Glossary of Micro 5

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___ developed concept of selective toxicity (“magic bullet”)
ie. chemicals exist which kill bacteria but not human host
Paul Ehrlich
Prontosil (leather dye) = first of the ____ class of agents
____ observes penicillin produced by molds = first natural antibiotic
____ purifies penicillin and demonstrates its therapeutic use
____ identifies ____ from soil microbe
Waksman identifies streptomycin
Sources of Antibiotics
♦ Most are natural metabolic
by-products of soil microbes
(esp. ____ species)
therapeutic index=____
Dose which is toxic to host ÷ Dose req. to kill bacteria
(must be >1), therefore high TI is good
Quinolones (nalidixic acid, novobiocin, etc.) Function:_____
Inactivate DNA gyrase→ no chromosome supercoiling → no DNA replication, etc
Rifampin Function:_____
Binds to RNA polymerase→ prevents initiation of transcription (no mRNA made)
Aminoglycosides (streptomycin) Function:_____
→ alters shape of 30S → mis-reads mRNA → faulty protein
Tetracycline Function:_____
→ blocks tRNA + amino acid from contacting 30S ribosome
→ protein synthesis stops
Erythromycin Function:_____
→ stops movement of ribosome down mRNA
Chloramphenicol Function:_____
→ stops peptide bond formation between amino acids
Sulfonamides Function:_____
Sulfa (antimetabolites) competes with PABA in Folic Acid pathway⇒ PABA cannot be used → no folic acid made → no DNA, RNA, proteins
Euc - obtain folic acid directly from diet (no PABA pathway exists)
Polymyxin B Function:_____
→ binds to phospholipids
→ inserts into membranes
- loss of membrane function
- physical disruption of membrane (leakage of ions from cell)
β - lactams (penicillin, cephalosporins, etc) Function:_____
→ Bind to proteins of inner membrane required for PG synthesis(“penicillin-binding proteins”)therefore Peptide cross bridges do not form (Osmotic lysis of bacterial due to incomplete PG layer)
non-β - lactams (Cycloserine,
Bacitracin, Vancomycin) Function:_____
all act at various
steps during PG
____ and ____ can achieve synergism because they act on the same biochemical pathway
sulfonamide + trimethoprim
____= lowest concentration that prevents growth
(gives estimate of dose needed to treat infection)
Minimal Inhibitory Conc. (M.I.C.)
____= lowest concentration that kills bacteria
(determines whether antibiotic is bactericidal
or bacteriostatic)
Measure Minimal Bactericidal Conc. (M.B.C.)
β - lactamase(penicillinase) enzymes Function: _____
→ hydrolyze β - lactam ring of penicillins
Tetracycline resistance Function: _____
rapid excretion via outer membrane “efflux” proteins
→ no accumulation of drug in cytoplasm
Cephalosporin resistance Function: _____
- altered porin protein in membrane prevents entry
streptomycin resistance Function: _____
→ mutated 30S ribosome
(ribosome retains function but streptomycin cannot bind)
Vancomycin resistance Function: _____
thickening of the cell wall

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