Antibiotics Flashcards
(35 cards)
What is an antibiotic?
Agent produced my a micro-organism that kills or inhibits the growth of other micro-organisms
Antibiotics can be put into classes depending on their binding sites and effects on the bacteria. Give 5 binding sites and one example of an antibiotic that works there.
- Bind to cell wall - B-lactams or glycopeptides
- Interfere with nucleic acid synthesis/function - Metranidazole
- Inhibit protein synthesis - Aminoglycosides, tetracyclines, macrolides, lincosamides, oxazolidonones
- Inhibit folate synthesis - Trimethoprim
- Inhibit DNA gyrase - Fluoroquines
Define bacteriocidal
Kills the bacteria
Define bacteriostatic
Prevents growth of bacteria
Which antibiotics are generally bacteriocidal?
Those that inhibit cell wall synthesis (B lactams and glycopeptides)
What are the MIC and MBC?
MIC = Minimum inhibitory concentration (level of antibiotic needed to prevent visible growth of the bacteria) MBC = Minimum bacteriocidal concentration
The antibiotics with the lowest minimum inhibitory concentration are not necessarily the best antibiotics, what two other factors have a large influence on anti-bacterial effects?
Concentration
Time (remains @ binding site)
For a staph aureus infection, what antibiotic would be your first port of call?
Flucloxacillin. If not, Vancomycin
What antibiotics increase the risk of C.Diff?
The C drugs - ciprofloxacin, clindamycin, cephalosporin, Co-amoxiclav (augmentin) and carbapenems
Give 4 different methods that bacteria use to resist antibiotics
- Change target site
- Destroy antibiotic
- Prevent antibiotic entry
- Remove antibiotic from bacteria (efflux pump)
What are the main 3 examples of bacteria changing their target site so that antibiotics can no longer bind?
- VRE
- MRSA
- MTB (mycobacterium tuberculosis) change in RNA polymerase so Rampificin no longer acts
Give 3 examples of natural resistance of bacteria
- Aerobic bacteria can’t reduce metranidazole to active form
- Anaerobic bacteria lack oxidative metabolism to take up aminoglycosides
- Gram -ve bacteria have an outer membrane that cannot be penetrated by Vancomycin
What are the 3 main ways that bacteria can acquire resistance other than spontanoeus mutation?
- Conjugation (pillus an plasmid)
- Transduction (bacteriophage)
- Transformation (picking up naked DNA0
Name two gram +ve resistant organisms
- MRSA
- VRE (Vancomycin resistant enterococci)
What gene in MRSA codes for resistance?
mecA
What is MRSA resistant to?
All beta-lactams and methicillin
Give 3 categories of gram -ve resistant organisms
- ESBL’s
- Carbapenemases (CPE’s) enterobactericae
- AmpC beta-lactamases
What are ESBL’s resistant to?
Penicillin, Amoxicillin, Cephalosporins, and combination antibiotics (Augmentin, Tazocin)
Which group of B-lactams are the most broad spectrum?
Carbapenems- will cover ESBL’s and AmpC
What are AmpC’s resistant to?
Penicillin, cephalosporin, monobactam
What antibiotic is the first port of call for a UTI, and prescribed for how many days?
Trimethoprim - 3 days
What antibiotic is the first port of call for cellulitis, if the individual was infected with S.Aureus?
Flucloxacillin (10-14 days)
Patient presents with 2 day history of cough and sputum. S. pneumoniae infection. What antibiotic would be used?
Amoxicillin
Patient presents with 2 day history of cough and sputum, pneumonia suspected but S.pneumoniae not present. What antibiotic would be used?
Clarithromycin
