just make a suspension enough turbid that you are not able to look at other side through it when in test tube. Then dilute it to 1:100 and measure the O.D. and standardize it to 0.1 O.D. When your parent culture is of O.D. 10 and after diluting as said to O.D. = 0.1. it would be nearly you require. It is my experience and may vary from machine to machine. You just take CFU of 0.1 O.D. on MHA/TSA plate and next day you would be able to know how many cells were there. In my case these are 10*8

Hope it would help.. 

Good luck.

Hello Muhammed,

For gram negative bacteria it is estimated that at 0.1 OD their will be 3*10^8 CFU/ml. So to get 3*10^10cfu/ml u need OD of 10. If your 24 or 48 hour culture do not make this OD u can centrifuge and concentrate it. I am not sure why you want this heavy innoculum concentration. In case of the gram positive bacterial the CFU will be less than the value of gram negative organism. This are all approximation. To get accurate results it is better to serial dilute them and plate them to get CFU.

For most common bacterial strains, such as E. coli and Staph aureus, you may not be able to get the cell density as high as 3x10^10. If so, you may have to centrifuge the cells and re-suspend them in a smaller volume.

Cell count (CFU)/ml and A600 (or 620) are cell strain dependent. If you need accurate measurements, you will need to determine it as others have already outlined.

Thanks to all of you for your suggestions. By hit and trial method I achieved my desire concentration.

Dear Samsher,

This is a Scientific forum where we can share our experience. By the way how much your energy is wasted? This is not a professional attitude to talk like this on this forum.

 As said above I would grow my organism and take a sample , dilute it and plate it out on media . That way you can refer to your table when making dilutions . I also used to make strain specific calculations !!!