Bacteriology Exam 5 (Enterobacterales) Flashcards
What is the only oxidase positive GNR?
Plesiomonas
What are the lactose positive GNR?
E. coli, Citrobacter, Klebsiella, Enterobacter
What GNR is non-motile at 37 degrees C?
Yersinia
What are the two non-motile GNR?
Klebsiella and Shigella
How do you differentiate between Klebsiella oxytoca and Klebsiella pneumoniae/granulomatis?
Klebsiella oxytoca is indole positive
Klebsiella pneumoniae/granulomatis are indole negative
How do you differentiate between Proteus vulgaris and Proteus mirabilis?
P. vulgaris is indole positive
P. mirabilis is indole negative
Which Enterobacterales is spread by fleas (bubonic plague)?
Yersinia pestis
What are the common characteristics of Enterobacterales?
All reduce nitrate to nitrite
All ferment glucose
All except one are oxidase negative (Pleseomonas is positive)
Referred to as Enterics
All members are facultative anaerobes
GNR
All are motile except for Kleb and Shigella
What are the primary pathogens of interest if a routine stool culture is ordered? What are they the causative agents of?
Salmonella and Shigella; they are the causative agents of typhoid fever and dysentery.
What are the primary pathogens of Enterobacterales?
E. coli
Salmonella sp.
Shigella sp.
Yersinia sp.
P. shigelloides
What Enterobacterales is the most common cause of UTI/Kidney infection?
E. coli
What color is E. coli on EMB?
Shiny green metallic color
What color would E. coli (or normal flora) be on XLD agar?
Bright yellow colonies
What color would Salmonella sp. be on XLD agar?
Black
Where is E. coli O157:H7 found as normal flora?
Cows
What meat can you consume and risk acquiring E. coli O157:H7
Beef (normal flora in cows)
What is the enterohemorrhagic E. coli (EHEC)? What can it cause?
E. coli O157:H7; may cause hemorrhagic colitis causing watery/bloody diarrhea and severe cramps due to consuming bad beef, can cause HUS (hemolytic uremic syndrome)
Does E. coli O157:H7 (EHEC) have a low or a high ID50? What does this mean?
Low; it means only a small amount of the bacteria is needed to cause disease
How do you test for E. coli O157:H7? What would it look like?
MacConkey Sorbitol Agar, O157:H7 would be clear on this plate
What do EHEC cause?
hemorrhagic colitis
What do ETEC cause?
“Travelers diarrhea” - toxins not related to EHEC; special toxins (LT and ST) cause lining of intestine to secrete excess fluid
What do EPEC cause?
Pediatric diarrhea with large amounts of mucus but no blood - often outbreaks in nurseries and daycares
EIEC
rare in U.S/less common worldwide; produces dysentery similar to shigella; EIEC E. coli are lactose negative and non-motile
What does EAEC cause? What group does it mostly affect?
Diarrhea by adhering to mucosal surface of intestine; watery diarrhea, vomiting, dehydration, abdominal pain; mostly affects infants and AIDS PATIENTS
Which members of Enterobacterales swarm the BAP?
Proteus spp.
What are the phenylalanine positive Enterobacterales?
Proteus, Morganella, Providencia
What members of Enterobacterales are H2S positive?
Salmonella, Proteus, Citrobacter
What members of Enterobacterales are indole positive?
Edwardsiella, Providencia, Morganella, P. vulgaris, E. coli, Citrobacter, K. oxytoca
What is the commonly recovered species from infections involving aquatic environmental wounds, contamination, or ingestion of contaminated water or fish?
Edwardsiella tarda
What Is the most common infection caused by Enterobacter spp.?
HAIs via catheterization
What citrobacter sp. is associated with nursery outbreaks of neonatal meningitis and brain abscesses?
C. koseri
Most common Citrobacter spp. infections:
UTI
Which species is slowly urea positive, and may be mistaken for Salmonella in stool cultures because it is H2S positive on HE/XLD?
Citrobacter species
Where are Klebsiella species found?
GI tract of animals and humans, soil, water, plants
What species has very mucoid colony morphology?
Klebsiella; also Enterobacter
What does Klebsiella oxytoca most commonly cause?
UTIs
What is a Donovan body?
Klebsiella granulomatis found intracellular (inside endothelial cells)
What is the most commonly recovered Enterobacter spp.?
E. cloacae
What is the main pathogen of Serratia spp? What do they most likely cause?
Serratia marcescens; infections in medical devices
What organism is DNase positive?
Serratia
What organism produces a unique red pigment?
Serratia marcescens
What are the two main Proteus species of interest?
P. vulgaris/P. mirabilis
Nearly all Proteus spp infections are associted with ____, _____, _____, and _____.
urine, ears, wounds, blood
What organism can cause a dog’s paws to smell like fritos?
Proteus spp.
Morganella epidemiology
Ubiquitous through environment and normal flora of the GI tract.
Emerging pathogen for skin, soft tissue, and UTIs as HAI
Motile, GNR that lives in freshwater environments and causes infections through ingestion or direct contact through wounds in humans/animals (Considered an emerging pathogen for food and waterborne illnesses)
Plesiomonas shigelloides
How to differentiate Aeromonas spp. and Plesiomonas spp. (since they are both oxidase POS)
Aeromonas spp. is DNase-positive
Plesiomonas spp. is DNase negative
What may cross react with Shigella antisera? What is the difference between these two?
Plesiomonas shigelloides; but it is much less virulence than Shigella
What organism will grow well on CIN agar?
Yersinia spp.
What organism grows best at room temperature, but grows at 37 C and shows no motility at this temp?
Yersinia spp
What organism has a safety pin appearance gram stain?
Yersinia spp.
What organism can survive cold temperatures, contaminating blood products, and causes appendicitis-like signs/symptoms?
Yersinia enterocolitica
Is Yersinia enterocolitica a part of normal GI flora?
No
What does Yersinia enterocolitica grow like on CIN agar?
Red bulls-eye colonies
What is the H antigen?
Flagellar
What is the O antigen?
Somatic
What is the normal habitat of S. enterica? Cold or warm blooded environments?
Warm-blooded animals (humans!)
Where are Salmonella species normally found?
GI tract of cold blooded animals and birds
Where does a human acquire Salmonella?
undercooked poultry, milk, eggs, and dairy products
Vi/K antigen
Capsular antigen
How can MLS manipulate samples to access the O antigen of Salmonella?
Boil sample to destroy heat labile Vi/K antigens and then retype to access heat stable O antigen
How do you ID Salmonella for routine stool culture?
XLD agar, HE agar, Selenite broth, Positive motility
Salmonella ID50
Salmonella is highly sensitive to gastric acid so a large ID50 is required –> need a lot of Salmonella to cause disease
What bacteria causes a BLOODY diarrhea and destruction of GI tissue through VERTICAL INVASION of colonic epithelial cells?
Salmonella
Non-typhoidal vs Typhoidal Salmonella
Typhoidal: systemic disease (Refers to S. typhi and S. paratyphia) can become bloodstream infections
Non-typhoidal: acute gastroenteritis (all serotypes of Salmonella enterica except above)
Is non-typhoidal or typhoidal salmonella more common? Which is more virulent?
Non-typhoidal is more common, Typhoidal is more virulent
When do GI symptoms start after ingestion of Salmonella?
8-36 hours and is self-limiting and resolves within 7 days (non-typhoidal)
Are antibiotics recommended with Salmonella? Why?
No; it can cause a carrier state and relapse in non-typhoid species of Salmonella
How is Shigella spread? Is it normal flora?
Shigella is NEVER normal flora; it is spread person to person by poor hygiene
Clear colony on XLD/HE
Shigella
4 Major O antigen groups of Shigella
(Group A, Group B, Group C, Group D)
A - S. dysenteriae
B - S. flexneri
C - S. boydii
D - S. sonnei
What is the most predominant group of Shigella worldwide?
Group B - S. flexneri
What is the most severe/high death rate Shigella group?
Group A - S. dysenteriae
What is the most predominant in industrialized countries and in the US Shigells group?
Group D - S. sonnei
Is the ID50 for Shigella low or high?
Low ID50 - can withstand gastric acid and is very contagious
What organism causes Notorious tissue invasion as an intracellular pathogen and multiplies/spreads to adjacent/HORIZONTAL epithelial cells?
Shigella
Does Shigella invade the bloodstream?
Rarely
When do symptoms appear after ingestion of Shigella?
2-4 days after ingestion, self-limiting, antibiotics useful in severe cases
How long can stool samples be held?
48 hours
What is the routine media for Enterobacterale?
BAP/CHOC/MAC
XLD/HE for Salmonella & Shigella
When is WellColex performed?
AFter API20E
Citrate and VP positive organisms?
How can they be further narrowed down?
- Enterobacter –> motile and LF
- Klebsiella –> non-motile and LF
- Serratia –> motile and NLF
E. cloacae vs E. aerogenes
E. cloacae is arginine and ornithine positive
E. aerogenes is lysine and ornithine positive
E. coli hemolysis
Beta hemolytic
E. coli citrate and VP
negative
E. coli IMViC reactions
++–
(indole, methyl red, BP, citrate)
K. pneumoniae IMViC reactions
–++
(indole, methyl red, VP, citrate)
What enzyme do CPEs produce? What is CPE?
AmpC; Carbapenem resistant enterbacteriaceae
