Antibiotics mode of action Flashcards
What are physical controls of microbial growth? (2 points)
- Heat sterilization
- Radiation sterilisation
What are chemical controls of microbial growth? (3 points)
- Antiseptics (biological) and disinfectant (inanimate)
- Natural antimicrobials
- Synthetic antimicrobials
What are common examples of transmitted pathogens? (8 points)
- HIV
- Herpes simplex virus types 1 & 2
- HBV
- Streptococci
- Staphylococci
- Myobacterium tuberculosis
- Cytomegalovirus
- Some upper respiratory tract viruses
What are common forms of infection control? (4 points)
- Disinfecrtion of non-sterilisable surface and equipment
- Heat sterilization of all compatible equipment
- Handwashing techniques + appropriate antiseptics
- Combined with appropriate barrier techniques: masks, gloves and eye protection
What are disinfectants?
Strong chemical agents that inhibit or kill microorganisms
What are antiseptics?
Disinfecting agents with sufficiently low toxicity for host cells -> can be used directly on skin, mucous membranes, or wounds
What are sterilants?
- Kill both vegetative cells and spores when applied to materials for appropriate times and temperatures
What are antiseptics?
Disinfecting agents with sufficiently low toxicity for host cells
Where are antiseptics used? (3 points)
- Skin, mucous membranes or wounds
What is antisepsis?
- Use of chemical to destroy most pathogenic organisms on animate surfaces
What is antiseptic used for? (5 points)
- Treatment of skin infections
- Prevention of infections in cuts and wounds
- Cleaning the skin area of surgery from microorganisms
- Prophylaxis and treatment of infection sin mucosal areas such as mouth, nose and vagina that are open to the environment
- As a scrub for surgeons and the medical personnel
What are the 3 classifications of antiseptics?
- Those that denature proteins (cidal)
- Those that cause osmotic disruption of the cell (cidal)
- Those that interface with specific metabolic processes (growth arrest/static)
What is the mechanism of action of phenols, iodine, al cohols, aldehydes and mettalic compounds?
- Denature proteins and DNA bases
What is the mechanism of action of cationic detergents?
Interfere with plasma membrane’s permeability and cause leakage of enzyme, coenzyme and metabolites
What is the mechanism of action of oxidizing compounds?
- Oxidize functional molecules in the microorganisms
What are iodophores used for?
Used either as an antiseptic or disinfectant
What do iodophores do?
Kill vegetative bacteria, mycobacteria, fungi, lipid containing viruses (spores on prolonged use)
What are 2 examples of alcohols that are effective antiseptic and disinfectant agents?
- Ethyl alcohol and isopropyl alcohol
When alcohols are applied to the skin, by what % are bacterial numbers reduced?
90%
What do alcohols do? (2 points)
- Rapidly kill vegetative bacteria, fungi, and inactive lipophilic viruses
- Denature proteins and disturb the membrane permeability of bacteria
What is water soluble chlorohexidine digluconate used as?
An antiseptic
How does chlorohexidine work?
- Strongly absorbs to bacterial membranes and causes leakage of small molecules and precipitation of cytoplasmic proteins
What is the most common oxidising compounds that have been used as antiseptics?
Hydrogen peroxide
What type of bacteria are oxidising agents effective against?
- Vegetative bacteria, higher concentrations are sporicidal
What can oxidising agents be used to disinfect? (5 points)
- Respirators
- Acrylic resin implants
- Plastic eating utensils
- Soft contact lenses
- Cartons of milk or juice
What % concentration oxidizing agents are sporicidal?
- 10-25%
Why is there a health warning with antiseptic, disinfectant and sterilant users? (3 points)
- Short-term and long-term toxicity
- General biocidal activity
- Accumulate in the environment OR in the patient’s/caregiver’s body
What are naturally occurring antimicrobials?
- Metabolic products of bacteria and fungi
What is an antibiotic?
A chemcical substance produced by one organism that is destructive to another
What are 2 categories of antibiotics?
- Bacteriostatic
- Bacteriocidal
What are the cellular targets of antibiotics? (4 points)
- Cell wall
- Cell membrane
- Nucleic acid
- Protein synthesis
What are the ideal properties of an antimicrobial agent? (8 points)
- Selective toxicity against microbial target
- Minimal toxicity to the host
- Cidal activity (kills micro-organisms)
- Long plasma half-life
- Good tissue distribution
- Low binding to plasma proteins
- Oral and parenteral preparation
- No adverse interaction with other drugs
What are the 4 main targets of antimicrobials on a cell?
- Inhibition of cell wall synthesis
- Inhibition of protein synthesis
- Inhibition of nucleic acid rep lication and transcription
- Injury to plasma membrane
What are 2 examples of inhibitors of cell wall synthesis?
- Beta-lactams
- Glycopeptides
What is the key concept you need to know for penicillin strictures?
- There are different ones
- There is the basic building block of penicillin and this produces modified antibiotics by adding synthetic side chains
What are 2 examples of nucleic acid synthesis precursors?
- Sulphonamides
- Trimethoprim
What is an example of an inhibitor of DNA replication?
- Quinolones
What is an example of an inhibitor of RNA polymerase?
- Rifamycins
Misuse of antibiotics selects for resistance mutants. What does misuse include? (5 points)
- Using outdated or weakened antibiotics
- Using antibiotics for the common cols and other inappropriate conditions
- Using antibiotics in animal feed
- Failing to complete the prescribed regimen
- Using someone else’s leftover prescription
