Final answer:
An infection with a count of greater than 100,000 CFU per ml typically indicates a severe infection, as CFU measures the viable bacteria or fungal cells in a sample.
Step-by-step explanation:
When an infection has a count of greater than 100,000 CFU per ml, it typically indicates a severe infection. CFU stands for colony-forming units, and it is a measure used by microbiologists to estimate the number of viable bacteria or fungal cells in a sample. The counts are based on the principle that each viable cell replicates and gives rise to a visible colony; however, it is recognized that this can underestimate the actual number of live cells. High CFU counts signify a high number of bacteria, which, depending on the context and the normal flora of the area from which the sample was taken, can indicate a severe infection. For example, a high CFU count in a urine sample could suggest a urinary tract infection. To maintain accuracy in such counts, microbiologists prefer to count plates with 30-300 colonies to minimize the chances of inaccuracies caused by too many cells forming a single colony or plates being too overcrowded to accurately count individual colonies.