<Li> The Miles and Misra Methods or drop - plate method wherein a very small aliquot (usually about 10 microliters) of sample from each dilution in series is dropped onto a petri dish . The drop dish must be read while the colonies are very small to prevent the loss of CFU as they grow together . </Li> <P> However, with the techniques that require the use of an agar plate, no fluid solution can be used because the purity of the specimen cannot be unidentified and it is not possible to count the cells one by one in the liquid . </P> <P> Counting colonies is traditionally performed manually using a pen and a click - counter . This is generally a straightforward task, but can become very laborious and time - consuming when many plates have to be enumerated . Alternatively semi-automatic (software) and automatic (hardware + software) solutions can be used . </P> <P> Colonies can be enumerated from pictures of plates using software tools . The experimenters would generally take a picture of each plate they need to count and then analyse all the pictures (this can be done with a simple digital camera or even a webcam). Since it takes less than 10 seconds to take a single picture, as opposed to several minutes to count CFU manually, this approach generally saves a lot of time . In addition, it is more objective and allows extraction of other variables such as the size and colour of the colonies . </P>

Why is cfu more applicable to a culture of streptococcus than to a culture of e.coli