Antibiotic Spectrum Mechanism of Action Penicillin Broad Inhibits functioning of
ID: 132333 • Letter: A
Question
Antibiotic
Spectrum
Mechanism of Action
Penicillin
Broad
Inhibits functioning of transpeptidase
Oxacillin
Narrow (Gram +)
Inhibits functioning of transpeptidase
Amoxicillin – clavulanic acid
Broad
Amoxicillin inhibits peptidoglycan formation; clavulanic acid inhibits beta-lactamases that destroy amoxicillin
Cefazolin
Broad
Inhibits peptidoglycan formation
Vancomycin
Narrow (Gram +)
Inhibits synthesis of peptidoglycan
Gentamicin
Narrow (Gram -)
Inhibits protein synthesis
Tetracyclins
Broad
Inhibits protein synthesis
Trimethoprim-sulfa-methoxazole
Broad
Inhibits synthesis of folic acid which is needed for bacteria to survive
Polymyxin B
Narrow (Gram -)
Disrupts cell membrane structure and therefore permeability
Streptomyocin
Broad
Inhibits protein synthesis
Objective of experiment : Determine which antibiotics/antibacterails that you test are effective at preventing growth B. subtilis (Gram +) and E. coli (Gram -) growth.
a. In a short paragraph, explain why the plates you set up with specific bacteria and disk combinations will best help you to answer the Experiment Objective.
b. In a short paragraph, describe your predicted results. For your antibiotics, use the table of common antibiotics and their properties (Table) to help you make your predictions. For your antibacterials, you can make more generalized predictions since you do not have a table of common antibacterials and their properties.
Antibiotic
Spectrum
Mechanism of Action
Penicillin
Broad
Inhibits functioning of transpeptidase
Oxacillin
Narrow (Gram +)
Inhibits functioning of transpeptidase
Amoxicillin – clavulanic acid
Broad
Amoxicillin inhibits peptidoglycan formation; clavulanic acid inhibits beta-lactamases that destroy amoxicillin
Cefazolin
Broad
Inhibits peptidoglycan formation
Vancomycin
Narrow (Gram +)
Inhibits synthesis of peptidoglycan
Gentamicin
Narrow (Gram -)
Inhibits protein synthesis
Tetracyclins
Broad
Inhibits protein synthesis
Trimethoprim-sulfa-methoxazole
Broad
Inhibits synthesis of folic acid which is needed for bacteria to survive
Polymyxin B
Narrow (Gram -)
Disrupts cell membrane structure and therefore permeability
Streptomyocin
Broad
Inhibits protein synthesis
Explanation / Answer
A) The objective of the experiment was to determine which antibiotics are effective at preventing growth of B. subtilis and E. coli. For this, different plates are setup with specific bacteria and antibiotic to test for the antibiotic sensitivity. This is known as antibiotic sensitive assay. The sensitive antibiotics are identified by greater zone of inhibition around the disc.
B) The broad prediction about antibiotics are that the penicillins and cephalosporins have a broad spectrum of action against both gram positive and negative bacteria. Vancomycin and oxacillin are effective only against gram positive while gentamicin and polymyxin B are effective only against gram negative bacteria.
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