CP3-1 Intro to antibacterial and anti fungal agents Flashcards
What is the function of antimicrobials?
Inhibit critical processes in bacterial/fungal cells with minimal harm to the patient (selective toxicity) to increase likelihood of the patient making a clinical recovery.
What are some processes that antimicrobials can disrupt?
Protein synthesis
DNA synthesis
RNA synthesis
Membrane function
The cell wall
What are antibiotics?
Chemical products of microbes that inhibit or kill other organisms
What are 6 examples of antimicrobial agents?
Antibacterial
Antifungals
Antivirals
Antibiotics
Synthetic compounds with similar effects
Semi-synthetic agents
What are antimicrobial agents that are modified from antibiotics known as?
Semi-synthetic agents
How to bacteriostatic and fungistatics work?
Inhibit growth mainly by protein synthesis inhibition
How to bacteriodal and fungicidal agents work?
Cause cell death mainly using wall active agents
What is minimum inhibitory concentration (MIC)?
The minimum concentration of antimicrobial agents at which visible growth is inhibited
What is minimum bactericidal/fungicidal concentration (MBC/MFC)?
The minimum concentration of antimicrobial agents at which most organism are killed?
What is synergy?
When the effect observed with a combination of drugs is greater than the sum of the effects observed with the two drugs independently.
What is antagonism?
When the activity of two antimicrobials given together is less than the activity of either given separately
What does it mean if an antimicrobial agent is broad spectrum?
It kills most types of bacteria/fungi encountered
What does it mean if an antimicrobial agent is narrow spectrum?
It only kills a narrow range of organisms encountered
When choosing an antibiotic, should you pick a more broad spectrum or the narrowest spectrum antibiotic that is appropriate?
The narrowest-spectrum antibiotic that would be appropriate.
What is peptidoglycan?
A major structural component of bacterial cell walls that is a polymer of glucose derivatives NAM and NAG with oligopeptide cross links called penicillin binding proteins (PBPs)
What part of the bacteria can be targeted by antibacterial agents and why?
Cell wall as no cell wall in animal cells so is ideal for selective toxicity
What are examples of cell wall synthesis inhibitors?
Beta lactams/penicillins and glycopeptides.
What are the properties of beta-lactam antibiotics?
Contain and beta-lactam ring
What was the first antibiotic used in clinical practice?
Benzylpenicillin
What are 4 sub-classes of beta-lactam antibiotics? What are there spectrums? What is the suffix for each?
Penicillins - narrow - cillin
Cephalosporins - broad - ime
Carbapenams - extremely broad - penem
Monobactams - affect gram-negative activity only due to slightly different ring structure - eonam
What sub class of antibiotic is arranged into generations?
Cephalosporins
What are examples of glycopeptide antibiotics?
Vanomycin and teicoplanin
How to glycopeptides work and antibacterial agents?
They bind to the terminal amino acids on NAM pentapeptides a day inhibit cross linking
Do glycopeptides work on gram + or gram - bacteria?
+
What are examples of bacterial protein synthesis inhibitors drugs?
Aminoglycosides (e.g.gentamicin)
Macrolides and lincosamides (suffix = -mycin)
Tetracycline and doxycycline
Oxazolidinoes (e.g. linezolid)
Mupirocin
Which bacterial protein synthesis inhibitor is used for gram positive infection?
Oxazolidinones
Which bacterial protein synthesis inhibitor agent is used topically to treat staphylococcal/streptococcal infections?
Mupirocin
What are the two DNA synthesis inhibitors inhibit the production of folate?
Trimethoprim and sulfonamides
What DNA synthesis inhibitor inhibits one or both of the bacterial enzymes DNA gyrase and topoisomerase IV? What is the suffix of this antibacterial?
Fluoroquinolones
Suffix = floxacin
What is an example of a RNA synthesis inhibitors drug?
Rifampin
What drug is used in anti-tuberculous chemotherapy?
Rifampin (a macrolide antibiotic)
What cell membrane agents treat gram - bacteria?
Colistin/polymyxin E
What cell membrane agents treat gram + bacteria?
Daptomycin (destroys outer or cytoplasmic membrane)
What are the three main pathogenic fungi?
Filamentous fungi
yeasts
Dimorphic fungi
What three processes to antifungals usually target?
DNA synthesis
Cell membrane function
Cell wall
Why is it more difficult to achieve selective toxicity with antifungals?
They are eukaryotes so have more similarities in cell structure
What is the cholesterol alternative in fungi?
Ergosterol
What are three antifungal agents that act on ergosterol? How?
Azoles e.g. clotrimazole - inhibit ergosterol formation
Terbinafine - squalene expoxidase inhibitor
Amphotericin B - binds to ergosterol damaging the cell membrane
What is the azole voriconazole usually used to treat?
Aspergillosis
What is the selective toxicity of amphotericin B like?
High as also damages human cell membranes just not to the same extent
How do echinocandins work?
Inhibit beta-1,3- glucan synthesis preventing formation of fibrous network on cell walls
What is the suffix for echinocandins?
-fungin
What is the only fungal RNA/DNA synthesis inhibitors agent used in practice?
5-flurocytosine
How does 5-flurocytosine work?
It is transported into fungal cells by cytosine permease and then metabolised by 5-fluorouracil into inhibitory molecules
What is 5-flutocytosine usually used to treat?
Cryptococcal meningitis
