Microbiological systems and methods of fluid sample analysis
Methods and systems for detecting the presence of a target microorganism in a liquid sample are provided. Methods comprise the steps of passing the liquid sample through a surface filter, placing the surface filter into contact with a culture device, incubating the culture device for a period of time and detecting the presence of a target microorganism. Methods may be used with an automated detection system.
1. A method for detecting a gas-producing microorganism, comprising the steps of:
providing an automated detection system, a sample suspected of containing a gas-producing microorganism; a flat film culture device comprising a cover sheet that optionally includes a dry medium layer adhered thereto, a self-supporting substrate having a cold-water-reconstitutable dry medium adhered thereto, and a culture medium containing a fermentable nutrient; and a membrane filter which is substantially transparent when in contact with a hydrated culture medium in the culture device, the filter having a first major surface and a second major surface opposite the first major surface;
collecting a gas-producing microorganism from the sample onto the first major surface of the filter;
placing at least one major surface of the filter with the microorganisms collected thereon into contact with the reconstitutable dry medium;
hydrating the reconstitutable dry medium and the optional dry medium layer, if present, with a predetermined volume of aqueous liquid before or after placing the filter into contact with the dry medium in order to form a semi-solid growth medium;
closing the culture device to bring the cover sheet or the optional medium layer, if present, into contact with a major surface of the filter opposite the at least one major surface of the filter;
incubating the closed culture device for a period of time; and
detecting the presence of a gas-producing microorganism;
wherein detecting the presence of the gas-producing microorganism comprises detecting the gas-producing microorganism with the automated detection system;
wherein detecting the presence of the gas-producing microorganism comprises detecting a colony;
wherein the colony is detected optically; and
wherein detecting the presence of the gas-producing microorganism further comprises detecting a gas bubble proximate to the colony.
2. The method of claim 1 wherein the gas bubble is detected optically.