Spirochaete infections

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Dan Freeman

Introduction

• The spirochaetes are a large, heterogeneous group of spiral, motile, gram-negative bacteria.

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• They have an outer sheath beneath which is the outer membrane, and move using axial filaments called endoflagella.

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• The family includes three genera whose members are human pathogens:
• Treponema
• Borrelia
• Leptospira

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Treponema��The genus Treponema includes: ��1. Treponema pallidum subsp. pallidum which causes syphilis��2. Treponema pallidum subsp. pertenue which causes yaws��3. Treponema pallidum subsp. endemicum which causes endemic syphilis (also called bejel)��4. Treponema carateum which causes pinta.

Morphology �Treponemes are long, slender, helically coiled, spiral or corkscrew-shaped, gram-negative bacilli, 0.2 µm wide and 5–15 µm long. � �Culture�Pathogenic T pallidum has never been cultured on artificial media, in fertile eggs, or in tissue culture. Non-pathogenic treponemes can be cultured anaerobically in-vitro.

Treponema pallidum subsp. pallidum (Syphilis)

Pathogenesis and clinical picture

• Syphilis affects only humans. Transmission is by direct contact, mostly during sexual intercourse.

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• Incubation period is 2 - 4 weeks.

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Syphilis _ contd

Untreated, the disease manifests in several stages:

• Stage I (primary syphilis): a hard, indolent (painless) lesion called hard chancre. There is also painless lymphadenitis. Treponemes can be detected in the ulcer.

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• Stage II (secondary syphilis): there is progression of disease within 4 - 8 weeks of primary disease, with macular or papulo-squamous exanthem, broad condylomas, and enanthem. Numerous organisms can be detected.

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• Latent syphilis: in this stage, no clinical symptoms are manifested, but the pathogens are present in the body and serum antibody tests are positive.

Syphilis _ contd

• Stage III (tertiary or late syphilis)
• Late gummatous syphilis: manifestations in skin, mucosa & various organs. Lesions are hardly infectious.
• Cardiovascular syphilis: endarteritis obliterans, syphilitic aortitis.
• Neurosyphilis: meningovascular syphilis and parenchymatous syphilis.

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• Congenital Syphilis: transmission from mother to foetus during pregnancy, leading to miscarriages or birth of severely diseased infant.

Diagnosis

• Isolation and identification of the pathogen. Methods: dark field microscopy, direct immunofluorescence.

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• Antibody assays:
• Reagin (antilipoidal) antibodies: serological test known as the VDRL flocculation reaction.�
• Antitreponema antibodies: TP-PA and TPHA�Immunofluorescence test (FTA-ABS)�Treponema pallidum immobilization test (TPI test)

Treatment�Penicillin G is the antibiotic agent of choice. Dosage and duration of therapy depend on the stage of the disease.� �Epidemiology and prevention�Syphilis is known worldwide. Prevention is by avoiding any contact with syphilitic efflorescences. Contact tracing is important in prevention. There is no vaccine.

�Treponema pallidum subsp. endemicum (Bejel)�

• This subspecies is responsible for non-venereal syphilis (but with similar presentation), occurring endemically in the eastern Mediterranean, Asia, and Africa. �
• The pathogens are transmitted by direct contact or indirectly on everyday objects such as clothes and other fomites. �
• The incub. period is 3weeks - 3months. Penicillin is the therapy of choice. Serological syphilis tests are positive.

�Other Treponema………�

• Treponema pallidum, subsp. pertenue (Yaws)�Yaws is a chronic disease endemic in moist, warm climates characterized by epidermal proliferation and ulceration. Transmission is by direct contact. The incubation period is 3 - 4 weeks. Serological syphilis reactions are positive. Penicillin G is the antibiotic of choice.� 
• Treponema carateum (Pinta)�Pinta occurs in parts of Central and South America, and characterized by marked dermal depigmentations. The pathogens are transmitted by direct contact. The incubation period is 1 - 3 weeks. Diagnosis and treatment are the same as for syphilis.

Borrelia - Relapsing Fever

• Borrelia species are mostly obligate anaerobes - some are aerotolerant. They are typically 20–30μm long and 0.2–0.3μm wide.

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• Borrelia recurrentis is pathogenic only in humans and causes an epidemic relapsing fever transmitted by body lice.

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• B. duttonii, B. hermsii, and other borreliae are the causative pathogens of the endemic, tick-borne relapsing fever.

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• Incubation period is 5 – 8 days, disease manifests with fever that lasts 3 - 7 days, then falls suddenly. Periodic relapses of fever characterize the infection.

Relapsing Fever

• Laboratory diagnostic confirmation requires identification of the borreliae in the blood.

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• Therapy: The antibiotic of choice is penicillin G. Alternatives include other betalactam antibiotics and doxycycline.

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• Epidemiology and Prevention:
• Epidemic form of relapsing fever has disappeared from most parts of the developed world today. Prevention involves eradication of the lice with insecticides.

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• Endemic relapsing fever, which is still seen in Africa, the Near and Middle East, and Central America; can be prevented by elimination of the insect vectors (ticks) with insecticides.

Lyme Disease

• B. burgdorferi is the causative pathogen in Lyme disease, a tick-borne infection.

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• The incubation period varies from three to 30 days. Left untreated, the disease goes through three stages.
• The primary clinical symptom of stage I is the erythema chronicum migrans.

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• Stage II is clinically defined by chronic lymphocytic meningitis (this is frequent in children).

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• The primary symptoms of stage III are chronic acrodermatitis and Lyme arthritis.

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Lyme Disease

• Detection of specific antibodies by means of immunofluorescent or EIA methods are more reliable than microscopy and culture.

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• Betalactam antibiotics are used to treat the infection.

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• Lyme disease is the most frequent tick-borne disease in central Europe.

Leptospira

• Leptospirae are fine spirochaetes, 10–20µm long, and 0.1–0.2µm thick.

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• They move by rotating motions of the cell body, as they possess no flagella.

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• They can be grown in in-vitro cultures.

Leptospirosis

• Leptospirosis is a zoonosis caused by Leptospira interrogans which occurs worldwide. The sole sources of infection are diseased rodents and domestic animals (e.g. pigs), which excrete the pathogen in their urine.

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• The incubation period is 7 -12 days. Signs and symptoms can range from none to mild headaches, muscle pains and fevers.

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• Weil's disease, the acute severe form of leptospirosis, causes jaundice, kidney failure, and severe bleeding in the lungs or meningitis.

Leptospirosis

• Laboratory diagnosis is by antibody identification in a lysis-agglutination reaction.

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• The therapeutic agent of choice is penicillin G.

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• Prevention involves mainly avoiding contact with material containing the pathogens, control of rodents and successful treatment of domestic livestock.