8.3 Antibiotics resistance Flashcards
What are plasmids?
Extrachromosomal genetic elements which replicate independently of the chromosome
Often carry genes for antibiotic resistance
What is recombination?
integration of plasmids and other DNA into the chromosome
What is homologous recombination?
takes place between regions of the same sequence in two different molecules
What is site specific recombination?
involves enzymes that integrate new DNA at specific sites in the chromosome
What are the types of transmission of resistance?
Transformation
Transduction
Conjugation
How does transformation of resistance occur, give an example and what are the limitations
Uptake of naked DNA from the environment and incorporation into the genome
Penicillin resistance of Strep Pneumoniae
Limitations: DNA must be from related bacteria
How does transduction of resistance occur, give an example and what are the limitations?
Transfer of DNA from one bacterium to another via bacteriophages. The bacteriophages will insert the DNA into bacteria and as the multiplies the resistance will be passed on
Limitations: transfer of DNA is limited by hosts bacteriophages
Integration of the donor DNA in recipient relies on presence of target sequences for integration which is more likely in related hosts
How does conjugation of resistance occur, give an example and what are the limitations?
Transfer of genetic material usually in the form of a plasmid, from one cell to another through cellular contact - usually through plasmids
Not many limitations - can take place between species and clinically the most significant
What are the forms of antibiotic resistance?
Drug inactivating enzyme
Alteration in target molecule
Decreased uptake
Increased elimiation
What are the forms of S.aureus resistance?
Penicillin: beta lactamase produced by bacteria destroys the beta lactam ring
Methicillin: MecA gene which alters the binding site
Vancomycin: thickening of peptidoglycan wall
What is the enterococcus resistance?
Vancomycin - change from D-ala-D-ala to D-lac
VanA = resistant to both glycopeptides (vancomycin and tecioplanin)
VanV = only vancomycin
What are the forms of strep pneumoniae resistance?
Penicillin: stepwise increase by acquiring different genes changing the binding proteins
Protein synthesis inhibitors: get mef pump in the 50s for macrolides and rRNA methylase changes in 50s subunit binding site for macrolides and clindamycin
