Lecture 3 Flashcards
What is the difference between sterilisation and sanitisation?
Sanitation is the process that destroys various microorganisms to meet quality and health standards
Sterilization is the removal of all microbes including bacterial spores
What is the difference between a disinfectant and an antiseptic?
Disinfectant is on inanimate areas
Antiseptic is on animate areas
What is the purpose of pasteurisation in the food industry?
It was originally invented to prevent the spoilage of wine, however, its mostly used for milk products.
It kills key pathogens, reduces spoilage bacteria and extends the shelf life of products
What are the temperatures and times for Low Temperature Long Time (LTLT) and High Temperature Short Time (HTST) relating to pasteurisation?
LTLT – 63 degrees, 30 mins
HTST – 72 degrees, 15 secs
List the 3 modes of action of chemical disinfectants?
Proetin coagulation / denaturation
Disruption of cell membrane
Chemical antagonism (inactivation of enzymes)
What is the optimal percentage of alcohol for disinfection?
Optimal is 70%
Betadine is a combination of iodophor and detergent which is used as a skin disinfectant in pre-surgical operations. List the advantages and disadvantages of Betadine for this use.
Advantages Good residual effect Effective of a wide range of microbes Disadvantages Skin discolouration Hypersensitivity Pseudomonas able to grow
What is the mechanism of action for Quaternary Ammonium Compounds (QUATs) against bacteria?
Disruption of the cell membrane
Why are QUATS no longer used in some hospital settings?
There are more effective agents that replaced it
How could the presence of organic matter interfere with the action of disinfectants? (3 ways)
Form a precipitate with disinfectant – removes disinfectant from contact with bacteria
Reacts with the disinfect and to produce a non-bactericidal agent
Coats bacteria – protects the bacteria from the disinfectant
UV radiation damages proteins and nucleic acids of bacteria. What is the main disadvantage of UV radiation as a disinfectant?
Low penetrating power
Moderate exposure time
What size particles are N95 masks rated to remove?
0.3 micrometers or µm
What is Sterilisation?
The removal of all microbes
Why are endospores difficult to kill?
They have a thick protective outer shell that shields them from radiation and chemicals
Why is moist heat better than dry heat? What are the typical conditions used for moist heat sterilisation?
Moist heat is a better conductor of heat and better heat penetrator
15 minutes @ 121 degrees at 15 psi above atmospheric pressure
In what circumstance would you probably use a dry heat oven instead of autoclaving?
To prevent sharp instruments becoming blunt
Glassware, oils and powders
What methods are used to ensure an autoclave is working?
Biological – spore strips Autoclave tape (Bowie-dick test)
Name two chemicals used for “cold sterilisation”.
Formaldehyde
Glutaraldehyde
Ethylene oxide
Plasma Sterilisation (hydrogen peroxide gas)
How does ionizing radiation affect microbes and kill them?
Damages DNA by disrupting chemical bonds in cells
State the filtration pore size needed to filter out a) bacteria, b) viruses.
Bacteria – 0.01 micrometers
Viruses – 10 nanometers
What is the difference between Bacteriostatic and Bactericidal agents?
Bacteriostatic stops the microorganisms from growing but does not kill them
Bactericidal agents kill microorganisms
List the 6 modes of action for anti-bacterial agents (i.e. 6 target sites).
Inhibitors of cell wall synthesis Membrane active antimicrobial agents Inhibitors of DNA replication Inhibitors of RNA synthesis Inhibitors of ribosome synthesis – protein synthesis Metabolic inhibitors
Describe the action of the β-lactam antibiotics.
Inhibits cell wall synthesis
Stops the last stage of cell wall production which results in cell lysis (disintegration of a cell by rupture of the cell wall or membrane)
How could incompletion of a prescribed course of antibiotics lead to bacterial resistance?
Should there be a small proportion of bacteria with antibiotic resistance, normally the antibiotics would kill the bacteria and the resistant bacteria would be taken care of by the immune system. If the course is incomplete, it leaves the susceptible bacteria alive for the resistant bacteria to then transfer their resistant genes. This results in the bacteria multiplying and the majority can become resistant.
Why are antibiotics of no use against the common cold?
Antibiotics only fight against bacteria and not viruses
Define “antibiotic”. Define the ‘Antibiotic Creed’.
Antibiotic Definition
Natural compounds produced by microorganisms that kill or inhibit other microorganisms
Antibiotic Creed
Microbiology guides therapy wherever possible
Indications should be evidence based
Narrowest spectrum required
Dosage appropriate to the site an type of infection
Minimize duration of therapy
Ensure monotherapy in most cases
Why are the β-lactam agents good choice for treating susceptible bacterial infections in humans?
Beta-Lactam agents work via inhibiting cell wall synthesis. Humans do not have cells with cell walls, therefore they do not become affected by the agents.
Why are many treatments for fungal infections often toxic to humans?
Fungi are Eukaryotic like human cells and therefore as the treatment kills the fungi, it can also have negative effects upon the human cells.
List two modes of action for anti-viral drugs.
Inhibit viral replication
Interfere with viral release
