Antibiotics Flashcards
What are the two broad modes of action of antibiotics?
Bacteriostatic: stop bacteria growing
Bactericidial: kill the bacteria
When might you choose a bactericidal antibiotic over and bacteriostatic antibiotic?
If the patient is immunosuppressed then halting the growth of the bacteria to allow for the immune response would be ineffective as there is no immune response to fight the bacteria
OR
If time is of the essence and you can’t afford to wait for the immune system to respond
Which category of antibiotics stops the growth of bacteria buying time for the immune systems response?
Bacteriostatic
You would want to give an antibiotic with which mode of action to a patient who is immunosuppressed?
Bactericidal
Give two examples of infections when time pressures mean you should administer bactericidal antibiotics?
Meningitis
Sepsis
What is an endotoxin?
An endotoxin is a toxin within a bacterial cell that is released when the cell disintegrates
What is a exotoxin?
A toxin released from a living bacterial cell into its surroundings
What are three main targets of antibiotics?
The cell wall
Ribosomes
DNA synthesis and damage
What classes of antibiotics target the cell wall of bacterial cells?
Beta-lactams:
Penicillins
Cephalosporins
Carbapenems
What classes of antibiotics target the ribosomes of bacterial cells?
Tetracyclines
Macrolides
Aminoglycosides
What classes of antibiotics target the DNA synthesis of bacterial cells and cause DNA damage?
Fluroquinolones/quiolones
Metronidazole
What other antibiotics can be dangerous to those with a penicillin allergy, and why?
Cephalosporin, monobactams, carbapenems.
Because of their similar chemical structure, they all contain a beta-lactam ring
What is beta-lactamase?
Beta-lactamase destroys beta lactam antibiotics
Which antibiotics are susceptible to beta-lactamase?
Penicillins, cephalosporins, carbapenems, and monobactams, because they all contain a beta-lactam ring
What is a narrow spectrum antibiotic?
An antibiotic that targets a specific group of bacteria
When would you use a narrow spectrum antibiotic?
When you know the causative agent of an infection
What is a broad spectrum antibiotic?
An antibiotic that kills a range of bacteria
When would you use a broad spectrum antibiotic?
When you don’t know the causative agent of the infection and you need to act quickly
What is moving from a broad spectrum antibiotic to a narrow spectrum antibiotic called?
De-escalation
Why do you want to de-escalate (move from a broad spectrum antibiotic to a narrow spectrum of antibiotic) quickly?
To prevent killing beneficial gut flora
What do beta-lactam antibiotics do?
Inhibit cell wall synthesis
What class of antibiotics are penicillins?
Beta lactam antibiotics
What is the postfix for penicillin antibiotics?
-cillin
Name three narrow spectrum penicillins
Cloxacillin
Oxacillin
Nafcillin
Name two aminopenicillins
Ampicillin, Amoxicillin
What is co-amoxiclav?
Amoxicillin + calvulanic acid (a beta lactamase inhibitor)
Name two broad spectrum antibiotics
Piperacillin
Ticarcillin
Do you treat MRSA with flucloxacillin?
No MRSA is resistant to flucloxacillin
What do you use to treat MRSA?
Vancomycin
Unless it is V-MRSA (vancomycin resistant MRSA) in which case you use Teicoplanin
What class of antibiotics are cephalosporins?
Beta lactam antibiotics
What is the prefix of cephalosporins?
Ceph- or cef-
Name the first generation cephalosporin
Cephalexin
Name the two second generation cephalosporins
Cefaclor
Cefuroxime
Name the third generation cephalosporin
Ceftazidime
Name the fourth generation cephalosporin
Cefepime
How does the coverage of gram positive bacteria by cephalosporins change over the generations?
High coverage for first generation
Decreases for second generation
Decreases again for third generation
Increases for fourth generation
How does the coverage for gram negative bacteria by cephalosporins change over the generations?
Low for first generation
Increases for second generation
Increases again for third
And again for fourth
What are the levels of resistance across the generation of cephalosporins?
Resistance decreases across the generations
What is the mode of action for cephalosporins?
Binds to binding proteins and destroy the bacterial cell wall
What microorganisms do narrow spectrum penicillins cover?
Gram positive bacteria
What microorganisms do broad spectrum penicillins cover?
Gram positive and gram negative bacteria and anaerobes
What are the potential side effects of penicillin use?
Hypersensitivity (rash, or rarely anaphylaxis)
What microorganisms do first generation cephalosporins cover?
Gram positive bacteria
What microorganisms do second generation cephalosporins cover?
Gram positive bacteria, some gram negative bacteria, and anaerobes
What microorganisms do fourth generation cephalosporins cover?
Gram positive bacteria, and gram negative bacteria, and anaerobes
What are potential side effects of cephalosporin use?
Hypersensitivity, pseudo membranous colitis, bone marrow suppression, nephrotoxicity
What is psuedomembranous colitis?
Swelling or inflammation of the large bowel due to overgrowth of Clostridioides difficile
What is nephrotoxicity?
Toxicity in the kidneys
Give four examples of tetracyclines
Tetracycline, doxycycline, minocycline, demeclocycline
What is the mode of action of tetracyclines?
They inhibit protein synthesis by binding to 30s ribosome subunit and stopping tRNA interaction
Tetracyclines and bacteriostatic
What are some possible side effects from tetracycline use?
GI upset, teeth staining, photosensitivity, hepatotoxicity, nephrotoxicity
What microorganisms are covered by tetracyclines?
Gram positive and gram negative bacteria, atypical bacteria, spirochaetes, malaria
What is a spirochete?
A group of spiral shaped bacteria that include syphilis, yaws, Lyme disease and leptospirosis
Give three examples of macrolides
Erythromycin
Azithromycin
Clarithromycin
What is the mode of action of macrolides?
They inhibit protein synthesis by binding to the t0s subunit and inhibiting pepdidyl transferase
They are bacteriostatic
What microorganisms are covered by macrolides
Gram positive and gram negative bacteria
Atypical (intercellular) bacteria
What are some potential side effects of taking macrolides?
Hepatotoxicity, GI upset
Which penicillin is not water soluble?
Nafcillin
Which spriochaetes are gram negative?
All spirochaetes are gram negative
Which cocci are gram positive?
All cocci are gram positive (except neisseria and moraxella)
Which bacilli are gram negative?
All bacilli are gram negative (except anthrax, tetanus, botulism, and diphtheria bugs)
Which antibiotics are used for intercellular bugs?
Tetracyclines and macrolides
