[Six semi-sold media methods for detecting motility of gram negative bacilli]

Motility is recognized as a significant biological character of certain bacteria, and is used as a fundamental basis of classification in many taxonomic systems. We compared wet mount method, semi-solid medium method and flagella stain method to evaluate the motility activity of 538 Enterobacteriaceae and 300 glucose non-fermentative gram negative bacilli. The results showed a sensitivity of 100% in flagella stain, Gilardi medium, Mueller Hinton semisolid medium and sulfide-indole-motility (SIM) medium (Difco); 99.6% in SIM (Kyokuto) and SIM (BBL); 99.3% in motility test medium (BBL) and 97% in wet mount. Motile Enterobacteriaceae grow well, and turbidity changes clearly and is easy to interpret. Motile glucose nonfermentative gram negative bacilli grow so lightly and rapidly diffuse throughout the medium and are hardly to interpret. It is better to use colorless Gilardi medium and Mueller Hinton semi-solid medium and to read within 4-8 hours or 24 hours. The advantages of the semi-solid medium method are particularly evident in teaching schedules and routine testing, because the results are cumulative, macroscopic, highly sensitive, and easy to manipulate.