An optical measuring instrument for determining a concentration of bacteria in a plurality of fluid samples, comprising: a housing with a substantially light-tight enclosure; a single cuvette assembly having a plurality of individual fluid containers, each of the fluid containers holding a corresponding one of the plurality of fluid samples, each of the fluid containers having a lower portion having an input window disposed on a first side of the fluid container and an output window disposed on a second side of the fluid container that is opposite the first side of the fluid container, each container further including an upper portion located over the lower portion, the upper portion including an opening to provide the corresponding fluid sample a light source within the housing for providing an input beam for transmission into the input windows disposed on the first sides of the fluid containers and though the corresponding fluid samples, the input beam creating a forward-scatter signal associated with the concentration of bacteria; at least one sensor within the housing for detecting the forward-scatter signal exiting from the output windows disposed on the second sides of the fluid containers; the improvement comprising: a code on an exterior surface of the single cuvette assembly, the code providing information for a protocol for a test to be conducted by the optical measuring instrument; a heating element within the housing to maintain the fluid samples at a desired temperature to encourage bacterial growth in the fluid samples over a period of time, the desired temperature being defined by the protocol indicated by the code; the light source periodically providing the input beam into each one of the fluid samples such that the multiple forward-scatter signals are detected over a period of time for each of the fluid samples; and wherein each of the plurality of fluid containers are stationary and the input beam is movable relative to the plurality of fluid containers so that the input beam sequentially addresses each of the plurality of fluid samples. a housing with a substantially light-tight enclosure; a single cuvette assembly having a plurality of individual fluid containers, each of the fluid containers holding a corresponding one of the plurality of fluid samples, each of the fluid containers having a lower portion having an input window disposed on a first side of the fluid container and an output window disposed on a second side of the fluid container that is opposite the first side of the fluid container, each container further including an upper portion located over the lower portion, the upper portion including an opening to provide the corresponding fluid sample a light source within the housing for providing an input beam for transmission into the input windows disposed on the first sides of the fluid containers and though the corresponding fluid samples, the input beam creating a forward-scatter signal associated with the concentration of bacteria; at least one sensor within the housing for detecting the forward-scatter signal exiting from the output windows disposed on the second sides of the fluid containers; the improvement comprising: a code on an exterior surface of the single cuvette assembly, the code providing information for a protocol for a test to be conducted by the optical measuring instrument; a heating element within the housing to maintain the fluid samples at a desired temperature to encourage bacterial growth in the fluid samples over a period of time, the desired temperature being defined by the protocol indicated by the code; the light source periodically providing the input beam into each one of the fluid samples such that the multiple forward-scatter signals are detected over a period of time for each of the fluid samples; and wherein each of the plurality of fluid containers are stationary and the input beam is movable relative to the plurality of fluid containers so that the input beam sequentially addresses each of the plurality of fluid samples. a code on an exterior surface of the single cuvette assembly, the code providing information for a protocol for a test to be conducted by the optical measuring instrument; a heating element within the housing to maintain the fluid samples at a desired temperature to encourage bacterial growth in the fluid samples over a period of time, the desired temperature being defined by the protocol indicated by the code; the light source periodically providing the input beam into each one of the fluid samples such that the multiple forward-scatter signals are detected over a period of time for each of the fluid samples; and wherein each of the plurality of fluid containers are stationary and the input beam is movable relative to the plurality of fluid containers so that the input beam sequentially addresses each of the plurality of fluid samples.