A culture and sensitivity test or a CS test is a two test divided into two part first a culture test in which is used to determine the infection causing organism from the sample body fluid like blood, pus, saliva etc. The Sensitivity test is done to check which medication will be effective in controlling and eradicating the infection. Pus in urine or stools are an indication of the presence of leucocytes in them. Leucocytes is the collective term for different types of White Blood Cells. Their function is to protect the body from invading infections. Determining the number of Leucocytes helps the doctors determine the infection.