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Assist.Proph.Dr.Ilham alsaedi
Spore-Forming Gram-Positive Bacilli
Bacillus & Clostridium Species
The G+ve spore-forming bacilli are the Bacillus and Clostridium species.These bacilli are worldwide distributed and because they form spores they can survive in the environment for many years.
Bacillus species are aerobes,whereas Closteridia are anaerobes.
Bacillus species:
General properties:-
1-The genus bacillus include large aerobic,gram positive rods occurring in chains.
2-Most members present in soil and water,e.g. B.cereus and B.subtilis.
3-B.cereus may cause food poisoning but B.anthracis are arranged in chains(long),spores are located in the center of the non-motile bacilli.
4-The colonies are round and forms ((Medusa’s head colonies) on blood agar.
5-The organism is capsulated and the capsular substance consist of a polypeptides of high M.W. composed of D- glutamic acid.
Bacillus anthracis
Pathogenesis:
Anthrax is primarily a disease of goats,sheep,cattle,horses,other animals e.g. rats are relatively resistant to the infection.
In humans, the infection is usually acquired by the entry of spores through injured skin(cutantaneous anthrax) or rarely the mucous membranes(gastrointestinal anthrax),or by inhalation of spores into the lung(inhalation anthrax).
The spores germinate in the tissue at the site of entry,and growth of the vegetative organisms results in formation of gelatinous edema and congestion.Bacilli spread via lymphatics to the bloodstream,and they multiply freely in the blood and tissues shortly before and after the animal’s death.
Anthrax toxin is made up of three proteins,protective antigen(PA), edema factor(EF),and lethal factor(LF).The mixture of these is more toxic and immunogenic than sigle substances.
In inhalation anthrax (woolsorter’s disease) which results from inhalation of spores from the dust of wool or hair leading to produce hemorrhagic mediastinitis, pneumonia,mining and sepsis which is usully fatal.
Clinical findings:
In human,approximately 95% of cases are cutaneous anthrax and 5% are inhalation.Gastrointestinal anthrax is very rare.
Cutaneous anthrax generally occurs on exposed surfaces of the arms or hands followed by the face and neck.
A papule develops 1-7 days after entery of the organisms or spores,the papule rapidly changes into a vesicle or small ring of vesicle and finally a necrotic ulcer developed.
In 20% of patients cutaneous anthrax can lead to sepsis, the consequences of systemic infection including meningitis and death.
Laboratory Diagnosis:
1-Specimens:fluid or pus from a local lesion,blood,and sputum.
2-Stained smears show chains of large gram-positive rods.
3-In blood agar plates,the organisms produce nonhemolytic gray to white colonies.
4-Ascoli precipitin test:
Extract of infected tissues show a ring of precipitate when layered over immune serum (anthrax antiserum).
5-Serologic tests
*agglutination test
*ELISA :Enzyme-linked immunoassay.
Treatment:
Many antibiotics are effective against anthrax in human but treatment must be started early.
Ciprofloxacin is recommended for treatment;Penicillin G with Gentamicin or streptomycin may be effective.
Control&Preventation
1-disposal of animal carcasses by burning or by deep burial in lime pits.
2-decontamination(usually by autoclaving) of animal products.
3-protective clothing and gloves for handling potentially infected materials and
4-active immunization of domestic animals with live attenuated vaccines.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .