Clostridium & Bacillus species PDF

Clostridium & Bacillus species Dr. Mustafa al-Musawi Department of Clinical Laboratory Science College of Pharmacy Medical Microbiology Clostridium Species  The clostridia are large anaerobic, spore-forming, gram- positive, motile rods.  Their natural h...

Clostridium & Bacillus species Dr. Mustafa al-Musawi Department of Clinical Laboratory Science College of Pharmacy Medical Microbiology Clostridium Species  The clostridia are large anaerobic, spore-forming, gram- positive, motile rods.  Their natural habitat is the soil or the intestinal tract of animals and humans. There are four medically important species; ‫اربع انواع طبية‬ Clostridium botulinum (botulism) Clostridium tetani (tetanus) Clostridium perfringes (gas gangrene) Clostridium difficile (pseudomembranous colitis, antibiotic- associated diarrhea (AAD). ‫( ي الكاذب واإلسهال املرتبط باملضادات الحيوية‬AAD). Clostridium botulinum C. botulinum is a large anaerobic bacillus that forms subterminal ‫طرفية‬ endospores. ‫داخلية‬ C.botulinum, causes the disease botulism. ‫تسم غذائي‬ It is found in soil and sometimes in animal.feces Toxins  Seven antigenic varieties of toxin (serotypes A– G) are known.  Types A, B, E, and F are the principal causes of human disease.  Types A and B have been associated with a variety of foods and type E usually with fish products.  Type C produces limber neck in birds (neck paralysis); type D causes botulism in mammals.  The lethal dose for a human is probably about ‫الجرعة القائلة لألنسان‬ 1–2 μg/kg.  The toxins are destroyed by heating for 20 Pathogenesis Botulism is serious disease caused by Botulinum toxins that attacks the body's nerves and causes difficulty breathing and muscle paralysis. 1.Foodborne botulism: most cases of botulism represent an intoxication resulting from the ingestion of food in which C. botulinum has grown and produced toxin. The most common offenders are spiced, smoked, packed or canned alkaline foods that are eaten without cooking. In such foods, spores of C. botulinum germinate; that is, under anaerobic conditions, vegetative forms grow and produce toxin. 2.Wound botulism is the result of tissue contamination with spores and is seen primarily in injection drug users. ‫االستنشاقي‬ Laboratory Diagnosis  Toxin can often be demonstrated in serum, gastric secretions, stool, wound swabs and pus from the patient, and toxin may be found in leftover food. ‫الطعام‬ ‫قيح بقايا‬  ELISA  PCR Treatment  Intensive care is key in the management of patients with botulism. Suitable respiration must be maintained by mechanical ventilation if necessary and in severe cases may need to be maintained for up to 8 weeks. These measures have reduced the mortality rate from 65% to below 25%.  Botulinum immune globulin (BIG) is used to treat infant. Antibiotics (e.g. penicillin G or alternatively metronidazole) are recommended for wound botulism in addition to debridement ‫ازالة االنسجة امليتة‬ if needed. Clostridium tetani -Morphology and Physiology Long thin gram-positive organism Round terminal spore gives drumstick appearance Motile by peritrichous flagella grow on blood agar or cooked meat medium with swarming beta-hemolysis exhibited by isolated colonies. swarming  Tetanus is acquired through contact with the environment.  The mode of entry is wounds ((such as those caused by rusty nails) Toxin The vegetative cells of C. tetani produce the toxin-.tetanospasmin (150 kDa) -Sensitive to heat. ineffective after 65℃, 30min The toxin is produced during cell growth. It migrates - along neural paths from a local wound to sites of action in.the central nervous system -Toxin blocks release of inhibitory neurotransmitters; continuous stimulation by excitatory transmitters ‫شلل رعاشي‬ muscle spasms (spastic paralysis), (trismus (lock jaw), risus sardonicus, opisthotonos, cardiac arrhythmias, fluctuations in blood pressure. ‫ مما يؤدي إلى استمرار التحفيز‬،‫يعمل التوكسني على منع إفراز الناقالت العصبية املثبطة‬ ‫ مثل‬،(‫ هذا التعطيل يسبب تشنجات العضالت )الشلل الرعاش‬.‫بواسطة الناقالت املحفزة‬ ‫ ريسوس ساردونيكوس )ابتسامة مشدودة بسبب تشنجات عضلية‬،(‫التيتانوس )قفل الفك‬ ‫ ويمكن أن‬،(‫ اوبيستوتونوس )تشنجات تؤدي إلى انحناء الظهر إلى الوراء‬،(‫في الوجه‬.‫يسبب أيضا اضطرابات في نظم القلب وتقلبات في ضغط الدم‬  Prevention and Treatment The results of treatment of tetanus are not satisfactory. Therefore, prevention is all important. Prevention of tetanus depends on: ,Active immunization with toxoids )1( A combined vaccine, DPT vaccine, which includes vaccines against diphtheria, pertussis, and tetanus. (2) aggressive wound care, (3) preventive use of antitoxin. (4) administration of penicillin. C. Perfringens‫كبيرة ومستطيلة‬ Large, rectangular bacilli (rod) staining gram-positive Spores are ovoid and sub terminal. Toxins  The alpha toxin of C. perfringens. Alpha toxin also aggregates platelets, destruction of viable tissue (gas gangrene).  The theta toxin; cytolysins that act by forming pores in cell membranes.  Epsilon toxin is a protein that causes edema, and hemorrhage  some strains of C perfringens produce enterotoxin (C. perfringens enterotoxin, CPE) that cause food poisoning. Pathogenesis Gas gangrene occurs when spores reach tissue either by contamination from soil and feces. The spores germinate, vegetative cells multiply, ferment carbohydrates present in.tissue, and produce gas Food poisoning usually follows the ingestion of bacterial cells that have grown in warmed meat dishes. The toxin forms when the organisms germinate in the gut, with the onset of diarrhea –usually without vomiting or fever--- in 6-18 hours. Diagnostic Laboratory Tests  Specimens consist of material from wounds, pus, and tissue.  Gram Stain  Lecithinase activity is evaluated by the precipitate formed around colonies on egg yolk media. ‫ يتم تقييمه بواسطة‬:(Lecithinase activity) ‫نشاط الليسيثيناز‬.‫الراسب الذي يتكون حول املستعمرات على وسط صفار البيض‬  stormy" fermentation of milk due to large amounts of acid and gas from lactose  double zone of hemolysis on blood agar.  :‫العالج‬ Treatment ‫إزالة األنسجة امليتة )التنظيف‬  The most important aspect of ‫ هذا هو الجانب األكثر أهمية في‬:(‫الجراحي‬ treatment is the removal of necrotic :‫ إعطاء األدوية املضادة للميكروبات‬.‫العالج‬ ‫ ويتم البدء في‬،‫يُفضل استخدام البنسلني‬ tissue (surgical debridement).‫العالج في نفس الوقت‬ Hyperbaric) ‫األكسجني عالي الضغط‬  Administration of antimicrobial ‫ قد يكون مفيدًا في إدارة التهابات‬:(oxygen drugs, particularly penicillin, is.‫األنسجة الناتجة عن الكلوستريديوم‬ begun at the same time.  Hyperbaric oxygen may be of help in the medical management of clostridial tissue infections.  Antitoxins. Clostridium difficile A spore-forming anaerobic rods (bacillus), gram-positive. C difficile that produces two toxins: Toxin A, a potent enterotoxin that also has some cytotoxic activity, binds to the brush border membrane of the gut at receptor sites. Toxin B is a potent cytotoxin. The methods in detecting C. difficile toxins are: enzyme immunoassay (EIA). enzyme-linked immunosorbent assay (ELISA). Bacillus Species B. anthracis, which causes anthrax B. cereus can grow in foods and cause food poisoning by producing either an enterotoxin (diarrhea) or an emetic toxin (vomiting). Morphology and identification A. Typical Organisms The typical cells, measuring 1 × 3–4 μm, have square ends and are arranged in long chains; spores are located in the center of the bacterial cell. Bacillus anthracis Pathogenesis  Anthrax is primarily a disease of herbivores goats, sheep, cattle, horses, and so on In animals, the entry of spores is via mouth and the gastrointestinal tract.  Clinical infections in humans, Humans become infected incidentally by contact with infected animals or their products. B anthracis causes three categories of disease in humans depending on the point of entry of the spores:  Cutaneous anthrax (95%) : the infection is usually acquired by the entry of spores through injured skin.  inhalation anthrax or wool sorters’ disease (5%): inhalation of the spores from the dust of wool, hair, or hides.  Gastrointestinal anthrax (rare): the infection is acquired by ingestion of contaminated meat.  Virulence factors  The poly-d-glutamic acid capsule is anti- phagocytic.  Anthrax toxins are made up of three proteins:  Protective antigen (PA),  Edema factor (EF),  Lethal factor (LF). PA binds to specific cell receptors, and after proteolytic activation, it forms a membrane channel that mediates entry of EF and LF into the cell. EF  Diagnostic Laboratory Tests Specimens to be examined are fluid or pus from a local lesion, blood, pleural fluid, and cerebrospinal fluid in inhalational anthrax associated with sepsis and stool or other intestinal contents in the case of gastrointestinal anthrax. Stained smears Gram stain show chains of large gram-positive rods  Culture  When grown on blood agar plates, the organisms produce Non-hemolytic gray to white, tenacious colonies with a rough texture and a ground-glass appearance. Comma-shaped outgrowths (Medusa head, “curled hair”) may project from the colony. - Detection of the capsule by fluorescent antibody,  In semisolid medium, anthrax bacilli are always non- - identification motile. of toxin genes by polymerase chain reaction (PCR), Enzyme-linked immunoassay (ELISA) -  Vaccines  (AVA BioThrax) In the United States, the current FDA-approved vaccine (AVA BioThrax) is made from the supernatant of a cell free culture of an encapsulated but toxigenic strain of B. anthracis.  Raxibacumab is a human monoclonal antibody against Bacillus anthracis protective antigen PA Treatment  Ciprofloxacin  Penicillin G, along with gentamicin or streptomycin. Bacillus cereus Produces emetic toxin and enterotoxins.  Food poisoning caused by B cereus has two distinct forms,  Emetic type, which is associated with cooked rice.  nausea, vomiting, abdominal cramps, and occasionally diarrhea  Incubation period 1–5 hours.  Diarrheal type, which is associated with meat dishes and sauces.  Incubation period of 1–24 hours  diarrhea with abdominal pain and cramps; fever and  Endocarditis, meningitis, osteomyelitis, and vomiting are uncommon. pneumonia.  Eye infections,  Treatment  Vancomycin or  Clindamycin with or without an aminoglycoside. Thanks