Antibiotics Flashcards
Name 4 antibiotic targeted mode of actions?
- Cell wall
- DNA
- Protein synthesis
- Mycobacterium
Name an antibiotic used that is a fungus
Penicillin
It causes the bacterial cell wall to rupture by autolysis.
What is the site of action for penicillin?
Transpeptidase
How does Penicillin work?
It works by binding to active site on the transpeptidase to inhibit its ability to cross link the peptiglycan. Making the cell wall more flexible and susceptible to regenerate which affects the cell membrane.
What kind of antibiotics are penicillins and why?
They are B-lactam antibiotics as they contain a B-lactam ring.
Are penicillins enzyme inhibitors?
Yes, they are irreversible enzyme inhibitors.
Name 4 types of penicillin
1) Penicillins
- Pen V
- Pen G
2) Broad spectrum
- Ampicillin
- Amoxicillin
3) B-lactamase resistant
- Flucoxacillin
- Co-amoxiclav
4) Anti-pseudo-monal
- Piperacillin with tazobactin
Give 3 facts for Phenoxymethylpenicillin (Pen V)
1) Effective against gram -
2) Narrow spectrum of activity therefore does not affect the gut area.
3) Variable absorption from the GI tract.
Give 4 facts for Benzylpenicillin (Pen G)
1) Effective against gram +
2) Unstable in acid, must only be given by IV/IM
3) Given in large doses and for severe infections
4) Given for following infections:
- Streptococcal (Pneumonia and endocarditis)
- Clostradia (tetanus)
- Meningococcal (meningitis and septisemia)
When would you prescribe Pen V?
Phenoxymethylpenicillin is prescribed to treat infections such as chest infections, tonsillitis, cellulitis, ear infections, and dental abscesses. It is used in particular for respiratory infections in children
Name 2 broad spectrum antibiotics
- Amoxicillin
- Ampicillin
When would you prescribe amoxicillin?
Amoxicillin is an antibiotic used to treat a number of bacterial infections. These include middle ear infection, strep throat, pneumonia, skin infections, and urinary tract infections among others.
What can Ampicillin cause?
1) Overgrowth of C.diff
2) Diarrhoea due to it being broad spectrum
3) Not metabolised by stomach acid
What are broad spectrum antibiotics used for?
- Pneumonia
- UTIs
- HAP
- H Pylori related infections
- Peptic ulcers
What are two side effects of penicillins?
1) Hypersensitivity
2) Neurotoxicity
How can penicillins cause Neurotoxicity?
When it gets to the brain, influences GABA-A receptor. thus, leading to seizures.
How can penicillins cause Hypersenstivity?
Hypersensitivity is classified into 3 types:
1) Immediate reactions
- 20 mins
- Mediated with IgE
2) Accelerated reaction
- 1-72 hours
- consists of urticaria
3) Late reaction
- 72 hours to several weeks
- usually a skin rash
How should penicillins be NEVER administered and why?
Intrathecal injection, cause a seizure.
Name 4 Cephalosporins
1) Cefalexin
2) Cefradine
3) Cefaclor
4) Cefradoxil
How do Cephalosporins work?
They work by inhibiting peptidoglycan cross linking.
They are more resistant to B-lactamases than penicillins. Therefore, 2nd/3rd line of treatment for Resp/UTI.
When can IV Cephalosporins be used?
Only for severe/complicated antibiotic resistance.
What are side effects of Cephalosporins?
1) Can cause diarrhoea
2) Hypersenstivity
3) Seizures
4) Vitamin K deficiency
- Reduces bacteria in the gut that produces Vit K
How should Cephalosporins be prescribed to patients with kidney impairment?
Should be given in less dose
What are carbapenems?
- Resistance against B-lactamases.
- Resistant against gram - & +
Which carbapenems is broad spectrum?
Meropenem (gram - & +)
Which carbapenems is less broad spectrum?
Ertapenem
Give one advantages of carbapenems?
Longer duration of action
What are monobactams?
Monobactams are a subgroup of beta-lactam antibiotics, where the beta-lactam ring is alone (not attached to another B-lactam ring)
What do they work against?
They only work against aerobic gram -
Must only be given IV/IM
How do monobactums work?
Monobactams work by inhibiting the peptidoglycan synthesis process; as a result, the bacteria lose the ability to resist and burst, leading to cell death.
Give examples of monobactums
Azactam
Aztreonam
Aztreonam inhalation
What is vancomycin used for?
Gram positive infections
- Endocarditis
- Antibiotic associated colitis (caused by C.diff)
How does vancomycin work?
It works by inhibiting growth and cross linking of peptidoglycan.
Inhibiting synthesis of the cell wall of gram +, thus killing the bacteria.
Affects the polymerisation of the sugar layer.
Why is vancomycin not effective against gram - bacteria?
Because it’s structure is too large to get through the walls of gram - bacteria.
When is vancomycin given orally?
Vancomycin is only given orally to treat C.diff colitis
How do you administer vancomycin for systemic infections?
Through IV otherwise it will not be absorbed well.
Which other drug work similar to vancomycin?
Teicoplanin
How does Bacitracin (Tracy’s antibiotic)?
Works by inhibiting enzyme dephosphorylation, preventing peptiglycogen building blocks from attaching to cell wall.
What and How is Bacitracin used?
Helps to prevent minor skin injuries such as cuts, scrapes, and burns from becoming infected, tattoo and circumcision.
Topically for:
Ear/nose/skin infections
How do polymixins work?
The only antibiotics that work on the lipopolyscharides layer outside the cell wall.
What type of bacteria is treated by polymixins?
Serious gram - bacteria
What type of infections does polymixins treat?
They are used to treat systemic infections caused by Pseudomonas aeruginosa.
How many types of polymixins are there?
2
- Colistin
- Polymyxin B
How is polymixins used in cystic fibrosis?
As a nebuliser
What is the structure of mycobacterium?
Mycolic layer
Arabinoglycon
Peptidoglycan
Phospholipids
Name 4 drugs used for the treatment of TB
1) Isoniazid
2) Ethambutol
3) Rifampicin
4) Pyrazinamide
How does Isoniazid work?
It works by influencing the mycolic layer and FAS 2 (Fatty acid synthase 2).
What does Isoniazid’s metabolism dependant on?
Genetic polymorphism
- This drug is under genetic control so genetically determined into fast/slow metabolism.
What organ is affected by ethambutol?
The eyes
Name 4 antibiotics that work on DNA
1) Sulphonamides
2) Quinolones
3) Metronidazole
4) Rifampicin
Name 3 Quinolones
1) Ciprofloxacin
2) Moxifloxacin
3) Levofloxacin
What species is Trimethoprim for?
Effective against gram -/+
- Stap species
- Enterabacter species
- E.Coli
- Proteus mirabilis
- Klebsiella pneumonia
Why is Trimethoprim used as a first line treatment for UTIs?
Because it is secreted unchanged by kidneys, thus high concentration in the urine (compared to blood).
When should Trimethoprim be avoided?
First trimester of pregnancy
What are 4 side effects of Trimethoprim?
1) GI upset
2) Hypersensitivity
3) Haematological disorder
4) Hyperkalemia
Why can nitrofurantoin not be used as a systemic antibiotic?
Due to it’s low plasma concentration
What is nitrofurantoin activated?
By Nitro-reductase
How does metronidazole work?
Generates free radicals in anaerobic cells which break strands in DNA.
Why should metronidazole be avoided with alcohol?
- It inhibits acetaldehyde dehydrogenase
- increases concentration of acetaldehyde
- Gives you glueing, headaches, nausea, vomiting, hypotension.
What do fluroquinololes?
- DNA gyrase
- Topoisomerase
Name the 4 fluroquinoloes?
1) levofloxacin
2) ciprofloxacin
3) ciprofloxacin
4) moxifloxacin
What are side effects of fluroquinololes?
1) Increases risk of arrhythmias
2) Rupture of muscle tendons
3) Promote C.diff colitis
Name two interactions for fluroquinololes?
1) NSAIDs increase risk of seizures
2) Theophylline - inhibits CYPR2
How does rifampicin work?
It inhibits RNA polymerase in prokaryotic cells.
What is the role of Pyrazinamide for the treatment of TB?
It doesn’t work directly but enhances the effects of other drugs.
What does Pyrazinamide affect?
It’s target site is ribosomes.
Name 5 proteins that work on protein synthesis
1) Tetracyclins
2) Aminoglycosides
3) Cholramphenicol
4) Macrolides
5) Linezolid
Give 2 examples of tetracyclins
- Doxycyclin
- Lymecyclin
How do tetracyclins work?
They bind to 30s segment of ribosome to prevent tRNA binding at a site.
What are common indications of tetracyclins?
Acne, LRTI, Ecercebation of COPD, chlamidya, malaria, anthrax, lyme disease.
What happens during tetracyclin resistance?
pump tetracyclin out of the cell
What are side effects of tetracyclins?
Avoid in pregnancy/breastfeeding/young children as it can stick to bones and teeth (teeth discolouration).
Name 3 Aminoglycasides
- Gentamycin
- Amikacin
- Neomycin
How are Aminoglycasides administered?
IV/IM
What organs do Aminoglycasides have toxic effects towards?
Kidney
Ear (kills inner ear auditory hair cells/loss of frequency leading to deafness)
What other antibiotics work well with Aminoglycasides ?
Penicillins
Treatment of C.diff
- Metronidazole
- Vancomycin
How does Chloramphenicol work and it’s indications?
Inhibits transpeptidation (interferes with substrate binding)
- Otitis externa
- Bacterial Conjunctivitis
How do macrolides work?
Inhibit aminoacyl translocation.
Give example of macrolides
Erythromycin
- Bacteriostatic
- Can be used as an alternative to penicillins (in case of allergies)
- Can be used in triple therapy for peptic ulcers.
Give a side effect of erythromycin
prolonged QT interval
How does linezolid work?
Binds to 50s segment
- Inhibits the initiation
Give examples of linezolids
- Used to treat aerobic Gram-positive bacteria.
- Should not be used
