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Learn about classifications, characteristics, and pathogenicity of anaerobic bacteria, focusing on Clostridium species like C. tetani, C. botulinum, C. perfringens, and C. difficile. Discover mechanisms, diseases like tetanus and botulism, and control strategies.
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Classification • spore-forming anaerobes Clostridium G+ • non-spore-forming anaerobes G+, G- cocci, bacilli
General characteristics • gram-positive, spore-forming bacilli • obligate anaerobes • motile -- peritrichous flagella (exception: C. perfringens—nonmotile) • the sporangia– swollen • typical clinical symptoms
Clostridium • C. tetani • C. botulinum • C. perfringens • C. difficile
Characteristics • anaerobic gram-positive rod that forms terminal spores • motile with peritrichous flagella • tetanospasmin
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
Pathogenicity • Virulence factors • Tetanospasmin • Protein (neurotoxin) • Heat-labile (65℃, 30min) • Mechanisms
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
Mechanisms of tetanospasmin spastic paralysis (rigid paralysis)
Pathogenicity • Disease-tetanus(neonatal tetanus) latent period: 4-5d ~ several weeks typical symptoms: Opisthotonos Lockjaw, sardonic smile
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
Immunity • Antitoxin immunity • Weak potent exotoxin rapid combination with target cells • Toxoid vaccine
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
Characteristics • Shape and structure • Subterminal endospore • Capsule • Nonmotile
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
Stormy fermentation Characteristics • Cultivation anaerobic double zones of hemolysis carbohydrate fermentation (lactose) Inner zone: θ toxin complete Outer zone: α toxin Incomplete
Pathogenicity • Virulence factors • α toxin • produced by all strains • acts as a lecithinase • diagnosis: Nagler reaction--egg yolk agar
Pathogenicity • Virulence factors • Enterotoxin • produced by types A(most), C, and D • heat-labile • Others • collagenase, hemolysin, proteinase, DNase (deoxyribonuclease)
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
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
Control • Care of trauma: debridement • Antimicrobial therapy • Antitoxin • Hyperbaric oxygen • Symptomatic care for food poisoning
Characteristics • Gram positive rod • Subterminal endospore • Noncapsule • Obligate anaerobe
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
Mechanisms of botulinum toxin flaccid paralysis
Pathogenicity • Disease—Botulism • from Latin botulus, "sausage" Sausages, seafood products, milk, and canned vegetables • Food poisoning • Infant botulism • Wound botulism Honey
Pathogenicity • Disease • Food poisoning • manifestation: flaccid paralysis: double vision, dysphagia, difficulty in breathing and speaking rare gastrointestinal symptoms cause of death: respiratory failure
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
Pathogenicity • Disease • wound botulism • Rare • Transmission: trauma
Medicine Blepharospasm
Pathogenicity • Virulence factor exotoxin A: enterotoxin exotoxin B: cytotoxin • Disease pseudomembranous colitis antibiotic-associated diarrhea
Control • Treatment discontinuation of causative antibiotics administration of sensitive antibiotics • Prevention no vaccine use antibiotics only in necessary
Characteristics • include both G+ and G- bacilli and cocci. • members of the normal flora • cause: endogenous infection
Conditions causing disease • Change of habitat • Decrease of host defense • Dysbacteriosis • Local anaerobic environment formation
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
Diseases • septicemia • infections in central nervous system • dental sepsis • pulmonary infections • intraabdominal infections • infections of the female genital tract
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