Antibiotic resistance Flashcards
What are examples of natural resistance?
Target not present
Target not accessible
Developmental structure
Metabolism
What are examples of resistance in which the target is not present?
Mycoplasma sp have no cell wall
Lactobacillus sp have D-ala-D-lactate side chains instead of D-ala-D-ala side chains so penicillins, cephalosporins and glycopeptides can’t affect cell wall production
What is an example of resistance in which the target is not accessible?
The membrane of gram -ve bacteria prevents entry of vancomycin into the cell
What are examples of developmental structure causing resistance?
C.difficile spores have no cell wall so many antibiotics won’t work
Persistor cells in biofilms are more resistant
What is a biofilm?
Organisms that behave as part of a multi-cellular community
They are 3D structures, permeated by water channels
What is a persistor cell?
A dormant or non-growing cell
This means it has no transcription or translation and has no cell wall production
This means that it is resistant to antibiotics as none of the processes they target are active
How does antimicrobial drug resistance arise?
By mutation or gene transfer between bacteria
This mutation creates a selective advantage
What are 3 ways in which genes are transferred?
Natural competence - DNA released from one bacteria to the other
Bacteriophage - bacteriophage transfers infected DNA from one bacteria to another
Sex pili - bacteria fuse and plasmids are transferred from one to the other
What are ways in which a bacteria can be anti-microbial resistant?
Changes to outer membrane
Energy dependant pumps can pump out antibiotics as soon as they enter
ß-lactamases can produced to destroy antibiotics
What are the different ß-lactamases?
Penicillinase
Cephalosporinase
Extended Spectrum ß-Lactamase
Carbapenamase
What is an example of a highly active carbapanemase?
Metallo ß-lactamases
How does MRSA become resistant?
It develops a new transpeptidase via gene transfer from a rat skin infection. This transpeptidase forms a improperly forms a cell wall so ß-lactams don’t affect it
