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Spirochete. Inroduction. The spirochetes are a large heterogenous group of bacteria. In some respects, this microorganism is similar to bacteria and protozoa .
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Inroduction • The spirochetes are a large heterogenous group of bacteria. • In some respects, this microorganism is similar to bacteria and protozoa. • They have cell wall and propagate by binary fission and move vigorously by the rotation and twisting of the endoflagella. They are sensitive to antibiotic.
Structural characteristics: ◇They are long, slender and spiral or helical-shaped, Gram-negative bacilli.
Protoplasmic cylinder Endoflagella Outer envelope • Structural characteristics: ◇There are endoflagella located between outer and inner membrane (envelope) and running parallel to the microbic body.
There are three genera whose members are human pathogens: • Leptospira • Treponema • Borrelia
Morphology • Leptospira are tightly coiled and flexible (5-15 µm long and 0.1-0.2 µmwide). One or two ends are usually bent to form hook-like shape. • While stained with silver stain (Fontana stain), they show a deep brown color.
Morphology • They are actively mobile, which is best seen using a darkfield microscope.
Classification • two species: • L. interrogans • causes human or animal diseases called leptospirosis • According to the antigenic differences of LPS and superficial glycoproteins, L. interrogans can be divided into at least 24 serogroups and 200 serotypes • L. biflaxa • Saprophytic, usually exists in water in nature.
Culture • Korthof medium with 10% rabbit serum • The optimal incubating temperature is about 28℃ • L. interrogans grows slowly • Sensitive to heating and various chemical agents • Can survive several months in wet soil and water • ◇L. interrogans has two chromosomes (one is large and the other is small).
Transmission • L. interrogans propagates in the kidney of infected patients or animals and can be shed in the urine. • Animal urine from infected rodents, infected farm animals (usually inapparent infection) • Contaminate soil and water • Enters body through healthy or broken skin. • Human leptospirosis. L. interrogans rapidly enters bloodstream to cause leptospiremia
Epidemiology • A common zoonosis: • A disease of animals that can be transmitted to humans. • Extensive animal hosts: • rats, mice, other wild rodents, swine, cattle, dog, sheep etc.
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Pathogenicity • Virulent factors produced by L. interrogans • LPS: lower toxicity than bacterial LPS • Hemolysin: unknown pathogenesis • Cytotoxicity factor (CTF) and cytopathic effect (CPE) substance: only show cytotoxicity • Pathological damage to the capillary endothelium is the main cause for disease.
Clinical finding • Leptospirosisaffects many internal organs e.g., lung, kidney, liver • The pathogenicity of different leptospiral serogroups is distinct. The clinical symptoms are quite different, from mild influenza-like clinical signs to death which is usually caused by pulmonary diffuse hemorrhage (PDH) • Macrophage can phagocytose L. interrogans, neutrophils can not
Laboratory Diagnosis • Peripheral blood in the first week of disease and urine from the second week on are collected as samples for detecting leptospire • Common diagnostic methods in clinic include direct darkfield microscopy and serological examination
Control • Penicillin is the first choice drug to treat leptospirosis • Multi-valent vaccine composed of whole dead cells of several leptospiral serovars is available. However side effect of the vaccine is relatively serious
Morphology of Treponema pallidum • Moves with endoflagella • There are 16 to 18 bends • Shows a deep brown color by silver stain. • Can be cultured in rabbit testicle but can not grow in vitro • Sensitive to temperature and dryness
Treponema pallidum in testis of infected rabbit
Transmission • via sexual contact • via placenta or during birth • via blood transfusion • Disease • Acquired syphilis • Congenital syphilis
I. Acquired Syphilis • Syphilis is the a most common STD in our country • This disease appears chronic and slowly progressive • Syphilis undergoes 3 stages
Stage 1: Primary Syphilis • Chancre appears (an area of ulceration/inflammation) usually in genital areas • The patient has influenza-like symptoms • The local lesion will heal within 4-6 weeks but the microbe spread systemically
Stage 2: Secondary Syphilis • Pale red rash (syphilid)appears on thepalms or soles or over theentire body • The sores around the genitals or anus secrete extremely infectious fluids • This stage will last 3-6 months
Syphilid Abdominal part palms soles
Stage 3: Latency Stage • No obvious symptoms and usually occurs 2-10 years after initial infection and last 3-6 months. • The infectious ability is decreased. • Later the complications in the skin, bones, central nervous system, heart and blood vessels appear, which frequently cause death. • The basic pathological lesion is chronic granuloma (Gumma).
Gumma (syphiloma) lesion in the heart Gumma (syphiloma) lesion in the skin
II. Congenital Syphilis • The disease can cause fetal death. • In infants, multi-organ deformity or latent infection are present.
I. Early Congenital Syphilis Runny nose Vesicular rash Osteochondritis
II. Late congenital Syphilis Saw-teeth Sabre shins Frontal bossing and saddle nose
Laboratory diagnosis • Samples • the secretions from chancre in Stage I and from syphilid in Stage II • the patient’s serum
Laboratory diagnosis Darkfield microscopy and fluorescence microscopy RPR (rapid plasma reagin) • Use cattle cardiolipin as the antigen to detect reagin (syphilis non-specific antibodies) in the serum TPPA (T. pallidum particle agglutination assay) or TPHA (T. pallidum hemagglutination assay) • micro-hemoagglutination assays for the detection of antibodies to Treponema pallidum
Treatment & Prevention • Penicillin • Tetracycline Erythromycin • No vaccine
Lyme disease is an emerging zoonosis mainly caused by Borrelia burgdorferi. In 1975, the disease was firstly found in a town named Lyme in the U.S.A. • Human is infected by bite of tickscarryingBorrelia burgdorferi. • The clinical characteristic is erythema chronicum migrans (ECM) at the bite site. • Borrelia burgdorferi can invade host cells, resist phagocytosis and produce endotoxin-like substance. Pathogenesis is considered to be closely associated with immunopathological injury because rarely the pathogen can be found in vivo.
Borrelia burgdorferiis a spiral microorganism. The microbe has variable numbers (7-11) of endoflagella to move actively.
Inn tick A kind of tick to transmit Borrelia burgdorferito human
Lyme Disease erythematous rash Erythema chronicum migrans (ECM)
Diagnosis & Treatment • Lyme disease is diagnosed based on clinical symptoms (e.g., ECM) and the possibility of exposure to infected ticks. • PCR and serological assays are helpful for clinical diagnosis. • Most of Lyme disease cases can be treated successfully with a few weeks of antibiotics (penicillin or tetracycline).