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
latent disease
periods of inactivity before or during herpes
localized infection
confined to one area- step throat.
septicemia
presence of multiple pathogens in blood
focal infection
confined to one area but pathogens or toxins move to a new area
bacteremia
bateria in blood, not multiplying just hitching a ride
viremia
presence of virus in blood but not multiplying just hitching a ride
exogenous infection
cause infection from outside of body
endogenous infection
cause of infection from inside of body, e.coli from intestine makes way to urinary tract resulting in utility
primary infection
infection previously healthy person
secondary infection
infection that immediately follows a primary infection
ex: secondary bacterial infection following primary viral infection, pneumonia after the flu or a yeast infection after antibiotics
nosocomial infection
acquired when patient in hospital or health care associated infection HCAI
5-15% of all hospital patients acquire one (also depends on population)
factors of nosocomial infections
-hospital microorganism bacteria brought to hospital and all but antibiotic resistant bacteria are killed off
-immunodefficient patient-weakened immune system due to treatment or condition
defective mean is different it means that b or t cells don’t work
-transmission- easily due to close proximity and also OPENINGS FROM SURGERY ARE MOST COMMON
what are antibiotics
- produced by microorganisms like funds and it inhibits bacterial growth or kills bacteriA
- inhibit the cell wall synthesis or protein synthesis
- penicilen discovered by alexander flemming in 1928
antibiotic susceptibility testing
this is used to choose which antibiotic is going to be used for treatment
the bacteria allowed to colonize agar plate and paper discs soaked in antibiotics are placed around plate and this culture is interpreted.
if clear area around disc- antibiotic effective
if bacteria grow right to disc its not effective
antibiotic resistant organisms or aro
multi drug resistant organisms called mdro
secondary antibiotic required, and the y are less effective they are difficult and expensive to treat and patients must be isoleted
ex: MRSA VRE
modes of resistance
some naturally become resistant
- over prescription causes the resistant bacteria to thrive and increases the likely hood for them to evolve
- people stop taking antibiotics and this makes the strong ones survive
- mutation-makes them resistant all regular bacteria die and the resistant ones to colonize
- -conjugation resistant bacteria and harmless bacteria share genes
MRSA
-spread in healthcare setting and transmitted by direct contact.
MRSA difficult to eradicate from an institution and increases patient mortality
prevention -identify cases and screen swab everyone coming in
-isolate case
-identify carriers either staff or patients
-eradicate MRSA from carriers
vancomycin resistant enterococcus
VRE
in normal bowel flora and if they get into urinary tract its a low grade pathogen with no real threat if individual is healthy
they are resistant to all drugs and untreatable so it can be fatal and it is mostly spread in a hospital setting
to combat this hospitals restrict the use of antibiotics and use rigorous hygiene procedures.
clostridium difficle
CDAD
spore formed in intestine
following antibiotic therapy, with vancomycin the normal flora decreases and the spore is able to vegetate and it produces a toxin which effects the intestinal wall and sometimes causes death, an indicator of this is water stool
miscellaneous modes of controlling infection
silver has antibacterial qualities and is put in bandaids catheters and clothing
phages are viruses that infect bacteria
infection prevention and control programs-what do they do
- surveillance and analysis of nosocomial infections
- surveillance of antibiotic resistance
- investigate control of outbreaks
- implement and monitor preventative measures
- education
- policies
- consult with epidemiologists they study the incidents, source and spread of disease
