Abstract: A composition, an analytical element and a method for the detection of bacteria in specimen samples, e.g. biological fluids, are disclosed. The composition optionally, but preferably, comprises a metabolizable substrate (e.g. glucose) and a benzindole dye which undergoes a detectable color change when incubated in admixture with a bacterial microorganism. Useful dyes include particular benz[cd]indole, benz[e]indole and benz[g]indole compounds. The described analytical element contains this composition, preferably, in a spreading zone. Detection of bacteria can be accomplished by bringing the composition or element into contact with a specimen sample. This invention is particularly useful in detection of significant bacteriuria.