It may be, that your orgnaism oxidizes glucose slowly under aerobic conditions, so that there is only a small amount of acid in the medium, not enough to change the colour.

In this video

https://www.youtube.com/watch?v=8c5FGTvaKcE

B. subtilis doesn´t cause a change in colour, although it should be able to utilize glucose.

@Uwe Wedger , thanks a lot !

But I have doubt on my sample.

Normally, bacteria are incubated in 24 hours. After that, the bacteria will grow beautifully on agar.

But my sample is incubated in 24 hours under anaerobic condition.

Not more than 24 hours, Maybe just 12+- hours. It is grow in the form of big colonies and no single colonies form on the agar. It is difficult to find a single colonies. It is fast growing.

I subcultured it many times still the same. Seems like I have to control the time of growing of the sample.

May I know what happen?

It is gram positive rod, non spore formers, non-motile, catalase positive, indole negative, have a configuration of v or y shape. It grows along the line when I streaked it on the stab agar.

What is that possible bacteria? I just wanna have a guildline.

Thanks a lot!

Do you have access to these books:

https://en.wikipedia.org/wiki/Bergey%27s_Manual_of_Systematic_Bacteriology

You might find a hint, which organism you have within them. They contain lists for many species, tellng you wich species is positiv or negative on which test. But keep in mind, that it is possible, that a strain may act different than other strains of the same species. It is recommended to make as many tests, mentiones in the manual, as possible. Additionally, you should confirm your results with 16s rDNA, if possible.

If your colonies grow too fast, try to cultivate them at a lower temperature. You mentioned, that you sampled them from skin, so I guess, you cultivate them at 37 °C? Just try to do it 30 °C, that should let them grow slowlier. Or provide less nutrients, have you tried to grow them on minimal medium?

I hope, that will help you a bit.