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Fastidious Gram Negative Rods Blood Culture Unit

Please click audio icon to hear Carol’s narration. Fastidious Gram Negative Rods Blood Culture Unit. Division of Medical Technology Carol Larson MSEd, MT(ASCP). Click icon for audio. General Information. Fastidious Complex / extensive nutrient requirements

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Fastidious Gram Negative Rods Blood Culture Unit

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  1. Please click audio icon to hear Carol’s narration Fastidious Gram Negative RodsBlood Culture Unit Division of Medical Technology Carol Larson MSEd, MT(ASCP)

  2. Click icon for audio General Information • Fastidious • Complex / extensive nutrient requirements • Faint staining Gram Negative Rods • Safranin counterstain for >2 minutes • Substitute carbolfuschin for safranin • Serological testing useful

  3. Click icon for audio Brucella speciesClinical Significance • Causes Brucellosis / Undulant fever / Malta fever • Transmission via: • Direct contact with infected animals • Ingestion of contaminated meat or dairy products • Inhalation of the aerosolized organism • Facultative intracellular organism

  4. Click icon for audio Brucella speciesSpecimen Collection • Blood, bone marrow or tissue • Risk of lab acquired infection • Specify on requisition when suspecting Brucella • BAP, CHOC, BCYE, Blood Culture broth

  5. Click icon for audio Brucella speciesGrowth Characteristics • 35C, 5-10% CO2 for 21 days • Colony morphology • Growth at 7 days • BAP = smooth glistening, translucent colonies that become brown with age

  6. Click icon for audio Brucella speciesIdentification • Gram stain: tiny, faint staining gram negative coccobacilli • Oxidase +, Catalase + • Nitrate + • Glucose oxidizer • Nonmotile • Additional tests to speciate

  7. Click icon for audio Brucella speciesSerological Testing • Tube agglutination test • Single titer of >=1:160 • Fourfold rise in titer between acute and convalescent specimens • Does not detect Brucella canis

  8. Click icon for audio Brucella speciesTreatment and Prevention • Doxycycline and rifampin for 6 weeks

  9. How long must cultures be held when Brucella is suspected? Culture plates and media must be held for at least 21 days because Brucella is a slow grower.

  10. Click icon for audio Eikenella corrodensClinical Significance • Normal flora of mouth, respiratory & GI tracts • Opportunistic pathogen • Associated with: • Dental / periodontal and head / neck infections / abscesses • Human bite wounds • Septicemia following tooth extraction • Endocarditis

  11. Click icon for audio Eikenella corrodensSpecimen Collection • Aerobic • Requires hemin • BAP, CHOC

  12. Click icon for audio Eikenella corrodensGrowth Characteristics • Tiny colonies at 48 hrs • Colony morphology • BAP • “Pits" the agar • Pale yellow pigment • Greening around colony • Bleach odor • MAC – no growth

  13. Click icon for audio Eikenella corrodensIdentification • Small, slender Gram Negative Bacilli • Oxidase + • Catalase – • Glucose non-oxidizer (asaccharolytic) • Nitrate + • Nonmotile

  14. Click icon for audio Eikenella corrodensTreatment and Prevention • Susceptibility testing not routinely done • Treat with: • Penicillins • 3rd generation cephalosporins • Tetracycline • Quinolones

  15. What are the key identifying characteristics for Eikenella corrodens? It pits the agar and has a bleach smell on BAP at 48 hours, it will not grow on MAC, it is oxidase positive, catalase negative, glucose N“F”/N“O”, and nitrate positive.

  16. Click icon for audio HACEK GroupOrganisms • Haemophilus aphrophilus • Actinobacillus actinomycetemcomitans • Cardiobacterium hominis • Eikenella corrodens • Kingella kingae

  17. Click icon for audio HACEK GroupClinical Significance • Subacute bacterial endocarditis • Blood Cultures • Subculture to various enriched media and hold for extended time beyond 1 week • BCYE

  18. What organisms are included in the HACEK group? Haemophilus aphrophilus Actinobacillus actinomycetemcomitans Cardiobacterium hominis Eikenella corrodens Kingella kingae

  19. Click icon for audio Fastidious GNRSummary • Looked at several organisms • Clinical significance • Specimen collection, transport & processing • Growth characteristics & identification • Serological testing • Treatment and prevention

  20. Who am I? BAP, growth appears at 7 days Gram Stain Causes Undulant Fever Brucella species

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