Organism: Treponema pallidum

Family: Spirochetes

Disease: Syphilis (primary → secondary → latent → tertiary)

Transmission: Sexual, vertical (transplacental), blood contact.

1. The Organism – Treponema pallidum

• Type: Spirochete (thin, spiral bacterium)
• Gram stain: Technically Gram-negative structure but cannot be visualized by Gram stain (too thin).
• Seen best with:
• Dark-field microscopy 🌙
• Direct fluorescent antibody (DFA-TP)
• Movement: Corkscrew motility due to axial filaments (periplasmic flagella).
• Growth:
• Cannot be cultured on artificial media → obligate human pathogen.
• Extremely sensitive to heat & drying → dies quickly outside body.

💡 Memory Hook:

“T.P. = Too Posh to grow in labs → needs human body only.”

Organism – Active Recall (Fill in the Blanks)

Organism: __________ __________

Family: __________

Disease: __________ (primary → __________ → __________ → __________)

Transmission: , __________ (), __________ __________.

1. The Organism – Treponema pallidum

• Type: __________ (thin, __________ bacterium)
• Gram stain: Technically structure but cannot be visualized by __________ stain because it is too __________.
• Seen best with:
• microscopy
• __________ __________ __________ (__________)
• Movement: __________ motility due to __________ filaments (__________ __________).
• Growth:
• Cannot be __________ on __________ media → __________ __________ pathogen.
• Extremely __________ to __________ & __________ → dies __________ outside the body.

💡 Memory Hook (fill in):

“T.P. = __________ __________ to grow in labs → needs __________ __________ only.”

2. How It Causes Disease (Pathogenesis)

• Enters through tiny breaks in skin/mucosa.
• Rapidly disseminates via lymphatics + bloodstream → explains systemic symptoms early.
• No classic toxins.
• Immune evasion via:
• Lack of many surface proteins → “immune invisible.”
• Slow division → fewer opportunities for immune attack.

⭐ Exam line: T. pallidum spreads systemically early, even before the chancre heals.

2. How It Causes Disease (Pathogenesis) — Active Recall (Fill in the Blanks)

• Enters through tiny breaks in __________ / __________.
• Rapidly disseminates via __________ + __________ → explains __________ symptoms early.
• No classic __________.
• Immune evasion via:
• Lack of many __________ __________ → “immune invisible.”
• __________ division → fewer opportunities for immune attack.

⭐ Exam line (fill):

T. pallidum spreads __________ early, even before the __________ heals.

3. Stages of Syphilis (Microbiological Basis)

Primary syphilis

• Painless chancre at entry site.
• Rich in spirochetes → dark-field positive.
• Chancre heals spontaneously → BUT infection persists.

Secondary syphilis

• Widespread hematogenous spread.
• Highly infectious.
• Features include:
• Generalized rash (including palms & soles)
• Condyloma lata
• Generalized lymphadenopathy
• Patchy alopecia
• Spirochetes abundant on lesions.

Latent syphilis

• Early latent (<1 yr) – infectious
• Late latent (>1 yr) – not infectious except vertical transmission

Tertiary syphilis

• Due to delayed-type hypersensitivity to persistent T. pallidum
• Features:
• Gummas
• Aortitis (vasa vasorum obliteration)
• Neurosyphilis

Stages of Syphilis (Microbiological Basis) — Active Recall (Fill in the Blanks)

Primary syphilis

• __________ chancre at entry site.
• Rich in __________ → __________-field positive.
• Chancre heals __________ → BUT infection __________.

Secondary syphilis

• Widespread __________ spread.
• Highly __________.
• Features include:
• Generalized __________ (including __________ & __________)
• __________ lata
• Generalized __________
• Patchy __________
• __________ abundant on lesions.

Latent syphilis

• Early latent (< __________ yr) – __________
• Late latent (> __________ yr) – __________ except __________ transmission

Tertiary syphilis

• Due to __________-type hypersensitivity to persistent Treponema pallidum
• Features:
• __________ (vasa vasorum __________)

4. Syphilis Serology – GOLD for exams

Most scoring part.

A. Non-treponemal tests (screening)

• VDRL
• RPR

Detect anticardiolipin antibodies (nonspecific).

Used to monitor treatment response.

Titers fall with successful treatment.

🧠 False positives:

• Pregnancy
• Viral infections (HIV, hepatitis)
• SLE / autoimmune
• TB
• Elderly
• IV drug use

Memory: “P-V-S-T-E-D” → Pregnancy, Viral, SLE, TB, Elderly, Drugs

B. Treponemal tests (confirmatory)

• TPHA
• FTA-ABS
• Enzyme immunoassays (EIAs)

Detect antibodies specific to T. pallidum.

Stay positive for life, even after cure.

📌 Exam pearl:

• Screening → VDRL/RPR
• Confirmation → TPHA/FTA-ABS
• Follow-up treatment response → VDRL/RPR titers

4. Syphilis Serology – GOLD for Exams

Active Recall (Fill in the Blanks)

A. Non-treponemal tests (__________)

• __________
• __________

Detect __________ antibodies (__________ specific).

Used to __________ treatment response.

__________ fall with successful treatment.

🧠 False positives:

• __________ infections (__________, __________)
• __________ / autoimmune
• __________ drug use

Memory: “” → *, __________, __________, __________, __________, __________*

B. Treponemal tests (__________)

• __________
• __________
• __________ immunoassays (__________)

Detect antibodies specific to Treponema pallidum.

Stay __________ for __________, even after __________.

📌 Exam pearl (fill):

• Screening → __________ / __________
• Confirmation → __________ / __________
• Follow-up treatment response → __________ / __________ __________

5. Diagnosis in Primary Syphilis

• Dark-field microscopy of chancre exudate → immediate test
• Serology may still be negative in very early disease.

6. Vertical Transmission / Congenital Syphilis

• Can cross placenta after 9–10 weeks
• Risk highest during primary & secondary stages
• Outcomes: miscarriage, stillbirth, congenital infection

Early congenital syphilis:

• Snuffles
• Desquamating rash
• Hepatosplenomegaly
• Osteochondritis
• Pneumonia alba

Late congenital syphilis:

• Hutchinson triad:
• Peg-shaped incisors
• Interstitial keratitis
• Sensorineural deafness

Vertical Transmission / Congenital Syphilis – Active Recall

Placental transmission

• Treponema pallidum can cross the placenta after ……– ……. weeks.
• Risk of vertical transmission is highest during __________ & __________ stages of maternal syphilis.
• Possible outcomes include:
• __________ infection

Early congenital syphilis – features

Fill in the blanks:

• Persistent nasal discharge → __________
• Generalized peeling rash → __________ rash
• Enlargement of liver and spleen → __________
• Bone involvement → __________
• Severe interstitial pneumonia → __________ alba

Late congenital syphilis

Hutchinson triad – name the three:

1. Abnormally shaped incisors → __________-shaped incisors
2. Eye involvement → __________ keratitis
3. Hearing loss → __________ deafness

7. Treatment (Microbiology-focused)

• Penicillin G is ONLY effective definitive therapy
• Jarisch–Herxheimer reaction:
• Acute febrile reaction
• Due to massive spirochete death releasing lipoproteins
• Common in early syphilis
• Treat with supportive care

Treatment of Syphilis – Active Recall

Definitive therapy

• The ONLY effective definitive treatment for syphilis is __________ __________.

Jarisch–Herxheimer reaction

Fill in the blanks:

• It is an __________ febrile reaction occurring after starting therapy.
• Caused by massive __________ death with release of __________.
• Occurs most commonly in __________ syphilis.
• Management is __________ care (not stopping antibiotics).

🎯 THE REAL 20% HIGH-YIELD FOR EXAMS

1. Treponema pallidum = thin spirochete → needs dark-field microscopy to see.
2. Cannot be cultured; extremely fragile.
3. Transmission: sexual, vertical, blood.
4. Primary = painless chancre, secondary = palm/sole rash + condyloma lata, tertiary = gummas, aortitis, neurosyphilis.
5. Screening = VDRL/RPR (nontreponemal).
6. Confirmatory = TPHA / FTA-ABS (treponemal).
7. Treatment response = falling VDRL titers.
8. Vertical transmission → congenital syphilis.
9. Penicillin G = treatment of choice.
10. Jarisch–Herxheimer = fever after treatment from sudden spirochete death.