Exam 2 - Enterobacteriaceae Flashcards
Which pathogen is the most common cause of nosocomial infections:
E. coli
Describe the colony appearance of Entero on SBAP and CAP:
large, gray, smooth colonies
Entero are all oxidase ____::
negative
Most entero are catalase____, the exception is _____ ______:
most are catalase+
Shigella dysenteriae is catalase-
List the 11 opportunistic EB pathogens:
Hint: CCEEEEHKMPS
Citrobacter Cronobacter Edwardsiella Enterobacter Escherichia coli Ewingella Hafnia Klebsiella Morganella Proteus Serratia
List the 3 EB intestinal pathogens:
Salmonella
Shigella
Yersinia
List the 5 EB that ferment lactose:
Hint: CEEEK
Citrobacter E. coli Enterobacter aerogenes Enterobacter cloacae Klebsiella pneumoniae
List the 5 EB that do NOT ferment lactose:
Hint: PSSSY
Proteus Salmonella Shigella Serratia marcescens Yersinia enterolitica
Which Shigella species does contain beta-galactosidase but not permease, and is therefor a LATE fermenter:
Shigella sonnei
List the two enzymes required to ferment lactose and what they do:
1) permease (allows lactose to penetrate bacterial cell wall)
2) Beta-galactosidase (hydrolyzes lactose to glucose + galactose)
These are defined as non-pathogenic strains of microorganisms, commonly used as bacterial indicators of food/water sanitation:
coliforms
Citrobacter, Enterobacter, Escherichia, Klebsiella, Serratia
T/F
Coliforms are rod shaped, Gram-, non-spore forming bacteria which can ferment lactose with production of acid and gas:
True
T/F
An example of horizontal transmission of disease would be nosocomial infections:
True.
person to person
What type of infection is caused when normal flora get into normally sterile body sites:
Endogenous
Is food poisoning from Salmonella or Shigella considered endogenous infections:
No.
S and S are not normal flora.
95% of all EB isolated are which 3 species:
1) E. coli
2) Klebsiella pneumoniae
3) Proteus mirabilis
(>99% of all isolates belong to 23 species)
List the 3 EB that are non- motile:
Hint: KSY
- Klebsiella
- Shigella
- Yersinia
EB all grow well on ___ and ____:
SBAP
CAP
T/F
Enterics from sterile body sites are not significant.
False. They are highly significant.
MacConkey agar is selective for ______ and differential for _____:
Selective for Gram- rods (inhibits Gram+)
Differential for lactose fermentation
What are the two additives in MacConkey besides lactose:
Bile salts
Crystal violet
If you see H2S concentrated between slant/butt, think this:
Salmonella typhae
What differentiates both Proteus species:
P. mirabilis: Indole-
P. vulgaris: Indole+
What is used to differentiate E. coli O157:H7 from other E. coli species:
O157:H7 does not ferment sorbitol (which would create clear colonies) on MacConkey w/ Sorbitol media)
How can EHEC be differentiated from dysentery caused by Shigella:
EHEC stool does NOT contain leukocytes
Treatment of ETEC, EIEC, EPEC, EHEC, and EAEC commonly involves _____, and use of of antibiotics is sometimes _____:
rehydration
Antibiotic use may be contraindicated due to acquired resistance
What is a similar infection to EHEC:
-STEC
Shiga like toxin producing E. coli
(the cytotoxin is similar to Shigella dysenteriae)
How is EHEC identified:
Serotyping O and H antigens
UTI’s account for ___% of nosocomial infections:
35%
Urine should be plated on ____ and ___ within _____ or refrigerated:
SBAP
MacConkey
30 minutes
The presence of 3+ different colonies on urine culture plate=
contamination, not worked up
What type of plate would be used to detect E. coli and Enterococcus in urine:
CHROMagar Orientation plates
allows for distinct colony morphologies, do not need additional testing
T/F
Suprapubic and cytoscopy urine speciments should be sterile:
True.
Any organism growing should be worked up.
Is it acceptable for clean-catch midstream and catheterized urine specimens to contain contaminants in low numbers:
Yes
What are the two species of Salmonella:
S. enterica (human)
S. bongori (animal)
Salmonella has more than 2500 _____:
serotypes
reflects the extensive diversity of the O and H antigens Salmonella posesses
List the 3 very important serotypes of the Salmonella subspecies enterica:
- Typhimurium (Group B)
- Enteriditis (Group D)
- Typhi
List the results of the following for Salmonella on TSI: Slant: Butt: Gas: H2S:
K/A Gas+ H2S+
What is thought to blame for the 1985 salmonellosis outbreak in Illinois:
contaminated milk
antimicrobials in the cows may have led to the resistant strains
Which two serotypes of Salmonella are associated with food poisoning:
- Typhimurium
* Enteriditis (most common in US)
T/F Salmonella type enteriditis can only infect the shell of an egg:
False. It can infect chicken ovaries and get inside egg before it is formed.
This Salmonella serotype only lives in humans, but is not normal flora, is spread via human feces/contamination, and can spread to vasculature:
Salmonella typhi
Typhoid Fever
List the results of the following tests for Salmonella serotype Typhi: H2S: Citrate: Ornithine decarboxylase: Gas from glucose:
H2S: Trace amounts at butt/slant interface
Citrate-
Ornithine decarboxylase-
Gas-
T/F
Death rates of Typhoid Fever are 12-30% w/out treatment, and people can become carriers for 2-3 months, but vaccinations are available:
True
T/F A large quantity of Shigella organisms is required to cause dysentary infection:
FALSE.
As little as 10 organisms is sufficient to cause infection..
This is the most fastidious of the EB, and grows well on MacConkey’s, HE, XLD agar:
Shigella
How many subgroups of Shigella are there:
4 *S. dysentariae *S. flexneri *S. boydii *S. sonnei Each has additional serotypes based on the O antigen
Shigella species have serotypes based on which antigen:
O antigen
TSI slant agar has more ___ and ____ than ____:
10x more lactose and sucrose than glucose
What results in the TSI slant with Salmonella and Shigella:
Initially converts to yelllow, but reverts back to red (alkaline) when read in 18-24 hours.
Why do Shigella and Salmonella turn TSI yellow, and then back to red:
Ferments glucose to yellow- when glucose is used up, oxidation of peptones occurs, forming amines, which are basic.
What color is the TSI butt with Salmonella/Shigella and why:
It remains yellow, because no O2 to oxidize peptones.
S/S can ferment glucose, but not lactose or sucrose. (there is much less glucose in TSA)
How do you inoculate TSI:
Stab to bottom and streak slant surface
Can TSI be used for definitive ID:
No. Additional biochemical tests must be performed.
How do you report TSI results:
slant/butt/gas/H2S
What are the incubation requirements for EB:
35 degrees in ambient air or increased CO2
Do most labs perform Gram stains of stool specimens: why:
No, because non-pathogenic intestinal flora look similar to enteric pathogens.
(Though presence of WBC/s could indicate invasive pathogen)
What is the ONPG good for:
Distinguishing late lactose fermenters from non-fermenters.
Green colony w/ black center on HE:
Salmonella
What is the media of choice for Yersinia:
CIN agar
Presumptive ID of E. coli strains is based on what characteristic:
Spot indole +
What 3 pathogens should labs always screen for in stool:
Campylobacter
Salmonella
Shigella
What makes plasmids a virulence factor:
They contain DNA distinct from chromosomal DNA, which may mediate antibiotic resistance
List the 3 virulence antigens and their location:
O (somatic, cell wall)
H (flagellar)
K (capsular)
Which antigens are heat labile, which are heat stable:
O –> heat stable
H–> heat labile
K–> heat labile
H antigens can be used to for ___ and ___:
E. coli
Salmonella
O antigens can be used for ___, ____, and ___:
E. coli
Salmonella
Shigella
K antigen is used to type ____, ____, etc:
Klebsiella pneumoniae
K1 antigen of E. coli
Presumptive ID for E. coli includes: Gram\_\_\_ \_\_\_ Oxidase Indole Growth on \_\_\_\_ Definitive includes: \_\_\_\_ hemolysis OR Lactose\_\_\_ AND PYR\_\_\_\_\_
Gram- rods
Oxidase-
Indole+
Growth on MacConkey
Beta hemolytic
Lactose+
PYR-
Describe the morphology of E. coli:
dry, pink (lactose+) colony with surrounding pink are on MacConkey
List the TSA slant results of E. coli: Indole Methyl red Simmons citrate Voges-Proskauer
A/A Gas+ H2S- Indole+ Methyl red+ Simmons citrate - Voges-Proskauer-
What differentiates the KIA from TIA:
KIA: glucose, lactose
TIA: glucose, lactose, sucrose
Which sugar in TIA is in the least amount:
glucose
What has a safety pin appearance on Gram stain, and from what group:
Yersinia spp.
EB group
Growth of this on CIN yields bullseye colonies, dark red center with surrounding clear halo:
Yersinia enterocolitica
EB group
This is a slow lactose fermenter, opportunistic organism from the EB group that can cause nosocomial acquired UTI, resp infection, neonatal meningitis:
Citrobacter spp.
Bile salts enhance the growth of this:
Yersinia spp.
Which species of Proteus is more antibiotic resistant, and known to be nosocomial:
Proteus vulgaris
Citrobacter can use _____ as its sole carbon source:
Citrate
This organism is DNAase+ and ONPG+ and has variable lactose fermentation, is also associated with contaminated catheters:
Serratia spp.
This organism produces red, water soluble pigment at room temp, but rarely at 35 C:
Serratia marcescens
This genus has mucoid colonies, and is associated with nosocomial infections with medical devices:
Enterobacter spp.
This organism is also known as ‘Friendlander’s bacillus’:
Klebsiella pneumoniae
Klebsiella pneumoniae has which antigens associated with it:
O
K
This organism has large, mucoid, stringy colonies, and antigens O and K associated with it:
Klebsiella pneumoniae
This organism causes an STD that causes genital nodules and scarring, it is seen in phagocytes from scrapings–> called Donovan bodies:
Klebsiella granulomatis
Which organism is the most fastidious of the EB group, and which media does it grow well on:
Shigella
*MacConkey’s, HE, XLD
Shigella spp. is catalase variable, S. dysenteriae is catalase ___:
Catalase+
Which antigens are associated with Salmonella:
O
H
T/F
Salmonella has endotoxins:
True. They enhance intracellular survival.
This subtype has the K antigen, is capsular, and will be H2S+ between butt/slant:
Salmonella (Typhi)
Which antigens are associated with E. coli:
O
H
This organism is uncommon in humans, but can cause diarrhea, wound infections, and bacteremia, and is associated with snakes and turtles:
Edwardsiella tarda
Which microbes can cause Traveler’s diarrhea:
- E. coli
- Salmonella spp.
- Salmonella
- Shigella
T/F
Specimens for Yersinia pestis (plague) include blood cultures, sputum, lymph node aspirates:
True
What is the most serious form of Plague:
pneumonic
90% fatal w/out treatment
This type of Plague causes painful buboes, and can invade blood vessels if untreated–>75% fatality rate:
Bubonic Plague
Where is the H antigen located:
Flagella
Describe results of the following on HE media:
Fermentation:
S/S growth:
Salmonella with H2S+
Lactose/sucrose ferment= yellow colonies
S/S = blue/green
Salmonella w/ H2S+ produces blue green colonies with black centers
This selective and differential media is especially good for isolating S & S:
XLD
How is XLD selective and differential:
Selective: inhibits Gram+
Differential: xylose fermentation
What is the ingredient in XLD that inhibits Gram+:
Sodium deoxycholate
In XLD, fermenting xylose means lysine-decarboxylase ____, so won’t ferment lactose/sucrose, and will cause ____ color colonies:
LD negative
yellow colonies
What does Lysine-decarboxylase do:
Reverts the pH back to alkaline
XLD with ______ is used to inhibit Proteus spp.: (in order to not get a false pos of Proteus)
Novobiocin
This is used as a control organism in autoclave effectiveness:
Bacillus stearothermophilus
List the TSI results of Proteus mirabilis:
K/A Gas+ H2S+
List the TSI results of Proteus vulgaris:
A/A Gas+ H2S+
List the TSI results of Citrobacter:
A/A Gas+ H2S+
Hafnia alvei is
Lactose__
Citrate___
Lactose-
Citrate-
List the TSI results of Serratia spp:
A/A or K/A Gas+ H2S-
List the TSI results of Enterobacter:
A/A Gas+ H2S-
Enterobacter is Lactose__, VP__, and Indole___:
Lactose+
VP+
Indole-
List the TSI results for Klebsiella pneumoniae:
A/A Gas+ H2S-
List the results for Klebsiella pneumoniae: Lactose Antigens Urease Indole MR VP Citrate
Lactose+ Antigens: O, K Urease weak+ Indole- MR variable VP+ Citrate+
Donovan bodies are associated with this:
Klebsiella granulomatis
List the TSI results for Shigella:
K/A Gas- H2S-
List the TSI results for Salmonella:
K/A Gas+ H2S+
Which produces gas and H2S on TSI, Shigella or Salmonella:
Salmonella
Do Salmonella and Shigella produce spores:
NO
List the TSI results for E. coli:
A/A Gas+ H2S-
List the following results for E. coli: Oxidase Indole Lactose PYR Methyl red Simmons Citrate VP
Oxidase- Indole+ Lactose+ PYR- Methyl red+ Simmons Citrate- VP-
List the TSI results of Edwardsiella tarda:
K/A Gas+/- H2S+
