A     Inoculating the Mueller-Hinton Agar Plate

Using a plate rotator or by hand, evenly streak the swab across the surface of a Mueller-Hinton agar plate. This creates a bacterial lawn, ensuring consistent exposure to the antibiotics.

B     Selecting Antibiotic Disks for Testing

Choose paper disks impregnated with antibiotics appropriate for the bacterial species being tested. For Escherichia coli, common antibiotics include ampicillin, ciprofloxacin, gentamicin, and trimethoprim-sulfamethoxazole. The selection should align with clinical relevance and treatment guidelines.

C     Applying the Antibiotic Disks

Using a disk dispenser, carefully place the antibiotic-impregnated disks on the agar surface. Ensure the disks are evenly spaced and make full contact with the agar. Lightly press the disks down to secure their position.

D     Incubation and Interpretation of Results

Incubate the inoculated plate at 35°C for 16–20 hours. After incubation, measure the diameter of the zones of inhibition around each disk. These clear areas indicate bacterial susceptibility to the antibiotics. Compare the measurements to clinical guidelines to determine susceptibility or resistance.