← microbiology 5 Test
5 Written Questions
5 Matching Questions
- What does a bacteriolytic agent do?
- Penicillin G and methicillin are active against ________ bacteria whereas ampicillin and carbenicillin affect ______
- How do Quinolones work?
- How do B-lactam antibiotics work?
- What is solid culture?
- 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.
- b inhibit cell wall synthesis, bind and inhibit penicillin binding proteins, enzymes that synthesise peptidoglycan. Inhibit the transpeptidation step of cell wall biosynthesis.
- c Kill and lyse bacteria. Toxicity is not reversed by dilution. Examples include antibiotics that inhibit cell wall synthesis.
- d gram positive, gram positive and gram negative
- 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
- kill bacteria. Some bacteriocidal agents lyse bacteria others don't. Toxicity is not reversed by dilution.
- Organism may be able to alter the to an inactive form. eg enzymatic phosphorylation of streptomycin, degradation of Penicillin G. Usually plasmid encoded.
- 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
- inhibit bacterial growth at concentrations that are not toxic to human or animal cells
- sulfa drugs, isoniazid, quinolones,
5 True/False Questions
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
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.
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.
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.
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