Presence Absence Broth

Presence Absence Broth is used for the detection of coliform bacteria in water treatment plants or distribution systems using the presence-absence coliform test in a laboratory setting. Presence Absence Broth is not intended for use in the diagnosis of disease or other conditions in humans.

The Presence Absence (PA) test is a presumptive detection for coliforms in water. The test is a simple modification of the multiple-tube procedure. One 100 mL test sample is inoculated into a single culture bottle to obtain qualitative information on the presence or absence of coliforms, through the presence or absence of lactose fermentation. This test is based on the principle that coliforms and other pollution indicator organisms should not be present in a 100 mL water sample.

Comparative studies with the membrane filter procedure indicate the PA test may maximize coliform detection in samples containing many organisms that could overgrow coliform colonies and cause problems in detection. The PA test is described in standard methods for water testing and U.S. EPA.