Capacitor for detecting viable microorganisms

Abstract

This invention relates to a capacitor comprising two electrical conductors separated by a dielectric, the dielectric comprising microorganisms. The dielectric may comprise a biological indicator. This invention relates to a process for determining whether the microorganisms are alive or dead. The number of microorganisms can be determined. This invention relates to a process for testing the efficacy of a sterilization process using the capacitor.

1 - 49 . (canceled) 
     
     
         50 . A process for analyzing a biological indicator, comprising:
 placing the biological indicator and an assay medium in a capacitor, the biological indicator comprising test microorganisms, the capacitor comprising two electrical conductors, the biological indicator and the assay medium being placed between the two conductors and forming a dielectric for the capacitor;   applying an electrical signal to the conductors;   measuring the capacitance of the capacitor; and   determining from the capacitance of the capacitor whether any of the test microorganisms are alive.   
     
     
         51 - 70 . (canceled) 
     
     
         71 . A process for determining the efficacy of a sterilization process, comprising:
 exposing an article to be sterilized and a biological indicator to a sterilant, the biological indicator comprising test microorganisms;   placing the biological indicator and an assay medium in a capacitor, the capacitor comprising two electrical conductors, the biological indicator and the assay medium being placed between the two electrical conductors and comprising a dielectric for the capacitor;   applying an electrical signal to the conductors;   measuring the capacitance of the capacitor; and   determining from the capacitance of the capacitor whether any of the test microorganisms are alive.   
     
     
         72 - 92 . (canceled) 
     
     
         93 . A process for determining the efficacy of a sterilization process, comprising:
 (a) exposing an article to be sterilized and a biological indicator to a sterilant, the biological indicator comprising test microorganisms and being positioned in a capacitor, the capacitor comprising two electrical conductors, the biological indicator being positioned between the electrical conductors;   (b) positioning an assay medium between the electrical conductors in contact with the biological indicator to form a dielectric for the capacitor;   (c) applying an electrical signal to the conductors;   (d) measuring the capacitance of the capacitor; and   (e) determining from the capacitance of the capacitor whether any of the test microorganisms are alive.   
     
     
         94 - 138 . (canceled) 
     
     
         139 . A method for determining the efficacy of a sterilization process, said method comprising:
 placing spores within a region containing at least one item to be sterilized;   exposing the at least one item and the spores to a sterilant;   after exposure to the sterilant, placing the spores in an assay medium located between a pair of electrical conductors, wherein the spores and assay medium serve as a dielectric of a capacitor;   measuring the capacitance of the capacitor; and   determining whether the measured capacitance falls within a first range of capacitance values indicative of the presence of live spores or falls within a second range of capacitance values indicative of the presence of dead spores, wherein the first range of capacitance values does not overlap with the second range of capacitance values.   
     
     
         140 - 184 . (canceled) 
     
     
         185 . The process of  claim 50  wherein the capacitor is connected to a capacitance bridge. 
     
     
         186 . The process of  claim 185  wherein the capacitance bridge has an accuracy level of about 1 pF or less. 
     
     
         187 . The process of  claim 50  wherein the dielectric has a capacitance in the range from about 0.1 nF to about 20 mF. 
     
     
         188 . The process of  claim 50  wherein the test microorganisms comprise bacteria. 
     
     
         189 . The process of  claim 50  wherein the test microorganisms comprise spores. 
     
     
         190 . The process of  claim 189  wherein the spores comprise spores of the  Bacillus  or  Clostridia  genera. 
     
     
         191 . The process of  claim 189  wherein the spores comprise spores of  Geobacillus stearothermophilus, Bacillus atrophaeus, Bacillus sphaericus, Bacillus anthracis, Bacillus pumilus, Bacillus coagulans, Clostridium sporogenes, Clostridium difficile, Clostridium botulinum, Bacillus subtilis globigii, Bacillus cereus, Bacillus circulans , or a mixture of two or more thereof. 
     
     
         192 . The process of  claim 189  wherein the spores comprise  Geobacillus stearothermophilus  spores,  Bacillus atrophaeus  spores, or a mixture thereof. 
     
     
         193 . The process of  claim 50  wherein the test microorganisms are on a carrier, the test microorganism population on the carrier being in the range from about 500,000 to about 4,000,000 colony forming units. 
     
     
         194 . The process of  claim 50  wherein the test microorganisms are on a carrier, the carrier comprising paper, plastic, glass, ceramics, metal foil, one or both conductors of the capacitor, or a combination of two or more thereof. 
     
     
         195 . The process of  claim 50  wherein the test microorganisms are on a carrier, the carrier having a length in the range from about 1 to about 5 cm, a width in the range from about 0.1 to about 1 cm, and a thickness in the range from about 0.5 to about 3 mm. 
     
     
         196 . The process of  claim 50  wherein the electrical conductors comprise aluminum, copper, silver, gold, platinum, or a combination of two or more thereof. 
     
     
         197 . The process of  claim 50  wherein the electrical conductors comprise indium tin oxide on glass. 
     
     
         198 . The process of  claim 50  wherein each electrical conductor has a length in the range from about 1 to about 5 cm, and a width in the range from about 0.5 to about 3 cm. 
     
     
         199 . The process of  claim 50  wherein the electrical conductors are separated by a gap, the separation provided by the gap being in the range from about 0.5 to about 5 mm. 
     
     
         200 . The process of  claim 50  wherein the assay medium comprises a liquid or a gas having a dielectric constant in the range from 1 to about 90, the dielectric constant being determined at a temperature in the range from about −10° C. to about 60° C. 
     
     
         201 . The process of  claim 50  wherein the assay medium comprises air, one or more solvents, alcohols, polyols, aldehydes, ketones, hydrocarbons, halogen substituted hydrocarbons, nitrogenous compounds, anhydrides, oils, acetates, cyanoacetates, thiocyanates, or a mixture of two or more thereof. 
     
     
         202 . The process of  claim 50  wherein the assay medium comprises water, dimethyl sulfoxide, deuterium oxide, methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, isoamyl alcohol, hexyl alcohol, octyl alcohol, phenol, biphenyl, benzyl alcohol, creosol, glycol, pentandiol, glycerol, acetaldehyde, benzaldehyde, butaldehyde, butraldehyde, saliylaldehyde, acetone, methylethyl ketone, diethyl ketone, heptone, benzophenone, benzoyl acetone, chloroacetone, cyclohexanone, hexanone, chloromethane, bromomethane, benzyl chloride, cyclohexane, cyclohexene, cyclopentane, acetonitrile, nitrotoluene, butronitrile, lactonitrile, ammonia, formamide, hydrazine, nitrobenzene, pyridine, proprionitrile, nitrobenzene, maleic anhydride, butyric anhydride, acetic anhydride, castor oil, methylscyanoacetate, methylchloroacetate, ethylacetoacetate, cyanoethylacetate, ethylthiocyanate, amylthiocyanate, hydrocyanic acid, hydrogen peroxide, trifluoroacetic acid, lactic acid, dichloracetic acid, or a mixture of two or more thereof. 
     
     
         203 . The process of  claim 50  wherein all of the test microorganisms are dead. 
     
     
         204 . The process of  claim 50  wherein some of the test microorganisms are alive, the number of live test microorganisms being in the range from 1 to about 4,000,000 colony forming units. 
     
     
         205 . The process of  claim 71  wherein the sterilant comprises vaporous hydrogen peroxide, steam, ethylene oxide, peracetic acid, ozone, ultraviolet light, radiation, or a combination of two or more thereof. 
     
     
         206 . The process of  claim 71  wherein the capacitor is connected to a capacitance bridge. 
     
     
         207 . The process of  claim 93  wherein the sterilant comprises vaporous hydrogen peroxide, steam, ethylene oxide, peracetic acid, ozone, ultraviolet light, radiation, or a combination of two or more thereof.