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  1. Helical bacteria
  2. Family spirochaetaceae: Treponema, Borrelia
  3. Family leptospiraceae: Leptospira
  4. Gram negative type cell wall
  5. Motile by endoflagella/ axial filament
  1. Treponema
    1. T. pallidum: venereal syphilis
    2. T. pertenue: yaws
    3. T. endemicum: endemic syphilis (bejel)
    4. T. carateum: pinta
    5. T. vincentii: along with leptotrichia buccalis causes ulcerative gingivostomatitis (Vincent’s angina)
    6. Non-pathogenic commensal treponemes-T. denticola, T. refringens
  2. Syphilis
    1. Caused by T. pallidum
    2. 6-14µm x 0.13µm (seen by dark ground microscopy)- 10 regular spirals
    3. Three types of motility: flexion/ extension, cork-screw like, translator
    4. Silver impregnation method (Fontanas , Levaditis)
    5. 3-4 endoflagella
    6. Cannot be cultivated in artificial media (Nichols strain: maintained in rabbit testis)
    7. Antigenic structure- Group specific antigen: present in pathogenic & nopathogenic treponemes (Reiter’s treponeme- T. phagedenis);
    8. Species-specific antigen
    9. Sexually transmitted, congenital, blood transfusion
    10. IP:10-90 days,

Clinical manifestation: 4 stages

  1. Primary syphilis: chancre, painless, indurated, hard chancre also called as huntarian chancre (soft chancre caused by H. ducreyi); large number of treponemes present in primary lesion; involvement of local lymph nodes (swollen, discrete, rubbery, nontender); heals in 3-6weeks without treatment
  2. Secondary syphilis: 2-6 months after primary lesion heals. Dissemination through blood. Cutaneous lesions on trunk, extremeties, mucous patches, condylomata, generalized lymph node enlargement. Lesions contain large number of organisms. Heals spontaneously in 4-5years.
  3. Latent syphilis: detected only by serological tests.
  4. Tertiary syphilis: slowly progressive, destructive inflammatory disease that may affect any organ. Gummata of internal organs, lesions of heart, aorta; CNS lesions (tabes dorsalis, GPI)

Laboratory diagnosis:

  1. Demonstration of the organism/ antigen
    1. Dark ground microscopy and India ink
    2. DFA-Tp (best method)
    3. Silver staining
  2. Serological tests
    1. Nontreponemal tests- also called standard test of syphilis. Use the cardiolipin antigen. Used for screening and followup
      Wasserman test
      Kahn test
      VDRL test
      RPR test
    2. Treponemal tests- use live treponemes/dead treponemes/treponemal antigens. Used for confirmation of diagnosis
      Using cultivable treponemes: RPCFT
      Pathogenic Treponeme (T. pallidum)
      Live: TPI
      Killed: TPA, TPIA, FTA, FTA-ABS, IgM-FTA-ABS
      Extract: TPHA, EIA

Important Points

  1. Most sensitive- FTA-Abs
  2. Most specific-TPI
  3. First test to become positive-FTA-Abs
  4. Test used for followup-VDRL/RPR
  1. False positive in VDRL- biological false positives
    Acute: less than six months: hepatitis, infectious mononucleosis, viral pneumonia, chicken pox, measles, malaria, immunizations, pregnancy, HIV infection.
    Chronic:> six months: SLE, narcotic addiction, ageing, leprosy, malignancy.
  1. Borrelia
    8-30µm x 0.2-0.5µm
    Relapsing fever: epidemic: louse borne, B. recurrentis; endemic: soft tick borne, B. duttoni, B. hermisii, B. parkeri, B. turicatae
    1. Relapses are due to antigenic variations
    2. Diagnosis is primarily by thick and thin smear Gram stain
    3. Treatment: Doxycycline or Macrolides

Lyme’s disease: B. burgdorferi, hard tick borne, reservoir is rodents and deer

  1. 3 stages
    Primary stage- red macule, spreads centrifugally (erythema chronicum migrans),
    Stage of dissemination- secondary annular lesions, LNAP, arthralgia, myalgia, carditis
    Stage of persistence- meningoencephalitis, arthritis, acrodermatitis, polyneuropathy
  2. Diagnosis primarily by ELISA and Western blot, Culture on Kelly’s medium
  3. Treatment- Doxycycline
  1. Leptospira
    1. Three species: L. interrogans (pathogenic), L. biflexa, L. parva (nonpathogenic)
    2. 6-20 micron long, 0.1 micron broad, closely wound spirals with hook-shaped ends
    3. L. interrogans: motile, aerobe, can be grown in artificial media, 22 serogroups, several serovars in each group

Leptospirosis: zoonotic disease, rodents, dog , pig, cattle. Localize in kidneys, shed in the urine. Human infection by water, soil, vegetation contaminated with animal urine. enter body through cuts, mucous membranes. Involvement of kidney, liver, meninges, conjunctiva (L. interrogans serovar icterohaemorrhagiae causes sever disease called Weil’s disease) Only 5-10% of infected develop disease.

  1. Laboratory diagnosis
    1. Demonstration in blood: dark ground microscopy, early stages
    2. Demonstration in urine: second week of disease onwards for 4-6 weeks. Dark ground microscopy.
    3. Culture: EMJH medium, Korthoff’s medium, Fletcher’s medium
  2. Serological diagnosis: antibodies appear towards the end of the first week.
    1. Genus specific: CFT, HA, ELISA
    2. Serogroup & serovar specific: Macroscopic, Microscopic agglutination test
  3. Treatment- 1-2 MU Penicillin I/V for 6hrly for 1 week
  4. Prophylaxis: 200mg weekly doxycycline for people at risk  

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