Please help: In reporting of Environmental Swabs testing, I am quite confused in my laboratory, because some worksheets write cfu/swab, and some cfu/cm2, for the same method of testing: I dry swab a surface area of about 100cm then vortex it into 10ml diluent for 30 secs, then pipette 1ml and dispense it into a petri dish, then pour about 10-15 ml VRBGA into the plate for EB or Enterobacteriacea enumeration. In the worksheet, the dilution is 1:10, so I multiply by 10 the total colony growth I count on the plate after incubation at 37C for 24hrs, e.g. 67 colonies counted x 10 = 670 cfu. My problem is, to know which is a correct unit, is it 670 cfu/swab or 670 cfu/cm2?
In our microbiology laboratory, no one knows the answer that is why I am writing in this forum. I tried to google but I did not find a definite answer. Your help is very much appreciated. Thank you in advance. Ruby