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Micro - Intro to Antibiotics + their Classification (ii) (Quinolones…
Micro - Intro to Antibiotics + their Classification (ii)
B-Lactams
inhibit cell wall synthesis
bactericidal
presence of 4-member b-lactam ring
4 types
pencillins
standard
benzylpenicillin
narrow spectrum
against gram +ve cocci (strep, staph, clostridia) + some gram -ve cocci (neisseria)
for meningitis, endocarditis, cellulitis
antistaph
flucloxacillin
not inactivated by b-lactamase
narrow
amino
ampicillin
amoxicillin
broader
incl gram -ve bacili (E coli, H influenzae)
acquired resistance v common
good oral absorption
for UTIs + RTIs
antipseudomonal
piperacillin
cephalosporins
10% crossreactivity with penicillin allergy
never prescribe these to a patient with an anaphylactic penicillin allergy
divided into gens
increasing anti-gram -ve activity, decreasing anti-staph activity
1GC
anti gram +ve
orally active
for RTIs + UTIs
cefaclor
2GC
anti gram +ve + -ve
oral + IV
surgical prophylaxis + RTIs
cefuroxime
3GC
anti gram -ve, some anti-strep
IV
cefotaxime for meningitis
ceftriaxome
carbapenems
CPE = public health emergency
monobactams
give b-lactamase inhibitors to overcome b-lactamase
enzyme normally hydrolyses b-lactam ring
e.g. clavulanate with amoxicillin = coamoxicalv
e.g. tazobactam with piperacillin = piptazobactam
Glycopeptides
inhibit cell wall synthesis
bactericidal
narrow spectrum - gram +ve only
IV for MRSA
PO for C diff (won't get systematically absorbed)
vancomycin + teicoplanin
Aminoglycosides
gentamicin
inhibits protein synthesis @ 30S
bactericidal
active against gram -ve bacilli, S aureus, mycobacteria, brucella
inactive against anaerobes
used in combination Tx to treat intra-ab infections + endocarditis
NB monitor serum levels - nephro + oto toxicity
IV, not orally absorbed
macrolides
clarithromycin, erythromycin, azithromycin
inhibit protein synthesis @ 50S
oral/IV
for atypical RTIs
mycoplasma, coxiella, chlamydia
no cell wall - b-lactams ineffective
Quinolones
bactericidal
inhibit DNA rep
ciprofloxacin = fluoroquinolone
levofloxacin = new
blackbox warning, SEs = tendonitis, neuropsych effects
good oral bioavailability
mainly anti gram -ve bacilli, but new ones are also anti-gram +ve
for RTIs
not 1st choice but can be used for UTIs + intra-ab infections
Tetracyclines
bacteriostatic
inhibit protein synthesis
doxycycline
for chlamydia, rickets, coxiella, mycoplasma
cause growing teeth to stain - contraindicated in children + pregnant women