1. SPIROCHETES

2. Classification of Spirochetes
Human pathogens belong to following 3 genera:
Treponema
Leptospira
Borrelia
Others (saprophytes) are found in water, sewage and in mouth & genital tracts of humans.

3. Treponema Main treponemes are:
T. pallidum - Syphilis:Venereal (sexual) disease
T. pertenue - Yaws Non venereal
T. carateum - Pinta disease
All three species are morphologically identical

4. Characteristics of T.pallidum
Elongated, motile (endoflagella- axial filament), spiral bacteria with tapering ends seen under Dark Ground Microscope by staining with silver salts
Culture –
Do not grow on artificial media.
Virulent strains can be maintained in rabbit testis by serial passages e.g. Nichol’s strain – used for diagnosis & research
Reiter’s strain – nonpathogenic strain cultivated for diagnosis.

5. Characteristics of T.pallidum
T pallidum may remain motile for 3–6 days at 25°C. In whole blood or plasma stored at 4°C, organisms remain viable for at least 24 hours
Very delicate, easily killed by drying or heating at 42C for an hr.
Antigenicity –has hyaluronidase
Induce Ab as
Non specific - Reagin Ab (cardiolipin extracted from normal mammalian )
Specific – Trponemal Ab, immobilizing and killing live motile T pallidum and fixing complement

6. Syphilis Sexually transmitted disease.
Entry through minute abrasions on mucosa or skin.
Incubation period - about a month (2–10 weeks ).
Infectivity is maximum during first 2 years of disease – primary & secondary stages

7. Stages of syphilis Primary syphilis –
hard chancre on genitals: painless, avascular, circumscribed, indurated & ulcerated lesion; covered with a thick glairy exudate rich in spirochetes
Heals spontaneously
in days

8. Stages of syphilis Secondary syphilis – Most infectious stage
2–10 weeks the "secondary" lesions appear after 1 lesion heals.
Pt is asymptomatic but widespread dissemination occurs via blood
Maculopapular skin rashes on the body, mucous patches in the oropharyngeal area & condylomata at mucocutaneous junctions

9. Stages of syphilis
Latent syphilis – quiescent stage which follows secondary stage
Tertiary syphilis – develop after years, characterized by the development of: granulomatous lesions (gummas) in skin, bones, and liver
Late tertiary or quaternary syphilis –cardiovascular lesions like aneurysm, aortitis neurosyphilis : tabes dorsalis or general paralysis of insane

11. Congenital syphilis
Mother to the fetus through the placenta beginning in the 10th to 15th weeks of gestation
infected fetuses die, and miscarriages result; others are stillborn at term.
Clinical features – keratitis, saddle shaped nose, Hutchinsons teeth, 8th nerve deafness.
The reagin titer in the blood of the child rises with active infection but falls with time if antibody was passively transmitted from the mother.
In congenital infection, the child makes IgM antitreponemal antibody.

12. Saddle shaped nose
Hutchinsons teeth

13. Laboratory Diagnosis
Specimens include tissue fluid expressed from early surface lesions for demonstration of spirochetes; blood serum for serologic tests.
Dark-Field Examination The exudate is examined under oil immersion with dark-field illumination for typical motile spirochetes.
Immunofluorescence Tissue fluid or exudate is fixed, stained with a fluorescein-labeled antitreponeme serum, and examined by means of immunofluorescence microscopy for typical fluorescent spirochetes.

14. Nontreponemal tests Test for reagin Ab using cardiolipin Ag.
VDRL (Venereal Disease Research Laboratory) test
RPR (Rapid Plasma Reagin) test
used as screening tests for syphilis.
Reagin is a mixture of IgM and IgG antibodies reactive with the cardiolipin-cholesterol-lecithin complex.
false positive reactions are seen in Influenza, carditis and connective tissue diseases

15. Treponemal antibody tests
Measure Ab against T pallidum antigens. The tests are confirmatory for positive result from a nontreponemal test, include:
T pallidum hemagglutination (TPHA)
T pallidum immobilization (TPI) test
Treponemal antibody tests using the EIA for T pallidum
Fluorescent treponemal antibody absorbed (FTA-ABS) test

16. Immunity &Treatment
A person with active or latent syphilis appears to be resistant to superinfection with T pallidum.
If early syphilis is treated adequately the individual again becomes fully susceptible
Penicillin is the drug of choice
2nd line- Erythromycin, Tetra/ Doxycycline
Neurosyphilis - Ceftriaxone

17. Borrelia
Are arthropod transmitted Spirochetes and they cause Relapsing fever – two types:
a. Epidemic – is caused by B. recurrentis and is transmitted by human lice. This is a more severe form of the disease than the endemic form.
b. Endemic – is caused by many Borrelia species and is transmitted by ticks

18. Borrelia Large Gram negative spirochetes with wide, irregular coils
can be cultured in fluid media containing blood, serum, or tissue
At 4°C, the organisms
survive for several months
in infected blood or in culture

19. Relapsing fever IP (12-15) days after.
Abrupt onset of fever, headache, and myalgia for 4-10 days.
Ab are formed and the number of organisms decrease → afebrile period → The fever then relapses because of antigenic variation « Ab are no longer effective and the organism numbers increase.
Blood specimens are obtained during the rise in fever, for smears and animal inoculation.

20. B.vincenti Normal mouth commensal
May give rise to ulcerative gingivostomatitis or oropharyngitis (Vincent’s angina) during malnutrition or viral infections
B. vincenti always associated with fusiform bacilli – fusospirochetosis
Diagnosis – gram staining of exudates
Treatment – Penicillin

21. B.burgdorferi Causes Lyme disease, transmitted by ticks
Characteristic rash – erythema chronicum migrans, may have (fever, headache, nausea, vomiting, myalgia, and fatigue).
If untreated → arthritis (acute or chronic), and cardiac or neurologic complications due to immune complexes.
B burgdorferi DNA detected by the polymerase chain reaction.

22. Leptospira
Pathogenic L. interrogans → Weil’s disease or leptospirosisis
Non pathogenic free living L. biflexa
Very thin, delicate spirochetes with hooked ends
They are actively motile, seen by dark-field microscope.
Leptospirae can survive for weeks in water(alkaline pH)

23. Weil’s disease
Leptospires in water contaminated by the urine of rats; enters the body through cuts or abrasions on the skin or through intact mucosa of mouth, nose or conjunctiva
Incubation period – about 10 days (2 to 20)
Mild fever to severe or fatal illness with hepatorenal damage
1- Blood – 1st week only- and Urine – 2nd week of disease-for microscopic examination and culture
The diagnosis is confirmed serologically. Agglutinating antibodies first appear by the end of 1st week & increase till 4th week of disease