Spi. PDF - Spirochaetes

Chapter (19): SPIROCHAETES • In humans they cause relapsing fever & Lyme disease • Borrelia can be pathogenic for humans, domes�c animals & rodents Borrelia • Ticks transmit all known species of Borrelia except B. recurrenits which is transmi�ed by human body louse Borrelia Morphology • Borreli...

Chapter (19): SPIROCHAETES • In humans they cause relapsing fever & Lyme disease • Borrelia can be pathogenic for humans, domes�c animals & rodents Borrelia • Ticks transmit all known species of Borrelia except B. recurrenits which is transmi�ed by human body louse Borrelia Morphology • Borreliae are highly mo�le Spirochaetas with irregular loose coils • They are best visualized with Giemsa stain Culture • Some are Gram nega�ve • Borrelia are microaerophilic, slowly growing Spirochaetes • They grow on highly enriched media containing serum & �ssue extract t a Relapsing fever • Febrile, sep�caemic disease in which several relapses may occur Transmission Clinical manifestations • There are two forms of relapsing fever: • Tick-borne (endemic) relapsing fever, which is caused by variety of Borrelia species → The most important species is B. hermsii → Rodents & small animals are the main reservoir from which they are transmi�ed to man (zoono�c disease) • Symptoms appear a�er • Fever lasts for 3 to 5 days, followed by afebrile period which lasts about I.P. of 3 to 10 days a week before 2nd a�ack of fever starts → These relapses may be repeated 3 to 7 �mes Lab diagnosis • Diagnosis is usually made during febrile stage, where abundant spirochaetas are present in blood Introduction Clinical findings • Leptospirae have a worldwide distribu�on → they may be free-living or may live in associa�on with human or animal hosts • Infected animals excrete large numbers of the organism in urine resul�ng in contamina�on of water & soil where leptospirae remain viable for several weeks Mode of transmission Clinical manifestations Diagnosis Treatment Lyme disease Lab diagnosis 2 Stage 2 • Organism disseminates via blood resul�ng in muscle & joint pain (arthralgia), secondary skin lesions & lymphadenopathy Morphology It can be grown on serum-containing media u Contact with contaminated water where the organism enters through small skin abrasions → this may occur: * As an occupational hazard → affecting mainly farmers, sewage workers and miners * During practicing water sports, e.g. swimming v Consumption of contaminated food or drink → where the organism penetrates the mucous membrane • The incubation period is usually 7 to 14 days • Leptospirosis is typically a biphasic illness with a quiescent period in-between 1. The first phase Characterized by a febrile influenza-like illness due to blood invasion (septicaemia) 2. The second phase Characterized by dysfunction of liver (jaundice), kidney (uraemia) & CNS (aseptic meningitis) due to invasion of these organs by leptospirae from the blood stream • Diagnosis is based on: 1. History of possible exposure, together with suggestive clinical signs 2. Marked rise in specific IgM (highly sensitive) 3. Occasional isolation of the organism from blood, urine or CSF Penicillin or doxycycline are the drugs of choice • → Tetracycline may be beneficial early in illness & may prevent relapses Bacteria (37) • Diagnosed serologically by ELISA → to be confirmed by Western blot 3 Latent stage 4 Stage 3 • This stage is characterized by arthri�s (specially large joints), CNS & cardiac dysfunc�on Borrelia • Leptospira interrogans is the causa�ve agent of leptospirosis (Weil’s disease), which is zoono�c disease Leptospira interrogans is an obligate aerobe • Rodents, dogs, swine and ca�le act as reservoirs for the leptospirae (Weil’s Disease; Infec�ous Jaundice) Culture m a h Treatment • This is done by detec�ng loosely coiled spirochaetas in blood films stained by Giemsa stain s e H • Symptoms include sudden onset of fever, severe headache & general malaise • Relapses occur as result of an�genic varia�ons in causa�ve Borrelia spp. → As Abs develop against Ags of exis�ng organism, new an�genic variants emerge & produce relapses of illness • Although caused by different spirochaetas → general similari�es in progression (stages) of Lyme disease & syphilis are striking 1 Stage 1 • Characteris�c spreading circular red lesion with clear center (erythema migrans) occurs at the sight of �ck bite Introduction Leptospirosis . r D • Disease is caused by B. burgdorferi, which is transmi�ed by �cks bite m s E • Louse-borne (epidemic) relapsing fever, which is caused by B. recurreni�s → Man is the only reservoir → transmi�ed from man to man by human body louse (not zoono�c disease). • Leptospirae are very thin and �ghtly coiled mo�le rods with hooked end • They can be seen by dark-field microscopy Growth usually occurs within 1-2 weeks II Fusospirochaetal Disease Under certain circumstances, par�cularly injury to oral mucous membranes, nutri�onal deficiency or concomitant infec�on (e.g. with HSV) → the normal spirochaetes of the mouth, together with anaerobic fusiform bacilli (fusobacteria) find suitable condi�ons for mul�plica�on They increase in numbers causing: 1 Trench mouth: • Condi�on of acute necro�zing ulcera�ve gingivi�s (ANUG) • Laboratory diagnosis: Gram-stained smear from the pseudomembrane → shows large number of Gram-nega�ve fusiform bacilli and spirochaetes in associa�on with pus cells and other commensals 2 Vincent's angina • fusospirochaetal infec�on of the pharynx with pseudomembrane forma�on, similar to diphetheria & follicular tonsilli�s