ENTEROBACTERIACEAE Flashcards
Characteristics of ENTEROBACTERIACEAE
- Non acid fast gram (-) baccili
- Commonly present in large intestine
- Non-spore forming gram – rods
- all are glucose fermenters, reduces nitrates to nitrites, oxidase (-)
- grows on bile containing agar
- motile except Shigella & Klebsiella
- non-capsulated except Kelbsiella
- non sporeforming
Cell wall -outer membrane of
ENTEROBACTERIACEAE
LPS (heat stable)
– O polysaccharide
– Core polysaccharide
– Lipid A
Lipid A
outer wall coponent responsible for producing fever and shock; inflammatory effect
Serological Identification of ENTEROBACTERIACEAE
– O polysaccharide
– K antigen
– H proteins
Virulence Factors of ENTEROBACTERIACEAE
O antigen, or somatic antigen- heat stable
H antigen, or flagellar antigen- heat labile
K antigen, or capsular antigen - heat labile
LPS (Lipid A)
Porins
Found on the outer membrane of cell wall that acts as sieve, allowing water-soluble mol. to enter cell
Lactose Fermenters Enterobacteriaceae
E.coli & Escherichia, Klebsiella
Late Lactose Fermenters Enterobacteriaceae
Shigella sonnei
Non-Lactose Fermenters Enterobacteriaceae
Salmonella & Shigella
MacConkey Agar
- bile containing agar
- selective and differential culture medium for bacteria
- designed to selectively isolate some Gram-positive and enteric
Lactose fermenters:
morphology
E. COLI
- appear in single or pairs
- motile by petrichate flagella
- 1-3 x 0.4-0.7 microns
Lactose fermenters: E.COLI
Culture characteristic
- grows between 10-40 c optimal at 37
- grown in simple medium
- large grayish, thick-white moist smooth opaque colonies
- may sometimes contain capsule
Lactose Fermenters in MacConkey Agar
- Briight Pink colonies
Non- Lactose Fermenters in MacConkey Agar
Colorless colonies
Lactose fermenters: E.COLI
on Blood Agar
- many strains are haemolytic on blood agar
Lactose fermenters: E.COLI
Biochemical Characteristics
- Glucose, lactose, mannitol, and lactose fermenters
- Citrate/ urease not produced
- A/G indole + methyl red + voges Proskauer
Lactose fermenters: E.COLI
Antigenic structure
K - capsular 100
H - flagellar 75
O - somatic 170
Virulence factors
Antigen of Enterobacteriaceae that protects the bacteria from phagocytosis
K antigen (capsular)
Antigen of Enterobacteriaceae that is important in cases of UTI
H antigen (flagellar spcifically fimbriae)
- absent in Shigella spp.
Antigen of Enterobacteriaceae that promotes endotoxic activity
O antigen (somatic)
Antigen of Enterobacteriaceae that is absent in shigella spp.
H antigen
Antigen of Enterobacteriaceae that present in extraintestinal infections caused by E. coli?
K antigen (capsular)
An isolated organism shows a negative lactose fermentation and negative in motility test. Which among the choices is the presumptive organism?
Salmonella spp.
Shigella spp.
Escherichia spp.
Shigella spp
- non lactose and non-motile
Escherichia is lactose fermenter
Salmonella is non-lactose fermenter but it is motile.
Virulence factor of E.coli that is present in large numbers and can cause mannose sensitive haemagglutination
Fimbriae
What strain of E.coli produce enterotoxin
Enterotoxigenic strains (ETEC)
E.coli produces these toxins which causes a movement of water and ions from the tissues to the bowel resulting in watery diarrhea
Enterotoxin
Types of E.coli involved in different types of gastroenteritis
Shiga toxin-producing E. coli (STEC)—STEC may also be referred to as Verocytotoxin-producing E. coli (VTEC) or enterohemorrhagic E. (EHEC) Enterotoxigenic E. coli (ETEC) Enteropathogenic E. coli (EPEC) Enteroaggregative E. coli (EAEC) Enteroinvasive E. coli (EIEC)
Types of E.coli:
Enteropathogenic EPEC
- EPEC 026/011
- produce Verocytotoxin
- frequent in summer months
- brush border of intestine is lost
- Intimacin (EPEC adhesion factor)
Types of E.coli: Identification
Enteropathogenic EPEC
- serotyping for B and o ags.
- routine culture for isolation
- fails to ferment sorbitol
Types of E.coli: Lab diagnosis
Enteropathogenic EPEC
- Confirm (Polyvalent sera)
- test sero groups w/ polyvalent and monovalent sera
- HEp2 adherence
Enteropathogenic EPEC adhesion factor
Intimacin
Enterotoxigenic ETEC adhesion factos
Fimbriae specific receptors
CFA mortality in children
Types of E.coli:
Enterotoxigenic ETEC
- produce heat stable/ heat labile toxins
- HL like cholera toxin
- causes accumulation of fluids
- adheres to epithelium of sm
Types of E.coli: Lab diagnosis
Enterotoxigenic ETEC
- Demonstration of Enterotoxin LT nd ST in tissue culture test
- Passive agglutination test
- Animal experiments in rabbit ileal loop test
Types of E.coli:
Enteroinvasive (EIEC)
- resembles shigella
- non lactose fermenter & non-motile
- penetrate HeLa cells
Types of E.coli: Lab diagnosis
Enteroinvasive (EIEC)
- Sereny test positive animal rabbit
- ELISA
Type of E.coli that is non lactose fermenter and non-motile
ENTEROINVASIVE E. COLI (EIEC)
Types of E.coli:
Enterohemorrhagic (EHEC)
- produce verocytotoxin or shiga like toxin
- hemorrhagic complication with 0157; H7
- present in human and animal feces
- disease may manifest as food poisoning
Type of E.coli that produces verocytotoxin
Enteropathogenic EPEC
Enterohemorrhagic (EHEC)
Types of E.coli: Lab diagnosis
Enterohemorrhagic (EHEC)
- DNA detection method
- ctotoxic effects on vero cells
- Detection w/ monovalent sera 0157/ h7
Type of diarrhea associated with EIEC
- mild diarrhea to frank dysentery
Type of diarrhea associated with ETEC
- travelers diarrhea
- present with nausea, vomiting and lose stool
Type of diarrhea associated with EPEC
- diarrheal disease in children
- infantile enteritis
Type of diarrhea associated with EHEC
- mild diarrhea; can be fatal hemorrhagic colitis and uremic syndrome
Type of diarrhea associated with EAEC
- persistent diarrheal
Types of E.coli:
Enteroaggresive EAEC
- appear aggregated in S stacked brick formation hep-2 cell
- produce weight heat stable enterotoxin called as low molecular heat stable enterotoxin
Types of E.coli: Lab diagnosis
Enteroaggresive EAEC
- Stool culture
- Detection of Enterotoxin
Leading cause of urinary tract infection which can lead to acute cystitis (bladder infection) and pyelonephritis (kidnet infection)
E. coli infections
Specimen used for Culturing of E.coli
- Mid stream sample of urine
- culture by standard loop method
- Antibiotic sensitivity tested
Which of the following choices grows on SMAC (MacConkey)
Blood culture for EHEC
Urine culture for EIEC
Stool culture for EHEC
Urine culture for EHEC
Stool culture for EHEC
Most commonly islated spp of Klebsiella
K. pneumoniae
Small cracks in the medium with black precipitates
Which E coli strains causes infantile diarrhea?
EHEC
EPEC
ETEC
EAEC
EPEC
Which member of Enterobacterales has a positive result on Neufeld Quellung test? *
Escherichia coli Proteus vulgaris Klebsiella pneumoniae Shigella dysenteriae Salmonella enteritidis
Klebsiella pneumoniae
Lactose fermenters: Klebsiella
morphology
- has polysaccharide capsule
- has distinctive “yeasty” odor
- non motile
- has moist and mucoid in its colonies
Enterobactericiae spp that is the frequent cause of nosomical pneumonia, speticemia, and meningitis
Klebsiella spp
Lactose fermenters: Klebsiella
Virulence factors
- capsule
- adhesions
- iron capturing ability
Lactose fermenters: Klebsiella
Significant biochemical reactions
- lactose positive
- Citrate (+)
- non motile
- urease (+)
- has both O and K antigens
- LIA K/K
Slow lactose fermenters:
Serratia spp
- 7 spp. but S.marcescnes is the only clinically important
- produce pink pigment esp. when cultures are left at room temp.
- fairly resistant to antibiotics
Non-lactose fermenters:
Hafnia spp
- H.alvei is the only specie
- occasionally isolated from stools
- delayed citrate reaction is major characteristic
pathogens of Enterobacteriaceae family that are part of normal intestinal flora—- also called as opporunistic pathogen
Proteus, Morganella, and Providencia spp.
- they deaminate phenylalanine
Non-lactose fermenters
Enterobacteriaceae
- Hafnia spp
- Proteus
- Morganella
- ## Providencia
Non-lactose fermenters:
Proteus spp.
P. mirabilis
P. vulgaris
- isolated from urine, wounds, and ear
- both produces swarming colonies on non-selective media
- distinctive “burned chocolate” odor
- both urease (+)
- both are phenylalanine deaminase (+)
Widely recognized Proteus spp human pathogens
P. mirabilis
P. vulgaris
Non-lactose fermenters: Proteus spp.
Biochemical characteristic
A- exhibits “swarming”
B shows urease (+) on right
Non-lactose fermenters:
Morganella spp.
- Morganella morganii is the only specie
- urease (+)
- phenylalanine deaminase (+)
- isolated from other anatomical sites
Non-lactose fermenters:
Providencia rettgeri
- pathogen of urinary tract and has caused nosomical outbreaks
- phenylalanine deaminase (+)
Non-lactose fermenters:
Providencia stuartii
- can cause nosomical outbreaks in BURN units nad has been isolated from urine
- phenylalanine deaminase (+)
Late lactose fermenters:
Citrobacter spp.
- C. freundii
- resembles salmonell spp.
- hydrolyze urea slowly
- differentiated by their ability to convert tryptophan to indole
A magenta color develops after incubating inoculated bacteria throughout the medium for urea utilization. Which species would give such a result? *
Providencia spp. Pasteurella spp. Hemophilus spp. Pseudomonas spp. Proteus spp.
Proteus spp.
Links:
https: //www.austincc.edu/microbugz/negative_stain.php
https: //drive.google.com/file/d/1MsBlYPVAYmg87vapD5WkkPl2wJHAipPA/view
