Lecture 7: Antibacterial Resistance Flashcards
What is antibacterial resistance
Ability of a bacterium to survive and multiple in the presence of an antibiotic
What is innate/intrinsic resistance
Innate ability of bacterial species to resist activity of antibiotic through its inherent structural or functional characteristics
Chromosomally encoded, relates to general physiology
What is acquired/ extrinsic resistance
Organism obtains the ability to resist the activity of an antibiotic to which it was previously susceptible
Mutation in resident gene
Transfer of genetic material through horizontal or vertical gene transfer
What is transformation
Uptake of naked DNA from a donor cell to a recipient cell
What is transduction
Phage mediated transfer of bacterial DNA from donor to recipient
What is conjugation
Transfer of plasmid DNA from a donor to a recipient during cell to cell contact
What are the two main reasons why antibiotic resistance is a huge problem
- Reversing progress of antibiotic development— antibiotics we do have are less effective
- New antibiotic development has rapidly slowed down
How many deaths occur from antibiotic resistant infections each year
23,000
What is the annual cost of antibiotic resistant infections
$20 billion
Many bacteria that are antibiotic resistant are found in ___
Livestock
Antibiotic use selects for drug resistant organisms. ___ is not induced by antibiotic itself but by the ___ created by antibiotics
Resistant, environment
To survive the presence of antibiotic bacterial organisms must be able to do ___ or ____ of the antibiotic
Disrupt or prevent the action of the antibiotic
What are the 5 bacterial resistant strategies
- Decreased uptake/ block entry
- Efflux pumps
- Inactivating enzymes
- Target alterations
- Alternative enzyme
What is one alteration bacterial cells can make to reduce the uptake of antibiotics
Altering porins
What is the effect of efflux pumps
Pump out antibiotics to decrease the concentration inside the cell thus it is too low to elicit an effect
How do bacterial cells produce antibiotic inactivation by modification or degradation
Use enzymes that can degrade or modify antibiotic so it is no longer effective
How does B-lactamase work
Bind and make bacteria resistant to B-lactam antibiotics (penicillin, cephalosporins)
What is the purpose of B-lactamase inhibitors
Inhibit the activity of B-lacatamse to extend the activity spectrum of B-lactam antibiotics
What is the purpose of bacteria modifying the antimicrobial target
Use acquired mutations or modified structures that are no longer recognized by antibiotic
How can bacterial cells bypass the antibiotic target
Acquired a new enzyme that allows bypass of metabolism pathway
What are ways we can slow down resistance
- Prescribe antibiotics for bacterial infections only
- Educate clients on proper use of antibiotics
- Determine most appropriate antibiotic
Important to prescribe antibiotics for bacterial infections, if prescribed for viral infections what happens
Decrease normal flora and could increase susceptibility to other pathogens
Why is it important to finish course of antibiotics
Need to kill all bacteria, if you stop it early you are leaving behind some bacteria that can then develop resistance to that antibiotic
What are 3 tests we can do to determine correct antibiotic to use
- Disk diffusion/ Kirby Bauer method
- Broth dilution (MIC)
- E-tests
How does a disk diffusion/ Kirby Bauer test work
- Use mueller-Hinton agar plates
- Filter plates with antibiotics placed on plate- highest concentration of antibiotic is around the disk
- After incubation the diameters of the zones of inhibition surrounding the disk are measures
- Compared to standardized chart to determine antibiotic that bacteria was most sensitive to
How does the broth dilution (MIC) method work
- Serial dilution of antibiotics
- Determine lowest concentration of antibiotic that inhibits bacterial growth is the MIC- minimum inhibitory concentration
- can also use micropipeter plate- same principle
How do you determine the MBC- maximum bactericidal concentration
- Take aliquot from each tube without any growth from broth dilution and plate it onto antibiotics free plate and incubate
- Lowest concentration kills 99% of bacterial cells- no growth on agar plate
How does the E-test work
- Combine use of Kirby Bauer/ disk diffusion with ability to determine MIC
- Use mueller Hinton agar plates that are inoculated with bacterial suspension
- Plastic trips impregnated with gradually decreased concentration of antibiotic placed on plate
- After incubation MIC value is determined where the elliptical zone of the inhibition crosses the E-test strip
