Antibacterial Resistance Flashcards
What is an antibiotic ?
A drug that kills or inhibits the growth of a micro-organism
Define resistant
Somewhat arbitrary designation that implies that an antimicrobial will not inhibit bacterial growth that clinically achievable concentrations
Define susceptible
Somewhat arbitrary designation that impes that an antimicrobial will inhibit bacterial growth that clinically achievable concentrations
What is “MIC”
Minimial inhibitory concentration, lowest concentration of antimicrobial that inhibits growth of bacteria, commonly used in clinical labs
what is “MBC”
minimal bactericidal condentration. Concentration of an antimicrobial that kills bacteria. Used clinically only in special circumstances
What is breakpoint ?
The MIC that is used to designate between susceptible and resistant. Arbitrarily set by a committee
What are the automated ways you can determine the minimial inhibitory concentration ?
You can test using a well plate for MIC testing. You can also use automated testing
What are some manual ways you can determine susceptibility ?
Kirby Bauer Disc dilution - Not precise
Agar Dilution- dilution conc in agar to see which conc will inhibit growth
E Test- strip of ABx that has different conc’s as you move down the strip to see the MIC
What does antibiotic use lead to ?
Antibiotic resistance
What is the break point for determining antibiotic resistance ?
The concentration that has to be achieved to get efficacy for a particular Abx. Any
Wgat happens when the MIC is greater than the break point ?
The bacteria will become resistant
What is the relationship between break point and MIC for a drug that is susceptible ?
The break point will be much higher than the MIC
What is the largest factor that contribues to ABx resistance ?
Abx use is the largest contributing factor. Especially in agriculture because the Abx used on animals can be spread to humans
Can resistant bacteria be transmitted between people ?
Yes
Is Abx resistance limited to that one Abx ?
No when a bacteria becomes resistant it could potentially be resistnat to numerous strains of bacteria. See bacteria example from lecture
What part of the bacterial genome will carry Abx resistance genes ?
The plasmids or chromosomes
What are the mechanisms of bacterial enzymatic resistance ?
Sulfonation, phosphorylation, or esterification which is ezpecially a problem for aminoglycosides
Why are B Lactamases more potent in gram - bacteria ?
It is located in the periplasmic space. It will have a higher concentration because they are located on the cell wall in Gram ( + ) bacteria.
What are B Lactamase capable of ?
They are capable of hydrolysind extended spectrum cephalosproins, penicillins, aztrenonam. They are usually plasma mediated. They are responsable for significant resistance determinate in acute and long term care facility enteric pathogens
What are two mechanisms of bacterial resistance that directly affect the bacterial membrane ?
- Decreased permeability which directly affects carbapenems
Efflux pumps- used promarly by pseudomonas and is effective against Tetracyclines and Macrolides
What are some target alterations that will aid in drug resistance .
DNA Gyrase- Fluroquinones and many gram ( - ) bacteria
Penicillin Binding Protein- Methacillin resistant S areus ( MRSA )
Gram Positive cell wall - works against Vanc
What are the Glycopeptide resistant strains of A aureus ?
Gycopeptide mediated resistance-
Glycopeptide high level resistance-
What is the major factor that is ontributing to antibiotic resistance ?
Inappropriate and excessive use of antibiotics is a major factor contrubuting to amergeing antibiotic resistance
What are the determinants of resistance ?
They are selected for by Abx use
What is the goal of antibiotic use ?
Prevention or cure of infection with a minimum of toxicity to the patient with minimial impact on the patients microbial flora of that patient and the other patients and environment
What is colonization pressure ?
The pressure
What are the three principles of antimicrobial resistance?
- Resistnace is likely to emerge
Once you have resistance will it decline?
Once resistance appears it is likely to decine slowly if at all.
