Topic 10 - Principals of diseases Flashcards
What is the difference between transient and normal microbiota?
Transient - present for days, weeks or months
normal - permanently colonize host
What is symbiosis?
The relationship between normal and microbiota and the host
What is the definition of:
Pathology, Aetiology, Pathogenesis, Infection and disease?
Pathology - Study of disease
Aetiology - Study of the cause of disease
Pathogenesis - Development of disease
Infection - Colonization of the body by pathogens
Disease - Abnormal state where body doesn’t function normally
Where are normal microbiota located?
Nose and throat - URT Eyes Mouth Skin Large intestine Urinary and reproductive systems
What are the different types of symbiosis?
Commensalism, mutualism, parasitism and opportunistic pathogens.
What is commensalism?
When one benefits and the other is unaffected.
What is mutualism?
When both organisms benefit
What is parasitism?
When one organism benefits at the expense of the other
What are opportunistic pathogens?
They are some normal microbiota which when given the opportunity thrive and cause disease.
What is microbial antagonism?
It is a competition between microbes.
What do normal microbiota do?
- occupy niches that pathogens
- producing acids
- producing bacteriocins
What are probiotics?
Live microbes applied or ingested into the body which are intended to exert a beneficial effect.
What are Koch’s postulates?
- Same pathogen needs to be present in every disease case
- Pathogen needs to be isolated from the diseased host and grown in pure culture
- Pathogen from pure culture must cause disease when inoculated into a healthy, susceptible lab animal
- The pathogen needs to be isolated from inoculated animal and must be shown to be the original organism
What did Koch’s postulates do?
They helped him prove a single agent was the cause of disease and it was a break through of how people thought about disease at that time.
Wha are the limitation to Koch’s postulates?
- they are used to prove cause of infectious disease
- some pathogens cause several disease conditions
- some pathogens only cause disease in humans
- cant be used for diseases linked with autoimmunity or ageing (such as cancers).
What are the factors taken into account for infectious diseases?
- symptoms: change in body function felt by patient as a result of the disease
- sign: A change in body that can be measured or observed as a result of disease
- syndrome: A specific group of signs and symptoms that accompany the disease
What are communicable, contagious and noncommunicable diseases?
- Communicable is a disease spread from one host to another
- Contagious is a disease which is easily spread from one host to another
- Noncommunicable is a disease that is not transmitted from one host to another
What are the differences in occurrence of diseases?
- Incidence: fraction of a population contracts the disease during a specific time
- Prevalence: fraction of the population have the disease at a given time
- Sporadic: a disease that occurs occasionally in a population
- Endemic: a disease which is constantly present in a population
- Epidemic: a disease acquired by many hosts in a given area in a short time
- Pandemic: worldwide epidemic
- Herd immunity: immunity in most of the population
What are the different severity/duration categories of diseases?
Acute, chronic, subacute and latent
What are acute disease?
Symptoms which develop rapidly
What are chronic diseases?
Diseases which develop slowly
What are subacute diseases?
Symptoms between acute and chronic
What are latent diseases?
Disease with a period of no symptoms when the causative agent is inactive.
What are the different disease severity?
Local infection - pathogens are limited to a small area of the body
Systemic infection - an infection throughout the body
Focal infection - systemic infection which began as a local infection
Sepsis - toxic inflammatory condition due to spread of microbes (mainly bacteria) from a focus infection
Bacteremia - bacteria in the blood
Septicemia - growth of bacteria in the blood
Toxemia - toxins in blood
Viremia - viruses in blood
Primary infection - acute infection which causes initial illness
Secondary infection - opportunistic infection following primary infection
Subclinical - no noticeable signs or symptoms (inapparent infection)
What is herd immunity?
Immunity that occurs when enough of the population is immune to the disease to break the chain of transmission. This can be produced as a result of vaccinations.
What makes an individual more susceptible to disease?
- short urethra in females = increased UTI chance
- inherited traits = sickle cell disease
- climate and weather
- fatigue
- age
- lifestyle
- chemotherapy
What are the stages of disease?
- Incubation period
- Prodromal period
- Period of illness
- Period of decline
- Period of convalescence
What is a reservoir of infection?
A continual source of infection
What are examples of reservoir infections?
Humans- HIV, gonorrhea or any disease that can be untreated or be inapparent and is transmissible.
Carriers have inapparent or latent disease
Animals- rabies or lyme disease which are zoonoses
some disease can be cased by non-living things (botulism and tetanus)
What are the three methods for diseases transmission?
- contact transmission
- vehicle
- vector
What are examples of contact transmission?
- direct: close association between infected and susceptible host
- indirect: spread by fomites
- droplet: transmission via airborne droplets
What are examples of vehicle transmission?
Transmission via an inanimate reservoir (food, water and air)
What are examples of vector transmission?
There are 2 methods:
- mechanical - arthropods (fleas, ticks, mosquitos) which carries pathogen
- biological - pathogen reproduces in the vector
What are nosocomial infections?
Infections which are acquired as a result of hospital stay. These affect 5-15% of all hospital patients
What is a compromised host?
A persons resistance which is impaired by:
1. disease
2. therapy
3. burns
The broken skin or mucous membrane make it an easy portal of entry and a suppressed immune system makes it easier for infection to start as lymphocytes are suppressed.
What are the principal sites of nosocomial infections?
UTI’s (40%), surgical site (20%), LRT infections (15%), bacteraemia transmitted primarily by IV cathetars (6%), cutaneous infections (8%) and other (11%)
How can nosocomial diseases be prevented?
aseptic techniques, correct contaminated material disposal, thorough and frequent hand washing, prescription of antibiotics only when appropriate and monitoring/sampling of clinic items such as air and instrument sterility.
The most important method is washing hands.
