PURPOSE: To judge susceptibility simply, by cultivating an antibiotic which is an object of inspection and an enteral bacterium which is an object of susceptibility inspection against antibiotic in a liquid medium containing bouillon blended with glucose, followed by measuring a pH of the culture solution after cultivation.

CONSTITUTION: By utilizing the characteristics that an enteral bacterium decompose glucose to form acidic decomposition products, the presence or absence of the decomposition products is confirmed by measuring the pH of the culture solution. For example, neutral red as a pH indicator is added to a medium wherein peptone is dissolved, a bacterium of object is propagated in the medium, and an antibiotic is added to the medium. After the initial cultivation is over, a glucose solution is added to the culture, and pH is determined after further cultivation. When a strain of inspection object has no subseptibility against the antibiotic added, glucose is decomposed to form acidic decomposition products, so that the indicator added exhibits red. When the strain has susceptibility, the indicator remains yellow as it is.