Lecture 5 Flashcards
Factors in disease process
- infectious agents
- disease reservoirs
- mode of transmission
- body’s defenses
- host resistance and susceptibility
10 bad pathogens
- salmonella
- campylobacter
- norovirus
- staphylococcus
- E. coli 0157:H7
- listeria
- shigella
- toxoplasma gondii
- vibrio vulnificus
- botulism
Normal microbiata
colonize the body’s surface without normally causing disease
- resident (lives for our entire lives)
- transient (come and go bc of body functions)
Opportunistic pathogens
normal microbiota that cause disease under certain circumstances
conditions for opportunities are:
- introduction of normal microbiota into unusual site
- immune suppression
- changes in normal microbiota (i.e. change in relative abundance)
contamination
the presence of microbes in or on the body
infection
when organism evades body’s external defenses, multiplies, and becomes established
colonization
when the microbe is allowed to fluorish/be established for growth
Adhesion and infection
- pathogens need to attach themselves to the cell to establish colonies in the host
- use adhesion factors
- bacteria can attach to each other by biofilm
Preventing adhesion and infection
- changing/blocking a ligand or its receptor
- inability to make attachment proteins or adhesins renders them avirulent
Symptoms of Disease
subjective characteristics of disease felt only by the patient
Signs
objective manifestations of disease observed or measured by others
Syndrome
symptoms and signs that characterize a disease or abnormal condition
Etiology
study of the cause of disease
Koch’s Postulates
- suspected agent must be present in every case of the disease
- agent must be isolated and grown in pure culture
- cultured agent must cause the disease when it is inoculated into a healthy, susceptible experimental host
- same agent must ne reisolated from the diseased experimentlal host
Exceptions to Koch’s postulates
- some pathogens can’t be cultured
- diseases caused by a combination of pathogens and cofactors
- ethical considerations prevent applying to human hosts
Pathogenicity
ability of a microorganism to cause disease
Virulence
degree of pathogenicity
- adhesion factors
- biofilm
- extracellular enzymes
- toxins
- antiphagocytic factors
Extracellular enzymes as a virulence factor
secreted by the pathogen
- dissolve structural chemicals in the body
- help pathogen maintain infection, invade, and avoid body defenses
Extracellular enzyme pathway
- invasive bacteria reach epithelial surface
- bacteria produce hyaluronidase and collagenase
- bacteria invade deeper tissues
OR
- bacteria produce coagulase
- clot forms
- bacteria produce kinase, dissolving clot and releasing bacteria
Toxins
chemicals that harm tissues or trigger host immune responses that cause damage
Exotoxin
Bacteria secrete exotoxins
- cytotoxin kills host cells
Endotoxin
endotoxin released by gram-negative bacteria from lipid A which induces effects like fever, inflammation, diarrhea, shock, and blood coagulation
- stimulate macrophages to secrete IL-1 causing prostaglandin production
- stimulate phagocytosis, complement activation, antibody production by B cells
- high amounts cause loss of fluid and lowering of blood pressure leading to shock
- often in sepsis
Ways to classify exotoxins
Location- where they are located in the host (i.e. neurotoxins, enterotoxin)
Structure and Function- AB toxins (two domains), Membrane Disruption, Superantigens
A-B Toxins
- A domain has particular function
- B domain is the binding component (binds to receptor on host cell)
- once bound, it is endocytosed into the host cell
- B domain creates a pore and the A domain is released into cytosol
- inhibition of protein synthesis
Membrane disrupting toxins
- form protein pores in plasma membrane
- disrupt phospholipid portion
- results in cell lysis
Superantigens
bacterial cytotoxins that stimulate an immune response
- causes proliferation of T cells
- T cells secrete excessive amounts of cytokines
- ex. staphylococcus aureus (food poisoning)
