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Spirochaetales. The Spirochetes. 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
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Spirochaetales The Spirochetes
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 protoplasmic cylinder with a peptidoglycan layer
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
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
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.
Spirochaetales • 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:
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: Venereal Disease Research Laboratory (VDRL) test, rapid plasma reagin card tests (RPR), and automated reagin test (ART)
Spirochaetales • 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
Spirochaetales • Virulence factors • Treponema • 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
Spirochaetales • Leptospira • Unknown • Clinical significance • Treponema • 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:
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.
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
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.
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.
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
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.
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.
Spirochaetales • 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
