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44 Cards in this Set
- Front
- Back
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What is the function of penacillin and cephalosporin?
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Both inhibit the transferase responsible for crosslinking the peptidoglycan units of the bacterial cell wall
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What enzyme can cleave penicillin and it's derivatives?
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Beta lactamase
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What are the 8 drugs used against gram negative bacteria?
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1) ampicillin 2)carbencillin 3) amoxicillin 4)ticeracillin 5)azlocillin 6)amdinocillin 7) piperacillin 8) mezlocillin
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What bacterial enzyme is essential for the optimal activity of the penicillins?
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Autolytic enzyme which makes holes in the peptidoglycan wall to allow it to be expanded; it must be activebecause the cell must be growing in order for the penicillins to work
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What are two mechanisms for resistance against beta lactam antibiotics?
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The production of beta lactamase and the ability to alter other penacillin binding proteins (methicillin resistance)
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What is an example of a monobactam used on gram negative organisms?
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Aztreonam
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What is an example of a thienamycin with a great spectrum?
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imipenem
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What are two examples of beta lactam antibiotics besides penicillin and cephalosporin?
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monobactams and thienomycins
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What are the seven penicillins that are resistant to beta lactamase?
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1) methicillin 2)oxacillin 3)nafcillin 4)cloxacillin 5) dicloxacillin 6) flucloxacillin 7) temocillin
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How does Vancomycin work?
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It inhibits cell wall synthesis by binding to the D-ala D-ala terminal end preventing polymerization of the peptidoglycan
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How is resistance against vancomycin mediated?
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An enzyme places a lactyl residue where the terminal D-ala should be in the peptidoglycan, causing Vanc not to recognize it's binding site
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How do clavulanic aicd and sulbactam work?
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They are useful for promoting activity of beta lactamase sensitive antibiotics such as amp and pipercillin, amoxicillin, ect. buy scavenging up the beta lactamase so the antibiotics can work
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How does Bacitracin work?
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It inhibits the enzyme which cleaves the phosphoryl group from the carrier protein after it deposits the newly formed peptidoglycan on the cell wall; The phosphorylated carrier protein cannot maintain the process of cell wall assemby
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Explain how peptidoglycan cell wall is made
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The five membered peptidoglycan is synthesized in the cytoplasm and transfered to a C55 isoprenoid alcohol carrier protein in the membrane, which picks up NAG and is then crosslinked to the peptidoglycan in the cell wall. Autolytic enzyme must open the peptidoglycan in the cell wall for incorporation of the new molecule. The terminal Dala is cleaved after the crosslinkage occurs
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Describe the structure of the bacterial ribosome including subunit sizes.
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It is 70S with one 30S and a 50S subunit
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How does oxazolidinone (Zyvox) work?
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It inhibits the association of mRNA and the 30S subunit
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What are some examples of aminoglycosides and what is their method of action? What bacteria do they work against?
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They work by inhibiting the tRNA from entering the 30S subunit and the formation of streptomycin monosomes which freeze movement of the mRNA; examples include streptomycin, gentomycin, neomycin, kanamycin tobramycin, amikacin, netilmicin, and the tetracyline group. They work against gram negative bacteria
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Describe the function of tetracylcin antibiotics and include examples
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They are bacteriostatic antibiotics that have a very broad spectrum; examples include minocyclene and doxycyclene
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What are some examples of antibiotics that inhibit at the 50S ribosomal subunit and how do they function?
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Chloamphenicol, erythromycin, lincomycin, and clindamycin; They inhibit transpeptidation reactions in protein synthesis
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How is chloramphenicol resistance achieved and what disease can it cause?
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Resistance occurs when it is acetylated renders it inacted; aplastic anemia is caused by chloramphenicol
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What is a derivative of erythromycin that is bacteriocidal?
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clarithromycin
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What are some organisms that chloramphenicol is bacteriocidal against?
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Haemophilus, Strept pneumonia, and Neisseria meningitidis
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What is the function of rifampin (rifampicin)?
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It is an inhibitor of the beta subunit of the bacterial RNA polymerase
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For what bacteria is rifampin commonly used?
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It is used to treat TB, leprae, and H. influenza infections
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What three drugs are given for TB treatment over the course of months?
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1)aminoglycosides 2)rifampin 3) isoniazid
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What two drugs are given to treat leprasy?
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1)rifampin 2) dapzone
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What is the mechanism of action of Quinolones and what are some examples?
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These drugs block bacterial DNA replication by inhibiting DNA gyrase; examples include naladixic acid and ciprofloxacin (cipro), and metronidazole
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What are quinolones used to treat?
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Gram positive and negative bacteria and psuedomonas
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What is metronidazole used to treat?
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Infections with anaerobic bacteria and some protozoa
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Why are there few membrane specific antibiotics?
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It would also effect the membranes of human cells
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What is an antibiotic used against cell membranes and what organism is it used to kill?
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Polymyxins bind to the outer surface ofthe cell membrane and alter the structure and osmotic properties which results in the leakage of cellular constituents and death of the cell; commonly used against pseudomonas and gram negative organisms
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Polymyxin E has synergy with what other drug?
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Penicillin (synergy 1+1=10)
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What class of drugs are used against fungal infections and what are examples?
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Polyenes are used against fungal infections; amphotericin B, nystatin; all are highly toxic
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What is the method of action of the antifungal polyenes?
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THey bind to ergosterol in membranes and cause the formation of pores
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What is an example of a surface anti-fungal?
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Nystatin
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What are the azoles used to treat and how do they work?
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Azoles such as miconazole and ketonazole are broad spectrum anti-fungals that also inhibit ergosterol synthesis; there is no cross reaction with human membranes
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What are some examples of anti-metabolites?
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Trimethoprim, sulfonamides, isoniazid, aminosalicylic acid, sulfone
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How do sulfonamides work?
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They complete with PABA in condensation to produce dihydropteroic acid and inhibit tetrahydrofolate synthesis
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How do bacteria develop resistance against sulfonamides?
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They overproduce PABA; sulfonamides are bacteriostatic
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Sulfonamides are used to treat what sort of infection?
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UTI
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How does trimethoprim work?
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It selectively inhibits dihydrofolate reductase and is similar to sulfonamides except it can be bacteriocidal
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How does isoniazid work?
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It inhibits wall formation by acting on an enzyme in the mycolic acid pathway
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How does resistance against tetracylcine develop?
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The bacteria develops the ability to actively pump the antibiotic out of the medium
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What are sulfones used to treat?
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Leprosy
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