Week 1 Flashcards
What are pathogenic microorganisms (5 types)
- bacteria
- virus
- parasite
- fungi
- parasitic protozoa
The pathogens that cause serious human infections (3)
BACTERIA is number one
then worms
then viruses
10 most burdensome infectious diseases in ontario
- hepatitis C virus
- streptococcus pneumoniae
- Human papillomavirus (HPV)
- Hepatitis B virus
- E. coli
- HIV/AIDS
- staphylococcus aureus
- influenza
- clostridium difficile
- rhinovirus
Leading cause of death - higher income
lower respiratory infections are the only to make the list
Leading cause of death - lower income
5/10 are infections (lower respiratory, diarrhoeal, malaria, TB, HIV/AIDS,
Social determinants of health + infectious disease
- when inequities are high, community assets low, health outcomes are WORST
Endemic Disease
- disease is always present in a population within a region
- “expected” levels
Epidemic (1)
a rapid increase in cases higher than expected in a population within a region
Epidemic examples
- EX SARS, Ebola, Cholera
Pandemic
an epidemic that becomes widespread over several regions, countries, continents
Outbreak
epidemic on a MUCH smaller scale (ex hospital floor)
Chain of infection
Infectious agent –> resevoir –> portal of exit –> mode of transmission –> portal of entry –> susceptible host
Resevoir
habitat where organism grows, lives, multiplies
- people
- equipment
- water
- animal
Portal of exit
means to leave the body
- excretions
- secretions
- droplets
Mode of transmission
- contact
- droplet
- airborne
- vector-borne
- vehicle-borne
Portal of entry
- respiratory tract
- GI tract
- Mucous membranes
- skin
Susceptible host
- people with chronic disease
- immunocompromised
- very young
- elderly
Opportunities to break chain of infection
- infectious agent is eliminated
- portal of exit is managed via IPC practices
- transmission does not occure due to IPC
- portal of entry is protected
- reducing susceptibility of patients recieving healthcare
Infectious agent is eliminated:
- rapid identification and management of organisms
- clean and disinfect environement
Portal of exit is managed
- hand hygeine
- PPE
- safe packaging
- disposal of waste
Transmission does not occur
- hand hygeine
- isolation of infected patients
- air flow control
Portal of entry is protected
- aseptic non-touch tequnique
- safe catheter care
- wound care
reduce susceptibility of patients
- treatment of underlying disease
- recognize high risk patients
Host-pathogen relationship - 3 factors
1) number of organisms in or on the host (higher = greater risk)
2) virulence of the organism
3) host defenses or degree of resistance
Virrulence
capacity of a microbe to cause disease
Why do some pathogens cause disease and others don’t
- Virulence (ability of organism to cause infectious disease)
- some infectious agents are easily transmitted but not very likely to cause disease (Ex polio)
- other infectious agents are very virulent, but not terribly contagious (ebola)
Virulence factors of pathogens
1) flagella , pili, capsules
2) exotoxins and endotoxins
Flagella
tails on bacteria for movement
Pili
aka fimbrae
short straight filaments that allow pathogens to bind to cells
Capsules
sugar coating on pathogens that make macrophages unable to target them
Exotoxins
exert biological effect on host cells
EX neurotoxins cause paralysis
others cause diarrhea, etc.
pyrogenic toxins = cause fever and rash
Endotoxins
- lipopolysachuride, gram - bacteria
- cause fever, malaise, etc.
Host susceptibility (5)
- immune system
- age
- nutrition
- genetic defects
- medications (ex chemo)
Host resistance (3)
- Barriers (epithelial layer, resp and GI tract,)
- Chemical (tears, saliva, gastric juice)
- Immunity against a particular agent (vaccines, antibody, etc.)
