Enterobacteriaceae
Part 1
Part 1
All Enteric organisms are motile at body temperature except for:
Klebsiella, Shigella, and Yersinia
What is the appearance of Klebsiella spp. on MAC agar and why?
Mucoid due to large polysaccharide capsule
Ferrous sulfate and sodium thiosulfate
What organism has a heat-stable hemolysin known as the Kanagawa phenomenon?
Vibrio parahaemolyticus
What organism has a metallic sheen on SBA?
Pseudomonas aeruginosa
Describe the O antigen, H antigen, and the K antigen and its temperature stability.
O antigen (somatic antigen)
-Heat stable antigen located in the cell wall (LPS)
H antigen
-Flagellar antigen; heat labile
K antigen
-Capsular antigen; heat labile
What is the lactose fermentation on MAC and H2S production of Salmonella and Shigella?
Both are non-lactose fermenters (NLF) on MAC
Salmonella: H2S (+) (black formation)
Shigella: H2S (=) (no black formation)
What is the difference between an oxidizer and fermenter?
Acid produced in aerobic tube = oxidizer
Acid produced in anaerobic tube = fermenter
What organism has a hallmark "seagull wing" appearance? What are the growth temperature and requirements for this organism?
Campylobacter spp. and Helicobacter pylori (Campylobacter-like spp.)
5-10% O2 and 10% CO2 in 42C
Describe the colony appearance of Pseudomonas stutzeri.
Wrinkled, leathery, colonies w/ light yellow or brown pigment
Describe the following biochemical reactions of E. coli.
Fermentation type on MAC:
IMVC:
TSI and H2S:
Fermentation type on MAC: Lactose Fermenter (Grow Pink and dry)
IMVC: (+,+,=,=)
TSI and H2S: A/A with gas, H2S = (no black)
What is a big characteristic of Proteus spp.?
What differentiates Proteus vulgaris from Proteus mirabilis?
Swarming on media
Differentiated by ornithine decarboxylase and indole:
P. mirabilis (indole = , ornithine +)
P. vulgaris (indole + , ornithine =)
When performing a nitrate reduction test, no color change was seen.
What are the two possibilities for this result?
What can be done to verify and how is it interpreted?
2 possibilities: nitrate has not been reduced or nitrate was reduced further to nitrogen
Add zinc dust - if red color change is seen then nitrate was NOT reduced (true negative test)
What are the three tests that can lead to the presumptive ID of Vibrio spp.?
Susceptibility to O/129
(+) string test
(+) oxidase test
What organism is primarily found in hospital ventilators and humidifiers?
Based on the organism listed before, what are the following biochemical reaction results?
Oxidase:
Catalase:
Motility:
Acinetobacter spp.
Oxidase (=)
Catalase (+)
Motility (=)
A 3-month old infant comes home from their normal daycare experiencing a low-grade fever and diarrhea. What organism is likely involved? What type of diarrhea is normally seen with this type of infection?
Enteropathogenic (EPEC)
Diarrhea - large amounts of mucus without blood
Enterobacter spp. is known for causing infections in various sites such as wounds, urine, and blood. What are the following biochemical reactions of this organism?
IMVC:
Ornithine decarboxylase (also what other organism does it differentiate it from):
IMVC: (=,=,+,+)
Ornithine decarboxylase (also what other organism does it differentiate it from): Positive (+) and differentiates Enterobacter spp. from Klebsiella spp.
Lactose fermenter (LF) - has both Beta-galactoside permease and Beta-galactosidase
Non-lactose fermenter (NLF) - has neither Beta-galactoside permease or Beta-galactosidase
delayed lactose fermenter (dLF) - lacks Beta-galactoside permease, but has Beta-galactosidase
What test distinguishes Aeromonas from Enterobacteriaceae?
What test distinguishes Aeromonas from Vibrio?
What test distinguishes Aeromonas from Plesiomonas?
1. Oxidase (+) in Aeromonas
2. String test (=) in Aeromonas
3. Susceptibility to Vibrostat disks in Aeromonas
A patient goes to the nearest urgent care for catheter-related sepsis. The organism is found to produce pyoverdin and has a positive reaction to gelatin hydrolysis. What is the likely organism?
Pseudomonas fluorescens
An elderly patient is brought into the urgent care a few days after Christmas with concerns of diarrhea. Based on the patient's history, they are very fond of drinking warm apple cider near the holidays.
What organism strain is likely involved and what is the clinical type?
What type of diarrhea is normally seen with this type of infection?
What toxin is involved?
What plate can be used to screen for this strain?
1. E. coli O157:H7
2. Watery diarrhea progressing to bloody diarrhea without pus
3. Shiga toxin
4. SMAC (sorbitol-containing MAC) plate
A patient comes into the ER complaining of prolonged fever, lethargy, a dull headache (flu-like symptoms) and showing symptoms of bacteremia. They stated that they have been constipated for the past few days.
What organism is likely causing this person's symptoms?
What antigen is important in the identification of this organism?
What disease is suspected and where does it invade?
1. Salmonella typhi
2. K antigen (Vi antigen)
3. Typhoid fever disease and it invades the gallbladder and Peyer's patches of the bowel
Describe the appearance of TSI interpretations (What does K and A mean and their implication, what is H2S, and gas).
What are the TSI results of the following:
Organism 1 ferments glucose only and produces H2S
Organism 2 ferments glucose, lactose and sucrose and produces H2S
Organism 3 does not ferment glucose, lactose, nor sucrose
K=alkaline, A=acid
A - acid production is the fermentation of carbohydrates
K - degradation of peptones
H2S formation of black precipitate in acidic environment
Gas - formation of bubbles, splitting of the medium, displacement of medium
Organism 1- K/A with H2S
Organism 2- A/A with H2S
Organism 3- K/K
A patient is experiencing self-limiting watery diarrhea after eating undercooked seafood. The organism grew opaque, nonhemolytic colonies with delayed lactose fermentation.
What organism is likely suspected?
What media enhances its growth?
What test confirms this organism?
1. Plesiomonas spp.
2. Inositol brilliant green bile agar (IBB)
3. Inositol fermentation
An organism that is known to commonly contaminate blood drawing equipment and disinfectants is grown in the micro lab. It grew with a bluish hue on MAC media.
What organism is suspected?
What are the following biochemical reactions for this organism:
Catalase:
Oxidase:
DNase:
Lysine decarboxylase:
Stenotrophomonas maltophilia
Catalase: (+)
Oxidase: (=)
DNase: (+)
Lysine decarboxylase: (+)