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What are the smallest free-living organisms - about the size of a large virus and beyond the resolution of light microscopes?
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Describe Mycoplasma and Ureaplasma
- Lack cell wall - making them pleomorphic
- Resistant to all antibiotics that inhibit cell wall synthesis (beta-lactams)
- Contain both RNA and DNA
- Can self-replicate
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How are infections of Mycoplasma and Ureaplasma diagnosed?
Serology
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What media is used to grow Mycoplasma and Ureaplasma and what do they sometimes look like on the media?
- SP4 agar
- A8 agar
- Shepard's 10 B broth
- Some species will grow on chocolate agar
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What does U. urealyticum produce?
Strong alkaline pH because of the activity of urease
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What organism is associated with:
Tracheobronchitis
Community-acquired primary atypical (walking) pneumonia (dry, nonproductive cough)
Spread by Direct repiratory contact
Produces hydrogen peroxide - which causes a lysis of RBCs in vitro
Mycoplasma pneumoniae
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What are the clinical conditions associated with Mycoplasma hominis?
- Opportunistic pathogen linked to PID (pelvic inflammatory disease) in sexually active partners
- Infant meningitis
- Postpartum fever
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What organism is associated with:
Nongonococcal urethritis
May cause other genital tract infections
Requires Urea
Ureaplasma urealyticum
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What organisms are:
Obligate intracellular parasites
Require nucleotides and other metabolic building blocks from the host cells
Spread by insect vectors (ticks, mites, and lice)
Rickettsia and Ehrlichia
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How is diagnosis made for Rickettsia and Similar Genera?
- Clinical symptoms
- Patient history
- Serology
- Immunohistology and PCR assays are also available
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How are Rickettsia and similar genera cultured?
- Bacteria can be grown in embryonated eggs and tissue cells
- Cultures require biosafety level 3
- Cutures are not recommended because of safety concerns
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Name some of the clinically important species of Rickettsia and similar genera
- R. rickettsii
- R. prowazekii
- R. typhi
- Coxiella burnetii
- Ehrlichia chaffeensis
- Anaplasma phagocytophilum
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What clinical condition is associated with R. rickettsii?
- Rocky Mountain spotted fever (RMSF)
- Death rates are approx. 25%
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What is R. rickettsii a member of?
Member of spotted fever group
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How is R. rickettsii transmitted?
Ticks
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What organism is associated with:
Typhus (also called epidemic or louse-borne typhus)
Brill-Zinsser disease is a reactivation of the original infections
Transmitted by Human lice
R. prowazekii
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What clinical conditions are associated with R. typhi?
Endemic or murine typhus
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How is R. typhi transmitted?
Fleas
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What organism is associated with:
Q fever
Transmitted by: Inhalation, Contact with fomites, Ingestion of contaminated milk
Coxiella burnetii
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What organism is associated with:
Ehrlichiosis or human monocytic ehrlichiosis
Spread by Ticks
Ehrlichia chaffeensis
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What clinical condition is associated with Anaplasma phagocytophilum?
Human granulocytic anaplasmosis
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What are general characteristics of Chlamydia and Chlamydophila?
- Obligate intracellular parasites
- Cannot produce ATP - require it from the host cell
- Contain both DNA and RNA
- Susceptible to antimicrobial agents
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How is chlamydia and chlamydophila diagnosed?
- Cytological methods - detect chlamydia inclusions in epithelial cells
- Cell cultures are required to grow the bacteria
- Nucleic acid amplification tests (NAATs) are the most common diagnositic method
- Serology - antibody to lipopolysaccharide and outer membrane protein antigens
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What organism is associated with:
Mild respiratory tract infections (flu-like symptoms)
May cause Guillain-Barre syndrome
Diagnosed with Fluorescence-labeled C. pneumoniae antibodies
Chlamydophila pneumoniae
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What organism is associated with:
Psittacosis (ornithosis) or parrot fever - disease of birds
Humans get infections by inhaling bird fecal dust
Chills, fever, malaise
Can progress to pneumonia, which can be fatal
Incubation period of 1-2 weeks
Diagnosed with serology
Chlamydiophila psittaci
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