Anaerobic Bacteria

1. Anaerobic Bacteria

2. Category • Spore-forming: rod, Gram (+)--- Clostridium • Nonspore-forming: see next slides

3. Category

4. Clostridium Species • The clostridia are opportunistic pathogens. Nonetheless, they are responsible for some of the deadliest diseases including gas gangrene, tetanus and botulism. Less life-threatening diseases include pseudomembranous colitis (PC) and food poisoning. • cause disease primarily through the production of numerous exotoxins. • perfringens, tetani, botulinum, difficile

5. Clostridium Tetani Pathogenesis of tetanus caused by C tetani

6. General introduction • C tetani is found worldwide. Ubiquitous in soil, it is occasionally found in intestinal flora of humans and animals • C.tetani is the cause of tetanus,or lockjaw. When spores are introduced into wounds by contaminated soil or foreign objects such as nails or glass splinters

7. BIOCHEMICAL CHARACTERISTICS • Morphology: long and slender; peritrichous flagella,no capsule, terminal located round spore(drum-stick apperance), its diameter greater than vegetative cell. • Culture:obligate anaerobic; Gram(+); swarming occures on blood agar, faint hemolysis. • Biochemical activities:does not ferment any carbohydrate and proteins. • Resistance: tolerate boiling for 60 min.alive several ten years in soil. • Classification and Antigenic Types: C tetani is the only species. There are no serotypes 2-5 x 0.3-0.5um

8. No invasiveness; toxemia (exogenous infection） produces two exotoxins: tetanolysin, and tetanospasmin(a kind of neurotoxin, toxicity strong) The actions of tetanospasmin are complex and involve three components of the nervous system: central motor control, autonomic function, and the neuromuscular junction. retrograde transport to (CNS) delitescence：a few days to several weeks The two animal species most susceptible to this toxemia are horses and humans. Pathogenicity

9. Clostridium tetani-Tetanospasmin • disseminates systemically • binds to ganglioside receptors • inhibitory neurones in CNS • glycine • neurotransmitter • stops nerve impulse to muscles • spastic paralysis痉挛性麻痹 • severe muscle contractions and spasms • can be fatal

10. Tetanospasmin

11. Clinical Manifestations • The initial symptom is cramping and twitching of muscles around a wound. The patient usually has no fever but sweats profusely and begins to experience pain, especially in the area of the wound and around the neck and jaw muscles (trismus). • Portions of the body may become extremely rigid, and opisthotonos角弓反张(a spasm in which the head and heels are bent backward and the body bowed forward) is common. • Complications include fractures, bowel impaction, intramuscular hematoma, muscle ruptures, and pulmonary, renal, and cardiac problems

12. Clinical Manifestations

14. Epidemiology • 1 million cases of tetanus occur annually in the world,with a mortality rate ranging from20% to 50%. But rare in most developed countries. • In some developing countries, tetanus is still one of the ten leading causes of death, and neonatal tetanus accounts for approximately one-half of the cases worldwide. • In less developed countries, approximate mortality rates remain 85% for neonatal tetanus and 50% for nonneonatal tetanus. • In the United States, intravenous drug abusers have become another population with an increasing incidence of clinical tetanus • In untreated tetanus, the fatality rate is 90% for the newborn and 40% for adults.

15. Immunity • Humoral immunity(antitoxin) • There is little, if any, inate immunity and the disease does not produce immunity in the patient. • Active immunity follows vaccination with tetanus toxoid

16. Diagnosis • Diagnosis is primarily by the clinical symptoms (above). The wound may not be obvious. • C tetani can be recovered from the wound in only about one-third of the cases. • It is important for the clinician to be aware that toxigenic strains of C tetani can grow actively in the wound of an immunized person. • Numerous syndromes, including rabies and meningitis, have symptoms similar to those of tetanus and must be considered in the differential diagnosis.

17. Vaccination • infant • DPT (diptheria, pertussis, tetanus) • tetanus toxoid • antigenic • no exotoxic activity

18. Control • The offending organism must be removed by local debridemen清创术 • toxoid • TAT; Metronidazole (For more serious wounds) • AIDS patients may not respond to prophylactic injections of tetanus toxoid

19. C. perfringens • soil, fecal contamination • gas gangrene • swelling of tissues • gas release • fermentation products • wound contamination

20. Toxins

21. Toxins • Many of these toxins have lethal, necrotizing, and hemolytic properties; • The alpha toxin produced by all types of C. perfringens, is a lecithinase that lyses erythrocytes, platelets, leukocytes, and endothelial cells. And its lethal action is proportionate to the rate at which it splits lecithin to phosphorylcholine and diglyceride. • The theta toxin has similar hemolytic and necrotizing effects. • DNAase, hyaluronidase, a collagenase are also produced

22. Enterotoxin • Many strains of type A produce enterotoxin, which is a heat-labile protein and destroyed immediately at 100 ℃. • Trypsin treatment enhances the toxin activity threefold. • The toxin is produced primarily by type A strains but also by a few type C and D strains. • It disrupts ion transport in the ileum(primarily) and jejunum by inserting into the cell membrane and altering membrane permeability. • As superantigen.

24. Pathogenesis • Tissue degrading enzymes • lecithinase [ toxin] • proteolytic enzymes • saccharolytic enzymes • Destruction of blood vessels • Tissue necrosis • Anaerobic environment created • Organism spreads

25. Without treatment death occurs within 2 days • effective antibiotic therapy • debridement • anti-toxin • amputation & death is rare

26. Gas gangrene • Gas gangrene is a life-threatening disease with a poor prognosis and often fatal outcome. • Initial trauma to host tissue damages muscle and impairs blood supply----lack of oxygenation • Initial symptoms : fever and pain in the infected tissue.; more local tissue necrosis and systemic toxemia. Infected muscle is discolored (purple mottling) and edematous and produces a foul-smelling exudate; gas bubbles form from the products of anaerobic fermentation.

27. Gas gangrene • As capillary permeability increases, the accumulation of fluid increases, and venous return eventually is curtailed. • As more tissue becomes involved, the clostridia multiply within the increasing area of dead tissue, releasing more toxins into the local tissue and the systemic circulation.

28. Food poisoning • Enterotoxin producing strains. • These bacteria are found in mammalian faeces and soil. • Small numbers of the bacteria may also be found in foods and they may propagate rapidly to dangerous concentrations if the food is improperly stored and handled.

29. Food poisoning • more than 108 vegetative cells are ingested and sporulate in the gut, the toxins can act rapidly in the body, causing severe diarrhea in 6-18 hours, dysentery, gangrene, muscle infections • The action of C. perfringens enterotoxin involves marked hypersecretion in the jejunum and ileum, with loss of fluids and electrolytes in diarrhea.

30. Cellulitis, Fasciitis • Cellulitis, Fasciitis • Fasciitis : a rapidly progressive, destructive process in which the organisms spread through fascial plan es. • Fasciitis causes suppuration and the formation of gas • Absense of muscle involvement • rapidity

31. Necrotizing Enteritis • Rare, acute necrotizing process in the jejunum • Abdominal pain, bloody diarrhea, shock, and peritonitis • Mortality: 50% • Beta-toxin-producing C. perfringens type C • Septicemia

32. Who is at risk? • Surgical patients; patient after trauma with soil contamination. • People who ingest contaminated meat products (without proper refrigeration or reheating to inactivate endotoxin)

33. Epidemiology • C. perfringens type A:the intestinal tract of humans and animals, soil and water contaminated with feces. forms spores under adverse environmental conditions and can survive for prolonged periods. • Type B to E strains colonize the intestinal tract of animals and occasionally humans.

34. Epidemiology • Type A: gas gangrene, soft tissue infections and food poisoning • Type C: enteritis; necroticans

35. Laboratory identification • lecithinase production Double Hemolysis Circles

36. C. botulinum

37. Biological Features • Anaerobic • Gram-positive • rod-shaped • sporeformer • produces a protein neurotoxic. • soil, sediments of lakes, ponds, decaying vegetation. • intestinal tracts of birds, mammals and fish.

38. Division ---A, B, C1, D, E, F, and G. ---type A. 62% ---Not all produce toxin. ---C and D not ---G plasmid encoded.

39. Transmission ---spores heat resistant. canning. anaerobic environment ---Botulism eating uncooked foods spores ---GI, duodenum, blood stream, neuromuscular synapses.

40. Virulence factors ---bacterial protease ---light chain,A,50 kDa; heavy chain,100kDa. ---disulfide bond. ---A potent toxin

41. Botulinum toxin • binds peripheral nerve receptors • acetylcholine neurotransmitter • inhibits nerve impulses • flaccid paralysis • death • respiratory • cardiac failure

42. Botulinum toxin • Bioterrorism • not an infection • resembles a chemical attack • 10 ng can kill a normal adult

43. Epidemiology ---4: foodborne, infant, wound, undetermined. ---Certain foods; wound not. ---Foodborne botulism, consumption. ---Infant botulism, 1976, under 12m. ---ingestion, colonize and produce toxin in the intestinal tract of infants. honey. ---increased. ---internationally recognized.

44. Clinical syndromes ---18-36 hours: ---weakness, dizziness,dryness of the mouth. ---Nausea,vomiting. ---Neurologic features: blurred vision, inability to swallow, difficulty in speech, descending weakness of skeletal muscles, respiratory paralysis.

45. Botulism(肉毒中毒) • food poisoning • rare • fatal • germination of spore • inadequately sterilized canned food • home • not an infection

46. Infection with C. botulinum • Neonatal botulism • uncommon • the predominant form of botulism • colonization occurs • no normal flora to compete • unlike adult

47. Wounds • extremely rare • an infection

48. Immunity ---specifically neutralized, antitoxin. ---toxoided, make good antigens. ---does not develop, amount toxic. ---Repeated occurrence. ---Once bound, unaffected by antitoxin. ---circulating toxin ,neutralized , injection of antitoxin. ---treated immediately with antiserum. ---multivalent toxoid,unjustified,infrequency. experimental vaccine.

49. Diagnosis ---by clinical symptoms alone ---differentiation difficult. --- most direct and effective: serum or feces. ---most sensitive and widely used: mouse neutralization test. 48h. Culturing of specimens 5-7d.

50. Treatment • Individuals known to have ingested food with botulism should be treated immediately with antiserum. • antibiotic therapy (if infection) • Vaccination will not protect hosts from botulism, however passive immunisation with antibody is the treatment of choice for cases of botulism.