Antibiotic resistance ( MUST KNOW ) Flashcards
What is Primary Intrinsic antibiotic resistance
Microorganism is naturally resistant to the drug
What is secondary acquired drug resistance
Microorganism is naturally sensitive the drug but becomes resistant after exposure to the drug
Name 4 ways that drug resistance may develop and an example
- Enzyme produces drug inactivation enzymes e.g Beta lactamases are produced that break the beta lactic rings in penicillin/cephalosporins - so the drug is no longer active
- Alters the drug target - the targeted site is changed - mutation in DNA gyrase ( resistance to quinolones)
3.Loss or reduction drug receptors so a barrier to drug penetration/entry into microorganism occurs
eg loss /modification porins in cell wall so less/no drug ( carbapenem ) penetrates
4.Active elimination of the drug (Efflux pumps )
so efflux pumps ( membrane bound proteins ) actively pump out the drug from the cell ( tetracyclines/fluconazole - for fungi)
Name 3 genetic mechanisms for antibiotic resistance
1.Chromosomal mutations ( single base or frameshift mutations
- Regulation of gene expression ( secondary to mutation )
- Horizontal gene transfer - Transduction
- transformation
OR - conjugation
What are transposons/insertion sequences
Mobile genetic elements within a genome ( a chromosomal plasmid ) that can carry antibiotic resistance genes and can jump from 1 species to another by conjugation
What’s a plasmid
Chromosomal genetic element that is outside of the main chromosome
Can carry antibiotic resistance
Name 4 things plasmids are essential for
Antibiotic resistance
Virulence ( disease ) factors
Toxins/antimicrobial proteins
Heavy metal resistance
What is horizontal transfer and name its 3 pathways
MUST KNOW THIS
A process where an organism ( donor ) transfers genetic material into another organism without it being the donors offspring
Way microbes can transfer a small piece of their DNA into another microbe
3 paths- transduction (virus mediated)
-transformation (uptake DNA)
-conjugation( bacterial mating )
Can cause antibiotic resistance
What is conjugation
A type of horizontal gene transfer-cell to cell DNA transfer between 1 organism to another organism (usually to a similar species or strain)-mediated by specific genes on conjugative plasmids or transposons
Involves a sex plus and hormones
Long stretches of DNA can be transferred
What is transformation
Donor DNA is released from bacteria by lysis
The “naked DNA “ is taken up by competent cells and recombined into their genome and maybe expressed
Multiple genes can be taken up and expressed
What is transduction
A bacteriophage incorporates a fragment of bacterial DNA into its genome then this piece of DNA is transferred into a newly infected cell during “phage”infection
DNA then incorporated by recombination and maybe expressed
only short DNA segments can be transduced
What is a bacteriophage
A virus that specifically infects bacteria ) relies on the host cell to reproduce )
2 types -lytic or temperate
What are the 2 types of bacteriophage
Lytic and temperate bacteriophages
What is a lytic bacteriophage
One that ALWAYS causes cell lysis ( death ) and release of viral particles
What is a temperate bacteriophage
May lyse or lysogenise (integrate phage genome into bacterial chromosome ) host cell.
Lysogenic phage can become lytic at anytime
