Enterobacteriaceae Flashcards
What are the characteristics of enterobacteriaceae?
Gram negative, non spore forming, rod shaped bacteria.
oxidase (-) negative
Ferment glucose and may or may not produce gas in the process
Reduce nitrate to nitrite
Are facultative anaerobes
Normal inhabitants of intestinal tract
Some are enteric pathogens and others are urinary or respiratory tract pathogens
How is differentiation based on in regards to enterobacteriaceae?
Its based on biochemical reactions and differences in antigenic structure
What do most enterobacteriaceae grow well on?
Lab media developed for the selective isolation of enteric pathogens
Addition of dyes and bile salts inhibit the growth of gram positive organisms
Many enterobacteriaceae are differentiated based on whether or not they ferment _________ and/or produce _______
Lactose
H2S
What are the three most useful media for screening stool cultures for potential pathogens are?
TSI (KIA)
LIA
urea
phenylalanine agar
The antigenic structure of enterobacteriaceae may be used to differentiate organisms within a genus or species. What are the three major classes of antigens found?
O antigens - heat stable
Flagellar H antigens - heat labile
Envelope or capsule K antigens - boiling destroys this and unmasks the O antigens
The K antigen is called what in salmonella?
It is called the Vi (virulence) antigen in salmonella
What bacteria is a major cause of urinary tract infection?
E. coli
E. coli?
Is a normal inhabitant of the GI Tract
Some strains cause various forms of Gastroenteritis
Is a major cause of urinary tract infection and neonatal meningitis and septicemia
E. coli biochemistry?
TSI = A/A + gas LIA = K/K Urea (-) Indole (+) Citrate (-) Motility (+)
K/K on KIA means?
No carbohydrate fermentation
K/A reaction on KIA means?
Examples of these species are?
Glucose is fermented but not lactose
Or in order: lactose not fermented
Glucose fermented
Example is the shigella species
A/A reaction on KIA means?
Examples of these species are?
Lactose and glucose fermented.
Examples: E. coli; klebsiella- enterobacter species
K/A / H2S reaction on KIA means?
Examples of these species are?
Lactose not fermented; glucose fermented and hydrogen sulfide produced.
Examples: salmonella; citrobacter; proteus species
What are the virulence factors of E. coli?
Hint: (it is a toxin)
Toxins: enterotoxins: which are produced by enterotoxigenic strains of E.coli. These cause a movement of water and ions from the tissues to the bowel resulting in watery diarrhea.
What are the two types of enterotoxins (ETEC) in E. coli?
LT and ST
LT: heat labile causes amplification of cAMP to increase movement of ions and water to bowel
ST: heat STABLE and causes amplification of cGMP to increase movement of ions and water to bowel
E. coli is the leading cause of what clinically?
Urinary tract infection!
Which can lead to acute cystitis (bladder infection) and pyelonephritis (kidney infection)
E. coli also causes what?
Neonatal meningitis and gastroenteritis
What are the several types of E. coli that lead to gastroenteritis?
ETEC
EIEC
EPEC
EAEC
EHEC (hemmoraging) caused by serotype O157:H7!! Also produces shiga like toxins!!!
Shigella species
Contains what four types?
S. dysenteriae
S. flexneri
S. boydii
S. sonnei
What is the biochemistry of Shigella species?
TSI: K/A with NO gas!
LIA: K/A
Urea (-)
Motility (-)!
Salmonella species have two species?
s. enterica which causes most human infections
s. bongori
Biochemistry of salmonella species?
TSI: K/A + gas and H2S Urea (-) Motility (+) Citrate +/- Indole -
How do salmonella species move?
They have flagella that allows them to move through intestinal mucous
Salmonella causes two difference kinds of disease ?
Enteric fevers: bacteria spread (paratyphoid and typhoid) typhoid being more severe due to s. typhi
Gastroenteritis: bacteria restricted to intestine where it produces a strong inflammatory response allowing bacteria to be constricted to only this area of body
Transmission is via the fecal oral route through contaminated water or food
What is the difference between shigella and salmonella species?
Salmonella species is more severe
Shigella species are nonmotile as are klebsiella species
Shigella species produce NO GAS
Biochemistry of citrobacter species
TSI : K/A or A/A both gas and h2s
Urea is usually +
Motility +
They are opportunistic pathogens causing urinary tract or respiratory tract infections and occasionally wound infections, osteomyelitis, endocarditis, and meningitis
Biochemistry of edwardsiella species
TSI: K/A + gas + h2s LIA: K/K + H2s Urea (-) Citrate (-) Indole (+)
Biochemistry of klebsiella species?
TSI : A/A + gas LIA : K/K Urea (+) Citrate (+) MR (-) VP (+) !!!!!!!!!! Motility (-)!!!!!!!!
Biochemistry of Enterobacter species
TSI LIA and urea vary with species
Citrate (+)
Motility (+)
Biochemistry of serratia species
TSI A/A or K/A +- gas
Citrate (+)
Motility (+)
Urea -/+
Biochemistry or proteus, providencia and morganella species
All motile with proteus swarming!! PA +!!!! Lysine deamination Urea (+) TSI varies for each! Indole + except for p. mirabilis
The urease produced by the proteus providencia and morganella species may damage what?
The ammonia produced by urease may damage the epithelial cells of the UT
Yersinia species have what three important species that important pathogens in man?
Yersenia Pestis - causes plague
Yersenis enterocolitica - entercolitis, septicemia
Yersinia pseudotuberculosis - mesenteric lymphadenitis
Which yersinia species is non motile
Y. Pestis
Biochemistry of yersinia Pestis
TSI : K/A no gas!
Urea (-)
Endotoxin is responsible for many of the symptoms
Murine toxin effects only rodents
What does y. Pestis cause in humans?
Bubonic plague - transmitted by fleas from infected rodent
Lymph nodes get very enlarged.
Bacteria in lymph nodes leak into bloodstream leading to septic shock
Bubonic plague from y. Pestis leads to what greater complication?
It leads to pneumonic plague when the bacteria reach the lungs from the bloodstream.
This is can be transmitted easily via aerosol
Mortality rate is very high!!!
Yersinia enterocolitica and yersinia pseudotuberculosis biochemistry?
Both are motile at 22-25 degrees but non motile at 37 degrees
Both exhibit bipolar staining
TSI A/A but with sucrose fermentation not lactose
Urea (+) for both!
ODC (+) for Y. Enterocolitica only!
Yersinia Pestis exhibits what appearance after staining?
A safety pin appearance
Yersinia are the only enterobacteriaceae that grow on what media?
CIN agar!!!!
Because it contains mannitol and phenol red for isolation
They will look like pink (due to mannitol fermentation) colonies with a BULLS EYE APPEARANCE
What is indole production? And why is it used as a detection method?
Indole is one of the degradation products of the amino acid tryptophan.
Bacteria that possess the enzyme tryptophanase are capable of cleaving tryptophan thereby producing indole, pyruvic acid and ammonia!
Shows RED only after adding a solution containing
p-dimethylaminobenzaldehyde called kovach’s reagent!
The methyl red test provides what?
A valuable characteristic for identifying bacterial species that produce strong acids from glucose
Vogues proskauer test?
A test who has positive members that consists of the species
Klebsielleae
Citrate utilization?
To determine the ability of an organism to use sodium citrate as the source of carbon for metabolism and growth
Shows blue!
Urease production test
Microorganisms that possess the enzyme urease hydrolyze urea, releasing ammonia and producing a pink-red color change in the medium
Phenylalanine deaminase production test
This test is useful in the differentiation of proteus, morganella, and providencia species from other enterobacteriaceae
Only members of these genera possess the enzyme responsible for the oxidative deamination of phenylalanine
Green color after ferric chloride is reagent is added.
Hydrogen sulfide production test
Shows as a black precipitate in the medium
Motility test
Important as well in making a final determination of a species
Shows as a diffuse of growth from the point of inoculation
Which two species are non motile?
Klebsiella and shigella!!!
Which species are hydrogen sulfide positive?
Edwardsiella tarda Salmonella Citrobacter freundii Proteus vulgaris Proteus mirabilis
Vogues proskauer positive species are?
Klebsiella
Enterobacter
And serratia species
Phenylalanine deaminase positive species are ?
Proteus
Morganella and providencia species
Which species are nonmotile at 36 degrees
Shigella
Yersenia and klebsiella species!
Cytochrome oxidase activity?
Any organism showing oxidase activity is EXCLUDED from the enterobacteriaceae group
Nitrate reduction in enterobacteriaceae?
All enterobacteriaceae reduce nitrate to nitrite. Zinc dust needs to be added and organisms will reduce within 24 hrs. Readings must be done as soon as possible.
Entero means what in regards to enterobacteriaceae?
It means intestinal
will be learning about most bacteria that occur in the gut
