### Typical Zone Diameters for Some Common Antibiotics This table provides information on the zone of inhibition diameters for various antibiotics, measured in millimeters, which are used to determine bacterial resistance, intermediate response, or susceptibility. | Antibiotic | Amount on Disc | Zone of Inhibition (Diameter in mm) | |-----------------|----------------|----------------------------------------| | | | Resistant | Intermediate | Susceptible | | **Ampicillin** | 10 µg | 13 or less | - | 17 or greater | | **Ampicillin** | 10 µg | 28 or less | - | 29 or greater | | **Bacitracin** | 10 units | 8 or less | 9 – 12 | 13 or greater | | **Chloramphenicol** | 30 µg | 12 or less | 13 – 17 | 18 or greater | | **Clindamycin** | 2 µg | 14 or less | 15 – 16 | 17 or greater | | **Erythromycin**| 15 µg | 13 or less | 14 – 22 | 23 or greater | | **Gentamicin** | 10 µg | 12 or less | 13 – 14 | 15 or greater | | **Neomycin** | 30 µg | 12 or less | 13 – 16 | 17 or greater | | **Norfloxacin** | 10 µg | 12 or less | 13 – 14 | 15 or greater | | **Penicillin G***| 10 units | 28 or less | - | 29 or greater | | **Penicillin G**| 10 units | 11 or less | 12 – 21 | 22 or greater | | **Polymyxin B** | 300 units | 8 or less | 9 – 11 | 12 or greater | | **Streptomycin**| 10 µg | 11 or less | 12 – 14 | 15 or greater | | **Disc-Diffusion Experiment: Antibiotic Efficacy Against Staphylococci** In this disc-diffusion experiment, the effect of four antibiotics on Staphylococci was analyzed. The patient in question has no known allergies or contraindications for broad-spectrum antibiotics. The results can help determine the most effective antibiotic for treatment. ### Experimental Setup - **Staphylococci Culture**: The bacteria were cultured with four standard antibiotic-impregnated disks placed on an agar plate. - **Antibiotics Tested**: - Norfloxacin (N) - Tetracycline (T) - Streptomycin (S) - Penicillin-G (P) ### Results The diameters of the clearance zones (areas where bacterial growth is inhibited) were measured as follows: - **Norfloxacin (N)**: 14 mm - **Tetracycline (T)**: 14 mm - **Streptomycin (S)**: 24 mm - **Penicillin-G (P)**: 29 mm ### Interpretation The size of the clearance zone is indicative of the antibiotic's efficacy: - Larger zones indicate greater effectiveness against the bacteria. - Penicillin-G shows the largest zone (29 mm), suggesting it is the most effective antibiotic for this strain of Staphylococci. - Streptomycin also shows significant effectiveness with a 24 mm zone. ### Conclusion Considering the absence of allergies and contraindications, Penicillin-G would be the preferred antibiotic to prescribe for a similar Staphylococci infection, based on this experiment.