Infection 4 Intro To Antibiotics Flashcards
Antimicrobial classification
Antibacterial agents
Antifungal agents
Antiviral agents
Antiprotozoal agents
Antibacterial agents classification
Bactericidal or bacteriostatic
Spectrum - broad vs narrow
Target site (mechanism of action)
Chemical structure - antibacterial class
What needs to be considered when choosing an antibiotic?
Cause of infection
Is it active against target organism?
Does it reach the site of infection?
Is it available in the right formulation? IV vs oral
Half life
Interaction with other drugs
Toxicity issues?
Drug monitoring needed?
Ways to measure antibiotic activity
- Disc sensitivity - paper on agar plate for zone of inhibition
- Minimal inhibitory concentration - first conc. of antibiotic that inhibits bacterial growth
What is a minimum inhibitory concentration test and what is it done via?
Test to identify the first conc. of antibiotic that inhibits bacterial growth
Done via broth microdilution or E-test strip
What is a bactericidal antibiotic?
Lethal to bacteria
What is a bacteriostatic antibiotic?
Stops/slows growth + reproduction
What is a broad spectrum antibiotic?
Attack a wide variety of bacteria
What is a narrow spectrum antibiotic?
Specific to only a few types of bacteria
What type of antibiotics inhibit cell wall synthesis?
Beta-lactams - penicillins, cephalosporins
Glycopeptides e.g. vancomycin
Examples of beta-lactams
Penicillins
Cephalosporins
Cerbapenems
Mechanism of action of beta-lactams
Inhibit cell wall synthesis
Mechanism of action of glycopeptides
Inhibits cell wall synthesis
What type of antibiotics inhibit cell membrane function?
Polymixins
Example of polymixin antibiotic
colistin
What type of antibiotics inhibit nucleic acid synthesis?
Quinolones - DNA gryase
Trimethoprim - folate synthase
Rifampicin - RNA polymerase
What drugs are penicillins?
Penicillin
Amoxicillin
Flucoxacillin
Suffix of penicillins
-cillin
Prefix of cephalosporins
Cef-
What drugs are cephalosporins?
Ceftriaxone
Suffix of carbapenems
-penem
What drugs are carbapenems?
Mecropenem
Imipenem
What drugs are glycopeptides?
Vancomycin
Teicoplanin
Examples of a drug which is a quinolones?
Ciprofloxacin
Suffix of quinolones
-floxacin
What type of antibiotics inhibit protein synthesis?
Tetracyclines
Aminoglycosides
Macrolides
Mechanism of action of polymixins
Inhibit cell membrane function
Mechanism of action of quinolones
Inhibit nucleic acid synthesis - DNA gyrase
Mechanism of action f trimethoprim
Inhibit nucleic acid synthesis - folate synthesis
Mechanism of action of rifampicin
Inhibit nucleic acid synthesis - RNA polymerase
Mechanism of action of tetracyclines
- Inhibit protein synthesis
- Act on 30s ribosome subunit
Mechanism of action of aminoglycosides
- Inhibit protein synthesis
- Act on 30s ribosome subunit
Mechanism of action of marcolides
- Inhibit protein synthesis
- Act on 50s ribosome subunit
Mechanisms of antibiotic action against bacterial cells
Inhibition of cell wall synthesis
Inhibition of cell membrane function
Inhibition of protein synthesis
Inhibition of nucleic acid synthesis
What are penicillins good against?
Mainly streptococci
Why is ceftriaxone good a treating meningitis?
Good level of activity in CSF as it can cross the blood brain barrier
Examples of tetracyclines
doxycycline
tetracycline
What are tetracyclines good against?
Example
Gram positive bacteria
doxycycline
tetracycline
What are aminoglucosides good against?
Example
Gram negative bacteria
gentamicin
Examples of macrolides
Clarithromycin
Erythromycin
Mechanisms of aciclovir
Use
Inhibits viral DNA polymerase
Herpes simplex
Varicella zoster - chicken pox + shingles
What does metronidazole target?
Use
Anaerobic bacteria - C.difficle
Protozoa
What are the three types of antibitoics resistance?
- intrinsic: no target - permanent
- acquired: acquires new genetic material or mutates - permanent
- adaptive: only resistant when exposed to antibiotic - susceptible once antibiotic is removed
What is amoxicillin good against?
Gram negative bacteria
Mechanism of oseltamivir
Use
Inhibits viral neuraminidase
Influenza A + B
What are two subgroups of antifungals?
Azoles
Polyenes
Mechanism of azoles
Examples + uses
Inhibit cell membrane synthesis
flucanazole- candida
Mechanism of polyenes
Examples and uses
Inhibit cell membrane function
nystatin - candida
Consequences of antibacterial resistance
Treatment failure
Prophylaxis failure
Economic costs
Mechanism of antibiotic resistance
- enzymatic modification of enzyme
- enzymatic alteration of antibiotic targets
- mutation of bacterial target site
Outline horizontal gene transfer
Plasma in donor shared through pili between DNA
Can share to more DNA
Why is co-amoxiclav more commonly prescribed than amoxicillin alone?
co-amoxiclav contains a beta lactamase inhibitor
Helps combat the resistance to amoxicllin
What are the classes of antibacterials?
Inhibition of:
- Cell wall synthesis
- Cell membrane function
- Nucelic acid synthesis
- Protein synthesis
Generally, antibitoics that begin with C (not co-) have an association with what?
Clostridioides difficile infection
Define antibiotic cross reactivity?
A hypersensitivity reaction to an antibiotic that is similar in structure to an antibiotic with a known allergy
