6.1 Flashcards
define pathogens
micro-organisms that cause disease
what is a culture
microorganisms are provided with the nutrients, level of oxygen, pH & temp that they require to grow large numbers so they can be observed & measured
why do aseptic techniques need to be carried out when culturing
risk that the bacteria mutates & becomes pathogenic (even if it wasn’t to begin with)
risk of contaminating with pathogenic microorganism & growing it
could contaminate pure samplesd
define sterile
something that is free from living microorganisms and their spores
how do you dispose of culture
seal in plastic bag
sterilize at 121’C for 15mins under high pressure
what is nutrient broth
a liquid nutrient for culturing microorganisms commonly used in flasks test tubes or bottles
what is nutrient agar
a jelly extracted from seaweed used as a solid nutrient for culturing, used in petri dishes
what is selective medium
a growth medium for microorganisms contaminating a very specific mixture of nutrients, so only a particular microorganism will grow on it
what is inoculating
the process by which microorganisms are transferred into a culture medium under sterile conditions
state 3 ways to grow a pure culture
grow under anaerobic/aerobic conditions
what is a hemocytometer
a thick microscope slide with a rectangular indentation and etched grid of lines that is used to count cells
what stain can be used to count only living cells
trypan blue
stains dead cells blue so only living cells can be counted
what is a turbidimetry
a method of measuring the concentration of a substance by measuring the amount of light passing through it
define turbid
something that is opaque or thick with suspended matter
what is dilution plating
a method used to obtain a culture plate with a countable number of bacteria colonies
what is a total viable cell count
a measure of the number of cells that are alive in a given volume of culture
how can you measure the growth of fungi
measure the diameter of the patches of mycelium
how can you measure the mass of cultured fungi
remove a sample from the separate the fungi & the liquid using a centrifuge or filtering
dry thoroughly at 100’C overnight then measure the mass
what is the time between bacterial divisions called
generation time
what limits the reproduction of bacteria
limited nutrients & space
build up of waste products
what is lag phase
when bacteria are adapting to their new environment are not yet reproducing at their maximum rate
what is log phase/exponential phase
when the rate of bacterial reproduction is close to or at its theoretical maximum, doubling in a given time period
what is stationary phase
when the total growth rate is 0 as the number of new cells formed by binary fission is equal to the number of cells dying
what is the death phase
when reproduction has almost ceased and the death rate of cells is increasing
give an example of waste product of bacteria leading to their decline
CO2 produced in respiration builds up and lowers the pH to a point where bacteria can no longer grow
define endotoxins
lipopolysaccharides that are an integral part of the outer layer of the cell wall of gram (-) bacteria
what are the symptoms produced by bacterial endotoxins
fever, vomiting & diarrhoea
how is salmonella spread
ingestion of food & water contaminated with infected feces
state 3 ways to avoid salmonella
cook all meat thoroughly wash hands after handling raw meat & using the toilet
avoid contaminated water
what are exotoxins
soluble proteins that are produced and released into the body by bacteria as they metabolize and reproduce in the cells of their host
which bacteria are exotoxins produced by
both gram (+) and gram (-) bacteria
what are some of the effects of exotoxins
damage cell membranes
-causing cell breakdown or internal bleeding
act as a competitive inhibitor to neurotransmitters
directly poison cells
-fatal bacterial diseases
give 3 facts about staphylococcus
only cause disease if they get inside tissues of the body
gram (+) bacteria
produce exotoxins that can cause mild skin diseases to rapid death
state the third way that bacteria act as a pathogen
invade host tissues and damage cells
what is tuberculosis
a lung disease caused by Mycobacterium tuberculosis & M.bovis
how is TB spread
droplet infection; coughing, sneezing
drinking infected milk
working close to cattle
what are the symptoms of tb
affects respiratory system damaging & destroying lung tissue
suppresses the immune system
coughing up blood
what is primary infection
the initial stage of tb when it has been inhaled evaded the cells and multiplied slowly but often causes no symptoms
what is a tubercule
the result of a healthy immune response to an infection, a localized inflammatory response forms a mass of tissue containing dead bacteria & macrophages
what adaptation allows tb to survive primary infection
bacteria produce a thick waxy outer layer to protect them from enzymes of macrophages
remain dormant in tubercules in the lungs
until immune system has weakened
define antibiotic
a drug that either destroys microorganisms or prevents them from growing & reproducing
what does selective toxicity mean
that a substance is toxic against some types of cells and organisms but not others
what is penicillin
the first antibiotic discovered
it affects the formation of bacterial cell walls and it is bactericidal
what’s the difference between bacteriostatic & bactericidal antibiotics
bacteriostatic - inhibit growth of bacteria
bactericidal - kill bacteria
state 6 factors which antibiotic effectiveness depend upon
concentration of the drug in the area of the body infected
how easily the drug can reach the tissue
how quickly it is excreted
local pH
susceptibility of pathogen
whether pathogen/host tissue can destroy the antibiotic
what is antibiotic resistance
micro-organisms that are not affected by an antibiotic even if they have been effected in the past
