Question

Chemical Methods of Control: Antimicrobial Drugs PURPOSE TO To provide technique Drovide an antibiotic Sorsitivity test the rationale for the agar discussion HYPOTHESES 1. All antibiotics will be equally effective against gram-positive and gram-negative bacteria. Aggredisagree 2. All antibiotics will be equally effective against gram-negative E.coli and Paeruginosa bacteria. Agradere RESULTS Pseudomonas aeruginosa B5L-2 Zone Size S. LorR" Escherichia coli Z one Size S,L, or R* Staphylococcus epidermidis Zone Size S. Lor Rº Disk Antimicrobial Agent 8 - susceptible: I - intermediate; R - resistant

Answer 1

For the given question the choice of antibiotics should be broad-spectrum so that they can affect both gram-positive and gram-negative bacteria. For testing the antibiotic, the disk diffusion technique is used because in this test the antibiotics diffuse from the area of administration in all directions around. If the bacteria are more sensitive to the antibiotic then there will be no growth at a longer distance (diameter) from the area of administration. If the bacteria is less sensitive then there will be no growth at a shorter distance from the area of administration. The diameter will define the effectiveness of the antibiotic against the particular bacteria. The choice of antibiotics can be-

Aminoglycosides

Amoxicillin

Chloramphenicol

Azithromycin

Vancomycin

Cephalosporin

Ciprofloxacin

Ceftriaxone