Bacteria and Disease Flashcards
Why is it important to use aseptic techniques when culturing microorganisms?
Mutant strain may be pathogenic
It could be contaminated with a pathogenic bacteria in the environment
Any other type of organism will contaminate it
What is a selective medium?
A growth medium containing very specific nutriants so only a particular type of microorganism will grow on it
What is a haemocytometer?
A microscope slide with a grid on it used to count cells
How is a cell culture perpared to be used on a haemocytometer?
Stained with trypan blue which indicates dead cells
What is turbidimety?
Measuring the concentration of a substance by seeing how much light passes through it
What is dilution plating?
Where you measure a culture by diluting the sample until you are able to count individual colonies.
What ways can you measure cell colonies?
Haemocytometer
Turbidimety
Dilution plating
What are the phases of cell growth in colonies?
Lag phase
Log phase
Stationary phase
Death phase
What is the leg phase of cell colonies?
The bacteria are adapting to their environment and are not repriducing at their maxiumum rate
What is the log phase of cell colonies?
When reproducton is at is maximum and repeatedly doubles in a given time period
What is the stationary phase of cell colonies?
The growth rate is 0 because the new cells are equal to cell death
What is the death phase of cell colonies?
The death rate of cells is increasing and reproduction is almost stopped
Whyc can’t bacteria continue to grow at an exponential rate?
Less nutrients avaliable
Buildup of waste products
What are the two types of toxins that bacterial cells can have?
Endotoxins
Exotoxins
What are endotoxins?
Lipopolysacchardies that are part of the outer layer of the cell wall in gram-negative bacteria
What are exotoxins?
Soluable proteins releaced by bacteria into the body that metabolise and reproduce in host cells
What is selective toxicity?
They interfere with the metabolism or function of the pathogen without damaging host cells
What is the function of antimetabolites?
They are a type of antibiotic that interupts metabolic pathways such as blocking nucleic acid synthesis which causes death
What is the function of protein synthesis inhibitors?
They are a type of antibiotic that interrupt or prevent transcripiton/translation so protein production is affected
What is the function of cell wall agents?
They are a type of antibiotic that prevent the formation of cross linking in cell walls so bacteria burst
What is the function of cell membrane agents
They are a type of antibiotic that they damage the cell membrane so water moves in and kills the cell
What is the function of DNA gyrase inhibitors?
They are a type of antibiotic that stops bacterial DNA from coiling up so it no longer fits in the cell
What does it mean when an antibiotic is bacteriostatic?
They inhibit the growth of bacteria
What does it mean when an antibiotic is bactericidal?
It destroys almost all of the pathogens
What affects the effectiveness of drugs?
concentration
local pH
pathogen
How do bacteria become resistant to antibiotics?
Some will have a mutation that allows them to survive so only they will pass their genetics on, meaning a higher proportion of bacteria are resistant
How does using antibiotics speed up the process of resistance?
It provides a selection pressure that selects for resistant bacteria
How can be reduce the development of antibiotic resistance?
Vary the antibiotics we use and find new ones
What are healthcare-associated infections?
Infections aquired by patients in hospitals like MRSA
How can we reduce healthcare-associated infections?
Iscolation of patients
Screen new patients
Hygiene measures
Controlling the use of antibiotics
