W2 interaction between microbe and host Flashcards
normal flora
covers body surfaces exposed to external environment and they are protective because they take up all the space
they are consistent at a given site but varies from site to site
large intestine has e.coli
upper respiratory track has streptococcus
what can make normal flora harmful
excessive moisture
antibiotic use
contamination
microorganism that is introduced where its not expected there is no growth yet therefore no damage
colonization
growth after contamination there is still no damage
DISEAse or infection
damage due to colonization
infection means the host is invaded there is still no signs yet
disease the host is invaded and injury is evident this occurs when symptoms begin
ex of colonization
bacteria occasionally grow on bladder mucosa with no harm
ex of infection
tb is growing in wbc but not yet causing harm
pathogen
causes disease
etiology
cause of disease
virulence and virulent factors
degree of pathogenicity
virulent factors increase the ability to cause disease
-enzymes that dissolve hyaloric acid (tissue cement)
-enzymes that destroy rbc so that iron is for bacteria
-slimy capsules around bacteria that prevent phagocytic abc from engulfing them
non pathogenic
can’t cause disease
low grade pathogens
don’t cause disease under most circumstances, they are opportunistic, they cause disease when the immune system is compromised.
ex. e.coli aren’t harmless until introduced to an are like bladder where they cause disease
what is a bacterial toxin
causes damage to sites far removed from initial infection site
exotoxin is usually gram positive and it is released from initial bacteria, carried by blood to specific tissue
endotoxin-usually from gram negative bacteria and it is in the cell wall, it is released when bacteria cell disrupted and it is a generalized effect such as fever malaise and decrease in blood pressure, this can be from antibiotics
chain of infection
3 elements required for transmission-outbreak cycle
1. source, 2.. transmission 3. susceptible host they all overlap to create the biohazards symbol.
to break the chain you must eliminate one element, stop source eliminate transmission or reduce susceptibility through handwashing immunizations, ppe, sterilization.
reservoirs
this is the source
human reservoir
the human body is the most common source and these people are known as CARRIERS they are harbouring pathogenic organism with no sign of infection this is the early most infectious stage and the carrier does not have any symptoms, this is the incubation period.
animal reservoir– called zoonoses found in animals and transmitted to humans- like salmonella
non living reservoir-soil or water
**moist environments in healthcare wet sinks and flowers
convalescent carrier
recovered but still carrying disease
chronic carrier
convalescent carrier for more than 6 months
transmission
3 possible ways
contact-direct, indirect and droplet
direct is person to person
indirect is person thing person
droplet is close proximity to someones fluids
vehicle-food/water/air it transmit live microbe** uncommon in clinical setting.
–droplet nuclei means its in air for more than 1 meter or a long time
vector-insect one host to another for example mosquitoes with malaria not common in hospital
susceptible host
someone will encounter microbe resulting in disease, factors related to health and age
ex: newborns highly susceptible because of low exposure and immature immune system, even therapeutic measures like chemo surgery and catheters can make people more susceptible.
portals of entry
skin- hair follicle, sweat gland **broken skin or very moist skin
mucous membrane in respiratory tract, gastrointestinal tract, or genitals
-placenta- filter moms blood only a few like AIDS, hep B and rubella can get through
parental-introduction bipasses gastrointestinal tract-intramuscular and intravenous
signs and symptoms of infection
fever- increase in temp of 1 degrees celsius also known as pyrexia BLOOD VESSELS CONSTRICT increase metabolism and shivering the skin is cold, when the fever breaks people sweat.
lymph node swelling- microbe from tissue trapped in lymph node or multiplication of lymphocyte. cervical lymph node in neck axillary lymph node in armpit and inguinal lymphnode in groin
inflammation- host cells invaded release histamine and this initiates inflammation– heat red pain swell histamines cause vasodilation and increased permeability of blood vessels so fluid goes into tissue and phagocytic white blood cells can get there–antibodies travel there too as well as platelets to surround microbes.
purulent exudates
plus and this is phagocytic abc that are dead
acute disease
symptoms develop rapidly and go away rapidly like a cold
chronic disease
symptoms develop slowly and are slow to go away
