3 - Hospital acquired infection and antibiotic resistance Flashcards
What is an antibiotic?
an antimicrobial agent produced by a microorganism that kills or inhibits other microorganisms
What is meant by ‘antimicrobial’?
chemical that selectively kills or inhibits microbes (bacteria, fungi, viruses)
What is meant by ‘bactericidal’?
kills bacteria
What is meant by ‘bacteriostatic’?
inhibits growth of bacteria (stops bacteria growing)
What is meant by ‘antiseptic’?
chemical that kills or inhibits microbes to prevent infection
What is ‘resistance’?
the ability of an organism to replicate in the presence go an antibiotic at a particular concentration
What is MIC (minimal inhibitory concentration)
the lowest concentration of the antibiotic required to inhibit growth
What is the name of the process of action of antibiotics?
SELECTIVE TOXICITY - they tend to inhibit processes that are unique to bacteria
What is the mechanism of action of beta lactams?
interfere with the synthesis of peptidoglycan (bacterial cell walls)
What type of antibiotic is tetracycline?
bacteriostatic (inhibits growth of bacteria)
What is the mechanism of action of tetracycline?
inhibits protein synthesis
by binding to the 16S component of the 30S ribosomal subunit,
thus preventing charged aminoacyl tRNAs from binding to the mRNA/ribosome complex
What type of antibiotic is chloramphenicol?
bacteriostatic
What is the mechanism of action of chloramphenicol?
inhibits protein synthesis
by binding to the 50S subunit,
thereby blocking the peptidyl transfer step
What type of antibiotic is quinolones?
bactericidal
What type of antibiotic is sulphonamides?
bacteriostatic
What type of antibiotics are aminoglycosides?
give some examples
bactericidal
e.g. gentamicin, streptomycin
What type of antibiotics are macrolides?
give an example
only for gram positive infections
e.g. erythromycin
What is responsible for the altered target site mechanism of AB resistance?
acquiring a gene that encodes a target modifying enzyme
(e.g.
MRSA has an acquired gene that produces an alternative penicillin binding protein, that performs the same function but has lower affinity to beta lactams)
What is responsible for the inactivation of AB mechanism of AB resistance?
acquisition of a gene for an enzyme that breaks down the AB
What is responsible for the altered metabolism mechanism of AB resistance?
- re-engineering the metabolic pathways so you bypass the shop that the AB affects
- increased production of an enzyme substrate to outcompete the AB inhibitor
What is responsible for the decreased drug accumulation mechanism of AB resistance?
the drug doesn’t reach the sufficient concentration to be effective:
- reduced permeability of AB into the bacterial cell
- increase efflux of AB out of the cell
What are the 3 sources of AB resistant genes?
plasmids
transposons
Naked DNA
