Syphilis Serology

Habitat of Syphilis

• free living species

• normal biota of humans/animals

Structure of Syphilis

• motile endoflagella

Treponema

• four pathogenic organisms

• high degree of DNA homology

Primary Syphilis 

• lengthy incubation period

• chancre 

Chancre

• single erythematous lesion that is nontender, ut firm with a raised border 

Secondary Syphilis

• rash is the main symptom 

What are the different outcomes of syphilis?

• spontaneous cure

• latent syphilis

  • early or late

• tertiary syphilis 

Tertiary Syphilis

• immunologically mediated 

• no longer infectious

• Gummas 

• Senility 

• Aneurisms  

Congenital Syphilis

• variable symptoms 

• occurs when treponemes cross placenta and infect fetus

• hutchinson’s teeth can occur

How is syphilis diagnosed

• direct exam

  • direct fluorescent antibody test to detect T. pallidum in lesions 

Nontreponemal Tests

• detect reagin antibodies in patient serum

• RPR or VDRL

Flocculation reaction with reagin

• IgG or IgM to lipids released from damaged host cells during infection 

Advantages of nontreponemal antigen tests

• widely available

• inexpensive

• titers correlate with disease progression 

Disadvantages of nontreponemal antigen tests

• low sensitivity in primary stage

• prozone effect

• biological false positives in low prevalence populations 

Treponemal Tests

• not intended for routine screening 

• used for confirmation of reactive RPR or VDRL

• highly specific

• fewer false positives

TP-PA assay

• uses gelatin particles sterilized w T. pallidum antigens 

• agglutination means presents of anti-treponemal abs. 

Test for serology if lesion is present

• conduct DFA test)

  • positive result 

    • treat 

  • negative result 

    • conduct nontreponemal tests (RPR, VDRL)

Tests for serology if lesion is NOT present

• conduct nontreponemal tests (RPR,VDRL)

  • reactive

    • conduct titer treponemal test

      • reactive: treat

      • non reactive: false positive 

  • nonreactive

    • no further action 

Cerebralspinal fluid testing for neurosyphilis

• if blood is present, reject sample

• patient should have symptoms compatible with syphilis and reactive serum test

RPR Test

• uses charcoal bound antigens to help enhance the reaction 

VDRL

• looks for flocculation microscopically 

Treponemal tests

• detect antibodies in patent serum 

• used to CONFIRM nontreponemal reactive tests

Fluorescent treponemal antibody absorption

• uses fluorescent labeled Ab that detects patient anti-trep antibodies