RAPID METHODS FOR THE DETECTION OF GELATIN HYDROLYSIS,

Abstract

A plate modification of Frazier''s method in which the cultures are spot-inoculated on a nutrient gelatin-agar medium and the plate is developed after incubation with an acid HgCl2 solution gave more rapid results than the other methods tested, showing hydrolysis after 1 hour with rapid liquefiers and after 24 to 72 hours with slow liquefiers that requirs up to 9 weeks with the routine stab culture method. A tube method using a (NH4)2SO4-NaCl medium, without a developer, gave results almost as rapidly. Both methods gave accurate results. Lautrops method and a modification of Greene and Larks'' also gave reliable results, but not quite as rapidly. The production of H2S from cysteine or sodium thiosulfate could be determined simultaneously with gelatin hydrolysis using the tube method with the (NH4)2SO4-NaCl medium by adding the S source to the medium and placing lead acetate papers in the tubes. The production of H2S from cysteine could also be determined with a tube modification of the Frazier method or the Greene and Larks method.