Gram Negative Rods

What are the gram negative bioterrorism agents?

• Brucella spp

• Francisella tularensis

• Yersinia pestis

What are the human pathogen of Brucella?

• B. melitensis (Goat/ sheep)

• B. abortus (Cattle)

• B. canis

• B. suis

What is important about Brucella and blood cultures?

Slow growers, blood cultures are kept for 4 weeks

What are key characteristics to identify Brucella?

• Nonmotile gram negative small coccobacilli

• Oxidase, nitrate, urease and catalase positive

What disease does Francisella tularensis cause?

Tularemia (aka tick fever, deerfly fever ect)

Where does F. tularensis lives in the body and what is it classified as?

Macrophages; agent of bioterrorism

What are key characteristics to identify Francisella tularensis?

• Poorly staining gram-negative tiny pleomorphic coccobacilli

• Non-motile

• Requires cysteine for growth

• Strict aerobes, poor growers

• Can grow on Thayer-Martin medium, BCYE

• Catalase positive

• Oxidase and Urease negative

What media would you grow Francisella tularensis?

Thayer-Martin medium BCYE

Which sps are group II?

• Aeromonas hydrophila

• Pleisiomonas shigelloides

• Vibrio spp

What is the shared characteristics for Group II?

• Glucose fermenters

• MacConkey positive

• Oxidase positive

Which species are in group III?

• Achromobacter xylosoxidans

• Acinetobacter spp

• Alcaligenes faecalis

• Burkholderia spp

• Chryseobacterium spp

• Psudomonas

• Sheanella putrefaciens

• Stentrophomonas maltophilia

What is the shared characteristics of group III?

Gram negative rods: Non-fermenters

Which strain in Vibrio causes cholera?

V. cholerae

What is the specific media do you use to culture Vibrio sp?

TCBS (Thiosulfate-Citrate-Bile salt-Sucrose)

What are key aspects of Vibrio sps?

• Halophiles

• Oxidases Positive

• TCBS selective media for this sp

What are the 4 key characteristics for P. aeruginosa?

1) Metallic sheen on BAP

2) Corn / grape smell

3) Beta hemolytic

4) Oxidase positive

What is AST?

Antimicrobials susceptibility testing

What is the characteristics of group 4?

Gram negative Rods, fastidious, nonculturable or difficult to culture and/or identify

Which species are in group 4?

• Bordetella spp

• Camplylobacter spp

• Chlamydia

• Haemophilus spp

• HACEK group

• Legionella spp

• Mycoplasma

• Pasteurella sp

• RIckesttsia sp

• Spirochetes

Which gram negative rod sp won’t grow on MAC?

P. multocida

What are key characteristics of Camplobacter?

Grows 42C

What is the key characteristic of Helicobacter pylori?

Strong Urease production

What is the organism responsible for B. pertussis?

B. pertussis

When would you use buffered charcoal yeast extract agar?

To isolate Legionella spp

Which two species are needed for a satellite test?

Haemophilus + S. aureus

What is the principle behind growing Haemophilus spp?

Haemophilus spp requires either X factor (hemin) or V factor (NAD) or both to grow out on a plate

Which Haemophilus sp requires both X and V factor?

H. influenzae

Which Haemophilus sp requires only V factors?

H. parainfluenzae

What does HACEK stand for?

• Aggregatibacter (Haemophilus) aphrophilis

• Aggregatibacter (Actinobacillus) actinomycetemcomitans

• Cardiobacterium hominis

• Eikenella corrodens

• Kingella spp

What disease does the HACEK group cause?

Endocarditis (inflammation of the heart)

What are characteristics of HACKE group?

• Gram negative bacilli

• Need 5-10% CO2 for growth

• Usually flora of oral cavity