To provide a high practical method which is the method for efficiently and effectively detecting an antimicrobial used in the treatment for infectious diseases caused by pathogenic microorganisms, namely a growth inhibitor for bacteria.

On the method of detection for antimicrobials this method is carried out by separating a temperature sensitive mutant strain from the wild-type strain of a pathogenic microorganism, identifying the mutant gene of the temperature sensitive mutant strain, carrying out the mass production of a gene product due to a temperature sensitive gene, establishing a method for assaying the activity of the resultant gene product, detecting an activity inhibitor for the gene product, elucidating the mechanism of activity inhibitory effect due to the detected activity inhibitor and investigating the growth inhibitory effect of the activity inhibitor on the pathogenic microorganism.