Boards and beyond Flashcards
Bacteria with capsules
- Strep pneumonia
- H. influenza
- N. meningitidis
- E. coli
- salmonella
- Klebsiella
- Group B strep (agalactiae)
how does the body defend against encapsulated bacteria?
- B cells secrete capsular antibodies (IgG) - antibodies bind capsule
- Phagocytosis consumes bacteria via Fc receptors from antibodies
- Antibodies also bind complement leading to
- formation of MAC -> cell death
- Formation of C3b -> opsonizing for further phagocytosis
Mechanism of recurrent encapsulated bacterial infections
- If there is a deficiency or loss of B cells, antibodies or complement
- Also asplenia (risk of sepsis from encapsulated bacteria because of loss of splenic phagocytes)
What are capsular vaccines?
- many vaccines utilize bacterial capsule polysaccharides because they are often weakly immunogenic
- often conjugated to an immmune-stimulator protein such as (diphtheria toxoid, tetanus toxoid, meningococcal outer membrane protein, mutant diptheria protein
What conjugated vaccines are available for encapsulated bacteria?
- Neisseria meningitides
- Streptococcus pneumonia
- Haemophilus influenzae type B
What is a glycocalyx?
a “sugar coat” made of polysaccharides that is similar to a capsule
forms biofilms
often adheres to catheters
Glycocalyx vs capsule
- bacteria with distinct firmly attached gelatinous layer have a capsule
- Bacteria with irregular slimy fuzz layer have a glycocalyx (biofilms)
Bacteria with glycocalyx
common one is S. epidermidis
Pili and fimbria structure
- structurally similar to flagella
- made of proteins
- appendages or arms of bacteria
Functions of pili
- ordinary pili (allows adherence to surfaces)
- sex pili (attaches to another bacteria for conjugation)
Bacteria that have pili and fimbriae
commonly
E coli ( pili allow( attachment to urinary tract) UTIs/pyelonephritis)
Neisseria Gonorrhea (pili have antigenic variation so at risk for subsequent infections) (antigenic variation) because antibodies made for previous infection may not apply to another infection
What are plasmids?
- small DNA molecules in a cell that are physically separate from chromosomal DNA
- Can replicate independently
- can contain genes for things like antibiotic resistance or toxins
- They can be transferred from bacteria to bacteria
bacterial ribosomes subunits
50s and 30s Syedberg units
Tetracyclines bind
bacterial 30s subunit of ribosome
aminoglycosides interferes with?
bacterial 30s protein synthesis
What are spores?
dormant state called a spore where they become very highly resistant to starvation orenvironmental conditions
does not have metabolic activity but can later convert back to a metabollically active bacteria (like a seed)
Spore structure
- outermost layer is Coat
- made of “keratin-like” protein
- impermeable to many chemicals and antibacterial agents
- Cortex/Core wall
- innermost layer
- made of peptidoglycans
- Dipicolinic acid
- large amounts inside spore
- may help with heat resistance
spore forming bacteria to know
5 listed
- Bacillus anthracis
- Bacillus cereus
- Clostridium perfringens
- Clostridium tetani
- Clostridium botulinum
