Microbial detection and enumeration method and apparatus
AssigneeUniversity of Virginia and National Aeronautics & Space Administration
InventorsJudd R. Wilkins, Glenn E. Stoner
Life of this patent
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Abstract
The presence of microorganisms in a sample is determined by culturing micrganisms in a growth medium which is in contact with a measuring electrode and a reference electrode and detecting the change in potential between the electrodes which arises by the migration and accumulation of said microorganisms adjacent the surface of the measuring electrodes thus forming a charge-charge interaction between said measuring electrode and accumulated microorganisms, by measuring the potential change with a high impedance potentiometer.
Claims21
A method for detecting the presence of hydrogen producing bacteria in a fluid sample, which comprises:
- culturing a hydrogen producing bacterium in a fluid growth medium which is in contact with a measuring electrode and a reference electrode which are conductively attached to a high impedance potentiometer having an input impedance of 10.sup.7 to 10.sup.10 ohms, wherein the growing bacteria gradually concentrate about said measuring electrode thus concentrating the evolved hydrogen gas about said measuring electrode and forming a charge-charge interaction between said measuring electrode and accumulated microorganisms, whereby the evolved hydrogen gives rise to a modified measuring electrode which has the nature of a hydrogen electrode;
- achieving a stable baseline response from said potentiometer prior to reaching the minimum detectable concentration of said bacterium;
- and
- monitoring the change in potential between said modified electrode and said reference electrode.
A method for measuring the influence of an anti-microbial agent or event on a growing microorganism, which comprises:
- culturing a microorganism in a liquid growth medium which is in contact with a measuring electrode and a reference electrode which are conductively attached to a high impedance potentiometer having an input impedance of 10.sup.7 to 10.sup.10 ohms wherein the growing bacteria gradually accumulate about said measuring electrode thus forming a charge-charge interaction between said measuring electrode and accumulated microorganism;
- achieving a stable baseline response from said potentiometer prior to detecting the minimum detectable concentration of said microorganism;
- subjecting said microorganisms to an anti-microbial agent or event;
- and
- monitoring the change in potential between said electrodes as a result of the influence of said anti-microbial agent or event on said microorganism.
A cell for the electrochemical detection of living microorganisms in a fluid medium, which comprises:
- a chamber with an opening containing a fluid growth medium suitable for the culturing of microorganisms;
- means for sealing said opening of said chamber which means is self-sealing after having been punctured by a means for delivering a microorganism containing sample to said chamber;
- measuring electrode means fixedly attached to the exterior of said chamber, one end of which penetrates through said chamber into the interior thereof and is in contact with said fluid growth medium, about which accumulates said microorganisms thereby setting up a charge-charge interaction at said electrode, said electrode being responsive to said charge-charge interaction established at the electrode;
- reference electrode means fixedly attached to the exterior of said chamber, one end of which protrudes into the interior of said chamber and which is covered with a fluid growth medium permeable shielding means that prevents contact of said reference electrode with said microorganisms, for establishing the potential of said cell in cooperation with said measuring electrode;
- and
- a potentiometer having an input impedance of 10.sup.7 to 10.sup.10 ohms which is conductively connected to said measuring and reference electrodes.
Dependencies are inferred from the claim text.