Rapid method for detection of lactose fermenting oral microorganisms

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Abstract
A rapid inexpensive assay for lactose fermentation which can be performed on individual colonies in situ and which does not negate subcultivation is described. The assay is based on the ability of bacterial β‐galactosidase to hydrolyze 4‐methylumbelliferyl‐β‐D‐galactoside (MUG) and form 4‐methylumbelliferone, a compound which is brightly fluorescent under long‐wave ultraviolet light. 1% MUG in dimethyl sulfoxide was stable at room temperature for at least 21 days. Maximal MUG fluorescence reactions required viable bacterial cultures. The MUG test represents a convenient means to distinguish the lactose‐negative Bacteroides intermedius and Haemophilus actinomycetemcomitans, both suspected major periodontopathogens, from the lactose‐positive Bacteroides melaninogenicus group and Haemophilus aphrophilus, organisms of little or no periodontopathic significance. The MUG test may also greatly help in distinguishing lactose from nonlactose fermenting organisms of nonoral origin.