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

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Presentation on theme: "Fastidious Gram Negative Rods Blood Culture Unit Division of Medical Technology Carol Larson MSEd, MT(ASCP) Please click audio icon to hear Carol’s narration."— Presentation transcript:

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

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

4 Brucella species Clinical 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 Click icon for audio

5 Blood, bone marrow or tissue Risk of lab acquired infection Specify on requisition when suspecting Brucella BAP, CHOC, BCYE, Blood Culture broth Click icon for audio Brucella species Specimen Collection

6 35C, 5-10% CO 2 for 21 days Colony morphology –Growth at 7 days –BAP = smooth glistening, translucent colonies that become brown with age Click icon for audio Brucella species Growth Characteristics

7 Gram stain: tiny, faint staining gram negative coccobacilli Oxidase +, Catalase + Nitrate + Glucose oxidizer Nonmotile Additional tests to speciate Click icon for audio Brucella species Identification

8 Tube agglutination test –Single titer of >=1:160 –Fourfold rise in titer between acute and convalescent specimens Does not detect Brucella canis Click icon for audio Brucella species Serological Testing

9 Doxycycline and rifampin for 6 weeks Click icon for audio Brucella species Treatment and Prevention

10 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.

11 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 Click icon for audio Eikenella corrodens Clinical Significance

12 Eikenella corrodens Specimen Collection Aerobic Requires hemin BAP, CHOC Click icon for audio

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

14 Eikenella corrodens Identification Small, slender Gram Negative Bacilli Oxidase + Catalase – Glucose non-oxidizer (asaccharolytic) Nitrate + Nonmotile Click icon for audio

15 Susceptibility testing not routinely done Treat with: –Penicillins –3rd generation cephalosporins –Tetracycline –Quinolones Click icon for audio Eikenella corrodens Treatment and Prevention

16 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.

17 H aemophilus aphrophilus A ctinobacillus actinomycetemcomitans C ardiobacterium hominis E ikenella corrodens K ingella kingae Click icon for audio HACEK Group Organisms

18 Subacute bacterial endocarditis Blood Cultures Subculture to various enriched media and hold for extended time beyond 1 week –BCYE Click icon for audio HACEK Group Clinical Significance

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

20 Looked at several organisms Clinical significance Specimen collection, transport & processing Growth characteristics & identification Serological testing Treatment and prevention Click icon for audio Fastidious GNR Summary

21 Who am I? BAP, growth appears at 7 daysGram Stain Brucella species Causes Undulant Fever


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