Lecture 8 Flashcards
Susceptible host
non-infected, non-immune at risk individual
risk
Travel to places which have high rates of certain infectious diseases
Unprotected sex
Pneumonia in air spaces in lung lungs. younger more at risk
Immune Senisence: Immune system becoming senile. Diminishing in its capacity with age.
Other illness
Immune deficiency
Other factors
Immune senisence
Immune system become senile/diminishing in its capacity with age
What are the possible areas where a pathogen could be caught?
Exogenous human to human transmission
endogenous infection (bulk of hospital infectious disaese. bacteria getting to wrong place in the body)
exogenous the environment
Exogenous zoonosis (from animal/other living entity)
Colonisation
similar to sub-clinical infection
different to normal body flora
(10x more bacteria living on you than there are cells in your body) -bacteria more unique than dna. Gut flora/bacteria mostly there to help you. if ruin (with antibiotics) can lead to problems
another species invades
20% are colonised with staflacoccus aures nose. never get disease.
1. no symptoms. +/- host immune response. potentially infectious
Primary Pathogens
isolation is always pathogenic
-gonorrhoea
Principle pathogen
isolation is usually pathogenic cause infections in otherwise well people with intact defences -TB -cough, from sputum -almost never just hanging around
Opportunistic pathogen
Cause infections only when defences are down
older or young people
Gonorrhea
Primary pathogen most people illustrate symptoms -can cause subclinical infection (more in woman) (esp. throat) -treated as could be transmissable Exogenous Human to human risk associated behaviour Does NOT live in the environment
Setting of infection
Infections can occur in the community or in healthcare settings
-community onset (cold/flu upper respiratory tract infections, chickenpox, diarohhea. common, generally pretty mild, no treatment required)
-community acquired (doesnt have to be community onset disease. staph aureas, colonised people has hip operation, gets infected with staph aureas, has been caught in hospital. illness only apparent becuase of hip operation)
-hospital acquired (
-hospital onset (healthcare associated)
nosocomial (health care associated)
Healthcare associated: not hospital required but is anything provokes/related to modern health care. dialisis machines at home, needles into arm blood comes out. opportunities for infection, as blood for a period of time is exposed to outside world, and access for germs to enter into blood. (blood stream infections are more common for people on dialisis than people who aren’t)
-related to environmental exposure.
What is the importance of health care associated infections?
often Preventable
-hand hygiene
is a very common complication of health care
kills people (hosts often sicker/older people
is often avoidable
costs NZ: 300 mil each year
What is the single most important activity that you need to do to reduce HAI?
hand hygiene 5x moments: 1. before patient contact 2. after patient contact (before going elsewhere) 3. 4. 5. after leaving patient environment
What are one of the large “at risk groups” for infectious diseases?
Health care workers
- Noro virus
- cough
- protect via washing hands
Infection and disaese
to cause infections an organism must possess an array of factors that regulate interaction with the host
-infection:outcome of replication (something driving it to replicate and produce offspring)
the disease occurs when these factors damage the host and/or incite a substantial host immune response
Virulence factors=in bacteria
Virulence factors
in bacteria. usually proteins(sometimes carbs)
the genetic determinants that allow a pathogen to cause disease (interact and damage host cells)
-Adherence/Interaction (scaffolding strut on outside enabling bacteria to bind to human epithleial cells)-bacteria that cant interact themselves often cant cause disease
-Invasion (produce things to enable it to get into tissues)
-Immune evasion (as soon as bacteria interacts/damages human cell, immune system is activated, bacteria need to have some skills to avoid immune system)
-Toxins (proteins bacteria releases outside of themselves (exotoxins) which can damage human tissues)
Ecoli gets into bladder, must be able to bind to bladder cells (some strains cannot bind and therefore do not cause infection). Must be able to invade layers beneath outer lying cells via releasing alpha toxin which damaged bladder lining, enabling it to invoke new response and pain, difficulty with urination/possibly fever
How does a skin infection develop?
use virulence principles
Virulence
description of the capacity of the bacteria to cause disease
- the capacity to cause disease in hosts with intact defences (highly virulent e.g. Staph aureaus - can causes disease without any invitation. Micobacterium TB- can causes disease in otherwise perfectly health human)
- requires some breach of host defence(s)
- commensal that rarely causes disease
- commensal that “never” causes disease (low virulence)
Humans covered in bacteria
human flora
approx 5000 different species live in humans
1 quadrillion bacteria mostly in the gut (there are 100 trillion cells in the body)
Gut flora
anaerobic bacteria
enterobacteriaceae (E coli)
Enterococcus faecalis
non-uniform : germs in small intestine are different to germs in large intestine. germs in saliva have different properties to the germs under the gum
-organisms adapted to grow where oxygen levels are low, tolerate bile
help breakdown carbohydrates such as lactose
