Antimicrobial chemotherapy Flashcards
What are bacteriostatic agents?
Inhibitors of protein synthesis - they bind to ribosomes
If the concentration of the bacteriostatic agent is lowered, growth of microbe resumes. True or false?
True
When a bacteriostatic agent is given, both the total cell count and the viable cell count stay the same. True or false?
True
What are bacteriocidal agents?
Bind tightly to cells and kill them
Are dead cells destroyed when administering a bacteriocidal agent?
No
What happens to the total cell count and viable cell count when a bacteriocidal agent is used?
Total cell count remains the same
Viable cell count decreases
What is a bacteriolytic agent?
Kills cells by lysis
What happens to the total cell count and the viable cell count when bacteriolytic agent is given?
Both decrease
What are the two ways in which antimicrobial activity can be measured?
Minimum inhibitory concentration (MIC)
Disc diffusion assay
What does the MIC indicate?
The minimum amount of agent needed to inhibit growth of a test bacterium
What does disc diffusion assay do?
Determines the zone of inhibition
Can antiseptics be used on living tissue?
Yes - non toxic
Biocides sterilise. True or false?
False - not necessarily
What does the efficacy of a biocide depend on?
microbial load
concentration of biocide used
presence of organic matter
What is the most resistant microbe to biocides?
Prions
What is the least resistant microbe to biocides?
Gram positive bacteria
Are mycobacterium more or less resistant to biocides than gram negative bacteria?
More resistant
Are spores more or less resistant to biocides than prions?
Less
What is meant by intrinsic resistance?
The bacterium lacks the structure that the antibiotic targets. E.g. mycoplasmas don;t have a cell wall so they are resistant to penicillin (targets cell wall) OR
bacterium is impermeable therefore has low level of uptake of antibiotic - e.g. produces biofilm
What is meant by extrinsic resistance?
Bacteria produces degradative enzymes e.g. Staph produce B-lactamases which cleave penicillin
Bacteria modify target site
Pump agent out of cell: efflux
What drives antimicrobial resistance?
Not finishing the course
Use of inappropriate antimicrobials
Poor infection control
Bacteriophages are new antimicrobials that can be used. What are they?
Viruses that infect the bacteria
