Spirochetes

Question 1

Spirochetes

Answer 1

Bacteria shaped like coils

5-20 microns long, <1 micron across

Gram negative - don’t stain with Gram stain but structurally negative

Have outer membrane, periplasmic space, thin cell wall, cell membrane, and flagella, including endoflagella (flagella inside periplasmic space)

Question 2

Treponema pallidum

Answer 2

Treponema pallidum pallidum –> syphilis

Other species involve skin and bone and spread by direct contact

Question 3

Syphilis Transmission

Answer 3

Sexual but also mother-to-child (congenital)

No other natural hosts - relies on host for nutrients; minimal surface proteins allows for immune evasion

Question 4

Primary Syphilis

Answer 4

Painless chancre at infection site (anywhere where spirochete enters body)

10-90 days after initial infection

Heals on its own after a month

Question 5

Secondary Syphilis

Answer 5

Spirochete disseminated throughout body, symptoms all over

Flu-like: sore throat, fever, malaise, adenopathy (swelling of lymph nodes)

Disseminated rash - contagious; includes palms, soles, and mucous membranes; can have condyloma lata (wart-like)

Begins weeks to months after infection, resolves slowly on its own

Question 6

Latent Phase Syphilis

Answer 6

After rash and systemic symptoms resolve

No symptoms but 1/3 progress to tertiary syphilis (over years to decades)

Dormant

Question 7

Tertiary Syphilis

Answer 7

Gumma: effects of long-term tissue destruction; anywhere on body but typically mouth; start as mass that is caused by spirochetes –> immune response –> ulcer and erosions

Vascular problems: Aortitis, aortic aneurysm

Neurologic problems: Tabes dorsalis

Question 8

Tabes dorsalis

Answer 8

From Tertiary Syphilis

Demylination of dorsal spine

Loss of position sense –> wide-based gait

Question 9

Neurological Syphilis

Answer 9

Spirochetes invade CNS early in infection

Early: Can cause tabes dorsalis

Later: Can cause tabes dorsalis or dementia

Anytime: Can cause uveitis (eye pain and blurry vision)

Question 10

Treponema pallidum Diagnosis

Answer 10

Cannot be cultured in lab - has no genes for tricarboxylic acid cycle; dependent on host cells for purines, pyridimines, and amino acids

Cannot be seen on traditional microscope

Relies on clinical impression, dark-field microscopy, and serology

Question 11

Treponema pallidum Diagnosis: Dark-field Microscopy

Answer 11

Shine light from side and look for deflected light

Question 12

Treponema pallidum Diagnosis: Serology: Screening enzyme immunoassay

Answer 12

AKA EIA and ELISA

Quick and easy

Good sensitivity and specificity - but requires confirmation test

Once positive, always positive - can’t tell if currently have syphilis or just in the past

Question 13

Enzyme Immunoassay EIA

Answer 13

1. Syphilis antigen in bottom of test tube
2. Patient serum added, antibodies bind if present
3. Anti-human Ig antibody with attached enzyme added; binds to bound antibody
4. Enzyme substrate added
5. Enzymatic reaction produces color change if positive for antibodies for syphilis

Question 14

Treponema pallidum Diagnosis: Serology: Non-treponemal tests

Answer 14

Doesn’t detect antibodies to spirochete - detects antibodies to lipids released from damaged cells

Mix serum with cardiolipin and look for clumping

Non-specific but quantitative - can monitor response to treatment and check for re-infection

Question 15

Antibody titer

Answer 15

Indicates concentration of antibody present, measure by testing serial dilutions of serum

Expressed as ratio - Indicates highest dilution of patient’s serum that gives postive result (titer of 1:64 has more antibody present than someone with 1:2)

Question 16

Treponema pallidum Diagnosis: Serology: Treponemal tests

Answer 16

High specificity

Slow and difficult

Tie-breaker

Question 17

Syphilis Treatment

Answer 17

Penicillin

Primary: 1 dose of intramuscular penicllin
Secondary: 1 dose of intramuscular penicillin
Latent/Tertiary: 1 or 3 weekly doses of intramuscular penicillin
Neuro including ocular: 2 weeks of intravenous penicllin

Question 18

Jarisch-Herxheimer Reaction

Answer 18

Inflammatory responses to toxins released by dying spirochetes –> fever, flu-like symptoms

Question 19

Syphilis Prevention

Answer 19

Sexual transmission: condoms, monogamy, abstinence, partner treatment

Mother-to-child (congenital): testing and treatment during pregnancy (initial visit, repeat in 3rd trimester if high risk)

Question 20

Lyme Disease: Borrelia burgdorferi

Answer 20

Spirochete

Tiny genome - linear chromosome; 9 circular and 12 linear plasmids

Depends on host for nutrition

Makes no toxins that we know of

Question 21

Lyme Disease Transmission

Answer 21

Vector: Ixodes tick (especially nymphs)

Reservoir: White footed mice

Question 22

Early Localized Lyme Disease

Answer 22

Erythema migrans rash at site of tick bite - expanding, not usually painful or itching

May also have fever, aches, lymph node swelling

3-30 days after bite

Will resolve on its own, within weeks

Question 23

Early disseminated Lyme disease

Answer 23

Weeks after infection
Dermatologic - multiple erythema migrans

Days to weeks after infection
Neurologic: meningitis, Bell’s palsy
Cardiac: heart block
Musculoskeletal: arthralgias, arthritis

Can resolve without treatment

Question 24

Late Lyme disease

Answer 24

Months to years after infection

Large joint arthritis (can relapse)

Neurological symptoms: Neuropathy, encephalopathy (short-term memory problems, word-finding difficulty)

Question 25

Lyme Disease Diagnosis: Serology

Answer 25

Early localized Lyme disease is clinical diagnosis

Antibody testing often negative within 1st 4-6 weeks - IgM develops at 2-4 weeks (2 bands required), IgG at 4-8 weeks (5 bands required)

Later, use two-tiered serology (antibody-based) testing - Screening ELISA (sensitive, not specific); Westerns (specific but complicated)

Question 26

Sensitivity VS Specificity

Answer 26

Sensitivity: Ability to detect all cases; minimize “false negative”; good for screening

Specificity: Ability to not detect anything else; minimize “false positive”; good for confirmation

Question 27

Lyme Disease: Treatment

Answer 27

Doxycycline: oral; 14-21 days for most, 28 days for arthritis

Ceftriaxone: intravenous; used for Lyme meningitis and advanced heart block (up to 28 days)

Question 28

Post-treatment Lyme Disease Syndrome

Answer 28

Fatigue, musculoskeletal pain, difficulty concentrating/ thinking

10 - 20% of patients

No proven effectiveness of longer/additional antibiotic treatment