Chapter 14 Flashcards
etiology
establishing cause of disease
disease
disturbance in the state of health where the body cannot carry out all its normal functions
normal microbiota
microbes always present on or in the human body
ex. gut or skin
transient microbiota
microbes that may be present in or on host under certain conditions and for certain lengths of time at sites where resident microbiota are found
what is symbiosis
describes interactions that occur between different organisms that live close together
3 types of symbiosis
mutualism
commensalism
parasitism
mutualism
association where both partners benefit
commensalism
an association in which one partner benefits but the other remains unaffected
parasitism
one organism (parasite) benefits at the expense of the other organism (host)
parasite
organism that benefits at the expense of the host
host
any organism that harbors another organism
pathogen
anything that can produce disease
contrast normal and transient microbiota
disturbances of normal microbiota can allow transient microbiota into host
how is human colonized with their normal microbiota
when foreign microbial growth becomes normal microbiota
3 conditions that create opportunities for normal microflora to cause disease
- Failure of host normal defenses (immunocompromised)
- Introduction of the organisms into unusual body sites (location)
- Disturbances of the normal microflora (microbial antagonism)
Kock’s postulates
- Suspected pathogen must be present in every case of the disease
- Pathogen must be isolated and grown in pure culture
- Cultured pathogen must cause the disease when it is inoculated into a healthy, susceptible host
- Same pathogen must be reisolated from the disease experimental host
Exceptions to Koch’s postulates
- some pathogens cannot be cultures in the lab
- some disease are caused by combination of pathogen, or a combination of pathogen + physical, environmental or genetic factors
- ethical considerations (infect healthy person)
- no single cause established
- pathogens ignored
any change is normal body function
disease
infection
organism or pathogen establishes itself in the tissue and starts to reproduce or grow - increase in number
5 fundamental requirements for a pathogen to infect host
- contamination
- portal of entry
- adherence
- avoid detection by the host
- virulence factor
portals of entry
eye nose mouth mammary glands urethra vagina anus placenta broken skin ear
portals of exit
- secretions - eyes (tears), ears (wax), nose, mouth
- skin - flakes or blood
- blood - needles, bites, wounds
- vaginal secretions/semen
- excreted body waste - urine, feces, sweat
how microbes adhere to host cells
- fimbriae, flagella, glycocalyx
- attachment proteins - viruses and bacteria, ligands bind to receptor on host cell
strategy pathogens employ to avoid host defense systems
prevent phagocytosis or detection by WBC
capsules
- prevent phagocytosis
- increase virulence of pathogens
virulence
- ability to cause disease
- degree of pathogenicity
exoenzyme produced by bacteria that destroy WBC (neutrophils and macrophages)
leukocidins
Exoenzyme that lyse (rupture) RBC
hemolysis
exoenzyme that clot blood
coagulase
exoenzyme that breaks down blood clot
kinases
exoenzyme - basement membrane, digest hyaluronic acid, helps hold cells of certain tissues together, making tissues more accessible to microbes
hylauronidase
Exoenzyme that breakdown collagen
collagenase
exotoxins
- gram positive bacteria
- soluble substances secreted into host tissues
- highly specific, some act as neurotoxins or cardiac muscle toxins
- unstable, denature above 60C and by ultraviolet light
- among the most powerful toxins
- little to no fever
type of exotoxins that damages cells
cytotoxins
type of exotoxin that damages nerve cells
neurotoxins
type of exotoxin that damages digestive system
enterotoxins
counter act the exotoxin
antitoxins
endotoxins
- gram negative bacteria
- part of cell wall and released into host tissues when bacteria die or divide
- lipopolysaccharide complex
- weak toxicity, fatal in large dose
- chills, high fever, muscle aches
- Disseminated intravascular clotting -DIC
objective, observable, or measured by others
sign
Ex. vomiting, swollen lymph nodes, fever
sign
subjective, felt by patient
symptom
Ex. cramping, muscle ache, headache
symptom
a group of signs and symptoms that collectively characterize a particular disease
syndrome
after effects of an infection
sequelae
an infectious disease that is easily transmitted from one host to the next
Ex: measles, chicken pox
contagious
an infection that is transmitted from one host to the next
Ex: influenza, herpes
communicable
disease arising from outside of hosts or from microbiota; not spread from host to host
Ex: tooth decay, tetanus, acne
noncommunicable
disease in which symptoms develop rapidly and runs its course quickly
acute disease
disease in which symptoms develop slowly and slow to disappear
Chronic disease
disease with intermediate symptoms
subacute disease
presence but not multiplication of viruses in the blood
viremia
presence but not multiplication of bacteria in the blood
bacteremia
presence and multiplication of bacteria in the blood
septicemia
presence of toxins in the blood
toxemia
initial infection in a previously healthy person
primary
infection that immediately follows primary infection
Ex. flu then strep
secondary
secondary infection that results from the destruction of normal microflora Ex after use of broad spectrum antibiotic
superinfection
infection caused by 2 or more pathogens
Ex. periodontal disease
mixed infection
5 typical stages of infectious disease
- Incubation period
- Prodromal period
- Illness (Invasive phase)
- Decline phase
- Convalescence phase
time between infection and appearance of signs or symptoms
incubation period
incubation period
- virulence - degree of pathogenicity
- infective dose - how many particles it takes to get the infection
- state of health - poor nutrition, stress, lack of sleep, unemployment
- nature of pathogen
- generation time - double in number
prodromal period
- mild symptoms
- not present in all illnesses
Illness (invasive) phase
-most severe stage
-immune system not yet responding
Acme- signs and symptoms most intense
-pyrogens -fire; fever production
-pyogens - puss; white patches on throat
decline phase
- number of pathogens decrease
- immune system responds or medical treatment works
- symptoms/signs subside
convalescence phase
- patient recovers
- tissues/systems repair
- return to normal
modes of transmission
contact
vehicle
vector
pathogenicity
- ability to invade host
- multiply in host
- avoid hosts defenses
use precise genetic techniques to determine the pathogenicity of disease or disease producing capabilities
molecular postulates
disease process
contamination -> infection -> disease
exoenzymes
hyaluronidase, collagenase, coagulase, kinases, hemolysis, leukocydins
