Enterobacteriaceae Flashcards
What is the predominant reservoir for enterobacteriaceae?
Lower GI tract and environment
Which sites are frequently colonized by enterobacterial species?
Human genitourinary tract and oropharynx
Which individuals are particularly prone to colonization by enterobacteriacheae?
Hospitalized or immunosuppressed individuals
What is a major global health threat related to enterobacteriaceae?
Antimicrobial resistance
What are the main resistance mechanisms found in Enterobacteriaceae?
- Extended-spectrum β-lactamase (ESBL)–producing strains
- Metallo-β-lactamase (MBL)–producing strains
- Carbapenem-resistant Enterobacteriaceae (CRE)
What gram type are enterobacteraceae?
Gramnegative
What are the key functions of the inner membrane in Enterobacteriaceae?
- Maintaining the proton motive force for energy storage.
- Regulating the passage of molecules to and from the cytoplasm.
What are some functions of the proteins in the inner membrane of Enterobacteriaceae?
- Electron transfer and oxidative phosphorylation
- Efflux pumps, solute transporters, protein translocation systems, and polysaccharide export systems
- Histidine kinase signaling proteins
This is an aqueous, oxidizing environment between the inner and outer membranes.
Periplasmic space
What types of proteins are found in the periplasmic space of Enterobacteriaceae?
- Oxidoreductases, isomerases, chaperones, proteases for protein folding and degradation.
- Lipoprotein-sorting proteins.
- Detoxifying enzymes.
- Solute-binding proteins that ferry molecules across the periplasmic space.
What biosynthetic processes occur in the periplasmic space of Enterobacteriaceae?
Biogenesis of:
* Peptidoglycan
* Lipopolysaccharide
* Capsule
Alternative name for the thin layer of peptidoglycan in enterobacteriaceae?
Murein
What are the primary functions of the peptidoglycan layer in Enterobacteriaceae?
- Mantaining shape
- Providing osmotic stability
Membrane proteins with a β-barrel fold that regulate the passage of hydrophilic molecules.
Porins
How does the polarity of LPS affect molecule penetration?
Prevents the penetration of lipophilic molecules, including:
* Detergents
* Dyes
* Hydrophobic antimicrobials
What antigen does LPS has?
O antigen
What are the main surface polysaccharides found in Enterobacteriaceae?
- Enterobacterial common antigen
- Colonic acid
- Capsule
How are true capsules linked in Enterobacteriaceae?
They are linked to either LPS or α-glycerol phosphate.
What antigen do capsules have?
K antigen
Flexible, rotating appendages that allow bacteria to propel through liquid environments.
Flagella
This is the protein component of flagella and is recognized by the host innate immune system, triggering neutrophil recruitment and an inflammatory response.
Flagellin
What antigen does flagella has?
H antigen
This are are thin nanofilaments extending from the bacterial surface, mediating autoaggregation, adhesion to host cells, and bacterial conjugation/genetic exchange.
Pili
What are the key functions of type IV pili?
Aid in:
* Aggregation
* Disaggregation
* Twiching motility
What are the main types of adhesins in Enterobacteriaceae?
- Pili
- Outer membrane proteins
- Surface carbohydrates
How do Enterobacteriaceae export toxins across their inner and outer membranes?
They require specific secretion machinery
Toxins capable of lysing host cells, leading to zones of clearing on blood agar plates.
Hemolysins
E. coli hemolysin is secreted in a single step across both the inner and outer membranes by a…
Type I secretion system (T1SS)
Multiprotein complex spanning the periplasmic compartment. It is involved in the extracellular secretion of toxins and hydrolytic enzymes.
Type II secretion system (T2SS)
This not only exports proteins through the bacterial membrane but also injects them into the host cell membrane forming a pore.
Type III secretion system (T3SS)
Enterobacteriaceae have developed efficient systems to compete with host iron-binding proteins. These systems are called…
Iron scavenger systems
These are low-molecular-weight compounds that have high affinity for iron.
Siderophores
This protein is present in the cytoplasmic membrane, is involved in all iron uptake systems.
TonB
