Overnight culture?

Question

I have been told I need to prepare an overnight culture of bacteria in order to be able to dilute it down to 10-5, can someone explain what I need to do and how it works?

Answer 1

You need to get a mixture of nutrients (TSB would be good Aka triple soy broth) and put it into a tube. Then you need to contaminate it with your bacteria and incubate it overnight to let it grow. Then you dilute samples of it several times and make pour plates so you can count the number of colonies visible. When you do this, keep track of which plate is which dilution so you can adjust the number of colonies/microliter acordingly. Then you have to do a little math and come up with how diluted it must be to get it down to 10-5.

Answer 2

does your initial solution have to conform to a certain McFarland Standard? This is a VERY important step in medical laboratory practice. this is the initial turbidity of the solution as compared to prepared standard solutions. if you don't start off with the right McFarland standard, you're screwed.