antiBiotics Flashcards
what are the categories of antibiotics that target cell wall synthesis?
penicillins
cephalosporins
carbapenems
monobactams
(all B-lactams)
- vancomycin
- tercoplanin
(both glycopeptides)
bacitracin
(polypeptide)
name the different types of penicillin.
penicillin V
penicillin G
fluctoxacillin / methicillin
amoxicillin / ampicillin
piperacillin
outline the pharmacokinetics of b-lactams.
- target penicillin-binding proteins (PBPs), enzymes involved in peptidoglycan synthesis.
- peptoglycans maintain the strength and rigidity of the bacterial cell wall.
- without this the cell wall is compromised and the cell dies via lysis
name some bacterium which penicillin can be used to treat and outline some cases when penicillins should be used.
S. pneumoniae
S. pyogenes
S. aureas
N. meningitidis
N. gonorrhoea
H. influenza
- effective for many gram-positive
- narrow mechanism of action meaning can disrupt certain species without effecting flora
- not effective against lactamase producing species.
name the bacterial species of cephalosporins.
- cefa-lexin
- cefu-roxime
- cefo-taxime
- cefria-xone
- cefta-zimide
outline when you would prescribe cephalosporins and what species of bacteria they are effective against.
- versatile and broad spectrum of activity
- usually prescribed when penicillins are ineffective
outline the different species of the carbapenems.
- metropenem
- ertapenem
- imipenem
outline when carbapenems are used.
- broad spectrum
- resistant to beta lactamases
- reserved for treating serious infections caused by multi-drug resistance
- usually a last resort
outline when monobactams are used.
- primarily effective against aerobic gram-negative bacteria
- unique structure - only consist of a single beta lactam ring
- resisstant to beta-lactamase producing organisms
- used in severe gram negative infections
what drug is under the catagory monobactams?
aztreonam
name the 2 glycoproteins that target the cell wall and when you would use each one
vancomycin:
- serious infections caused by gram positive
- MRSA
- binds to petidoglycan precursors, inhibiting cell wall synthesis
teicoplanin:
- topical because very toxic effects
- prevents encorporation of new peptoglycan into cell wall
- gram positive
- superficial skin infections - minor cuts, burns, eye infections
outline why beta lactams work best with gram positive antibiotics.
- to bind to PBPs, it must diffuse through the cell wall
- gram-negative organisations have an additional lipopolysaccharide layer that decreases andibiotic penetration
why are penicillins ineffective at treating intracellular pathogens?
because they poorly penetrate mammalian cells
outline why the different B-lactams have different acitivity.
due to their relative affinity for different PBPs
name the antibiotics that work by targeting nucleic acid synthesis.
rifampicin
metronidazole
fluoroquinolones:
- ciprofloxacin
- levofloxa§cin
- moxifloxacin
how do floroquinolones work?
inhibit bacterial DNA gyrase and topoisomerase IV enzymes critical for DNA replication and repair
- cell death
outline when the floroquinolones would be used?
Ciprofloxacin: Best for Gram-negative and Pseudomonas.
Levofloxacin: Respiratory infections with better Gram-positive coverage.
Moxifloxacin: Broader spectrum, including anaerobes.
rifampicin
- rifamycin class antibiotic
- inhibits rna polymerase, preventing rna synthesis and bacterial replication leading to death
- bacteriacidal
- Broad-spectrum, effective against Mycobacterium tuberculosis, Gram-positive bacteria, and some Gram-negative bacteria.
Metronidazole
- a nitroimidazole class antibiotic
- disrupts bacterial DNA in anaerobic organisms and protozoa
- bacteriacidal
name the classes on antibiotic that affect protein synthesis.
30s:
tetracyclines:
- doxycycline
aminoglycosides:
- gentamicin
50s
macrolides:
- erythromycin
- clarithromycin
- azithromycin
clindamycin
linezolid
chloramphenicol
name the antibiotics which work by inhibiting folate synthesis.
sulphonamides:
- sulphamethoxazole
blocks conversion of PABA to DHFA
trimethopim
blocks conversion of DHFA to HFA
both bacteriastatic but co-trimoxazole is bacteriacidal
co-trimoxazole - combination of sulfamethaxazole and trimethropim
outline the difference between bacteriostatic and bactericidal antibiotics.
bacteriostatic - inhibit protein synthesis, dna replication or metabolism (prevents bacteria multiplying)
bacteriacidal - inhibit cell wall synthesis (kills bacteria)
what are the 2 major determinants of antibiotics to be effective?
- concentration - must bind to an adequate number of binding sites
- time that the antibiotic remains on the binding sites
but for this to happen the antibiotic must reach and stay at the site of bacterial infection - this depends on pharmacokinetics eg release, absorption, distribution, elimination
- therefore when choosing an antibiotic you must choose one which will be able to reach the site of infection, in a large enough concentration, in an amount of time suitable
nitrofurantonin
- used for UTIs
- S. Saprophyticus
- bacteriacidal
- works by being low level in the blood but being excreted in the urine so high levels in there and working that way
- targets dna, protein synthesis and other cell components
Discuss the patient and pathogen factors considered for choosing antibiotics
patient:
- neonates and infants
- elderly
(weaker liver and renal for excretion and metabolism)
- penicillin alergy
- immunocomprimised
(broad spectrum antibiotics needed to treat opportunistic infections)
pathogen:
- likely organism causing the infection
- consider local resistance patterns eg MRSA
- sensitivity of the organism to the antibiotic
bacitracin
- inhibits cell wall synthesis
- glycoprotein
- topical
- gram positive
