10 Antibiotics Flashcards
Bactericidal
Penicllins Cephalosporin Aminoglycosides cotrimoxazole Erythromycin in high conc ( but not typically) Isoniazid vanc Metro Quinolones
Bacteriostatic
Clindamycin Tetracycline macrolide Sulphonamide chloramphenicol lincomycin
Tetracycline
Type abx
MOA
Bind to
S/E
what given simultaneous impede absorb
Probs with what neurolog condit & GI
Tetracyclines are broad-spectrum antibiotics that penetrate macrophages and are often the drugs of choice for treating infections due to intracellular organisms.
Sensitive organisms accumulate the drug by both active and passive transport, for example, Chlamydia and Rickettsia.
30S subunit (not 50S) bacterial ribosome inhibit the binding of the aminoacyl-transfer-RNA.
Deposition of tetracyclines in growing bone and teeth due to calcium binding causes dental discolouration (and dental hypoplasia) and they should be avoided in children under the age of 12 years and in pregnant or lactating mothers.
Aluminium hydroxide if given simultaneously with oral tetracyclines may form complexes that can impede its absorption.
Tetracyclines may increase the muscle weakness in myasthenia gravis and should be used with caution in patients with hepatic impairment.
chloramphenicol
MOA
Traspeptidation is inhibited by chloramphenicol.
ifferentiate between a type I and a type II hypersensitivity
Spec IgE can allergic sensitisation
Penicllin resistance
D/T
What in what bug
penicillinase
E. coli,
Staphylococcus aureus
Enterobacter.
N. meningitidis is generally sensitive to penicillins and less than 20% resistance is found in Pseudomonas and Haemophilus influenzae species.
Regarding virulence factors:
- Can be exotoxins or endotoxins (such as the cell wall of Haemophilus influenzae)
- M protein on some bacteria prevent phagocytosis
Pili on gonococcus allow them to adhere to mucosal surface - Beta lactamase or penicillaminase hydrolyse penicillin but have no direct effect on host tissue.
Penicillin
Mech
Resist - d/t caused by
Allergy incidence
bactericidal
inhibiting the transpeptidase enzyme which cross-links the peptidoglycans in the cell wall
Weakens the cell wall and allows the cell to lyse
Resistance to penicillins is due to beta lactamase enzymes
Plasmid coded
can be translocated bact to bac
specific spectra may be changed by altering the beta lactam side chain.
True allergy rare 1-5/10000 cases therapy
Metronidazole
activity against anaerobic micro-organisms. & protozoal
MOA is not fully known
Cytotoxic effects in anaerobes by a reduction reaction probably via the hydroxylamine derivative.
Bind DNA destab - AA helix
59-94% of a dose is absorbed rectally
Some recommend dose reductions (for example, 500 mg) q12h in patients with CrCl < 10 mL/min, however this is debatable.
Hepatic failure: Dose reduction by 50% to avoid drug accumulation and possible toxicity.
It is associated with a disulfiram-like reaction with alcohol in some patients, and there has been one reported death
peripheral neuropathies primarily with high doses of long duration in children. These are commonly mild sensory deficits that are reversible.
Pens - how work
Colinsation SAur - how much pop
MRSA resistant to fluclox?
Penicillins and other beta-lactam antibiotics act
preventing cross linking in the cell wall which surrounds
cell membrane of Gram positive bacteria.
Gram negative organisms are therefore usually resistant to beta-lactam antibiotics, although the broad spectrum penicillins have some efficacy against Gram negative organisms.
Colonisation with Staphylococcus aureus is seen in 20-30% of the population.
Methicillin resistant Staphylococcus aureus (MRSA) is resistant to flucloxacillin.
Trimethoprim
inhibits tetrahydrofolate reductase.
E.Coli resistant & susceptible to
Ampicillin and amoxicillin are broad spectrum antibiotics active against non-beta lactamase producing Gram positive and Gram negative organisms. They are inactivated by penicillinases and since up to 50% of Escherichia coli strains are now resistant, they would be an unsuitable choice.
Co-amoxiclav consists of amoxicillin and the beta-lactamase inhibitor clavulanic acid. Thus it is active against beta-lactamase producing bacteria that are resistant to amoxicillin, including strains of Escherichia coli.
Cefuroxime is a cephalosporin that is resistant to inactivation by bacterial beta-lactamases and so may be used against Escherichia coli.
Ciprofloxacin has a 6-fluoro substituent which confers enhanced antibacterial potency against both Gram positive and Gram negative organisms, including Escherichia coli.
inhibit bacterial cell wall synthesis.
penicillins,
cephalosporins
Vancomycin is a complex and unusual glycopeptide active against Gram positive bacteria and inhibits cell wall synthesis.
inhibits protein synthesis by interrupting ribosomal function.
Erythromycin
block thymidine and purine synthesis by inhibiting microbial folic acid synthesis.
Sulphonamides
block the terminal cross-linking reaction between alanine and glycine of bacterial cell wall mucopeptide formation.
Penicillins
Amphotericin B
PD
Amphotericin B is highly protein bound and penetrates body tissues poorly.
The toxicity is reduced in lipid formulations of amphotericin B.
Ciprofloxacin and norfloxacin
class
Mechanism
Suitable vs P. Aeurginosa
Quinolones
Prevent bacterial DNA supercoiling -> DNA gyrase,
Suitable antibiotics- Pseudomonas aeruginosa.
Nucleoside analogues
Mechanism
Treat
Other treatments for the inefction Rx by
inhibit reverse transcriptase and are one of the main classes of drugs used in human immunodifficiency virus (HIV) infection.
Other drugs include protease inhibitors and non-nucleoside reverse transcriptase inhibitors, which are given in combination in order to reduce side effects.
Ciprofloxacin
Class
PD
Useful vs
Anthrax
Safe in RF?
Ciprofloxacin is a fluorinated 4-quinolone that is well absorbed orally with a good bioavailability.
It has a wide spectrum of activity against Gram negative organisms but has only moderate activity against Gram positive organisms. Most anaerobic organisms are not susceptible.
Inhalational, gastrointestinal and cutaneous anthrax may be treated initially with either ciprofloxacin or doxycycline.
In moderate renal failure a reduction in dose by 50% is required.
