Anti Biotics Flashcards
Group represents of beta lactams
Penicillins, cephalosporins, carbapenems
Group representatives of quinolones
Ciprofloxacin
Group representatives of macroslides
Erythromycin
Group representatives of aminoglycosides
Gentamicin
Group representatives of glycopeptides
Vancomycin
Group representatives of tetracycline
Oxytetracyclines
Group representatives of folate antagonists
Trimethoprim/sulphonamide
Group representatives of imidazoles
Metronidazole
What are beta lactams selective for
Peptidoglycan cell wall
Penicillin hypersensitivity
Rare and dramatic - angiogenic oedema
Cross reaction in 10% with cephalosporins
Can use carbapenems and aztreonam
Skin testing does NOT work
Patients on amoxicillin/ampicillin can get a maculopapular rash
So its usage is dependent on the severity of the infection and if there are alternative treatments
Carbapenems
E.g.
Imipenem
Meropenen
Ertapenem
Fantastically stable to all GNB beta lactaminases
Only rare acinetobacter/pseudomonas resistant and New Delhi metallobetalactamase NDM
No activity against MRSA/VRE but covers lots of other common pathogens
Glycopepetides
E.g.
Vancomycin
Teicoplanin
Important for MRSA and resistant enterococci
Clostridium difficile - taken orally not absorbed
Potentially nephrotoxic - i.v. Only
Can be given by bolus - no red man syndrome - used for prophylaxis
Best treatment for c diff. - fecal transplant
Quinolones
Nalidixic acid
Ciprofloxacin
Levofloxacin
Moxifloxacin
Expensive - better gram +ve activity and -ve but not MRSA
Particularly valuable for uni resistant bacteria
Resistance rising 15-20%
Pseudomonas - resistance can emerge by mutation - targets DNA gyrase
Safe but c diff issues
Macrolides
Erythromycin
Clarityromycin
Aminoglycosides
Gentamicin
Tobramycin
Amikacin
Tetracycline
Oxytetracyclines
Minocycline (better absorbed, expensive)
Tigecycline ( new compound active against MRSA and acinebacter)
Antibacterial orphans
Chloramphenicol Fusidic acid Linezolid Mupirocin Nitrofurantoin Daptomycin Fidaxomicin Metronidazole
Folate antagonists
Sulphonamide
Trimethoprim
Co-trimoxazole
Metronidazole
What do beta lactams do?
Bind to and inhibit enzymes which catalyse the link between subunits that from the peotidoglycan cell wall
What do glycopeptodes do
Bind to terminal D-ala-D-ala, prevent incorporation of subunit into growing peptidoglycan
Carbapenems facts
Stable to all Gram negative bacteria beta lactamases
Only rare acinetobacter/pseudomonas resistant and New Delhi metallobetalactamase NDM
No activity against MRSA or VRE (vancomycin resistant enterococcus)
Action against
S. Pneumoniae, group A strep
Glycopeptides facts
Important for MRSA and resistant enterococci
C diff diarrhoea - used for severe disease oral not absorbed
Potentially nephrotoxic (I.v. Only)
Quinolones facts
Active against Gram+ve and -ve but NOT MRSA streptococci
Particularly valuable for UTI (resistant bacteria)
Resistance rising (15-20%)
Pseudomonas: resistance can emerge by mutation (target DNA gyrase), safe but c diff issues
Expensive but better Gram +ve activity
Macrolides facts
Active: S pneumonia (+ resistance) Beta-haemolytic strepts S aureus (+resistance) H influenzae Legionella, mycoplasma NOT active: Enterobacteriaceae Enterococci Pseudomonas
Safe particularly penicillin allergy
Adverse effects:
Vomiting
Hunger pains
Aminoglycosides facts
Relatively nephrotoxic toxic so: given only I.v./i.m.
Active: pseudomonas, GNBs including some nosocomial staph aureus
NOT active: streptococci, anaerobes
Tetracycline facts
Do not give in pregnancy - children TEETH
Uses: chlamydiae infections, COPD, acne
Poorly absorbed with antacids
Orphans - chloramphenicol
Rarely used in U.K. Broad spectrum particularly against +ve
Orphans - fusidic acid
Related to steroid hormones
Specific activity against staphylococci
Orphan - linezolid
Valuable anti- staphylococcal agent (good for MRSA and VRE) oral and I.V. Can be toxic over 2 weeks, monitor WBC
Orphans- mupirocin -
For topical nasal decolonisation of MRSA carriage
Orphans - daptomycin
Potent I.v. Anti-MRSA (also VRE) agent v cidal good in endocarditis and foreign body infections inc CPK sometimes
Orphans - nitrofurantoin
Lower UTI (no tissue levels) Adverse effects GI common
Orphans - fidaxomicin
A macrocyclic alternative to metronidazole /vancomycin for c diff - £1300 course
Folate antagonists - sulphonamide
Widespread resistance only used against strenotrophomonas and as co-trimoxazole for pneumocystis jirovecii
Folate antagonists - trimethoprim
Cheap, oral heavily used for UTI
Resistance 20-30%
Folate antagonists co-trimoxazole
Trimethoprim and sulphamethoxazole combined
No advantage in UTI
Folate antagonists - metronidazole
Active agent almost all anaerobes
Long term use –> peripheral neuropathy
Antabuse effect with alcohol
How does trimethoprim work
Bacteria have to make there own folic acid where as humans can use folic acid
Trimethoprim has a greater affinity for bacterial DHFR (dihydrofolate reductase) so acts on it preventing its use
3 main mechanisms by which resistance is mediated
1) inactivation of antibiotic such that it becomes unable to bind to target molecule e.g. Production of beta-lactamases as with penicillins
2) mutation in target molecule: antibiotic cannot bind e.g. Streptomycin
3) altered permeability of cell membrane prevents entry of antibiotic e.g. Tetracyclines
