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General information about Spirochetes (shape, motility, gram, aeration, growth factors, important human pathogens w/ disease)
- long and slender corkscrew shape
- undulating motility
- varies depending on species
- some cannot be cultured
- Treponema pallidium: syphilis
- Borrelia burgdorferi: Lyme disease
- Borrelia recurrentis: relapsing fever
- Leptospira interrogans: leptospirosis
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Describe the structural features of Spirochetes
- cylinder bounded by plasma membrane and gram negative cell wall surrounded by outer sheath
- Endoflagella (axial filaments) propel the cell in a corkscrew manner and allow movement through viscous solutions (tissue)
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General information about T. pallidum (disease, aeration, culture requirements, strength of organism, other important info)
- syphilis
- anaerobic
- cannot be cultured in lab
- very fragile (heat, drying, disinfectants, etc)
- divides slowly
- True intracellular parasite (lacks TCA, ETC, catalase, and oxidase)
- Cannot be observed by light microscopy (too thin)
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Transmission of T. pallidum
- Sexual contact: oral, vaginal, anal
- Transplacental transmission: doesn't occur in birth canal (bacteria dies too quickly)
- Enters body through break in skin/penetrates mucous membrane
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Describe the diseases caused by T. pallidum w/ description
- Primary syphilis: chancre (genital or oral)
- Heals after 6 weeks, but organism spreads via lymph and blood
- Secondary syphilis: after asymptomatic period
- Maculopapular rash that is EXTREMELY infectious
- A latent period occurs after rash heals
- Tertiary syphilis: degeneration of nervous system (resembling severe mental illness)
- lesions on liver, skin, and bones
- Not transmissible at this stage
- Congenital syphilis: transmitted through placenta to fetus
- Most often causes death and spontaneous abortion, stillbirth
- If infants survive they develop a condition similar to secondary syphilis
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lab ID of T. pallidum
- Serological ID using antibodies against T. pallidum
- enzyme immunoassays
- problem-assays remain positive for years after treatment
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Treatment of T. pallidum
- One treatment with penicillin (no resistance)
- Treatment for mother prevents congenital syphilis
- Patients are often associated with HIV and should be tested for additional diseases
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Prevention of T. pallidum
- No vaccine
- Depends on safe sexual practices
- 8000+ new cases each year despite effective cure
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What is unique about B. burgdorferi?
- Linear, no circular, chromosome!
- 3rd genome ever sequenced
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Describe the disease caused by B. burgdorferi in detail
- Lyme disease (endemic relapsing fever)
- The most common arthropod-transmitted disease in the US
- Transmitted by bite of tick
- Rodents and deer act as primary reservoires
- First stage: red circular lesion with clear center at site of bite
- 3-6 days of fever, 7-10 days of wellness, repeated 3-10 times
- Second stage: arthritis, arthralgia, meningitis (weeks to months later)
- Third stage: appearance of chronic arthritis (months to years later)
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Lab ID of B. burgdorferi
- Can be cultured, but takes 6-8 weeks
- Serological tests provide too many false-positives
- Most definitive test is PCR assay
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Treatment and prevention of B. burgdorferi
- Treatment with antibiotics.
- If arthritic symptoms have appeared, longer courses of antibiotics are required
- Prevention includes insect repellents, and proper clothing to protect from ticks
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Difference between endemic relapsing fever and epidemic relapsing fever
- Endemic relapsing fever: (Lyme disease) caused by B. burgdorferi
- Occurs in most areas of the world and is tickborn
- Fatalities are rare
- Epidemic relapsing fever: caused by B. recurrentis
- Transmitted from human to human by body lice
- Fatalities can be as high as 30% if untreated
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Describe symptoms caused by B. recurrentis. What causes them?
- High fever, severe headache, muscle pains for 3-5 days with abundant spirochetes in blood
- Latent period (with no spirochetes in blood) for 4-10 days follows
- Rinse/repeat up to ten times
- Caused by the antigenic variation of B. recurrentis
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Diagnosis, treatment, and prevention of B. recurrentis
- Diagnosis based on spirochetes in blood during fever portion of disease
- Antibiotics are effective, but it is hard to tell difference between latency and cure
- No vaccines are available
- Protect against lice
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Describe the epidemiology of L. interrogans
- A zoonosis which is coincidentally transmitted to humans by water or food contaminated with animal urine
- Entrance to body via small skin abrasions or conjunctiva
- Very rare in developed countries
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Describe the disease of L. interrogans
- Leptospirosis
- Fever occurs 1-2 weeks after infection, when spirochetes appear in blood, and decrease after a week
- In biphasic disease spirochetes reappear and invade liver, kidneys, and CNS
- This results in jaundice, hemorrhage, tissue necrosis, and/or aseptic meningitis
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Diagnosis, treatment, and prevention of L. interrogans
- Diagnosis based on serologic agglutination tests and visual demonstration of spirochetes in blood, urine, or CSF
- Antibiotics are effective during first stage, but ineffective at later stages
- No vaccine is available
- Prevention of exposure to contaminated water/food
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