Enterobacterales Flashcards
Classification
Dear King Phillip Come Over For Good Soup
Members of the family
Enterobacteriaceae - 5
- Ubiquitous
- Commensals of human and animal intestinal tract (fecal coliforms)
- Known as Enterics
- Some are pure commensals
- mostly found in clinical specimens
Transmission
- Exogenous - transmitted from outside source- ingestion of contaminated water or food
- Endogenous - from the host’s normal flora = medical or surgical therapy
characteristics of enterobacterales - 2x FF CORS
- gram negative and non spor forming (vulnerable to adverse environments
- non motile or motile by means of peritrichous flagella
- ferment glucose (anaerobic metabolism)
- facultative anaerobes
- caspase positive
- oxidase negative
- reduce nitrate to nitrite
- some are capsulated
LFTs
KEEC
non LFTs
SSPY
Motile
SEE
(salmonella)
non motile
SK
(shigella)
two types of enterobacterales pathogenecity
- primary intestinal pathogens
- opportunistic pathogens
primary intestinal pathogens
- true pathogens, not commensals in the intestines of humans
- produce infection through consumption of contaminated food and water
-shigella and salmonela
opportunistic pathogens
- commensals in the untestinal tract of humans and animals
- cause infection in susceptible hosts
Capsule
- extracellular capsular polyssacahride
- immune evasion ( interfere with antibody binding, major virulence factor, anti phagocytic)
components that play a role in pathogenesis - 6
- Capsule
- LPS
- Urease
- Fimbrae (pilli)
- Toxins
- Genetic exchange
example of how capsules cause infection
- the K and Vi antigen allow serotyping
- The K (k1)antigen associated with neonatal meningitis and speticaemia…
- salmonella typhi has the Virulence antigen
- EKS .. so klebisella as well
serotyping
a method used to identify and classify bacteria based on the specific antigens on their surface. It helps differentiate bacterial strains and can be used for identifying pathogens in infections.
LPS
- protects bacteria against complement
- Oligosaccharide
- O antigen (polysaccharide)
- Lipid A - stimulates macrophages which secrete cytokine leading to schock and fever
Urease
- potent enzyme that converts urea to CO and ammonia, it is produced by enterobacteriaceae
Example of urease activity
- in UTI
- low pH- urea increases the pH (by ammonium) making it basic- this environment causes precipitation of phosphates and calcium - everntually forming kidney stones
Fimbrae
- Adhesion to mammalian cell surface
Mannose binding fimbrae
low UTI
P fimbrae
upper UTI- in ecoli
Endotoxins
LPS, Lipid A
what are exotoxins
proteins released by the organisms (bacteria??)
function of exotoxins
Adhesion to host cell- type 1 = membrane acting, stimulate transmembrane proteins
Damage to host cell- type 2 = membrane damaging, forms pores and disrupt bilayers
Invasion of host cell - type 3 = intracellular, translocate int the cell and modify target molecules
example of exotoxin pathogenesis
- ETEC
- produce LT and ST toxins
- acts on enterocytes to secret fluids - diarrhea
mechanisms of genetic exchange
transduction, conjugation, transformation
how do enterobacterales gain DNA
- rapidly from other organisms through mobile genetic elements transposons, phages, plasmids
- antibiotic resistance genes
- gain pathogenecity determinants - virulence factors
Laboratory identification of enterobacterales
- Appear pink on the Gram stain
- Rod-shaped
- Aerobes, Facultative anaerobes,
how to see presence of lactose
- Lactose fermentors (pink)
- Non-lactose fermentors (colorless)
what do they mostly utilise for energy
carbohydrates
Clinical syndromes associated with the
Enterobacterales - 7
DABULLN
Diarrhea
ecoli, shigella, salmonella
Abdominal wound
e coli, klebisella
Bacteraemia
SKEP
(salmonella)
UTI
ecoli, klebisella (the p.. mhh) - proteus
Liver abcess
mk..wuu enkay… klebisella, mixed infection
Lower RTI
nna, ek… enterobacter, klebisella
Neonatal meningits
e. coli
