Enterobacteriaceae Flashcards
General biochemical characteristics of Enterobacteriaceae
Gram-negative rod reduce nitrates to nitrites Inability to produce oxidase Facultative anaerobic metabolism (prefers reduced oxygen environment) Fermentation of glucose
Lactose positive Enterobacteriaceae
E. coli
K. pneumoniae
C. freundii
Lactose negative Enterobacteriaceae
P. mirablis
Salmonella
Shigella
Media to know
MacConkey Hektoen Enteric XLD MacSor Tetrathionate TCBS CIN
O Antigens
associated with cell wall; are heat stable and allow for groupings (0157)
K Antigens
associated with capsule around cell wall; responsible for inhibition of agglutination by specific antibody
H Antigens
associated with flagella;
EHEC Enterohemorrhagic E. Coli
produces a deadly bloody diarrhea often associated with Hemolytic Uremic Syndrome, caused by strain 0157:H7 from undercooked beef or raw milk
IMVIC
Indole
Methyl red
Voges proskaur
Citrate
Indole Principle
Determine the presence of the enzyme tryptophanase
Indole Spot Test Result
Positive - blue color within 20 seconds
Negative - no color or slight pink
Indole Results
Positive - pink to wine colored ring
Negative - no color change
Methyl Red/Voges Proskaur Principle
determines ability of an organism to produce and maintain stable acid products from glucose fermentation
MRVP Results
Positive - Red color
Negative - Yellow color
Citrate Principle
To determine the ability to convert citrate to pyruvate
Citrate Results
Positive - growth with or without color change
Negative - Absence of growth
Oxidase Principle
To ID oxidase negative Enterobacteriaceae from other gram negative bacilli
Oxidase Results
Positive - dark purple within 10 seconds
Negative - Absence of color
TSI Results
Acid (A) - yellow
Alkaline (K) - red
H2S production - black
Gas: bubbles
LIA Results
Acid (A) - yellow
Alkaline (K) - purple
H2S - black butt
Deaminase (R) - Red slant
TSI A/A
glucose and lactose or sucrose fermented
TSI K/A
only glucose fermented
TSI K/K
no carbohydrates fermented
LIA K/K/black
LDC pos/glucose neg/H2S positive
LIA K/A
LDC neg/glucose positive
LIA A/A
LDC neg/glucose positive
LIA R/A
LDA pos/glucose pos
E. coli
biochemical features
Lactose +
Oxidase -
Indole +
H2S -
K. pneumoniae
biochemical features
Lactose +
Oxidase -
Indole -
H2S -
C. freundii
biochemical features
Lactose +
Oxidase -
Indole -
H2S +
P. mirablis
biochemical features
Lactose -
Oxidase -
Indole -
H2S +
Salmonella
biochemical features
Lactose -
Oxidase -
Indole -
H2S +
Shigella
biochemical features
Lactose -
Oxidase-
Indole -
H2S -
Y. enterocolitica
biochemical features
Lactose -
Oxidase -
Indole -
H2S -
P. aeruginosa
biochemical features
Lactose -
Oxidase +
Indole -
H2S -
V. cholera
biochemical features
Lactose +
Oxidase +
Indole +
H2S -
Acinetobacter
biochemical features
Lactose -
Oxidase -
Indole -
H2S - -
S. maltophilia
biochemical features
Lactose -
Oxidase -
Indole -
H2S -
E. corrodens
biochemical features
Lactose +/-
Oxidase +
Indole -
H2S N/A
P. multocida
biochemical features
Lactose -
Oxidase +
Indole +
H2S -
L. pneumophilia
biochemical features
Lactose ?
Oxidase +
Indole ?
H2S ?
E. coli Habitat
Normal gut flora
E. coli special media and growth
MacSor to isolate 0157:H7, EMB green metallic sheen
E. coli diseases
UTI, neonatal meningitis, gastroenteritis & nosocomial infections
E. coli notes
Most common clinical isolate
K. pneumoniae habitat
Humans, animals, soil, sewage