method for the quick determination of the susceptibilities of various unidentified bacteria contained in an aqueous physiological fluid sample , particularly urine , to one or more antibiotics . a bacterial adenosine triphosphate assay is carried out after the elimination of non - bacterial atp to determine whether an infection exists . if an infection does exist , a portion of the sample is further processed , including subjecting parts of the portion to one or more antibiotics . growth of the bacteria in the parts are determined , again by an atp assay , to determine whether the unidentified bacteria in the sample are susceptible to the antibiotic or antibiotics under test .