A method and device for determining the presence and concentration of total microbial contamination or the presence and concentration of a specific microbial species on a surface is described. The method consists of a means of a collection device and fluid for removing the microbes from the surface and suspending them in a fluid phase. An aliquot of the fluid phase is introduced into a disposable test ticket which allows filtration of the sample to remove extraneous substances including somatic cells, and concentration of the microbes. The total concentration of microbes is determined by adding a somatic and bacterial releasing reagent to a disposable test device which comprises a membrane containing the luminescent reagents luciferin and luciferase, and introducing the disposable test device into a luminometer that can read the luminescence from the underside.