Questions: Rather than measure the zone diameters, can you make an accurate treatment determination by comparing the presence and relative size of the zones of inhibition?

The answer is the second one (No): Each zone of inhibition must be measured and compared with the CLSI table values to determine the best treatment option.

Explanation for each option:

1. Yes. The best treatment option is a drug whose disk has the largest zone of inhibition.

   • Incorrect. While a larger zone of inhibition generally indicates greater effectiveness of the drug against the bacteria, it is not sufficient to determine the best treatment option without comparing the measurements to standardized values provided by the Clinical and Laboratory Standards Institute (CLSI). These values take into account the specific bacteria and drug characteristics.

2. No. Each zone of inhibition must be measured and compared with the CLSI table values to determine the best treatment option.

   • Correct. The CLSI provides standardized tables that correlate the size of the zone of inhibition with the susceptibility of the bacteria to the drug. This comparison is necessary to accurately determine the best treatment option.

3. Yes. The best treatment option is a drug whose disk has the smallest zone of inhibition.

   • Incorrect. A smaller zone of inhibition typically indicates that the bacteria are less susceptible to the drug, making it a less effective treatment option.

4. Yes. The best treatment option is a drug whose disk has a zone of inhibition (regardless of the zone size).

   • Incorrect. Simply having a zone of inhibition does not provide enough information to determine the best treatment option. The size of the zone must be measured and compared to CLSI standards.

5. Yes. The best treatment option is a drug whose disk does not have a zone of inhibition.

   • Incorrect. No zone of inhibition indicates that the bacteria are resistant to the drug, making it an ineffective treatment option.

In summary, accurate treatment determination requires measuring the zones of inhibition and comparing them to CLSI table values.