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
K. pneumoniae diseases
Rarely pathogenic in healthy population, but severe pneumonia in compromised population
K. pneumoniae notes
Non motile
C. freundii habitat
Environment
C. freundii diseases
Associated with hospitalized and compromised patients, URI and RTI
C. freundii notes
Only lactose + H2S producer
P. mirablis habitat
Moist environments
P. mirablis diseases
Antibiotic resistant diarrhea, chronic UTIs, kidney stones
P. mirablis notes
Swarms on blood and chocolate (*vulgaris strain indole pos)
Salmonella habitat
Environment
Salmonella special media
SS agar, tetrathionate broth
Salmonella Diseases
Gastroenteritis/diarrhea, bacteremia/extraintestinal infections, typhoid fever
Salmonella Notes
Only lactose - H2S producer
Shigella habitat
Not normal flora
Shigella special media
SS agar, tetrathionate broth
Shigella diseases
Diarrhea, dysentery
Shigella notes
Non motile
Y. enterocolitica habitat
Domesticated animals, not normal human flora
Y. enterocolitica special media
CIN agar
Y. enterocolitica diseases
infections of wounds, joints, UTI
P. aeruginosa habitat
Environmental, not normal human flora
P. aeruginosa special media or growth
Cetrimide agar, growth at 42 degrees C
P. aeruginosa diseases
Opportunistic and nosocomial infections; folliculitis, otitis externa, cystic fibrosis, UTI, septicemia.
P. aeruginosa notes
Resistant to antimicrobials. Common in soil/water. Colonies blue-green, has grapelike odor
V. cholera habitat
Not normal flora
V. cholera special media or growth
Yellow colonies on TCBS
V. cholera diseases
Rice water stools
V. cholera notes
not normal flora, contaminates water
Acinetobacter habitat
Environment, may be normal in patients
Acinetobacter Diseases
Nosocomial, esp. during warm months, UTIs, respitory, wounds, soft tissue and bacteremia
Acinetobacter notes
Major outbreak during Iraq and Afghanistan wars
S. maltophilia habitat
Environment, may be normal in patients
S. maltophilia diseases
Opportunistic and nosocomial
S. maltophilia notes
Intrinsic resistance to antibacterials, ammonia odor
E. corrodens habitat
Normal flora of mouth and GI tract
E. corrodens Diseases
Bite wounds, head and neck infections, pneumonia aspirations, endocarditis (slow to develop)
E. corrodens notes
bleach like odor, pitting or corrosion of agar
P. multocida habitat
wild animals, nasopharynx and GI
P. multocida diseases
Bite or scratch or animal exposure leads to soft tissue infections, systemic; meningitis, endocarditis, septicemia
P. multocida notes
may have mushroom or musty odor
L. pneumophilia habitat
Community & nosocomial acquired
L. pneumophilia growth or media
serotyping required, growth on BYCE
L. pneumophilia diseases
Acute pneumonia w/non productive cough, myalgia, diarrhea, hyponatremia, elevated liver enzymes
E. coli media growth
Blood - growth
Mac - LF - flat dry pink colonies
XLD - yellow
HE - yellow
K. pneumoniae media growth
Blood - growth; mucoid
Mac - LF, mucoid
HE - Yellow
XLD - Yellow
C. freundii media growth
blood - growth
Mac - Late LF
HE - no color
XLD - Red or yellow with black center
P. mirablis media growth
blood - swarm growth
Mac - NLF, swarm
HE - no color
XLD - yellow or colorless with black center
Salmonella media growth
blood - growth
Mac - NLF
HE - green blk center
XLD - red w/blk center
Shigella media growth
blood - growth
Mac - NLF, flat w/jagged edges
HE - Green
XLD - colorless
Y. enterocolitica media growth
Mac - NLF; may be colorless to peach
HE - Salmon
XLD - yellow or colorless
P. aeruginosa media growth
Mac - NLF
HE - Colorless, media turns dark blue
XLD - pink, flat rough colonies
Which test in the IMViC will indicate glucose fermentation byproducts?
Methyl Red/Vioges Proskaur
Which organism appears to swarm on BAP?
P. mirabilis
Which organism may exhibit a red pigment on BAP, that differentiates it from other Enterobacteriaceae
S. marcescens
Which organisms in the Enterobacteriaceae family will be subject to serotyping to confirm their identity? Which antigens are involved?
Salmonella, O, H, and K
Which organisms exhibits slow lactose fermentation?
C. freundii
Which organism produces a characteristic mucoid colony?
K. pneumonia
Which biochemical reactions would you use to differentiate Proteus spp. from Salmonella spp.?
Urea test?
How would you differentiate Klebsiella spp. from Enterobacter spp?
Motility
Which test would differentiate P. mirabilis from P. vulgaris
Indole
Name the only lactose fermenting, H2S producer in the family of Enterobacteriaceae.
Citrobacter
Name special selective agars for E. coli 0157:H7, Y. enterocolitica, V. vulnificus, Salmonella and Shigella, B. cepacia
NEED ANSWER!!!
Which organism produces a distinctive purplish hue on MacConkey? Is this lactose fermentation
Acinetobacter spp. and no
How would you differentiate an organism like S. maltophilia from Acinetobacter spp. or Pseudomonas spp.
NEED ANSWER!!!
What are the pigments produced by P. aeruginosa?
NEED ANSWER!!!
How can P. aeruginosa be distinguished from fluorescent pseudomonads?
NEED ANSWER!!!
How would an LIA slant help you differentiate P. aeruginosa from V. parahemolyticus?
NEED ANSWER!!!
What odors are associated with P aeruginosa and S. maltophilia
P. aeruginosa - grapelike or corn-tortilla
S. maltophilia - ammonia
What characteristic color may be associated with Acinetobacter on Mac?
Purple
How does salmonella spp. appear on HE and Mac plates?
HE - green w/black center
Mac - NLF
How does E. coli appear on HE and Mac plates?
HE - orange
Mac - fluorescent pink