Antimicrobial Therapies Flashcards
Why are anti-bacterials safe for humans to use?
They target proteins found in bacterial cells but not found in humans
Describe the mechanism of action of beta-lactams?
They have a beta-lactam ring which binds to the serine residue on penicillin binding protein, which inactivates the enzyme. This means that the cross bridges between peptidoglycan molecules that form the outer layer of the bacteria cannot form so the cell wall doesn’t form. This means that water enters into the bacteria and it dies
What are some examples of beta-lactams?
Penicillin and Methicilin
What is the definition of an antibiotic?
An anti-microbial agent produced by microorganisms that kills or inhibits other microorganisms
What is an anti-microbial?
A chemical that selectively kills or inhibits microbes
What is the difference between bactericidal and bacteriostatic antibacterials?
Bactericidal kills the bacteria whereas bacteriostatic stops the bacteria from growing
What is an antiseptic?
A chemical that kills or inhibits microbes that is used topically to prevent infection
What is the minimal inhibitory concentration?
The lowest concentration of antibacterial which is required to inhibit growth
what are some effects of antibacterial resistance?
- Longer time needed for therapy to be effective
- Require additional approaches
- Use of expensive therapy (newer drugs)
- Use of more toxic drugs
- Use of less effective “second choice” antibiotics
How does antibiotic resistance emerge?
A population of bacteria will have some bacteria that are resistant and some that are not due to genetic variation
A selection pressure then acts on the population such as the antibiotic - those that are not resistant die, and patient starts to feel better
Patient then stops course of antibiotic but those that can survive still do not die - they live and proliferative meaning the entire population is now resistant
What are the three gram positive bacteria which are resistant to antibiotics?
Streptococcus Pneumoniae
Clostriduim difficle
Enterococcus spp
What are three gram negative bacteria which are resistant to antibiotics?
E.coli
Salmonella
Pseudomonas Aruginosa
Which different processes do antibiotics target?
DNA replication Cell wall synthesis Plasma membrane damage Protein synthesis - Transcription - Translation Enzymatic activity/synthesis of metabolites
Why might you give a patient multiple different antibiotics?
They may act on different stages of bacterial growth and give a symbiotic effect.
e.g. sulfonamides and trimethoprim act on two different stages of bacterial development.
What type of antibiotic is prontosil?
A sulphonamide antibiotic
What is prontosil used to treat?
UTIs and RTIs, bacteraemia and prophylaxis for HIV+ individuals
What bacteria does prontosil act on?
Gram positive bacteria
How does Rifampicin work?
It is a bactericidal antibiotic and targets the RpoB subunit of RNA polymerase - this blocks transcription meaning bacteria cannot replicate
What happens to secretions like urine and sweat when a person is on Rifampicin?
Makes them turn orange / red
How does vancomycin work?
targets lipid II component of cell wall biosynthesis & wall crosslinking via D-ala residues
How does daptomycin work?
It is a bacteriocidal antibiotic which ragets bacterial cell membranes
What is the problem with daptomycin?
toxicity limits the dose