Enterobacteriaceae Overview Flashcards
What organism is this?
(Blood Agar)
Proteus mirabilis
Swarming on blood agar
What are the general characteristics of Enterobacteriaceae?
Gram-negative rod shaped organisms
Ability to reduce nitrates to nitrites (NO3->NO2)
Inability to produce the respiratory enzyme oxidase (oxidase negative)
Facultative anaerobic metabolism (prefers oxygen reduced environment)
Fermentation of glucose (glucose positive)
Growth on MacConkey agar
What tests are part of IMViC?
What is a positive result?
Used to identify an organism in the coliform group (a gram negative aerobic/non-aerobic lactose producing rod)
I: Indole- tests organism for indole production
POSITIVE: a pink/red layering forming on the top of the liquid
M: Methyl Red- detects fermentation of glucose based on acids produced
POSITIVE: red color change
V: VP- tests to see if bacteria can produce acetoin from fermenting glucose
POSITIVE: red color change
C: Citrate: determines if an organism can use citrate for it’s sole carbon source
POSITIVE: blue color change
Which Enterobacteriaceae are lactose positive?
- Escherichia*
- Klebciella*
- Enterobacter*
- Citrobacter*
- Serratia marcescens*
Which Enterobacteriaceae are lactose negative?
- Proteus*
- Providentia*
- Salmonella*
- Shigella*
What is the most common clinical isolate?
Eschericha coli
Which Enterobacteriaceae are non-motile?
How would you differentiate these two organisms?
- Klebsiella* (lactose positive)
- Shigella* (lactose negative)
Which organism is a lactose positive H2S producer?
Citrobacter
Are Pseudomonas and Vibro enterobacteriaceae?
NO
Serratia an Yersinia are _________ (common/rare) clinical isolates.
rare
Which lactose positive organism is indole postitive?
E. coli
Which lactose positive organisms are citrate and VP positive?
How would you differentiate between the two?
Klebsiella (non-motile)
Enterobacter (motile)
Describe the Lysine Iron Agar slant test
Tests for glucose fermentation, lysine decarboxylation, lysine deamination, and H2S production.
LIA Slant- interpret slant number 3
purple slant/ purple butt
Alkaline slant/ Alkaline butt
K/K
Lysine decarboxylation
No glucose fermentation
LIA slant- interpret tube #1
Purple slant/ yellow butt
Alkaline slant/ Acid butt
K/A
Glucose fermentation
LIA slant- interpret slant # 2
Red slant/ yellow butt
Red slant/ alkaline butt
R/A
Lysine Deamination
Glucose fermentation
LIA slant- interpret slant #4
H2S production
Describe the Triple Sugar Iron Agar slant
Tests and organisms abilty to ferment glucose, lactose, sucrose and tests for gas production and H2S.
TSI slant- interpret slant number 2
Red slant/ Yellow Butt
Alkaline slant/ acid butt
K/A
Glucose positive (glucose only)
TSI slant- interpret slant #4
Yellow slant/ yellow butt
Acid slant/ Acid butt
A/A
Glucose + Lactose/Sucrose positive
*** this also shows gas production
TSI slant- interpret slant #1
Red slant/ red butt
alkaline slant/ alkaline butt
K/K
No fermentation
TSI slant- interpret slant #3
H2S production
Describe the urea hydrolysis test (Christiansen’s).
What is a positive result?
Tests an organisms ability to produce the enzyme urease.
POS: magenta
NEG: light orange
E. coli is normal flora in which part of the body?
The gut
Most lactose positive gram negative rods will be E. coli if they are also…
Indole +
VP -
Citrate -
Which are the atigenic determinants of E. coli?
What are they associated with?
O antigens- associated with cell wall, heat stable (0157)
K antigens- associated with capsule around cell wall, responsible for inhibition of agglutination by specific antibody
H antigens- associated with flagella (H7)
Pathogenic E. coli is most commonly associated with…
UTI (uropathogenic E. coli)
Neonatal meningitis
Intestinal disease (gastroenteritis)*** 5 classes (or virotypes) now recognized
Nosocomial Infections
E. coli 0157:H7 or EHEC
Gastrointestinal E. coli
most life threatening (O and H antigens)
Selective media: MacConkey Sorbitol (SOR -)
Shiga-toxin producer
Enterohemorrhagic E. coil (EHEC)
Gastrointestinal E. coli
Produces bloody diarrhea often associated with Hemolytic Uremic Syndrom
Enteroaggregative E. coli (EAEC)
Gastrointestinal E. coli
Recovered from children with chronic diarrhea
Enterotoxigenis E. coli (ETEC)
Gastrointestinal E. coli
Produces heat stable (ST) and heat labile (LT) toxins
Traveler’s diarrhea
Enteroinvasive E. coli (EIEC)
Gastrointestinal E. coli
Produces a dysentery-like disease in poor nations
Enteropathogenic E. coli (EPEC)
Gastrointestinal E. coli
Produces a profound diarrhea in infants in poor nations
Klebsiella pneumoniae has ____ and ____ antigens which may be typed.
O and K antigens
Klebsiella pneumonia specimens of choice
urine (UTI)
deep cough (pneumonia)
Citrobacter freundii is normal flora in…….
It causes infrequent cases of…….
human gastrointestinal tract
UTI and RTI
Proteus mirabilis is found in…
manure
sewage
soil
Proteus mirabilis is responsible for…
Antibiotic diarrhea (multiple drug resistance)
UTI
Promotes kidney stones
Abscesses, pyelonphritis, cystis, infant diarrhea
What are the 3 categories of Salmonella?
Gastroenteritis and diarrhea
Bacteremia/ extraintestinal infection
Enteric Fever (typhoid fever)
How does the Kauffman-White scheme of serotyping identify diffrent groups of Salmonell?
heat stable O antigen
heat-liable H antigen
heat-liable Vi antigen
Where is Salmonella commonly found?
What dieseses are associated with it?
Animals- reptiles, pet turtles, fowls
Food- eggs, meat, mayo
Food poisoning
Paratyphoid fever
Bacteremia
Salmonellosis
* Mistaken as Fever of Unknown Origin (FUO)
How long does it take for symptoms to present with Salmonella food poisoning?
Staphylococcal food poisoning?
Salmonella: 10-28 hours
Staphylococcus: 2-6 hours
Shigella are identified ________ with _____antigens.
serologically, O
Shigella sonnei
Host?
Infections?
Humans
Watery diarrhea (crowding and unsanitary conditions)
Shigellosis (from fecally contaminated water or food)
** Produce potent toxins, no bacteremias
Yersinia enterocolitica
Reservoir?
Infections?
Dogs, cats, rodents, pigs, cattle
Food/Drink vehicle
Infection mimics appendicitis
Agar?
Organism?
Colony Appearance?
CIN
Yersinia
Dark-red bullseye colonies
