Exam 5

What is the principle of the cytochrome oxidase test?

Combination of alpha naphthyl and N,N-dimethyl-p-phenyldiamine in the presence of O2 forms indophenol blue and water

When is each type of oxidase test used?

The strip test is used for non-fermenters, the drop test is needed for fastidious organisms

What are the ingredients/reagents used in the nitrate test?

N,N-dimethyl-alphanapthylamine, acetic acid, sulfanilic acid, and a 0.1% potassium nitrate broth

Which non-fermenter has peritrichous flagella?

Achromobacter species

Pseudomonas aeruginosa - Key Biochemicals

Lysine negative

Arginine positive

Glucose positive, maltose negative, lactose positive

Pyocyanin on Flo slant

Grows at 42 C

Nitrate positive to gas

Motile (polar flagella)

Acinetobacter - Key Biochemicals

Oxidase Negative

Lysine and Arginine Negative

Maltose Negative

Glucose and Xylose oxidation in beta hemolytic form

Non-motile

Stenotrophomonas maltophilia - Key Biochemicals

Oxidase Negative

Lysine Positive

Arginine Negative

Motile (multiple polar flagella)

Positive for all three sugars, especially maltose

Pasteurella multocida - Key Biochemicals

Drop oxidase positive

Catalase positive

Ornithine positive

Indole positive

Ferments glucose

Nonmotile

What organism is grey and smooth with an indole odor on SBA?

Pasteurella multocida

What medias are used for recovery of B. pertussis?

Bordet-Gengou Agar (glycerol and animal blood)

Regan-Lowe Agar (Charcoal, cephalexin, animal blood, starch, amphotericin B)

Stainer Scholte (Casamino acids)

What media is used for recovery of Legionella?

BCYE

Yeast extract, ferric salts, and L-cysteine promote Legionella growth

Cefamandole covers Gram positives

Polymyxin B covers Gram negatives

Anisomycin is an antifungal

What is the MALDI-ToF matrix?

alpha-cyano-4-hydroxycinnamic acid dissolved in 50% acetonitrile and 2.5% trifluoroacetic acid

When would you need to perform a full extraction on a MALDI-ToF sample?

For identifying a yeast or mucoid organism, or for organisms where conventional testing has failed to give an ID

What organisms can MALDI-ToF mix up?

Streptococcus pneumoniae and Streptococcus mitis

E. coli and Shigella

Klebsiella oxytoca and Raoultella species

Enterobacter cloacae complex species

Streptococcus bovis species

Acinetobacter species

Neisseria polysaccharea and Neisseria meningitidis

Which MALDI-ToF device requires a control to be run each batch?

BioMerieux’s Vitek MS

Which MALDI-ToF device doesn’t have specified controls beyond a monthly calibration?

Bruker’s MicroFlex LT

Which two organisms are known for being rapidly urea positive?

Bordetella bronchiseptica (will grow on EMB or MAC)

Brucella species (won’t grow on EMB or MAC)

Bordetella pertussis - Key Biochemicals

Oxidase Positive

Catalase Positive

Urea Negative

Nitrate Negative

Nonmotile

Won’t grow on SBA or MAC

How are Kingella kingae and Neisseria distinguished?

Kingella kingae is catalase negative; Neisseria are catalase positive

(Both are oxidase positive, grow on Thayer-Martin, and require 5-10% CO2)

What does Francisella tularemia require for growth?

Cysteine, cystine

Which organism is known for “ground glass” colonies on BCYE?

Legionella species

How does Acinetobacter lwoffii differ from Neisseria gonorrhoeae?

It will grow on MAC and EMB

Which organism is known for its characteristic violet pigment on SBA?

Chromobacter violaceum (found in soil and water, causes infection in the immuocompromised)

How can Acinetobacter be differentiated from Moraxella?

Acinetobacter is oxidase negative

Moraxella is oxidase positive

Which organism causes “cat scratch fever?”

Bartonella henselae

Which organism causes '“rat bite fever?”

Streptobacillus monoliformis

Aggregatibacter aphrophilus

Catalase negative (most Haemophilus are catalase positive)

Ferments glucose, sucrose, maltose, and lactose

Associated with endocarditis, bone infection, and joint infection

Aggregatibacter actinomycetemcomitans

Ferments only glucose and maltose

Small, star-shaped colonies on SBA

Associated with endocarditis, dental abscess, rapid jawbone degeneration, and juvenile periodontal disease

Cardiobacterium hominis

Known for forming rosettes on Gram stain

Catalase negative

Indole positive

Doesn’t grow on EMB or MAC

Eikenella corrodens

Known for producing colonies that pit SBA and smell of bleach

Won’t grow on TSIA

Associated with endocarditis, polymicrobial tissue infection, and human bites

Kingella kingae

Poorly decolorizing Gram-negative

Ranges from coccoid to bacillary, may form chains or pairs

Beta hemolysis directly under colonies

Drop oxidase positive

Catalase negative

Endocarditis and pediatric joint infections

Burkholderia pseudomallei

Causes meliodosis

Can lie dormant in the patient for decades

Found in areas around the equator

Requires BSC and Level III precautions

Brucella species

Cause Brucellosis (undulating fever)

Can live in the soil and water for years, and infects a variety of animals

Endemic in the eastern and western hemispheres, particularly in the Middle East