Exam 1 Flashcards
What are the steps involved in bacterial infection?
- Bacteria attach to host tissue
- Bacteria invade tissue
- Bacteria colonize the tissue
- Colonization/replication cause damage to the tissue
- Bacteria exit the host
- Transmission to new host
How does bacteria colonize the tissue?
Establish an infection
Creates proper conditions for replication
Hide from or fight host immune system
What are the first line of defenses?
Skin
Mucosa
What are the innate immune system defenses?
Inflammation Complement Phagocytes Neutrophil extracellular traps Natural killer cells Apoptosis
What are the adaptive immune system defenses?
Antibodies
CTLs
Activation of macrophages
Memory
Examples of simple squamous epithelium layer?
Mouth
Lungs
Example of simple cuboidal epithelium layer?
Kidney
Examples of stratified squamous epithelium layer?
Skin
Vaginal tract
Examples of simple columnar epithelium layer?
Intestinal tract
Example of ciliated columnar epithelium layer?
Upper respiratory tract
What exists on ciliated columnar epithelium layer that does not exist on other types of skin?
Mucus with goblet cells
Cilia
What are tight junctions?
Connection between epithelial cells that prevents bacteria from moving between them. Combined with protein called occludin
What can WT bacteria do to tight junctions?
Fragment the occludin to separate tight junctions
Why do endothelial cells not have tight junctions?
To allow cells of the immune system to freely move across the internal surfaces.
* bacteria can easily cross the endothelium
What are the defenses of the skin and what does each defense do against bacteria?
Dry, acidic environment: prevents growth of many bacteria
Dead, keratinized cells: hard to degrade, and dead cells discourage colonization
Sloughing of surface cells: removes bacteria that adhere
Toxic lipids, lysozyme: protects hair follicles, sweat glands, & sebaceous glands
Normal microbiota: competes with pathogens for nutrients/colonization sites
Underlying immune cells: combat bacteria that manage to reach the dermis and tissue below
What are the mechanisms of resistance due to lysozyme?
Gram negative: outer membrane
Capsule
Proteases
What are the characteristics of antimicrobial peptides?
Small peptide
Many have helical structures
Positively charge region
Hydrophobic region
What are possible resistances to antimicrobial peptides?
Production of peptidase
Capsule
Incorporation of D-alanine into teichoic acids
Incorporatio nof D-lysine into phosphatidylglycerol
Incorporation of aminoarabinose and additional fatty acids into lipid A
What are the benefits of normal microbiota?
Occupy surfaces so pathogenic bacteria can’t colonize them
Competes with incoming pathogens fro essential nutrients
Some produce bactericidal compounds (pore-forming toxins, growth inhibitors)
In GI tract: provide metabolic pathways beneficial to host (synthesize vitamins & other nutrients)
Play role in development of immune tissue (teaching role)
What are the defenses of the eye?
Tears (washing action & antibacterial substances)
What are the defenses of the airway entrance?
Mucus traps
Ciliated epithelial cells (propel bacterium-laden mucin blobs out of airway)
What are the defenses of the stomach?
Acidic environment
What are the defenses of the small intestine?
Rapid flow of contents
Sloughing of epithelial cells
What are the defenses of the colon?
Resident microbiota
Sloughing of epithelial cells
Flow of contents
What are the defenses of the vaginal tract?
Resident microbiota
Sloughing of epithelial cells
Flow of vaginal fluid
What are the defenses of the bladder?
Sphincter keeps bacteria out of urethra
Flushing action of urine washes bacteria out of bladder
What are the consequences of venous catheters?
Biofilm formation on catheter
Movement of bacteria into bloodstream
What are the consequences of burns?
Infection of burned tissue (bacteria may move into underlying tissue & blood)
What are the consequences of damage to cornea caused by contact lenses?
Infection of cornea
What are the consequences of a respirator?
Allows bacteria to bypass defenses of upper airway
What are the consequences of perforation of the intestinal mucosa during surgery or other abdominal trauma?
Release of bacteria into otherwise sterile tissue and blood
What are the consequences of buffering of stomach acid?
Bacteria that cause intestinal infections are more likely to gain access to small intestine
What are the consequences of indwelling urinary catheters?
Constantly drains bladder, eliminating washing action of urine
Keeps sphincter open
