microbiology 5

5 Written Questions

1. inhibit translation by binding to the small (30S) ribosomal subunit. Tetracylines block binding of aminoacyl-tRNA to the A site of the ribosome. Inhibits growth of almost all gram positive and negative bacteria. Used in treatment of STDs, legionnaire's disease, anthrax
2. Organism able to pump out an antibiotic entering the cell eg chromosomally or plasmid encoded efflux pumps for tetracycline, erythromycin
3. eg mutations in genes coding DNA gyrase (resistance to quinolones), RNA polymerase (resistance to ritampicin) or S12 protein of small 30s ribosome subunit (resistance to streptomycin)
4. inhibit growth but do not kill bacteria, impairment of growth reversed by dilution. Eg antimicrobials that inhibit protein synthesis
5. An antimicrobial agent produced by a microorganism (natural)

5 Matching Questions

1. What does a bacteriolytic agent do?
2. Penicillin G and methicillin are active against ________ bacteria whereas ampicillin and carbenicillin affect ______
3. How do Quinolones work?
4. How do B-lactam antibiotics work?
5. What is solid culture?

1. a Prevent growth of a wide range of gram positive and gram negative bacteria by inhibiting DNA gyrase, an enzyme critical for DNA structure and replication. Used for treating urinary tract infections.
2. b inhibit cell wall synthesis, bind and inhibit penicillin binding proteins, enzymes that synthesise peptidoglycan. Inhibit the transpeptidation step of cell wall biosynthesis.
3. c Kill and lyse bacteria. Toxicity is not reversed by dilution. Examples include antibiotics that inhibit cell wall synthesis.
4. d gram positive, gram positive and gram negative
5. e disk diffusion technique. Disk of filter paper is soaked with an antimicrobial agent. Disk then placed onto an agar plate that was previously inoculated with a bacterium. Antimicrobial agent diffuses from the disk onto agar, creating a gradient, further from disk= lower conc of antimicrobial. If microbial= bacteriostatic, bacteriocidal a zone of inhibition results

5 Multiple Choice Questions

1. kill bacteria. Some bacteriocidal agents lyse bacteria others don't. Toxicity is not reversed by dilution.
   1. What is an antimicrobial agent?
   2. What does a bacteriolytic agent do?
   3. What does a bacteriostatic agent do?
   4. What does a bacteriocidal agent do?
2. Organism may be able to alter the to an inactive form. eg enzymatic phosphorylation of streptomycin, degradation of Penicillin G. Usually plasmid encoded.
   1. What is an antibiotic?
   2. Lack of target antibiotic- resistance?
   3. impermeable barrier- resistance?
   4. Inactivation of antibiotic- resistance?
3. inhibits the initiation step of transcription in bacteria by binding to RNA polymerase. Used in combination with isoniazid to treat TB, or with fusidic acid to treat MRSA
   1. How does glycopeptide vancomycin work?
   2. How does Rifampin/ rifampicin work?
   3. How does isoniazid work?
   4. How do Aminoglycosides work?
4. inhibit bacterial growth at concentrations that are not toxic to human or animal cells
   1. What is an antimicrobial agent?
   2. What must an antimicrobial do to be clinically useful?
   3. How can antimicrobial agents be classified?
   4. Less than ____ of known antibiotics are clinically useful
5. sulfa drugs, isoniazid, quinolones,
   1. How do you measure antimicrobial activity?
   2. What is an antimicrobial agent?
   3. What are some examples of synthetic antimicrobial drugs?
   4. Why is there rising rates of antimicrobial resistance?

5 True/False Questions

1. How does isoniazid work? → inhibit protein synthesis by interacting with large (50s) subunit of the ribosome and blocking peptide bond formation. Examples: erythromycin used in patients who are allergic to penicillin

   True        False

2. What inactivates penicillin G, amphicillin and carbenicillin? → Organism may be able to alter the to an inactive form. eg enzymatic phosphorylation of streptomycin, degradation of Penicillin G. Usually plasmid encoded.

   True        False

3. How do Aminoglycosides work? → Inhibit protein synthesis by targetting the small (30s) subunit of the ribosome (s12) protein. No longer used as bacterial resistance occurs frequently.

   True        False

4. How do R (resistance) plasmids confer antimicrobial resistance? → contain genes encoding proteins that confer antimicrobial resistance, referred to as R plasmids. Can be transmitted from one bacterium to another through genetic exchange (conjugation), thought to be one of the main ways resistance spreads.

   True        False

5. How does glycopeptide vancomycin work? → inhibits the initiation step of transcription in bacteria by binding to RNA polymerase. Used in combination with isoniazid to treat TB, or with fusidic acid to treat MRSA

   True        False