1. Spirochaetales
The Spirochetes

2. Spirochaetales
Classification Spirochetes are members of the order Spirochaetales which contains 2 families
Spirochaetaceae – contains 2 medically important genera
Treponema
Borrelia
Leptospiraceae – 1 medically important genus
Leptospira
Morphology and general characteristics
Is composed of:
A helical protplasmic cylinder with a peptidoglycan layer similar to G-B, cytoplasmic membrane, and cytoplasm

3. Spirochaetales
A multilayered outer membrane that surrounds the cylinder
Periplasmic flagella which are attached to each end of the protoplasmic cylinder and extend toward the opposite end.
Are not typical flagella and are often called axial filaments

4. Spirochaetales
None of the pathogenic Treponemes have been successfully cultured on artificial media
T. pallidum is usually cultured in the testes of rabbits, although it has been grown in tissue culture for short periods of time.
T. pallidum does not survive for long outside the host.
Visualized by darkfield microscopy or iron staining

5. T. pallidum

6. Spirochaetales
Borrelia may be grown on a complex media called Kelly’s media, but this is not usually done in diagnostic labs.
Borrelia may be observed with darkfield microscopy or be stained in a blood sample with a Giemsa stain or Wright stain.

7. Borrelia sp. in blood smear

8. Spirochaetales Identification
Leptospira can be grown on semi-solid media containing peptone, beef extract supplemented with rabbit serum or bovine serum albumin and tween 80.
Incubation may be for as long as 28 days.
Visualize using darkfield microscopy
Identification
Treponema
Observation of organisms in lesions
Detection of antibodies made in the host.
Two types of tests may be used:

9. Spirochaetales
Nonspecific, nontreponemal tests – used for screening purposes
Very sensitive, but not specific
Many diseases give positive results
Is inexpensive and easy to do
Detects non-treponemal antibodies, called reagenic or Wasserman antibodies, that react with a phospholipid (cardiolipin-lecithin) that is a normal tissue constituent
Tests include: VDRL test, rapid plasma reagin card tests (RPR), and automated reagin test (ART)

10. Spirochaetales Borrelia Leptospira
Specific, treponemal tests – used to confirm positive nontreponemal results
Very specific, expensive, and more difficult to perform
Include T. pallidum immobilization tests, Fluorescent Treponemal antibody absorption test, indirect Treponemal hemagglutination test
Borrelia
Demonstration of Spirochetes in the blood
Leptospira
Isolate and culture
Specific agglutination test or C’ fixation test – look for 4-fold rise in titer in patient’s antibodies against the organism

11. Spirochaetales Virulence factors Treponema Borrelia
Molecular mimicry – the outer sheath contains molecules that resemble the molecules commonly found on the surface of human cells.
This allows the organism to resist host defenses.
Hyaluronidase
Borrelia
Antigenic variation

12. Spirochaetales Clinical significance Leptospira Treponema Unknown
T. pallidum causes venereal (transmitted by sexual contact) and non-venereal (transmitted by directly by non-sexual contact, and indirectly by common usage of eating and drinking utensils) syphilis.
In venereal syphilis the primary lesion is on the genitals
In non-venereal syphilis it is on oral mucous membranes.
The normal untreated course of the disease occurs in several stages:

13. Spirochaetales
Primary stage – following penetration of the skin or mucous membranes, a characteristic, painless hard chancre develops at the site of entry within 3 weeks.
The chancre is highly contagious and filled with Treponemes.
Simultaneously the organism enters the lymphatics and becomes disseminated.
The chancre heals without treatment in a few weeks due to local immunity, but by that time the organism has already disseminated.

14. Primary syphilis

15. Spirochaetales
Secondary stage – 4-8 weeks after the primary stage, the secondary stage develops.
Typically there are lesions (filled with treponemes) throughout the body including the skin, mucous membranes, organs, and eyes.
Most lesions are on the skin and mucous membranes.
The patient may also have a loss of hair, a mild fever, and the development of malaise.
This also heals without treatment and the patient may either spontaneously get well or develop a latent infection

16. Secondary syphilis

17. Secondary syphilis

18. Spirochaetales
Latent infection – during this stage there are no symptoms, but specific anti-treponemal antibodies are found.
This stage may last 3-10 years.
During this time these is a biological balance between the organism and the host.
1/3 to ½ may eventually progress to the next stage.
Tertiary syphilis – this stage is characterized by granulomatous lesions, called gummas, of the skin, internal organs, CNS, bones, eyes, and cardiovascular system.
They are cause by the body’s hyperimmune reaction to remaining spirochetes.
When lesions develop in the CNS it is called neurosyphilis and it can lead to paralysis.
In the eyes it can lead to blindness
In the heart it can lead to aortic damage or aneurisms.

19. Tertiary syphilis - gummas

20. Spirochaetales
Congenital syphilis – occurs when the treponemes cross the placenta during the fifth month to infect the unborn fetus (occurs usually when mom is in the latent stage).
This can result in damage to mental development or other neurological symptoms or the child may be born with generalized syphilis.
In a pregnant woman who has a primary or secondary stage of the disease, this usually results in stillbirth.
T. pertenue - causes Yaws or tropical syphilis which transmitted by non-venereal direct contact.
T. carateum – causes Pinta, a skin disease with hyperpigmentation in patches.

21. Spirochaetales
Borrelia – are arthropod transmitted Spirochetes and they cause:
Relapsing fever – two types:
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.
Endemic – is caused by many Borrelia species and is transmitted by ticks
Both types of relapsing fever follow the same clinical pattern.
12-15 days after infection there is an abrupt onset of fever, headache, and myalgia for 4-10 days.
Antibodies are formed and the number of organisms decrease.
This leads to an afebrile period for a few days to several weeks

22. Spirochaetales
The fever then relapses because the organism has undergone antigenic variation.
The antibodies are no longer effective and the organism numbers increase.
Several relapses may occur with each one being less severe than the previous one.
Lyme disease – caused by Borrelia burgdorferi and transmitted by ticks.
This is a systemic illness that may begin with the appearance of a red skin lesion called erythema chronicum migrans (ECM) because the lesion expands in a circular manner.
The patient may also have a fever, headache, nausea, vomiting, myalgia, and fatigue.
If untreated, the patient may develop arthritis (acute or chronic), and cardiac or neurologic complications weeks or months later due to immune complexes.

23. Lyme disease

24. ECM – from Lyme disease

25. Spirochaetales
Leptospira – L. interrogans causes Weil’s disease or leptospirosis
This disease is acquired by contact with the urine of an infected animal or ingestion of contaminated food or water.
It is more a disease of animals other than man.
Infection can vary from asymptomatic to fulminant.
The CNS, liver, and kidneys are most commonly infected.

26. Spirochaetales Antibiotic therapy/treatment
In most cases the incubation is 2-20 days followed by fever, chills, severe headache, myalgia, malaise, nausea and vomiting.
Jaundice occurs in severe cases
Death may occur due to renal failure.
Antibiotic therapy/treatment
Treponema – penicillin, tetracycline, or erythromycin
Borrelia - for relapsing fever use tetracycline or erythromycin; for Lyme disease use amoxicillin or doxycycline
Use protective clothing and repellents to prevent infection
Leptospirosis provide supportive care; antibiotics (penicillin or erythromycin) are only effective if given during the first 2-4 days of illness