Antibacterial Agents and Resistance Flashcards
What is the difference between sterilization and disinfection?
Sterilization - kills all forms of microbial life
- chemical: gas, formaldehyde vapor
- physical: autoclave, hot air oven, incineration
Disinfection - doesn’t kill all microorganisms (likes spores)
- chemical: alcohol, hydrogen peroxide, chlorine, chlorhexidine, formaldehyde
* antiseptics - can be used with living tissue - hydrogen peroxide
- physical: boiling, filtration, pasteurization
NOTE: disinfectants are used for non-living things, antiseptics are used for living tissue
What are antibacterials?
used for treatment of infectious disease. Derived from either fungi or bacteria (e.g.. like penicillin, tetraclylcinesm sulfonamides)
What are nosocomial infections?
acquired in a hospital (hospital setting), symptoms may show during or after stay in hospital
sources:
1) endogenous: patients own microbiota
2) exogenous: transmission from external environment
What are known pathogens?
bacterial: MRSA and VRSA - often caused by staphylococcus aureus that is common on the external skin layers but not within the body. It causes infections and even pneumonia.
What antibacterial drugs target cell walls?
- beta lactams - which inhibit PBP
- non beta lactams - which inhibit linear peptidoglycan assembly
What are antibacterial agent targets?
- selective toxicity toward the microbe rather than the host . these are the actions taken to insure the invading organism dies not the host cells
- things not present in the host - like bacterial cell wall, 70s bacterial ribosomes, folic acid synthesis
What are the typical targets of antibacterials?
1 ) cell wall synthesis
2) protein synthesis (70s)
3) nucleic acid synthesis in DNA or RNA (folic acid)
4) cell membrane integrity
Cell wall synthesis inhibition
both beta lactam and non beta lactams interfere with cross-linking and kill growing bacteria by lysing cell walls
- penicillin - beta lactams - bind to transpeptidase (PBP)
- vancomycin - non-beta lactams - binds to amino acid side chains
Inhibition of protein synthesis
- most will prevent tRNA from initiation or translocating
- most will prevent the ribosome from completing their task
- one will prevent the formation of peptide chains
Inhibition of nucleic acid synthesis
either DNa or RNA will be inhibited or broken down and folate synthesis will be stopped
cell membrane inhibition
cytoplasmic membrane permeability is lost - cellular materials leak out
- altering gram negative other membrane or binding to sterol containing fungi
What is the mechanism of drug resistance - the basic?
drugs kill most bacteria, the surviving bacteria are resistant to the drug, the new bacteria can now thrive w/o the old bacteria that is dead, these bacteria can sometimes give their resistance to other bacteria - antibiotics can create selection for resistance
What are some mechanisms of drug resistance?
- efflux pump - happens at cell wall and controls what passes through
- blocked penetration - happens at cell wall and controls what passes through
- altered target - some organisms have altered receptors preventing drugs from binding (MRSA for example is modified so penicillin can’t bind, this is why we have to use vancomycin for MRSA and VRSA is modified so vancomycin can’t bind)
- enzymatic activation:
1) first is beta-lactam inhibitors - where a penicillin (beta-lactam - shaped like a ring) is inhibited by certain bacteria, the way it works is the bacteria works to modify the shape of the beta-lactam ring,( by opening the ring the drugs is no longer effective- penicillin resistance = broken beta-lactam ring
2) second is amino glycoside resistance - where a group of phosphates are removed from the drugs structure inactivating it preventing it from binding to the bacteria
- penicillin resistance = broken beta-lactam ring
- genetic resistance:
1) intrinsic - structure provides a tolerance of certain drugs
2) acquired - developing resistance over time
3) mutational - resistance due to a genetic mutation
