Pathogenesis Flashcards
What are the structures that pathogens use to adhere to host cells?
-capsules
-proteins
-fimbriae
-pili
What environmental factors affect the ability of a pathogen to colonize a host?
-pH
-Temperature = 37
-Oxygen = body mostly aerobic
-Nutrients
How is virulence measured?
-LD50=Lethal Dose to kill 50% of infected animals
What is a virulence factor?
-Any protein or cell structure expressed by a pathogen that increased its ability to cause disease
-are things produced by the pathogen that increase its ability to cause disease
What are Exotoxins?
-Exo is protein released from bacterial cell that affects host cells
-travels in the host and cause damage elsewhere
-hemolysin
-can lyse other host cells
What are Enterotoxins?
-Entero is an exo that works in the intestinal tract (SI)
-causes fluid release (diarrhea)
What are Endotoxins?
-Endo is LPS on the outer membrane of Gram-negative bacteria.
-causes inflammation, fever, diarrhea, cytokine release and excitation of immune cells
-shock -> death
What are the mechanisms of action of the various toxins discussed in class?
-Hemolysins
-Botulinum and Tetanus toxin
-Cholera
Hemolysins
-Hemolysins lyse cells by acting as lipase or as membrane pore
-lyses red blood cells (RBC)
Botulinum toxin and Tetanus toxin
-block neurotransmitter function to cause either inability to contract muscles (BOT) or inability to relax muscles (Tetanus)
Cholera toxin
-cholera toxin produces cAMP, triggering cells to block Na uptake and to release CL into intestinal lumen
-Water follows the salt to produce diarrhea
What diseases are caused by Streptococcus species?
-Pharyngitis
-Otitis media
-Mastitis
-Impetigo
-Erysipalas
-Scarlet fever
-Rarely necrotizing fasciitis
-Rheumatic fever
How does Borrelia burgdorferi spread and what are the characteristics of its infection of humans?
-Tick vector from Deer or mice
-No toxins, just inflammation
-Erythema migrans = red rash spreading from tick bite
-gram negative spirochete
tick must be on human for >24 hours (48 hours)
What is the subclinical zone?
-zone where a person shows no symptoms
-or have an asymptomatic infection
-look at graph
When a person no longer shows symptoms does that mean the infection is gone? example?
-No, just because a person has no symptoms does not mean the infection is gone
-Malaria
Steps of infection/pathogenesis
-exposure
-adherence
-invasion
-multiplication
-toxicity
-invasiveness
-tissue or systemic damage
What is part of the infection process?
-adherence
-invasion
-multiplication
what is part of the disease process?
-toxicity
-invasiveness
-tissue or systemic damage
What is the first step in the infection process?
-exposure
Adherence
-to skin or mucosa
-no adherence, no infection
-adhesin
-host receptor
Invasion
-through epithelium
-Colonization/Infection
-evade immune system
-find hospitable environment
-acquire nutrients
multiplication
-growth and production or virulence factors and toxins
-bacteria need to grow, grow faster than getting killed
Toxicity
-toxin effects are local or systemic
Invasiveness
-further growth at original and distant sites
What are adhesins and host receptors?
-adhesins=substance that adheres
-host receptor= adhesin receptor, binds (specifically)
Capsules
-pathogenic E.Coli
-Streptococcus mutans
Proteins
-Streptococcus pyogenes=M proteins bind to respiratory mucosa
-Neisseria gonorrhea=Opa protein bind to CD66
Fimbriae/Pili
-Neisseria gonorrhea
-Salmonella species
-Pathogenic E. Coli
Lipoteichoic acid
-Streptococcus pyogenes
Are Fimbriae sticky?
yes
How are vaccines designed?
-create antibodies to block receptors
-only effective when the pathogen adherence stays the same
When a pathogen invades what nutrients do they need to acquire?
-Iron (Fe) is usually a limiting factor
-Human proteins transferrin and lactoferrin tightly bind Fe
-Some bacteria can bind these host proteins and acquire iron
-some bacteria make their own chelators (siderophores) to trap the limiting iron
What bacteria can bind to host proteins and acquire iron?
-Neisseria makes a transferrin receptor protein
What bacteria can make their own chelators (siderophores) to trap the limiting iron?
-E. Coli makes Aerobactin that binds iron and returns it to the cell.
What is a chelator?
-molecules that have the ability to bind to metal ions and form stable complexes
-siderophores are specialized molecules that scavenge for iron from their surroundings
Virulence
-a measure of ability to cause disease
-how many bacteria does it take to cause an infection
Does Streptococcus pneumonia or Salmonella need more bacteria to infect?
-Salmonella needs more which means it has a low virulence
How many virulence factor will a single pathogen make?
-multiple virulence factors
What are some non-protein toxin virulence factors?
-endotoxin
What are some protein toxin virulence factors?
-Exotoxins
-Enterotoxins
How do exotoxins act?
-cleave membrane lipids (lipases)
-forming pores in the membrane and killing the cells
What are some examples of extoxins?
-C. botulinum toxin blocks nerve stimulation of muscle contraction: Botulism, flaccid paralysis
-C. tetanus toxin causes constant nerve stimulation of muscle contraction: Tetanus (lockjaw)
Streptococcus
-Gram-positive cocci in chains
-common member of normal flora of upper respiratory tract
-pathogenic strains generally produce capsules
-broad range of species and strains
-everyone has some in their upper respiratory tract
When does streptococcus cause a problem?
-you acquire a strain that is not apart of your normal flora and it has a greater virulence than your normal flora
-when the flora strains move out of their normal location
Streptococcus: Pharyngitis
-strep throat
Streptococcus: otitis media
-ear infection
Streptococcus: matitis
-mammry glans
Streptococcus: erysipelas
-very red skin
Streptococcus: necrotizing fasciitis
-flesh eating bacteria
Streptococcus: Rheumatic fever
-autoimmune reaction against heart valves due to similar antigens
-for life, permanent damage
Neisseria meningitidis
-gram negative diplococci
-bacteremia
-meningitis
-rapid progression10% death even with aggressive treatment
-common in college student populations
-GET VACCINATED
Bactermia
-invasion of bloodstream
-toxins cause coagulation and interrupted blood flow to extremities
Meningitis
-inflammation of the membranes around the central nervous system
Borrelia burgdorferi
-grows in many wild animal mammals without clear disease
-Lyme disease
-common in northeast and Midwest
-increase incidences
-treatable with antibiotics
Why have incidences of Borrelia Burgdorferi gone up?
-increase in reporting
-increase deer population
-increase human/tick contact
What are the symptoms and initial symptoms of Borrelia Burgdorferi?
-Initial=erythema migrans spreads from bite over several days
-bulls eye rash
-headache, chills fatigue
What happens if Borrelia Burgdorferi is untreated?
-arthritis as bacteria invade joints
-invasion of NeuroSystems
-palsy, facial ticks, weakness
Enterotoxin pathway
- normal ion movement, Na+ from lumen to blood no net Cl- movement
- Colonization and toxin production by V. cholerae
- Activation of epithelial adenylate cyclase by cholera toxin
- Na= movement blocked, net Cl- movement to lumen
- Massive water movement to the lumen; cholera symptoms
-diarrhea
what is Enterotoxin and its treatment
-cholera toxin: AB-form toxin
-increase amount of cyclic AMP
-water with salt
