae, species of Chlamydia and Rickettsia, and various viruses, including adenoviruses and parainfluenza virus; it is marked by extensive but tenuous pulmonary infiltration and by fever, malaise, myalgia, sore throat, and a cough which at first is nonproductive but becomes productive and paroxysmal
What are the clinical features of Primary atypical pneumonia
Insidious onset, fever, malaise, headache, cough (usually non-productive), myalgia, and sore throat. Constitutional symptoms often predominate over respiratory symptoms
Sputum production variable
Chest Xray shows pulmonary involvement often greater than expected from physical findings
What are the pathogenic mechanisms for Mycoplasma pneumoniae
Entry via inhalation of infected respiratory secretions
Organism attaches to cells of lower respiratory tract. Bacteria remain extracellular. P1 adhesion found in the attachment organelle. Cell membrane receptor is a neuraminic acid containing glycoprotein
Deterioration of cilia in the respiratory epithelium
What is the immunopathology of Mycoplasma pneumoniae
Autoimmune phenomena- related to antigenic similarity
Possible role for cell-mediated immunity in pulmonary response. Cytokine production and lymphocyte activation may either minimize disease through the enhancement of host defense mechanisms or exacerbate disease through immunological lesion development
What is the epidemiology of Mycoplasma pneumoniae infection
Worldwide, no seasonality. Transmission by close contact. 2-3 week incubation period. May cause up to 40% of community acquired pneumonias
How is Mycoplasma pneumoniae diagnosed
Culture from sputum or throat washings
Should see greater than 4 fold rise in specific antibody to Mycoplasma pneumoniae
Test for cold hemagglutinins
DNA probes and ELISA are being developed
What is the treatment for Mycoplasma pneumoniae
Tetracyclin and erythromycin. There is no vaccine
Besides primary atypical pneumonia, what are some other diseases associated with mycoplasmas
Mycoplasma hominis- possible role in pelvic inflammatory disease
Mycoplasma genitalium- nongonococcal urethritis
Ureaplasma urealyticum- nongonococcal urethritis (more often due to Chlamydia trachomatis). Can cause infertility
What are the characteristics of Legionella spp
Distinct from all other known organisms by biochemical and DNA relatedness. 48 different species; Legionella pneumophila is the most important
Motile, gram negative rods, non-spore forming
Slow grower, obligate aerobe, requires cysteine and iron, grow over wide temperature range
Distinct fatty acid composition (14-17 carbon branched chain acids)
Oxidase and catalase positive
Produces Beta-lactamase, a hemolysin, and a cytotoxin
What are the clinical features of Legionella infection
Pontiac fever- acute, self-limited febrile illness (no pneumonia)
Legionnaires' disease- fever, malaise, chills, cough, chest pain, headache, diarrhea. Acute pneumonia (consistent). Pulmonary lesions. Multiorgan involvement is common. Long incubation period
What is the pathogenesis of Legionella infection
Inhalation route of entry
Facultative intracellular pathogen (coiling phagocytosis)
Block phagosome-lysosome fusion. Robust intracellular growth
Proteolytic enzymes and nucleases may contribute to host cell death.
Cell mediated immunity is important part of host defense. IFN-gamma activated macrophages restrict intracellular replication
85% of all cases of Legionellosis are caused by what
Legionella pneumophila
What are the sources of infection of Legionellosis
Spread via aerosol to lungs, e.g. from contaminated cooling towers and evaporative condensers, contaminated shower heads, tap water facets, vegetable misters, etc. No evidence of person-to-person spread
How is legionellosis diagnosed
Demonstration of bacteria in tissue or secretions. Culture requires experienced lab. Identify intracellular bacteria via silver impregnation. Direct fluorescent antibody test can detect bacteria in pleural fluid or lung tissue, but has low sensitivity. Can also use the urine antigen test
Serologic diagnosis- can detect 4 fold rise in antibody titer; serum antibody titer rises 5-7 days after onset of symptoms and may be delayed in some patients
How is legionellosis treated and prevented
Fluoroquinolones and macrolides plus supportive measures. Hyperchlorination of suspect water supply. Treatment of A/C units implicated in outbreak with biocides