Principles of Anti-Bacterial Chemotherapy Flashcards
When should anti-bacterial agents ideally be chosen?
After the infecting organism has been identified, and the results of susceptibility tests are available
How long does it commonly take for results of tests investigating organism type and susceptibility to develop?
24-48hours
What is the result of tests into organism type and susceptibility taking 24-48 hours to develop?
Empirical treatment is often initially started
What is empirical treatment of bacterial infections based on?
Clinical insight and epidemiological data
What can happen once the infecting organism has been identified?
Organism-based therapy can start
What are bactericidal agents?
Those able to kill bacteria directly
What are bacteriostatic agents?
Those that inhibit bacterial growth and require the immune system to eliminate the remaining pathogens
How can the types of antibiotics be grouped together for classification?
- Penicillins
- Cephalosporins
- Monobactams
- Carbapenums
- Tetracyclines
- Aminoglycosides
- Macrolides
- Metronidazole
- Sulphonamides
- Trimethroprim
- Vancomycin
- Teicoplanin
What kind of antibiotics are the penicillins?
Bactericidal
What do the penicillins contain?
A ß-lactam ring
How do the pencillins act?
By interfering with the peptioglycan cell wall production, inhibiting the action of transpeptidase
How well do pencillins diffuse?
Well though bodily tissues, poorly into cerebrospinal fluid
When will penicillin diffuse well into cerebrospinal fluid?
When meninges are inflamed
What % of the population are allergic to penicillins?
1-10%
Give 6 examples of pencillins
- Benzylpenicillin
- Phenoxymethylpenicillin
- Flucloxacillin
- Ampicillin
- Amoxicillin
- Piperacillin
What is benzylpenicillin also known as?
Penicillin G
What is benzylpenicillin important for?
Important antibiotic against streptococcal infection and many other bacteria
How must benzylpenicillin be administed?
Via IV
Why must benzylpenicillin be given via IV?
It is inactivated by gastric acid
What is phenoxymethylpenicillin also known as?
Penicillin V
How is phenoxymethylpenicillin similar to benzylpenicillin?
It has a similar antibacterial spectrum
How does phenoxymethylpenicillin differ from benzylpenicillin?
It is not inactivated by gastric acid
How is phenoxymethylpencillin administed?
Orally
What is phenylmethylpenicillin used for?
- Respiratory tract infections in children
- Streptococcal tonsillitis
Not used against serious infections
What is flucloxacillin resistant to?
Penicillinases
What is the result of flucloxacillin being resistant to penicillinases?
It is acid stable
What is flucloxacillin used against?
Streptococcal infections
What kind of antibiotics are ampicillin and amoxicillin?
Broad spectrum
What can ampicillin be used for?
Most gram positive and gram negative bacteria
What is amoxicillin used for?
Similar purposes as ampicillin, but also for prophylaxis for endocarditis
What is co-amoxiclav?
A mixture of amoxicillin and clavulanic acid
What is clavulanic acid?
A ß-lactamase inhibitor
What does co-amoxiclav do?
Makes amoxicillin effective against ß-lactamase bacteria
What kind of antibiotic is piperacillin?
Extended spectrum
What can piperacillin be used as?
An antipseudomonal activity
What kind of antibiotics are cephalosporins?
Broad spectrum
What are cephalosporins closely related to?
The penicillin group
What are cephalosporins used for?
Used in the treatment of;
- Septicaemia
- Meningitis
- Peritonitis
- UTIs
How well do cephalosporins diffuse?
Diffuse well through body, but cannot enter the CSF (unless the meninges are inflamed)
What is seen with long term cephalosporin treatment?
Antibiotic associated colitis
Why is antibiotic associated colitis seen with long term cephalosporin treatment?
Due to the broad spectrum nature of the antibiotic
How many generations are there of cephalosporins?
5
What are the important generations of cephalosporins?
- Cefotaxim
- Ceftazidime
- Ceftriaxone
What is cefotaxim used against?
Gram-negative bacteria
What is ceftazidime good for?
Good activity against pseudomonas
What is ceftriaxone used for?
- Serious septicaemias
- Pneumonias
- Meningitis
What are monobactams?
Monocyclic beta-lactams
What are monobactams used against?
Gram negative bacteria of pseudomonas, Neisseria meningitidis, and Haemophilus Influenzae
What is the main monobacteum?
Aztreonam
How is aztreonam given?
Intravenously
How are carbapenums given?
Intravenously
What kind of antibiotics are carbapenums?
Broad spectrum
What are carbapenums used against?
Aerobic and anaerobic Gram positives and negatives
What do carbapenums have a similar mechanism of action to?
Other beta-lactams
What kind of antibiotics are tetracyclines?
Broad spectrum
What has happened to tetracyclines activity?
It has decreased
Why has tetracyclines activity decreased?
Due to increased bacterial resistance
What are tetracyclines used against?
- Chlamydia
- Ricketts
- Mycoplasma
How do tetracyclines work?
By interfering with protein synthesis in the bacteria and lock the tRNA and the septal site of the mRNA molecule
What is the most used tetracycline?
Doxycycline
Give two examples of aminoglycosides?
- Streptomycin
- Gentamicine
How do aminoglycosides work?
By preventing the translation of mRNA into protein
Are aminoglycosides bactericidal or bacteriostatic?
Bactericidal
What kind of antibiotics are aminoglycosides?
Quite broad spectrum
How are aminoglycosides given?
Injection
Why must aminoglycosides be given by injection?
Because they are not absorbed by the gut
What is the problem with aminoglycosides?
- They are nephrotoxic in high concentrations
- They can damage cranial nerves
What is gentamycin widely used as?
The treatment of choice for many serious bacterial infections
What is the most commonly used macrolide?
Erythromycin
What is the action of erythromycin similar to?
Penicillin
What is erythromycin used for?
- Alternative to penicillin in penicillin-allergic patients
- Respiratory infections
- Some penicillin resistant staphylococcus
What is the problem with erythromycin?
It has numerous side effects, even in low doses
What are the side effects of erythromycin?
- Nausea
- Vomiting
- Diarrhoea
What kind of drug is metronidazole?
Antimicrobal
What does metronidazole have high activity against?
Anaerobic bacteria and protozoa
What is metronidazole used for?
- Pseudomembranous colitis
- Surgical and gynaecological sepsis
What has happened to the clinical use of suphonamides and trimethroprim?
It has reduced
Why has the clinical use of sulphonamides and trimethroprim reduced?
Resistance has been increased towards them
What are sulphonamides and trimethroprim used together with?
Trimoxazole
Why are sulphonamides and trimethroprim used with trimoxazole?
For their synergistic action
What is the problem with using sulphonamides and trimethroprim together with trimoxazole?
Can cause serious side effects
What is trimethoprim used for?
UTIs and RTIs
What kind of antibiotics are vancomycin and teicoplanin?
Glycopeptides
Are vancomycin and teicoplanin bactericidal or bacteriostatic?
Bactericidal
What are vancomycin and teicoplanin used against?
Aerobic and anaerobic Gram positive bacteria. Can be used against multi-resistant S. Aureus
How well is vancomycin absorbed?
Poorly
What is the result of vancomycin being poorly absorbed?
It is only given orally for a psuedomembranous colitis
