Introduction Flashcards
(22 cards)
What is the sub-MIC selective window?
Concentrations below the MIC that can also select for the resistant strain
What is SOS-mediated mutagenesis?
mutations due to the sos system being triggered and resulting in resistance because of the mutation
Why do we want an empty vector?
This is to have control and to ensure that the effect is from the construct and not from the vector and to have a backbone
What do we use E.coli MG1655 for?
It is the most regular lab strain, its no longer clinical transferrable but its easier to work with
Why is MG1655 no longer clinical transferrable?
E. coli MG1655 is no longer clinically transferable because it is a genetically tame, non-pathogenic, antibiotic-sensitive, lab-optimized organism that has lost the traits necessary for survival, adaptation, and spread in clinical environments.
What do we use dh5a for and why?
It is a crippled strain and more responsive when constructing so its easier to manipulate and thats why we use it for transformation and then move it to the final vector
Why do we not want to use a strain/plate more than 1 week?
Because of mutations
Why do we put MH4 on ampicillin?
To select for the resistance gene because it can grow on ampicillin
Why did we use K56-23?
It is costly, easy to use in evolution and bacteria will easily release it
What is the MIC and whats the difference to MSC?
It is the minimum concentration that can visibly inhibit growth
why do we say that dh5a is crippled
its been genetically modified to be easy to manipulate, it lacks recombination ability and restriction systems
what is the difference between MBC and MIC?
MIC is the minimum inhibitory concentration, meaning lowest concentration that visibly inhibits growth. MBC refers to the concentration that reduces bacterial density by 1000 times.
what is the difference between bacteriostatic and bactericidal?
if the ratio of MBC to MIC is greater than four its classified as bacteriostatic, but if the ratio of MIC is less or equal to four its classified as bactericidal
what is the difference between intrinsic and acquired?
intrinsic is about a natural resistance meaning the bacteria has never been affected by that antibiotic. acquired however talks about that bacteria acquire a mechanism that enable it to tolerate a significant higher concentration than other strains within that same species.
Why is NDM-1 so alarming?
carbapenems are usually used as last resort antibiotics and NDM-1 belongs to a grouo that can hydrolyze a broad spectrum b-lactam antibiotics which is alarminig due to ndm-1 and similar resistance genes being located on mdr-plasmids which easily can transfer between bacteria due to hgt
what is the difference between point mutation and HGT?
point mutation: single base pair is added, removed or substituted and encoding a change in a protein that interacts with an antibiotic is exposed to and these changes will be transferred from a mother to offspring during cell division, vertical gene transfer
HGT is the process where bacteria can acquire and exchange genetic material such as ARGs via MGEs like plasmids and transposons. Faster, rapid and across species. plasmids can have more resistance genes and easy for them to transfer between microorganisms.
what does high fitness cost do?
affects the AMR determinant’ stability and persistence in the host and often in absense of antibiotic be lost due to it affecting growth rate and competitiveness. it will also affect their transmission so other hosts wont accept them. in some cases compensatory evolution can reduce fitness cost by mutations in the determinant or the host genome.
competitiveness in the ability to grow, divide and compete for nutrients and space
what is plasmid stability?
the ability to maintain in a population, dependent on plasmid’ factors but also the cellular environment in the host, including the fitness cost associated with it bearing the plasmid
Why did u use e-strip for imipenem and microbroth for bleomycin?
Because microbroth dilution is whats considered gold standard for assessing MIC and also because its not usual to assess MIC for cancer drugs so there is no strips for bleomycin. however there is estrips available for imipenem and thats more efficient and simple so we decided to use that and then a reference strain to control that everything works with the strp tests.
what are other drivers of resistance other than hgt?
poverty and inequality. misuse and overprescribing. suboptimal antibiotic dosing.
what are the different forms of HGT?
Conjugation, transformation and transduction
conjugation: direct cell to cell contact usually via adhesions. contact forms a bridge and is the major form.
transformation: uptake of free DNA fragments from the environment into the cell. several conditions need to be present, such as competent bacteria and free DNA fragments.
transduction: bacterophages; viruses infecting bacteria. gene is packaged into genome of the bacteriohage and transferred into the recipient during infection. limitations: limited in how much they can pack and reduced efficiency in mediating hgt. narrow host range.
