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Anaerobes

Anaerobes. Environmental Conditions . Obligate Anaerobes only grow in the absence of oxygen (O2) Aerotolerant / Microaerophilic anaerobes grow in reduced concentration of oxygen (~5% O2), but grow best under strict anaerobic conditions . Anaerobic cocci. Peptostreptococcus

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Anaerobes

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  1. Anaerobes

  2. Environmental Conditions • Obligate Anaerobes • only grow in the absence of oxygen (O2) • Aerotolerant / Microaerophilic anaerobes • grow in reduced concentration of oxygen (~5% O2), but grow best under strict anaerobic conditions

  3. Anaerobic cocci Peptostreptococcus Vieonella??? Get correct spelling

  4. Peptostreptococcus (Peptoniphilus) spp. Intestinal gram positive cocci • Causes: • Head, neck , genital and gut infections • Key reactions • Nitrate (+) • SPS –sensitive • Indole (-) P. assacharolyticus Form tetrads or pairs Key reactions : SPS resistant, Indole (+), Nitrate (-) • P. anaerobius • Elongated • Produce sweet odor due to the presence of isocaproic acid

  5. Key reactions • Nitrate (+) • Non-fluorescent, may pigment red Indigenous to oral cavity, upper respiratory, G.I and genitourinary tract Kanamycin (S ) Vancomycin (R ) Colistin (S) Causes : Endocarditis and bacteremia Viellonella species Small Gram negative cocci

  6. Positive Bacilli Clostridium species Others ?????

  7. Clostridium spp. Gram positive rods • Four common species • Clostridium perfringens • Clostridium difficile • Clostridium tetani • Clostridium botulism • Other Clostridium Produce Virulence factors that are responsible for infections • Causes : • Food poisoning • Gas gangrene(myonecrosis) • Neoplasm s • Lock jaw • Pseudomembraneous colitis Spore formers Found commonly in stool specimen

  8. Clostridium perfringens • Appearance: box-shaped gram positive rod • Two zone beta hemolytic on SBA • Produces alpha and Theta toxin • Key reactions: • Lecthinase (+), nitrate (+) • Reverse camp with group B Strep. • Stormy fermentation of litmus milk • Kanamycin (S ), Vancomycin (S), Colistin (R) • Causes: • Gas gangrene, Food poisoning (Enterotoxin A), Soft tissue infections in diabetics and Necrotizing bowel disease

  9. Clostridium difficile • Subterminal spore • Chartreuse fluorescence • Key reactions • Ferment fructose • Lecthinase (-), Lipase (-) • Causes: • Pseudomonas colitis and Antibiotic associated diarrhea (AAD) due to enterotoxin A and B

  10. Clostridium tetani • Toxin: tetanospasmin (neurotoxicexotoxin) • Motile, swarms • Appearance: Gram positive rods. Produce terminal spores that appear as drumsticks • Biochemical reactions: • Lipase (-), Indole (+) • Causes: • Lockjaw, respiratory failure and tetanus neonatorum

  11. Clostridium botulism • Toxin:botulin • Key reaction: • Lipase (+) • Causes: • Botulism: Inhibits acetlycholine release from motor neurons

  12. Other Clostridium spp. Clostridium novyi Clostridium septicum • Beta hemolytic • Key reactions: • Lecithinase (+), lipase (+), indole (-), urease (-) • Causes: Gas gangrene (myonecrosis) and toxic shock • Rapid swarmer • Characteristic: medusa head, subterminal spores • Key reactions: • Lipase (-), Indole (-) • Causes: Neoplasm of the colon, breast leukemia, lymphoma, enterocolitis. myonecrosis

  13. Key reactions • Catalase (-) • Cephalosporin (R) • Vancomycin (R ) • Infections caused: • Bacterial vaginosis • Pelvic inflammatory disease Normal flora in the oral cavity, G.I. and female genital tract Lactobacillus Gram positive Non-spore forming bacilli • Protect female genital tract • Produce lactic acid to • lower vaginal pH

  14. Can cause: • Subacute bacterial endocarditis • Bacteremia • Reactions • Catalase (+) • Indole (+) • Nitrate (+ ) Normal flora of the skin Proprionibacterium acnes Gram positive Non-spore forming bacilli (appear as diptheroids)

  15. Negative Bacilli Bacteroides fragilis Bacteroides ureolyticus Fusobacteriumnucleatum Fusobacteriumnecrophorum Other Fusobacterium Porphyromona spp. Prevotella spp.

  16. Key reactions • Catalase (+) • Indole (-) • Nitrate (-) Bile tolerant, Non-motile Gram negative rod Penicillin (R ) Kanamycin (R ) Vancomycin (R ) Colistin (R ) Clindamycin (S) • Causes : • Inflammation of the intestinal wall • Septic abortion • Thrombosis • G.I. infections Bacteroides fragilis

  17. Key reaction • Urease (+) Bile sensitive, Non-motile Gram negative rod Kanamycin (S ) Vancomycin (R ) Colistin (S) • Causes : • Respiratory infections • Intestinal tract infections Bacteroides ureolyticus

  18. Key reactions • Lipase (-) • Indole (+) Fusiform Gram negative bacilli Kanamycin (S ) Vancomycin (R ) Colistin (S) Causes : Metastatic brain abscess Fusobacteriumnucleatum

  19. Pleomorphic filamentous gram negative rod Causes : Pertonsillar abscess in children and young adult • Key reaction • Lipase (+) Fusobacterium necrophorum

  20. Produces foul odor • Slow producer of • protoporphin Normal flora in the oral, G.I and vaginal area Kanamycin (R ) Vancomycin (R ) Colistin (S) Penicillin (R) Causes : Lung and dental infections Prevotellamelaninogenica Gram negative coccobacilli

  21. Specimen transport and processing • Acceptable specimens : • Aspirates from sterile site deep wounds , bodily fluids (except urine, sputum and saliva), and suprapubic bladder aspirates • Primary media: • Brucella (CDC or Schaedler) blood agar- contains hemin, vitamin K and yeast extract. Detect hemolysis in anaerobes • Special media: • Bacteroides bile esculin (BBE) agar- contains gentamycin (inhibits facultative aerobic gram negative rods ) and 20% bile. • Laked Kanamycin Vancomycin (LKV) blood agar – identify pigmented gram negatives . (Kanamycin inhibits facultative gram negative rods and Vancomycin inhibits gram positive rods) • Phenyl-ethyl Alcohol (PEA) plate : inhibits swarming • Cycloserine cefoxitin fructose (CCFA) agar: selective for Clostridium difficile • Egg yolk agar-selective for Lecithinase and lipase production • Thioglycollate broth: provides reduced O2 environment

  22. Specimen transport and processing • Identification tests : • Catalase test: distinguish aerotolerant anaerobes from anaerobic organisms • Indole: identify organisms that produce tryptophanase (Note: media needs to contain tryptophan) • Nitrate test: • Urea test: identify organisms that produce urease. Observe pH change. Urea is converted to ammonia • Incubate media in anaerobic gas chambers • Contains H2, N2, carbon dioxide , palladium catalyst and desiccants (absorb water) • Keep media for 7 days

  23. Clinical Treatment • Metronidazole –best treatment. Confirms the presence of an anaerobe • Clostridium infection: Use antitoxins , antibiotics (i.e. Chloramphenicol, pipercillin, imipramine or ampicillin/sulbactam) and supportive therapy

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