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Anaerobic bacteria

Anaerobic bacteria. Classification. spore-forming anaerobes Clostridium G + non-spore-forming anaerobes G + , G - cocci, bacilli. Section Ⅰ Clostridium. General characteristics. gram-positive, spore-forming bacilli obligate anaerobes motile -- peritrichous flagella

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Anaerobic bacteria

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  1. Anaerobic bacteria

  2. Classification • spore-forming anaerobes Clostridium G+ • non-spore-forming anaerobes G+, G- cocci, bacilli

  3. Section Ⅰ Clostridium

  4. General characteristics • gram-positive, spore-forming bacilli • obligate anaerobes • motile -- peritrichous flagella (exception: C. perfringens—nonmotile) •  the sporangia– swollen • typical clinical symptoms

  5. Clostridium • C. tetani • C. botulinum • C. perfringens • C. difficile

  6. C. tetani

  7. Characteristics • anaerobic gram-positive rod that forms terminal spores • motile with peritrichous flagella • tetanospasmin

  8. Pathogenicity • portal of entry: wound • conditions of infection regional anaerobic environment • deep and narrow wound, contamination of soil or foreign bodies • necrotic tissues • contamination of aerobes or facultative anaerobes

  9. Pathogenicity • Virulence factors • Tetanospasmin • Protein (neurotoxin) • Heat-labile (65℃, 30min) • Mechanisms

  10. Mechanisms of tetanospasmin toxin → peripheral nerve fibers / lymph and blood → spinal cord and brain stem → inhibitory interneuron → blocks the release of neurotransmitters from the presynaptic membrane of inhibitoryinterneurons→ inhibit the motor neuron → spastic paralysis (rigid paralysis) 麻痹性痉挛 excitatory transmitter: acetylcholine inhibitory transmitter: glycine and γ–aminobutyric acid

  11. Mechanisms of tetanospasmin spastic paralysis (rigid paralysis)

  12. Pathogenicity • Disease-tetanus(neonatal tetanus) latent period: 4-5d ～ several weeks typical symptoms: Opisthotonos Lockjaw, sardonic smile

  13. Pathogenicity • Disease-neonatal tetanus • a frequent cause of death in developing countries • most common causes: cutting the umbilical cord with unsterilized instruments or infection of the umbilical stump • the fatality rate: around 90% • the common death cause: respiratory failure

  14. Immunity • Antitoxin immunity • Weak potent exotoxin rapid combination with target cells • Toxoid vaccine

  15. Control • Proper care of wounds: surgical debridement • Active immunization: tetanus toxoid for children: basic immunization: DPT(diphtheria toxoid, pertussis vaccine, tetanus toxoid) for a high-risk group : toxoid booster • Passive immunization: tetanus antitoxin urgent prevention (along with toxoid) As soon as possible • Special treatment • administration of antibiotics • supportive measures

  16. C. perfringens

  17. Characteristics • Shape and structure • Subterminal endospore • Capsule • Nonmotile

  18. Type α, Alpha β, Beta ε, Epsilon ι, Iota A + B + + + C + + D + + E + + Characteristics • Classification • five toxigenic types (A through E) • αtoxin: the most potent toxin→exhibits lecithinase activity→destroys erythrocytes, leukocytes, and platelets→ hemolysis, tissue necrosis

  19. Stormy fermentation Characteristics • Cultivation anaerobic double zones of hemolysis carbohydrate fermentation (lactose) Inner zone: θ toxin complete Outer zone: α toxin Incomplete

  20. Pathogenicity • Virulence factors • α toxin • produced by all strains • acts as a lecithinase • diagnosis: Nagler reaction--egg yolk agar

  21. Pathogenicity • Virulence factors • Enterotoxin • produced by types A(most), C, and D • heat-labile • Others • collagenase, hemolysin, proteinase, DNase (deoxyribonuclease)

  22. Pathogenicity • Disease • Gas gangrene • Occurrence • Transmission: trauma • Pathogens: 60～80％cases by type A • Manifestation: sudden outset, emphysema, edema, necrotic tissues, foul-smelling, toxemia, shock

  23. Pathogenicity • Disease • Food poisoning • transmission: gastrointestinal tract • pathogens: type A • manifestation: short incubation period (10hrs) diarrhea self-limiting • Necrotizing enteritis • pathogens: type C • highly fatal in children

  24. Control • Care of trauma: debridement • Antimicrobial therapy • Antitoxin • Hyperbaric oxygen • Symptomatic care for food poisoning

  25. C. botulinum

  26. Characteristics • Gram positive rod • Subterminal endospore • Noncapsule • Obligate anaerobe

  27. Pathogenicity • Virulencefactor—botulinum toxin • neurotoxin • relatively heat-labile and resistant to protease • types: A, B, C, D, E, F, G • the most potent toxic material known potassium cyanide(KCN) 10,000 times • mechanism of action Toxin → gut → blood → cholinergic synapses → block the release of exciting neurotransmitter, e.g., acetylcholine → flaccid paralysis

  28. Mechanisms of botulinum toxin flaccid paralysis

  29. Pathogenicity • Disease—Botulism • from Latin botulus, "sausage" Sausages, seafood products, milk, and canned vegetables • Food poisoning • Infant botulism • Wound botulism Honey

  30. Pathogenicity • Disease • Food poisoning • manifestation: flaccid paralysis: double vision, dysphagia, difficulty in breathing and speaking rare gastrointestinal symptoms cause of death: respiratory failure

  31. Pathogenicity • Disease • infant botulism • manifestation: constipation, poor feeding, difficulty in sucking and swallowing, weak cry, loss of head control. Floppy baby • prevention: free of honey

  32. Pathogenicity • Disease • wound botulism • Rare • Transmission: trauma

  33. Medicine Blepharospasm

  34. C. difficile

  35. Pathogenicity • Virulence factor exotoxin A: enterotoxin exotoxin B: cytotoxin • Disease pseudomembranous colitis antibiotic-associated diarrhea

  36. Control • Treatment discontinuation of causative antibiotics administration of sensitive antibiotics • Prevention no vaccine use antibiotics only in necessary

  37. non-spore-forming anaerobes

  38. Characteristics • include both G+ and G- bacilli and cocci. • members of the normal flora • cause: endogenous infection

  39. Non-spore forming anaerobes

  40. Conditions causing disease • Change of habitat • Decrease of host defense • Dysbacteriosis • Local anaerobic environment formation

  41. Characteristics of infections • endogenous infection throughout body, most chronic • nonspecific manifestations, most pyogenic • foul-smelling discharge, sometimes gas formation • direct smear positive, aerobic culture negative • have no response to some antibiotics such as aminoglycisides

  42. Diseases • septicemia • infections in central nervous system • dental sepsis • pulmonary infections • intraabdominal infections • infections of the female genital tract

  43. occurrence development of anaerobic environments (e.g., deep wound) spores → vegetative cells ↓ tissue destruction and necrosis; carbohydrate fermentation and gas (H2; ,CO2) formation and accumulation in the tissue ↓ restrict the blood supply (flow) →increases the tissue necrosis

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