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23 Cards in this Set
- Front
- Back
Mycoplasma and Ureaplasma: Physiology and structure
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Cell size: .1-.3 micron
Cell wall: absent Atmosphere: Facultative aerobe Nutritional requirement: sterols (then incorporated into cell membrane) Nutritional supplements: vitamins, AA, nucleic acid precursors Penicillin resistant (no cell wall!) |
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Mycoplasma/Ureaplasma pathogens
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M. pneumoniae:
-respiratory tract -URT disease, atypical pneumonia, tracheobronchitis M. genitalium: -GU tract -Urethritis U. urealyticum: -RT, GU tract -Urethritis |
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Mycoplasma pneumoniae : PHYSIOLOGY AND STRUCTURE
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The smallest free-living bacterium; able to pass through 0.45-μm pore filters (“artificial bacterium”)
Highly pleomorphic and flexible cells; very difficult to stain Absence of cell wall and a cell membrane containing sterols are unique among bacteria Sterols are not synthesized; incorporated from host or serum in culture media; (time for colonies <1 week) Slow rate of growth (generation time, 1 to 6 hours) Strict aerobe |
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Mycoplasma pneumoniae : clinical diseases
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Upper respiratory infections:
Atypical pneumonia, often termed “Walking pneumonia” mild chronic respiratory symptoms; can last for weeks Dry non-productive cough with scant sputum; low grade fever, headache & malaise Immune responses to M. pneumoniae infection Early IgM, late IgG, IgA Cell mediated immunity may protect -Many different types/clones, cross protection is poor In children, 50% develop secondary cold agglutinin disease -Transient autoimmune disease caused by high levels of circulating antibody reactive with RBC |
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Mycoplasma pneumoniae : virulence, pathogenesis
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Virulence factors
Surface structures: P1 adhesin protein binds cilia leading to eventual loss of ciliated epithelial cells Adhesions acts as superantigen, stimulating migration of inflammatory cells and release of TNF-alpha and Il-1 Capsule: polysaccharide, may be involved in attachment or may have additional toxic effects Hemolysins: alpha or beta hemolysin (cytolytic) kill host cells |
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Mycoplasma pneumoniae : epidemiology
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Worldwide disease with no seasonal incidence
Estimated 100,000 hospitalizations and 2 Million cases/yr in U.S. Outbreaks occur in schools and where indoor crowding in restricted space is common Transmitted by inhalation of aerosolized droplets Strict human pathogen |
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Mycoplasma pneumoniae: lab diagnosis
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Diagnosis of exclusion
Microscopy: no cell wall, don't stain Culture: 2-6wks before positive dx and insensitive Molecular diagnosis: PCR based amplification w/excellent sensitivity is test of choice, not routinely available Cold agglutinin: Sensitivity 65%, poor specificity; cross reactions |
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Mycoplasma pneumoniae: prevention and treatment
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No vaccine
Treat with macrolides |
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Ureaplasma urealyticum
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Genitourinary tract
Benign carriage is common, esp. in women Can cause nonspecific urethritis (men) or cervicitis (women). Some have postulated as cause of infertility. Diagnosis and epidemiology are virtually unexplored Treatment: broad spectrum antibiotics |
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Chlamydia overview
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Gram negative
Obligate intracellular pathogen |
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Chlamydia life cycle
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Elementary body: Infectious form. Metabolically inactive.
Similar to an endospore Reticulate body: replicative form. Grows until nutrients within endosomal compartment are depleted, elementary bodies are formed, then released by endosomal fusion with cytoplasmic membrane. |
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Cell envelope architecture of elementary bodies
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P layer– cysteine rich proteins that are highly
Crosslinked by disulfide bonds Functional equivalent of peptidoglycan layer Elementary body form has no peptidoglycan |
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“Chlamydial anomaly”
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Peptidoglycan has not been detected in any Chlamydial
life stage -Most studies are with elementary bodies However….some β-lactam and cephalosporin drugs have efficacy against Chlamydia How can that be? -Chlamydial genome sequences indicate that most of the enzymes in peptidoglycan biosynthesis are present Based on current data, reticulate bodies may have some unusual type of peptidoglycan -It’s not thick or heavily cross-linked -Never been seen by EM Role of PG may be more related to cell division than to osmotic protection |
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Chlamydia trachomatis: clinical diseases
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Trachoma: Chronic, inflammatory granulomatous process of eye surface, leading to blindness
Adult inclusion conjunctivitis: Acute process with mucopurulent discharge, corneal infiltrates Neonatal conjunctivitis: Acute process with mucopurulent discharge Urogenital infections: Mucopurulent discharge in GU tract; asymptomatic infections common in women May have mild symptoms in men... mild burning on urination |
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Chlamydia trachomatis : sexually transmitted diseases
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Predominantly caused by serovars D-K
Men: non-gonococcal urethritis Women: urethritis, cervicitis Sequelae: Pelvic Inflammatory disease, ectopic pregnancy, infertility >10% of sexually active population infected, men are reservoir; 2.8 million new infections/yr in U.S. LGV (serovars L1-L3): more tissue-invasive > inguinal lymphadenopathy Neonatal infections from passage through infected birth canal: conjunctivitis, pneumonia |
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Chlamydia trachomatis: physiology and structure
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Small, gram-negative rods with unusual cell envelope/cell wall
Strict human intracellular pathogen; energy parasite Major outer membrane proteins are species specific Two biovars associated with human disease: trachoma 15 serovars LGV; four serovars Infects non-ciliated columnar, cuboidal, and transitional epithelial cells |
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Chlamydia trachomatis: VIRULENCE & PATHOGENESIS
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Proposed Roles of Type III Secretion in Pathogenesis and Development:
Inhibition of phagolysosome fusion Acquisition of host lipids and nutrients Fusogenicity of early inclusions (IncA) Induction of anti- and/or pro-apoptotic activities Modulation of intracellular development Delayed Type Hypersensitivity (Hsp60 as DTH agent) Autoimmunity (immune response to Hsp60) |
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Chlamydia trachomatis: EPIDEMIOLOGY, DIAGNOSIS
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Epidemiology
Most common sexually transmitted bacterial disease in US Ocular trachoma worldwide with blindness developing in 7 to 9 million patients LGV highly prevalent in Africa, Asia, and South America Diagnosis Culture is highly specific, relatively insensitive -As a routine matter, this is not likely to be available to you Molecular amplification tests with NA probes: PCR or LCR fast and accurate |
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Chlamydia trachomatis: TREATMENT, PREVENTION & CONTROL
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Treat LGV, ocular or genital infections and newborn conjunctivitis or pneumonia with common antibiotics
Safe sex practices and prompt treatment of patient and sexual partners help control infections Face washing (trachoma); education re: hygiene/transmission………No vaccine …. yet |
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Chlamydia pneumoniae
Overview |
Wordwide distribution, >50% sero-prevalence
probably recently ‘jumped’ from an animal host to humans Community-acquired pneumonia |
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Chlamydia pneumoniae: Clinical features
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Murky
chronic bronchitis, asthma, exacerbation of COPD lung cancer, stroke, sarcoidosis, reactive arthritis, MS, Alzheimer disease strongest association with coronary heart disease: |
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Chlamydia pneumoniae: Dx, Tx, prevention
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Dx not usually attempted
Tx: doxycycline, erythromycin for at least 10 days No vaccine |
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Chlamydia psittaci
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Respiratory infection (psittacosis) after exposure to wild exotic animals
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