S4 Intro to Antibiotics and Resistance Flashcards
What are the 4 classes of antimicrobials?
- antibacterial
- antifungal
- antiviral
- antiprotozoal
What ways can antibacterials agents be classified?
- bactericidal or bacteriostatic
- broad or narrow
- what is the target site? (Mechanism of action)
- what is the chemical structure? (Antibacterial class)
How can you measure antibiotic activity/sensitivity?
- disc testing (disc diffusion testing)
* minimum inhibitory concentration (MIC) - broth microdilution or E test
What are the 4 mechanisms of actions by antibacterials?
- cell wall synthesis
- protein synthesis
- cell membrane function
- nucleic acid synthesis
What antibacterials affect bacteria cell wall synthesis?
- beta-lactams: penicillins, cephalosporins
* glycopeptides
What antibacterials affect bacteria cell membrane function?
- polymixins e.g. colistin
What antibacterials affect bacteria protein synthesis?
- tetracyclines
- aminoglycosides
- macrolides
What antibacterials affect bacteria nucleic acid synthesis?
- quinolones
- trimethoprim
- rifampicin
What are the 3 types of resistance?
- Intrinsic
- Acquired
- Adaptive
Describe intrinsic resistance.
- has no target to access for the drug
* usually permanent
Describe acquired resistance.
- acquires new genetic material or mutates
* usually permanent
Describe adaptive resistance.
- organism responses to a stress e.g. sub-inhibitory levels of antibiotic
What are the 3 mechanisms of resistance?
- Enzymatic modification/destruction of antibiotics
- Enzymatic alteration of antibiotic targets
- Mutations of bacterial target sites
How can gene for resistance get to other bacteria cells?
- chromosomal gene mutation then bacterial replication
- horizontal gene transfer - two bacterial cells can conjugate and transfer plasmids from one to another (pilus conjugates cells, cells “fuse” partially, DNA polymerase replicates plasmid, pilus separate)
What classes of antibiotics are beta-lactams?
- penicillins e.g. amoxicillin, flucloaxcillin, penicillin, etc
- cephalosporins e.g. cefalexin, ceftriaxone, cefepime, etc
- carbapenems e.g. meropenem, imipenem
- monobactams e.g. aztreonam
What is penicillin active against?
Streptococci
What is amoxicillin active against?
Streptococci and some activity against gram-negatives
What is flucloaxcillin active against?
Staphylococci and streptococci
What is Co-amoxiclav active against? What is it’s advantage?
Streptococci, staphylococci, gram negatives, anaerobes
It is a beta-lactamase inhibitor combination (between amoxicillin and clavulanate
What is piperacillin/tazobactam active against? What is it’s advantage?
Streptococci, staphylococci, gram negatives (incl. pseudomonas), anaerobes
What are cephalosporins? What is an example of one, where does it have good activity?
Broad spectrum antibacterials with no anaerobes activity
Cetriaxone, good activity in the CSF
What are 3 carbapenems? Are they broad or narrow spectrum? What are they active against?
- meropenem, ertapenem, imipenem
- broad
- most gram negatives
What are two types of glycopeptides?
- vancomycin (active against most gram positives)
* teicoplanin (easier to administer)
Are tetracycline and doxycycline broad or narrow spectrum? What are they active against? Who shouldn’t they be given to?
- broad spectrum
- chlamydia and some protozoa
- children under 12 years, pregnant and breastfeeding women
What is the most common aminoglycoside? What do they work against? Where do they have good activity?
- gentamicin
- gram negatives
- blood/urine
What is an example of a macrolide? What do they act against?
- erythromycin
* alternative to penicillin for mild gram positive infections, also works against atypical respiratory pathogens
What is the most common quinolone? What do they inhibit? What are they active against? What if becoming increasingly resistant to them?
- Ciprofloxacin
- DNA gyrase
- gram negatives and atypical pathogens
- C.difficile
What do trimethoprim and sulphonamides inhibit? What does trimethoprim treat on its own?
- folic acid synthesis
* UTI
What are the two types of antifungals? What do they inhibit?
- azoles - inhibit cell membrane synthesis
* polyenes - inhibit cell membrane function
What is an example of an azole? What does it work against?
Fluconazole - against candida
What is an example of a polyene? What it is used against?
Nystatin - topical treatment for candida
What does the antiviral, aciclovir do?
When phosphorylated, it inhibits viral DNA polymerase (works against herpes simplex and varicella zoster)
What does the antiviral, oseltamivir do?
Inhibits viral nueraminidase (works against influenza A and B)
What is metronidazole? What is it active against?
An antibacterial and an antiprotozoal agent
anaerobic bacteria and protozoa - amoebae, giardia and trichomonas
