A microbial detection apparatus is provided. The apparatus includes a parabolic reflector. A light source is configured to direct a beam of light toward the focal point of the parabolic reflector. A fluid flow tube passes through the focal point of the parabolic reflector, such that the light beam path and the flow tube intersect at the focal point of the parabola. The fluid flow tube is configured to contain a flow of fluid. A first detector is included for detecting fluorescence light emitted from microbes within the fluid passing through the flow tube. A second detector is included for detecting Mie scattered light from particles within the fluid passing through the flow tube.