Lecture 4 Clostridium PDF

FirmicutesClostridiales Clostridium C. difficile C. botulinum C. tetani C. perfringens Genus Order Phylum Firmicutes Clostridiales Clostridium Phylum Order Genus Clostridium is an anaerobic, Gram- positive, endospore...

FirmicutesClostridiales Clostridium C. difficile C. botulinum C. tetani C. perfringens Genus Order Phylum Firmicutes Clostridiales Clostridium Phylum Order Genus Clostridium is an anaerobic, Gram- positive, endospore-forming bacillus that is ubiquitous in soil, water, sewage, and the gastrointestinal tracts of animals and humans. Pathogenicity is due in part to the ability of endospores to survive harsh conditions and to the secretion by vegetative cells of potent histolytic toxins, enterotoxins, and neurotoxins. Clostridium difficile Clostridium difficile is a motile, anaerobic intestinal bacterium that forms oval, subterminal endospores. C. difficile produces two toxins (toxins A and B) and the enzyme hyaluronidase. Toxin A and B cause damage to the epithelium resulting in an inflammatory response. C. difficile is a common member of the intestinal microbiota and an opportunistic pathogen. Disease appears in patients treated with broad-spectrum antimicrobial drugs. In such patients, the normal proportions of different bacteria in the colon can be significantly altered, enabling the hardy endospores of C. difficile to germinate to the extent that its toxins and enzymes produce hemorrhagic death of the intestinal wall. Old age and hospital stay… In serious cases, it can produce a life-threatening form of colitis, in which large sections of the colon wall slough off, potentially perforating the colon and leading to massive internal infection by fecal bacteria and eventual death. C. difficile is spread as airborne endospores, often from asymptomatic people. Diagnosis is based on direct detection of C. difficile toxins in feces, most commonly with the use of EIA assay  How does it Spread! Initial spore exposure from various sources does not necessarily result in disease, especially in a healthy individual. A healthy, diverse microbiota is capable of interfering with C. difficile spore germination and vegetative growth. However, if the metabolic and microbial environment of the gut has been perturbed (HOW???) , spore germination, vegetative outgrowth, and toxin production will occur. Leading to Epithelial cell in the colon damage and inflammation therefore the disease will start! This is termed Clostridium difficile infection (CDI) Leading to Sporulation of C. difficile, release of spores into the environment and transmission to new hosts perpetuates the infectious cycle.  Mechanism of CDI: Seekatz et al The Journal of Clinical Investigation, 2014, 124 Healthy Gut can provide Not so Healthy Gut Colonization Resistance Gut Microbiota Dysbiosis Dysbiosis refers to an imbalance or disruption in the composition of the gut microbiota, where the normal balance of microorganisms (including bacteria, fungi, viruses, and other microbes) is altered. This disruption can lead to a decrease in beneficial bacteria, an overgrowth of harmful microbes, or a reduction in overall microbial diversity. Main Causes: a. Diet: Processed foods, sugars, additives, and low fiber. b. Medications: Antibiotics and certain drugs. c. Lifestyle: Stress, poor sleep, inactivity. d. Health Conditions: Infections, inflammation, diseases. e. Genetics/Environment: Genetic factors and pollutants C. botulinum (bä-chə-ˈlī-nəm) an anaerobic, endospore-forming, Gram-positive bacillus that is common in soil and water worldwide. Its endospores survive improper canning of food, germinating to produce vegetative cells that grow and release into the can a powerful neurotoxin that causes botulism. Clostridium Neurotoxin (BoNT) is the deadliest biological substance currently known, with lethal dose values of 1 ng/kg in humans by the intravenous and subcutaneous routes and 3 ng/kg by the pulmonary route, based on experiments with non- human primates and investigations on naturally acquired botulism outbreaks. Non human primates research video (warning it can be very upsetting for some!!) BoNT has been classified as a category A biothreat agent by the US Center of Disease Control and Prevention due to this extreme toxicity and ease of production. However, BoNT is also used as a therapeutic agent for a number of indications such as movement disorders, hemifacial spasm, essential tremor, tics, writer’s cramp, cervical dystonia, cerebral palsy, vascular cerebral stroke and more recently for chronic pain, migraine headache and overactive bladder. C. botulinum Pathogenesis (how does it develop the disease) It has Seven antigenically distinct botulism toxins (A through G) are produced by the different strains of C. botulinum. BoNT is an AB toxin which are found in the Clostridium spp. Ingestion of a small amount of toxin can cause disease or even death. The BoNT are resistant to stomach acid. Botulism toxins bind irreversibly to the cytoplasmic membrane of neurons and prevent the release of acetylcholine and therefore prevent muscular contraction, resulting in a flaccid paralysis (def: paralysis in which muscle tone is lacking in the affected muscles and in which tendon reflexes are decreased or absent: Merriam Webster) Botulism Antitoxin (Heptavalent) (Equine) BAT® [Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G) – (Equine)] Emergent Biosolutions BAT is a sterile solution of F(ab')2 antibody fragments prepared from plasma obtained from horses that have been immunized with a specific serotype of botulinum toxoid and toxin.  Antiserum ImmunoglobulinProduction Antigen Antiserum Production (ex Anti Botulism hyperimmune) Immunoglobulin (Ig) found in Plasma NOTE: Animals can be; rabbit, goat, sheep, horse, chicken, rat, mouse, and guinea pig Table 25.2 Some Classic Exotoxins and Cytotoxins Produced by Human Bacterial Pathogens Organism Disease Toxin a Activity b Bacillus anthracis Anthrax Lethal factor Edema Combine to cause cell death factor Protective antigen (AB) Bordetella pertussis Whooping cough Pertussis toxin (A B) Blocks G protein function; kills cells Clostridium Botulism Botulinum toxin (A B) Causes flaccid paralysis botulinum Clostridium tetani Tetanus Tetanospasmin (A B) Causes spastic paralysis Clostridium Gas gangrene α, β, γ, δ toxins (A B) Hemolysis, lecithin destruction perfringens Clostridium Food poisoning Enterotoxin (C T) Alters intestinal tract permeability perfringens Corynebacterium Diphtheria Diphtheria toxin (A B) Inhibits eukaryotic protein diphtheriae synthesis Escherichia coli Gastroenteritis Shiga-like (E. coli) toxin Inhibits protein synthesis, induces (enterotoxigenic (AB) bloody diarrhea strains only) Pseudomonas Burn and certain Exotoxin A (A B) Inhibits eukaryotic protein aeruginosa wound and ear synthesis infections; cystic fibrosis lung Infections Salmonella s p. Gastroenteritis Enterotoxin (A B) Lyses cells; inhibits protein synthesis Figure 25.14 The Activity of Botulinum Toxin Neutralizing Antibody (BAT) Clostridium tetani (tuh·taa·nee) a small, motile, obligate anaerobe that produces a terminal endospore, giving the cell a distinctive lollipop appearance. It is ubiquitous in soil, dust, and the gastrointestinal tract of animals and humans. Its toxin causes tetanus. Pathogenesis The toxin produced by C. tetani causes the disease tetanus when endospores enter the body via a break in the skin. Tetanospasmin (tetanus toxin) is a potent neurotoxin that binds to a receptor on neurons, where it is endocytized, and eventually blocks release of inhibitory neurotransmitters. The result is uncontrolled muscle contraction, which can in severe cases break bones. The Activity of Tetanus Toxin (Figure 25.15 ) Clostridium tetani Tetanus occurs primarily where vaccination is unavailable or inadequate. If left untreated, it causes fatal disease. The initial, diagnostic sign of tetanus is tightening of the jaw and neck muscles, called lockjaw. The spasms and contractions can spread to other muscles and become so severe that the arms and fists curl tightly, the feet curl down, and the body assumes a stiff backward arch. Contraction of the diaphragm results in a final inhalation; patients die because they cannot exhale. Clostridium tetani Diagnosis, Treatment, and Prevention Tetanus infection is diagnosed by history and characteristic signs. Treatment begins with the thorough cleaning of wounds to remove endospores, immediate passive immunotherapy with immunoglobulin, administration of antimicrobials, and active immunization with tetanus toxoid. The CDC recommends six doses of tetanus toxoid vaccine beginning at two months of age, followed by a booster every 10 years for life Sharp Decline in Tetanus 1) widespread use of tetanus toxoid–containing vaccines since the late 1940s. 2) Other factors include improved wound care and antibiotic use 3) Post exposure with the use of tetanus immune globulin (TIG) Tetanus Toxoid Vaccine Production Tetanus Toxoid Vaccine Production Tetanus Toxoid Vaccine Production C. perfringens they most frequently isolated from clinical specimens, is a large, almost rectangular, nonmotile, Gram-positive bacillus. Pathogenesis, Epidemiology, and Disease C. perfringens is nearly ubiquitous in fecally contaminated soil and water due to its widespread presence in the digestive tracts of humans and animals. C. perfringens produces 11 toxins that lyse blood cells and cause diseases, such as food poisoning and gas gangrene, which is fatal in over 40% of cases even with aggressive treatment. In Gas gangrene or aka Clostridial Myonecrosis, traumatic injury introduces endospores into the body. After spore germination, the clostridial toxins produced can cause pain, swelling, and rapid tissue death. The gaseous smelly bacterial waste products give the disease its name. It is also a common cause of food poisoning when ingested in sufficient numbers. This commonly occurs when cooked food contaminated with the bacteria is left out. C. perfringens can survive the acid conditions in the gut and grow in the intestine producing enterotoxins… leading to diarrhea C. perfringens Diagnosis, Treatment, and Prevention The appearance of gas gangrene on wounds is frequently diagnostic and must be aggressively treated to stop the spread of necrosis. Application of oxygen under pressure to the site of injury is also effective….WHY? Proper cleaning of wounds can prevent many cases of gas gangrene since necrosis occurs when endospores are introduced deep into the tissues. Last resort….amputation! END….