Bacteriology lecture no.12 Spirochetes 3rd class
-The spirochetes: are a large ,heterogeneous group of spiral ,motile bacteria. Although, • there are at least eight genera in this family ,only the genera Treponema,Borrelia,and Leptospira which contain organism pathogenic for humans .
-There are some reports of intestinal spirochetes ,that have been isolated from biopsy material ,these are Brachyspira pilosicoli,and Brachyspira aalborgi.
*Objectives* Taxonomy
Order: Spirochaetales
Family: Spirochaetaceae
Genus: Treponema
Borrelia
Family: Leptospiraceae
Genus: Leptospira
-Gram-negative spirochetes
-Spirochete from Greek for “coiled hair "they are :
*1*Extremely thin and can be very long
*2* Motile by periplasmic flagella (axial fibrils or endoflagella)
*3*Outer sheath encloses axial fibrils
*4*Axial fibrils originate from insertion pores at both poles of cell
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Bacteriology lecture no.12 Spirochetes 3rd class
Spirochaetales Associated Human Diseases
Treponema
Main Treponema are:
- T. pallidum subspecies pallidum - Syphilis: Venereal (sexual) disease
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Bacteriology lecture no.12 Spirochetes 3rd class
- T. pertenue - Yaws Non venereal
- T. carateum - Pinta skin disease
All three species are morphologically identical
Characteristics of T.pallidum
1-They are long ,slender ,helically coiled ,spiral or cork –screw shaped bacilli.
2-T.pallidum has an outer sheath or glycosaminoglycan contain peptidoglycan and maintain the structural integrity of the organisms.
3-Endoflagella (axial filament ) are the flagella-like organelles in the periplasmic space encased by the outer membranes .
4-The endoflagella begin at each end of the organism and wind around it ,extending to and overlapping at the midpoint.
5- Inside the endoflagella is the inner membrane (cytoplasmic membrane)that provide osmotic stability and cover the protoplasmic cylinders .
6-Treponemes reproduce by transverse fission .
7-The spiral coils are regularly spaced at a distance of 1um from one another .
8-The organisms are actively motile ,rotating steadily around their endoflagella even after attaching to cells by their tapered ends .
9-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
10-Very delicate, easily killed by drying or heating at 42C for an hr.
11-Antigenicity –has hyaluronidase
-Induce Ab as
1-Nonspecific - Reagin Ab (cardiolipin extracted from normal mammalian )
2-Specific – Trponemal Ab, immobilizing and killing live motile T pallidum and fixing complement
-Virulence Factors of T. pallidum
1-Outer membrane proteins promote adherence
2-Hyaluronidase may facilitate perivascular infiltration
3-Antiphagocytic coating of fibronectin
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Bacteriology lecture no.12 Spirochetes 3rd class
4-Tissue destruction and lesions are primarily result of host’s immune response (immunopathology
Growth characteristics
1-T.pallidum is microaerophilic organism, it survive best in 1-4%O2. •
2-in proper suspending fluids and in the presence of reducing substance, • T.pallidum may remain motile for 3-6 days at 25 c.
3-In whole blood or plasma stored at 4c ,organisms remain viable for at least 24 hour, which is of potential importance in blood transfusion
Reaction to physical and chemical agents
1-drying kill the spirochetes rapidly, as does elevation of temperature to 42 c. •
2-Treponemes are rapidly immobilized and killed by trivalent arsenical ,mercury and • bismuth.
3-pencillin is treponemicidal in minute concentration ,but the rate of killing is slow ,presumably because of the metabolic inactivity and slow multiplication rate of T.pallidum.
Treponema pallidum ssp. pallidum
Venereal Treponemal Disease
- T. pallidum are slender spirals with spiral coils spaced at a distance of 1 μm from one another.
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Bacteriology lecture no.12 Spirochetes 3rd class
- Pathogenic T pallidum has never been cultured on artificial media, in fertile eggs, or in tissue culture.
- Nonpathogenic Treponema (Reiter strain) can be cultured anaerobically in vitro.
-T pallidum is a microaerophilic organism; it survives best in 3–5% oxygen. -
Cause Syphilis -
- Primarily sexually transmitted disease
- May be transmitted congenitally
Syphilis
Stages of syphilis
Primary syphilis –
-hard chancre on genitals: painless, avascular, circumscribed, indurated .1 & ulcerated lesion; covered with a thick glairy exudate rich in spirochetes
-Heals spontaneously .2
in 10-40 days
Secondary syphilis –
-Most infectious stage .1
-2–10 weeks the "secondary" lesions appear after 1 lesion heals. .2
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Bacteriology lecture no.12 Spirochetes 3rd class
-Patient is asymptomatic but widespread dissemination occurs via blood .3
-Maculopapular skin rashes on the body, mucous patches in the .4 oropharyngeal area & condylomata at mucocutaneous junctions .
Latent syphilis – quiescent stage which follows secondary stage
First 4 years = Early latent
Subsequent period = Late latent
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
Congenital syphilis
Mother to the fetus through the placenta beginning in the 10th to 15th weeks of gestation
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Bacteriology lecture no.12 Spirochetes 3rd class infected fetuses die, and miscarriages result; others are stillborn at term.
Clinical features – keratitis, saddle shaped nose, Hutchinson's 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.
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Bacteriology lecture no.12 Spirochetes 3rd class
Epidemiology of T. pallidum
Transmitted from direct sexual contact or from mother to fetus
Long incubation period during which time host is non-infectious
Diagnostic Tests for Syphilis
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Bacteriology lecture no.12 Spirochetes 3rd class
Cardiolipin is an important component of the Treponemal antigens. the spirochetes cause the development of antibody-like substance, reagin, which gives positive flocculation tests
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
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Bacteriology lecture no.12 Spirochetes 3rd class
Leptospirosis is an infection caused by corkscrew-shaped bacteria called Leptospira interrogans
Signs and symptoms can range from none to mild such as headaches, muscle pains, and fever; to severe with bleeding from the lungs or meningitis
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
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
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Bacteriology lecture no.12 Spirochetes 3rd class
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.
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
B.burgdorferi
Causes Lyme disease, transmitted by ticks
Characteristic rash – erythema chronicum migrans, may have (fever, headache, nausea, vomiting, myalgia, and fatigue).
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Bacteriology lecture no.12 Spirochetes 3rd class
If untreated → arthritis (acute or chronic), and cardiac or neurologic complications due to immune complexes.
B burgdorferi DNA detected by the polymerase chain reaction
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