Intro Microbiology Flashcards
What antibiotics affect bacterial cell wall synthesis?
phosphonomycin, bacitracin, D-cycloserine, vancomycin, B-lactams
what step of cell wall synthesis does phosphonomycin affect?
prevents addition of PEP to UDP-NAG. inhibits UPD-N-acetlyglucosamine synthetase. In the cytoplasm
What step of cell wall synthesis does D-cycloserine affect?
addition of 5 aa chain to NAM. Inhibits alanine racemase in the cytoplasm
What step of cell wall synthesis does bacitracin affect?
undecaprenyl-P recycling. needs to be dephosphorylated so it can transport UDP-NAM with aa chain to the outer leaflet of cell membrane
What step of cell wall synthesis does vancomycin affect?
binds D-ala-D-ala residue and sterically inhibits crosslinking reactions (transpeptidation and transglycosylation). This happens in the cell wall.
what step of cell wall synthesis does B-lactams affect?
bind directly to PBP and prevents transpeptidation and transglycosylation. This happens in the cell wall.
Do the antibiotics that act on cell wall synthesis work on cells that are growing or static?
growing!
Are biofilms growing or not growing?
Not growing, this is why they are antibiotic resistant.
What are autolysins?
they are produced by antibiotics and chew away at the cell wall leading to cell lysis.
What is the target of polymyxins?
bacterial cell membranes
How do polymyxins work?
has a fatty acid tail that inserts into the cell membrane and causes leakage by forming a pore. It induces autolytic mechanisms at high concentrations and can destroy non-growing cells
What is a downfall of polymyxins?
they aren’t very specific and can target both eukaryotic and prokaryotic cell membranes. Therefore, these are only used topically.
Do polymyxins prefer gram pos or gram neg and why?
Gram negative because they have an outer cell wall that is rich in LPS and phosphatidylethanolamine which polymyxins have a high binding affinity for.
What does novobiocin do?
Polymyxin that binds to the DNA-gyrase complex, preventing relaxation of DNA.
What do quinolines and floroquinolines do?
Polymyxins that bind to DNA-gyrase-ATP complex and prevents relaxation, leading to cell death. Ex: ciprofloxacin
What do sulfonamides and trimethoprim do?
prevent folic acid synthesis in bacteria. Sulfonamide is a PABA analog
What does rifampicin do?
inhibits transcription by binding to the DNA-RNApol-sigma factor complex and prevents initiation of transcription to mRNA
What does metronidazole do?
directly induces breaks into DNA preventing transcription and nucleic acid synthesis
What antibiotics prevent bacterial translation (protein synthesis)?
aminoglycosides, oxazolidinones/zyvox (linezolid), tetracycline, chloramphenicol, lincosamides, macrolides (erythromycin), streptogramins
What do aminoglycosides do?
prevent formation of initiation complex in translation. Binds 30S (16S rRNA and A site).
What do oxazolidinones/zyvox (linezolid) do?
prevent formation of the initiation complex in translation. prevents f-met:mRNA:30S subunit formation. active against MRSA, VRE and multi resistant S. pneumoniae
What does tetracycline do?
inhibits charged tRNA from entering A site. Interacts with 30S (16S rRNA)
What does cholramphenicol do?
inhibits peptide bond formation. binds 50S and blocks catalytic center for peptidyl transfer rxn.
What does lincosamides do?
binds 50S and inhibits peptide bond formation
What do macrolides (erythromycin) do?
prevents translocation of the growing peptide to the P-site to restart the cycle. binds 50S causing release of peptide chain
What do streptogramins do?
prevents translation of the growing peptide to the P-site to restart cycle. binds 50S and blocks translocation of peptide chain to the E (P) site
What do aminoglycosides need to function?
strong proton motive force, need aerobic respiration.
Do aminoglycosides affect your normals flora?
no because normal flora grow more slowly and most a fermentative anaerobes
What are the inhibitors of nucleic acid synthesis?
rifampin, quinolones, and metronidazole
What are the B-lactams?
Penicillin, cephalosporin, clavems, carbapenems, monobactams
