enterobacteriaceae Flashcards
● Enterics
● Gram-negative bacilli
● Facultative anaerobes
enterobacteriaceae
All species ferment glucose with the product of acid or acid and gas
enterobacteriaceae
All are motiles at 35
oC with peritrichous flagella
enterobacteriaceae
Catalase positive
- except for ___ type 1, which is
catalase-negative
Shigella dysenteriae
Oxidase negative
- except for ___
Plesiomonas
Non encapsulated
- except for ___ and ____
Klebsiella and Enterobacter
Reduce nitrate to nitrites
- except for ____ and ___
Photorhabdus and Xenorrhabdus
Most are commensal of the GI tract
- except for 3
Plesiomonas, Salmonella, Shigella,
and Yersinia
may grow at 1
oC to 5 oC
Serratia and Yersinia
They do not produce cytochrome oxidase
- except for
Plesiomonas
e, coli, citrobacter, klebciella. enterobacter
lactose fermenter
salmonella, shigella, proteus, yersinia
non lactone fermenter
most imoortant media for lf and nonlf
- MacConkey agar
- Eosin Methylene Blue (EMB) agar
- Salmonella Shigella (SS) agar
- Triple Sugar Iron (TSI) agar
The most important media used to
differentiate these two classifications is the
___, with a pink colony
appearance when lactose is fermented and a
colorless colony appearance in non-lactose
fermenting organisms.
MacConkey agar
– this is a heat-stable
antigen located on the cell wall.
o antigen (somatic antigen)
this is a heat-labile
antigen found on the surface of flagella, structures
responsible for motility.
● H antigen (flagellar antigen)
– this this is a
heat-labile polysaccharide found only in certain
encapsulated species
K antigen (capsular antigen)
indicator for TSI or triple sugar iron agar
phenol red
TSI = ALK/ALK or K/K, color red tube slant and butt means?
no fermentation
Alkaline slant/acid butt or K/A, red/yellow
an indicative of glucose
fermentation only.
Acid/acid, Yellow/Yellow, A/A
. Lactose (or sucrose or both) fermentation
blackening of the medium
- Blackening of the medium occurs in the
presence of H2S or hydrogen sulfide
H2S production
formation of bubbles or splitting of the medium
from the bottom of the tube
- Bubbles or splitting in the agar indicates a
production of gas.
Gas production (aerogenic) or no gas
production (nonaerogenic)
IMViC reactions are a set of four useful reactions
what does IMVic stands for
● Indole Test
● Methyl Red Test
● Voges-Proskauer Test
● Citrate Utilization Test
Tryptophan
Indole reacts with the aldehyde in the reagent to givea red color reaction. An alcoholic layerconcentrates the red color as a red ring at the top.
INDOLE TEST
red color after addition of
MR pH indicator
METHYL RED TEST
It measure the production of ACETOIN after the
addition of α-naphthol (catalyst or color
intensifier) followed by 40% KOH or NaOH
● Acetoin then oxidized into diacetyl
2,3-Butanediol
● Positive reaction – red complex
VOGES-PROSKAUER TEST
It determines whether an organism can use
sodium citrate as a sole carbon source
● Medium used – Simmons’ Citrate Medium
(SCA) – routinely used
CITRATE UTILIZATION TEST
are the nitrogen source in
the medium and utilization of these salts
results in the release of ammonia, causing a
pH change for citrate utilization test
Ammonium salts
pH indicator for citrate utilization test, with a blue positive result
bromothymol blue
Determines whether an organism has the ability to
reduce nitrate to nitrite
positive reaction turns red
Nitrate Reduction Test
Differentiates Enterobacteriaceae (oxidase-negative)
from pleisiomonas (oxidase-positive)
Oxidase Test
Determines the presence of the cytochrome oxidase
system that oxidizes reduced cytochrome with molecular
oxygen
Positive reaction - purple or lavender color
Oxidase Test
Determines whether a microorganism can hydrolyze
urea (by the action of urease enzyme), releasing a
sufficient amount of ammonia to produce a color change
by a pH indicator
Urease Test
pH indicator for urease test
- phenol red
Positive reaction for urease test
pink color
urease test primarily distinguisded genus__ from other enteric bacteria
proteus
indicator for h2s, hydrogen sulfide production
ferrous sulfate
lysine positive
salmonella
lysine negative
citrobacter
pH indicator for LIA
bromocresol purple
lysine deamination results to a what color slant?
red slant R/x
lysine decarboxylation results to a what color but ?
purple butt x/K
negative in decarb positive in deamine
R/A
positive both
K/R
, the most significant species in the
genus Escherichia
● E. coli
Strain of E. coli that is considered as the most
common cause of UTIs in humans
Uropathogenic E. coli (UPEC)
Associated with diarrhea of adults and especially
children in tropical and subtropical climates
● It is the most common cause of diarrheal disease
Enterotoxigenic E. coli
“traveler’s diarrhea”
Enterotoxigenic E. coli
Produce a heat-stable toxin (ST) or a heat-labile toxin
(LT) or both
Enterotoxigenic E. coli
Causes “infantile diarrhea”
Enteropathogenic E. coli
Stool contains large amount of mucus, no blood
present
Enteropathogenic E. coli
Produce dysentery with direct penetration, invasion,
and destruction of the intestinal mucosa
Enteroinvasive E. col
Enterohemorrhagic E. coli
Associated with hemorrhagic diarrhea and HUS
(hemolytic uremic syndrome)
Watery diarrhea - Bloody diarrhea with abdominal
cramps, low grade fever or an absence of fever
Enterohemorrhagic E. coli
Processed meats (undercooked hamburgers),
unpasteurized dairy products, apple cider, bean sprouts
and spinach, all have been implicated in the spread of
infection
Enterohemorrhagic E. coli
Shiga-like toxins)
Enterohemorrhagic E. coli
Cause of diarrhea in HIV positive patients
. EAEC Enteroaggregative E. coli
UTIs and diarrheal disease
- Cystitis in children and acute pyelonephritis in
pregnant women
- Chronic or recurring UTIs
DAECs Diffusely Adherent E. coli
virulence factor associated with
neonatal meningeal infections
K1 capsular antigen
All are MR- and VP+
- All give a negative reaction with the methyl red
test and a positive reaction with the
Voges-Proskauer test.
KLEBSIELLA
The absence of motility distinguishes ____
spp. from most other members of the family
Enterobacteriaceae.
Klebsiella
is the most commonly isolated
species and has the distinct feature of
possessing a large polysaccharide capsule.
K. pneumoniae
Responsible for the moist, mucoid colonies
characteristic of___ on MAC
K. pneumoniae
Linked to antimicrobial-associated hemorrhagic colitis
● Identical to K. pneumoniae except for its production of
indole, and there are reports of ornithine-positive isolates
as well
K. oxytoca
. pneumoniae subsp. ozaenae
Causes atrophic rhinitis - a tissue-destructive
disease restricted to the nose
an infection of the nasal
cavity that manifests as an intense swelling and
malformation of the entire face and neck
K. pneumoniae subsp. rhinoscleromatis
Composed of only one specie: H. alvei
hafnia
“Burnt chocolate” odor
● Proximal kidney tubules – A
PROTEUS
