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ANAEROBES

ANAEROBES. DEFINITIONS. OBLIGAETE ANAEROBE Lack superoxide dismutase and/or catalse toxic radicals formed by oxidative enzymes kill organisms AERO-TOLERANT ANAEROBES survive in presence of oxygen Do not use oxygen for energy requirements FACULTATIVE ANAEROBES .

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ANAEROBES

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  1. ANAEROBES

  2. DEFINITIONS • OBLIGAETE ANAEROBE • Lack superoxide dismutase and/or catalse • toxic radicals formed by oxidative enzymes kill organisms • AERO-TOLERANT ANAEROBES • survive in presence of oxygen • Do not use oxygen for energy requirements • FACULTATIVE ANAEROBES

  3. ANAEROBES OF CLINICAL IMPORTANCE • CLOSTRIDIA • C tetani; C perfringens; C difficile; C botulinum • BACTEROIDES • B fragilis; • Prevotella • Porphyromonas • ACTINOMYCES • FUSOBACTERIUM • ANAEROBIC STREPTOCOCCI

  4. CLOSTRIDIA • Gram positive spore forming bacilli • ubiquitous • intestines of manand animals • animal and human faeces contaminated soil and water • Several species associated with human disease

  5. Pathogenesis of anaerobic infections • Contamination of site with spores • Factors which promote anaerobiasis • ‘crush’ injuries with interruption of blood supply, contaminaton with foreign bodies (dirt), tissue damage • Germination of spores • Toxin release • Binding of toxin to receptor • Resulting effect produces symptom(s) of disease

  6. Clostridium perfringens • Large rectangular Gram positive bacillus • Spores seldom seen in vivo or in vitro • non motile • Produces several toxins • alpha (lecithinase), beta, epsilon ...... • enterotoxin • Causes a spectrum of human diseases • Bacteraemia • Myonecrosis • food poisoning • enteritis necrotica (pig bel)

  7. Diagnosis • Myonecrosis • clinical • Gram stain of exudate - typical organisms no pus cells • Culture -growth of C perfringens (and/or other clostridia associated with this clinical condition) • Food poisoning • abdominal pain, diarrhoea and vomiting 8-18 hours after a suspect meal. Self limiting • Enteritis necroticans • severe abdominal pain, bloody diarrhoea , shock and peritonitis (C perfringens type C)

  8. Treatment and prevention • Myonecrosis • Proper wound debridement and ensure adequate blood supply • Penicillin • antitoxin and hyperbaric oxygen - no proven value • Food poisoning • Proper preparation and storage of food • self limiting disease -antibiotics not indicated • Enteritis necroticans • Proper cooking of food • immunization of susceptible population

  9. Clostridium tetani • Small motile spore forming gram positive bacillus with round terminal spores • Causes tetanus • Pathogenesis: • produces tetanospasmin during stationary phase which is released when cell lysis occurs • heavy chain binds to ganglioside on neuronal membranes • toxin internalized and moves from peripheral to central nervous system by retrograde axonal transport • crosses synapse and localized within vesicles • acts by blocking release of inhibitory neurotransmittors (eg GABA)

  10. TETANUS • Clinical syndromes due to unregulated excitatory synaptic activity resulting in spastic paralysis • Generalised tetanus • Neonatal tetanus • localized tetanus

  11. Prevention and treatment • Active immunization with tetanus toxoid • Wound toilet and active/passive immunization of ‘risk’ injuries • management of wound • tetanus toxoid • Anti-tetanus serum (ARS -horse serum) or Human Tetanus ImmunoGlobulin (HTIG) • Penicillin or Metronidazole • Management of patient with tetanus • reduce stimuli • respiratory and CVS support

  12. Clostridium difficile • Associated with human disease in mid-1970’s • Found in human GIT in small numbers • With antibiotic use, increase in number in GIT • Clindamycin, ampicillin, cephalosporins ....... • Produces 2 entero toxins • Toxin A -enterotoxin & Toxin B -cytotoxin • Diagnosis • Detection of toxins in stools, culture of organism • Clinical - AAC Pseudomembranous colitis • Treatment • omit antibiotic if possible • oral vancomycin (125mg qds or metronidazole

  13. Clostridium botulinum • Fastidious spore forming anaerobic gram positive bacillus • Produces 8 antigenically distinct toxins • Human disease described with types A, B & E • Heavy chain binds to ganglioside receptor • Toxin internalized and prevents release of acetyl choline from vesicles • Clinical • Food borne botulism (weakness, dizziness, ocular palsy and progressive flaccid paralysis) • infant botulism (floppy baby) • wound botulism

  14. ANAEROBIC GRAM NEGATIVE BACILLI • Bacteroides, Prevotolla, Porphyromonas and Fusobacterium • Present in GI tract -form large component of normal flora • >80% of human infections associated with B fragilis • virulence factors - capsule, LPS, agglutinins and enzymes • Clinical - Endogenous infections • Intra-abdominal pyogenic infections • pleuro-pulmonary infctions • genital infection

  15. ACTINOMYCES • Strict anaerobic Gram positive bacilli typically arranged in hyphae which fragment into short bacilli • Normal flora of upper respiratory tract, GI tract and female genital tract. • Low virulence • produce disease when mucosal barrier isbreached (eg: following dental trauma or surgery) ENDOGENOUS • Establishes chronic infection that spreads through normal anatomical barriers • Clinical -cervicofacial, abdominal and thoracic • Diagnosis: • Gram stain of ‘sulpher’ granules • culture • Treatment - surgery and long term penicillin

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