Spirochetes Flashcards
1
Q
Spirochetes
A
- Unique class of bacteria shaped like coils
- 5-20 microns long, <1 micron across
- Gram negative* (don’t stain at all with Gram stain, but are structured like gram negative bacteria). So they have the characteristic outer membrane, periplasmic space, and inner cell membrane.
- Many have flagella, including endoflagella, which are flagella inside the periplasmic space. It contracts and helps with motility
2
Q
(In) Famous Spirochetes
A
- Treponema pallidum (syphilis)
- Borellia burgdorferi (Lyme disease)
- Borrelia recurrentis and others (relapsing fever)
- Leptospira interrogans (leptospirosis)
3
Q
T. pallidum subspecies
A
- T. pallidum pallidum causes syphilis. The first name is the genus (troponema), then the species (pallidum), and then the subspecies (pallidum). Syphilis is caused by just the sub-species T. pallidum pallidum
- Other subspecies of T. pallidum can cause a variety of other diseases, which primairly have involvement of the skin and bones and are spread by direct contact (not sexually, like syphilis)
4
Q
Transmission of Syphilis
A
- Transmission is primarily sexual
- Also mother-to-child transmission
- Congenital syphilis
- No natural host other than humans
- Completely dependent on the host for nutrients.
- Minimal surface proteins, which helps it evade our immune system
5
Q
Stages of Syphilis and Summary of Clinical Symptoms
A
Each stage is associated with specific symptoms and a specific time since the initial infection. The infection progresses through these states until the disease is recognized and treated.
- Primary: painless chancre
- Secondary: diffuse rash, flu-like illness
- (Latent): no symptoms
- Tertiary: gumma, aortitis and aortic aneurysm, and tabes dorsalis
6
Q
Primary Syphilis
A
-
Painless chancre (like an ulcer) at the site of infection.
- Occurs on the body where the spirochete enters. Often on the genitals b/c it’s mainly a sexually transmitted disease. Chancre develops 10-90 days after initial infection. It’s painless, so often goes unnoticed. Heals on its own after about a month.
7
Q
Secondary Syphilis (disseminated)
A
- Flu-like illness: sore throat, headache, malaise (feeling sick/tired), adenopathy (swelling of lymph nodes)
- Disseminated rash (contagious!)
- Includes palms and soles
- Includes mucous membranes
- Can have condyloma lata (wart-like)
- Begins weeks to months after infection; resolves slowly on its own.
8
Q
Secondary Syphilis (disseminated)
A
- Flu-like illness: sore throat, headache, malaise (feeling sick/tired), adenopathy (swelling of lymph nodes)
- Disseminated rash (contagious!)
- Includes palms and soles
- Includes mucous membranes
- Can have condyloma lata (wart-like)
- Begins weeks to months after infection; resolves slowly on its own
- Can look like a lot of other rashes
9
Q
Latent Phase
A
- After the rash and systemic symptoms resolve
- No symptoms, but ⅓ of patients will progress to tertiary syphilis (over years to decades)
10
Q
Tertiary Syphilis
A
- Effects of long-term tissue desctruction
- Gumma - a mass of dead and swollen tissue, often found in the mouth.
- Vascular problems
- Aortitis (inflammation of the aorta), aortic aneurysm (dilation of the blood vessel and can rupture)
- Neurologic problems
-
Tabes dorsalis
- Demyelination of the nerves in the dorsal spin
- Patients may lose their sense of position — and leading to a wide-based gait
-
Tabes dorsalis
11
Q
Neuro Syphilis
A
- Can occur in all 3 stages of syphilis
- Spirochetes invade the central nervous system early in infection
- Early on: can cause meningitis
- Later: Can cause tabes dorsalis or dementia (can be reversed)
- Anytime: can cause uveitis
- Eye pain and blurry vision
12
Q
Diagnosis of Syphilis
A
-
T. pallidum cannot be cultured in the lab
- Has no genes for the TCA cycle
- Dependent on host cells for purines, pyrimidines, amino acids
- Cannot be seen by traditional microscopy. Very hard to stain.
- Diagnosis relies on clinical impression, dark-field microscopy, and serology
13
Q
Diagnosis of Syphilis
A
-
T. pallidum cannot be cultured in the lab
- Has no genes for the TCA cycle
- Dependent on host cells for purines, pyrimidines, amino acids
- Cannot be seen by traditional microscopy. Very hard to stain.
- Diagnosis relies on clinical impression, dark-field microscopy, and serology
14
Q
Diagnosis of Syphilis - dark-field microscopy
A
- Shine a light from the side and look for the deflected light. Spirochetes will light up.
15
Q
Diagnosis of Syphilis - Serology
A
In Summary
-
Treponemal tests: specific; always remain positive after infection
- Enzyme immunoassay: used for screening
- TP-PA, FTA-Abs: used only as “tie-breaker” in case of positive enzyme immunoassay and then negative RPR - which rarely happens.
-
Non-treponemal tests: non-specific; quantitative by titer
- RPR: used for confirmation, to monitor response to treatment, and to check for re-infection
In detail:
- First step is screening enzyme immunoassay (I also added a notecard just about this w/ picture). Note, this is also considered a treponemal test b/c it’s specific for treponemal.
- a.k.a. EIA or ELISA
- Syphilis antigen is first place at the bottom of test tube
- Patient serum added; antibodies bind if present
- Anti-human Ig antibody with an attached enzyme is added; binds to bound antibodies
- Enzyme substrate added, which cause a reaction and produces a color change. So if positive for syphilis then you’d see a color change
- Benefits are that it’s quick and easy, good sensitivity and specificity, and once positive, always positive. However it doesn’t have perfect sensitivity and it doesn’t tell you whether the individual has active syphilis. Patient may have had syphilis in the past and been treated but will still have antibodies.
- If EIA comes back positive, then next step is “Non-treponemal tests:”
- RPR = rapid plasma reagent. It’s considered a non-treponemal test b/c it doesn’t actually detect antibodies to the spirochete.
- The RPR test detects antibodies to lipids released from damaged cells. Even thought it’s non-specific for treponemal, it’s used because it is quantitative so you can check for re-infection and monitor response to treatment
- The RPR test is quantitative because you can calculate an antibody titer, which indicates the amount of antibody present, measured by testing serial dilutions of serum. The way you do this is to take the patient’s serum and dilute it by 2, and keep diluting by a factor of 2. (1:2, 1:4, 1:8, 1:64, etc) Whatever the largest dilution of the serum that gives an antibody response (i.e., a positive result), is the titer. So someone with a titer of 1:64 has a lot more antibody present than someone with a titer of 1:2. So basically the higher/more you need to dilute, the higher the original concentration of antibody (i.e., antibody titer) is.
- IF RPR comes back negative, then conduct a Treponemal test, which is used as ‘tie-breaker’ as so far you have one positive and one negative test
- High specificity
- Slow and difficult
- These treponemal tests are: TP-PA (T. pallidum particle agglutination) and FTA-Abs (Fluorescent treponemal antibody absorbed) tests. It’s not important to know how they work.
16
Q
Enzyme Immunoassay for Syphilis
A
- a.k.a. EIA or ELISA
- Syphilis antigen is first place at the bottom of test tube
- Patient serum added; antibodies bind if present
- Anti-human Ig antibody with an attached enzyme is added; binds to bound antibodies
- Enzyme substrate added, which cause a reaction and produces a color change. So if positive for syphilis then you’d see a color change.
Pros and Cons
- Quick & easy
- Good sensitivity & specificity
- Once positive, always positive
- Con - not perfect specificity
- Con - doesn’t tell you whether they have active syphilis. Patient may have had syphilis in the past and been treated but will still have antibodies.
22
Q
Lyme Disease - Transmission/Prevention
A
Transmission:
- Vector: Ixodes ticks. In the northeast specifically Ixodes scapularis
- especially the nymphs. The larva have a very low infection rate b/c they generally need “reservoir” hosts to infect them (and then they’d go into the next stage), but in some cases the adult ticks can transmit the borellia to the eggs. And the adults are bigger, so more easily for humans to discover before getting infected
- Reservoir: white-footed mice
Prevention:
- Use DEET; wear long sleeves; perform tick checks
- Key to find and remove ticks (within 36 hours after attachment): using tweezer, grip near head and pull slowly
- There was also a vaccine developed in the 1990s
- Antigen was OspA, a protein on the surface of Borrelia, sold as LYMErix until 2002.
- It was pretty effective, however, after FDA approval reports emerged of the vaccine causing arthritis
- 59 cases after 1.4 million doses of the vaccine
- Not significantly different from background
- FDA investigated, found no evidence of a connection
- However, demand for the vaccine dropped so GSK stopped making it
24
Q
Early Localized Lyme Disease
A
-
Erythema migrans (bulls-eye) rash at the site of the tick bite
- Expanding, >5cm
- Usually not itchy or painful whereas bacterial infection is usually painful
- May also have fever, aches, lymph node swelling
- Rash develops usually 3-30 days after the bite
- Will resolve on its own, within weeks
28
Q
Sensitivity vs. Specificity in Diagnostic Tests
A
Sensitivity
- Ability to detect all cases
- Minimize “false negatives”
- Good for screening
- If negative result, you can rely on it
Specificity
-Ability to NOT detect anything else
- Minimize “false positive”
- Good for confirmation
- If positive result, you can rely on it
32
Q
Syphilis? Lyme? Both? or Neither? Questions
A
33
Q
Syphilis? Lyme? Both? or Neither? Answers
A
