Spirochetes

Question 1

Spirochetes

Answer 1

• 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

Question 2

(In) Famous Spirochetes

Answer 2

• Treponema pallidum (syphilis)
• Borellia burgdorferi (Lyme disease)
• Borrelia recurrentis and others (relapsing fever)
• Leptospira interrogans (leptospirosis)

Question 3

T. pallidum subspecies

Answer 3

• 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)

Question 4

Transmission of Syphilis

Answer 4

• 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

Question 5

Stages of Syphilis and Summary of Clinical Symptoms

Answer 5

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

Question 6

Primary Syphilis

Answer 6

• 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.

Question 7

Secondary Syphilis (disseminated)

Answer 7

• 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.

Question 8

Secondary Syphilis (disseminated)

Answer 8

• 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

Question 9

Latent Phase

Answer 9

• After the rash and systemic symptoms resolve
• No symptoms, but ⅓ of patients will progress to tertiary syphilis (over years to decades)

Question 10

Tertiary Syphilis

Answer 10

• 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

Question 11

Neuro Syphilis

Answer 11

• 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

Question 12

Diagnosis of Syphilis

Answer 12

• 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

Question 13

Diagnosis of Syphilis

Answer 13

• 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

Question 14

Diagnosis of Syphilis - dark-field microscopy

Answer 14

• Shine a light from the side and look for the deflected light. Spirochetes will light up.

Question 15

Diagnosis of Syphilis - Serology

Answer 15

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.

Question 16

Enzyme Immunoassay for Syphilis

Answer 16

• 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.

Question 17

Syphilis Treatment

Answer 17

• Penicillin
  
  • Primary: 1 dose of intramuscular penicillin
  • Secondary: 1 dose of intramuscular penicillin
  • Latent/Tertiary: 1 or 3 weekly doses of intramuscular penicillin. If not certain what stage it is, then give 3 weekly doses of intramuscular penicillin.
  • Neuro including ocular: 2 weeks of intravenous penicillin. Need higher concentration to get through blood-brain barrier
• One interesting reaction that can happen is a Jarisch-Herxheimer reaction: inflammatory response to toxins released by dying spirochetes and can result in fever, “flu-like” symptoms
• T. pallidum has no documented resistance to penicillin. But a person can get re-infected

Question 18

Syphilis Prevention

Answer 18

• Sexual transmission: condoms, monogamy, abstinence; partner treatment
• Mother-to-child transmission (congenital infection): testing and treatment during pregnancy (initial visit, repeat in 3rd trimester if high risk)

Question 19

Syphilis Summary

Answer 19

• Caused by Treponema pallidum, a spirochete
• Disease characterized by three stages: primary (localized, chancre), secondary (disseminated, rash), tertiary (neurologic and cardiac)
• Diagnosed by dark field microscopy or serology
• Treated with penicillin

Question 20

Borellia species

Answer 20

• Lyme disease is caused by Borrelia burgdorferi burgdorferi (Our focus)
• There are other Borrelia some that cause lyme-like diseases, such as:
  
  • Other Borrelia burgdoferi strains in Europe
  • Borrelia mayonii in the Midwest US
• Borrelia miyamotoi
• Borrelia recurrentis & others (relapsing fever)

Question 21

Borrelia burgdorferi

Answer 21

• A spirochete
• Tiny genome like all spirochetes (1.5 Mb)
  
  • Linear chromosome
  • 9 circular and 12 linear plasmids
• Depends on host for nutrition
• Makes not toxins that we know of

Question 22

Lyme Disease - Transmission/Prevention

Answer 22

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

Question 23

Lyme Disease - Clinical Manifestations

Answer 23

• Three phases … like syphilis
  
  • Early localized
  • Early disseminated
  • Late

Question 24

Early Localized Lyme Disease

Answer 24

• 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

Question 25

Early Disseminated Lyme Disease

Answer 25

* Weeks after infection * Many possible manifestations * Dermatologic: **multiple erythema migrans** * Neurologic: **meningitis, Bell's palsy** (one side of face is paralyzed) * Cardiac: **heart block** * Musculoskeletal: **arthralgias** (joint pain) and **arthritis** (join inflammation) * All of these symptoms could last for a long time or could resolve, even in some cases without treatment

Question 26

Late Lyme Disease

Answer 26

* **Months to years** after infection * **Large joint arthritis** (can come and go) * Neurological symptoms * Neuropathy (e.g., Bell's Palsy or inflammation of nerves down spine) * Encephalopathy (short-term memory problems, word-finding difficulty)

Question 27

Lyme Disease - Diagnosis

Answer 27

* Early localized Lyme Disease is a **clinical diagnosis** * Antibody testing often negative within first 4-6 weeks (IgM develops at 2-4 weeks, IgG at 4-8 weeks) * Looking for erythema [chronicum] migrans * Later, use **two-tiered serology (antibody-based)** testing * _Screening_ ELISA: **sensitive**, but **not specific** * _Confirmatory_ Western blot: **specific**, but complicated * Separate serum proteins by gel electropherisis * Then add specific antibodies for specific proteins/antigens * Then add an enzyme-conjugated secondary antibody, which will only bind to the antibody-antigen complex. And then if positive, will be detectable as the enzyme substrate is colorimetric or chemiluminescent * There are 2 antibodies you'd look for in Western blot: * 1) **IgM** * early infection (within 4 weeks) * 2 bands required for + * 2) **IgG** * Later * 5 bands required for + * The downside of serology is that it **remains positive** even after treatment (IgG and often also IgM)

Question 28

Sensitivity vs. Specificity in Diagnostic Tests

Answer 28

**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

Question 29

Lyme Disease - Treatment

Answer 29

* Doxycycline * Oral * 14-21 days for most Lyme manifestations; 28 days for arthritis * No resistance * Ceftriaxone * Intravenous * Used for Lyme meningitis and advanced heart block (up to 28 days)

Question 30

Post-treatment Lyme disease syndrome

Answer 30

* It's not in the presence of bacteria anymore, but rather a continued immune response * Symptoms include fatigue, musculoskeletal pain, difficulty concentrating/thinking * Impacts 10-20% of patients infected with Lyme disease * No proven effectiveness of longer/additional antibiotic treatment

Question 31

Lyme Disease - Summary

Answer 31

* Caused by *Borrelia burgdorferi*, a spirochete * Transmitted by *Ixodes* ticks * Three stages of illness: early localized (erythema migrans), early disseminated (e.g., Bell's palsy, meningitis, heart block, arthritis), late disseminated (e.g., neurologic problems, arthritis) * Treated with doxycycline or ceftriaxone * Prevented by avoiding ticks. Vaccine discontinued

Question 32

Syphilis? Lyme? Both? or Neither? Questions

Answer 32

Question 33

Syphilis? Lyme? Both? or Neither? Answers

Answer 33

Question 34

•Quiz: which RPR titer corresponds to before and after treatment? 1:2 OR 1:128

Answer 34

1: 128 before treatment. 1: 2 after treatment