mechanisms
penicillin
inhibits formation of crossbonds in peptidoglycan
1. target: DD-transpeptidase (aka penicillin binding protein)
2. precursor buildup activate bacterial cellw all hydrolases
cell wall weaken, osmotic pressure, lysis
Ciprofloxacin
nucleic acid synthesis (DNA gyrase / topoisomerase) inhibitor
both G+ and G- bacteria
resistance due to gyrase subunit mutation
rifampicin
RNA polymerase, interfere with transcription initiatin but not polymerisation
QUICK resistance due to Pol mutation
used in mycobacterium infections
protein synthesis related
examples
Streptomycin
30s ribosome. cause misread
Tetracyclines
block attachment of tRNA
Erythromycin
block protein synthesis after initiation
resistance due to enzymatic methylation of 23s rRNA
antimicrobial therapy
administer drug to an infected person to destroy the infective agent without harming the host cells
sources
natural origin
synthetic agents
semi-synthetic
drug combination
erduce emergence of drug resistance
synergisms
concepts
selective toxicity
target microbial not host
stability
must live their routine
enough half-life, effective concentration at target
antibiotic action
bacteriostatic
block growth, no harm to viability
likely reversible
bacteriocidal
block growth, viability loss
no direct lysis, e.g. quinolones
bacteriolytic
lysis. e.g. penicillin
assays
disk diffusion
liquid medium assay
MIC: minimum inhibitory concentration
tube
MBC: minimum bactericidal concentration
plate
