Vacuum detection of bacteria

Claim 3

A method as recited in claim 1 wherein said means for measuring reductions in the pressure of the gas is a continuously operating analog pressure transducer connected to recording means.

Claim 4

A method as recited in claim 1 wherein the material to be tested for the presence of bacteria is a liquid, said container being provided with a self-sealing rubber septum, and inoculation of the culture medium is effected by injecting a sample of said liquid test material into said container through said septum with a hypodermic syringe.

Claim 5

A method as recited in claim 1 wherein said culture medium comprises tryptic soy broth fortified with a material selected from the class consisting of glucose, dextrose and glycine.

Claim 6

A method as recited in claim 1 wherein said gas in said test container is air.

Claim 7

A method as recited in claim 1 wherein the volume of said test container is from about 20 to about 100 ml and the volume of said culture medium in said container is from about 1/5 to about 4/5 of the volume of said container.

Claim 8

A method as recited in claim 1 wherein said means for measuring reductions in the pressure of the gas comprises a vacuum operated switch which actuates an indicator system when a predetermined threshold decrease is reached in the container.

Claim 9

A method as recited in claim 7 wherein said predetermined threshold decrease detection level is from about 3 to about 5 cm H 2 O.

Claim 10

A method as recited in claim 1 wherein a plurality of said containers are inoculated with test material samples and said containers are repeatedly monitored seriatim at intervals throughout the time periods during which the containers and their contents are subjected to conditions conductive to bacterial growth.

Claim 11

A method as recited in claim 9 wherein said periodic time intervals range from about 10 minutes to about 1 hour.

Claim 12

A method as recited in claim 1 wherein said culture medium in said container is agitated during the period of time the container and its contents are subjected to conditions conductive to bacterial growth.

Claim 13

A method as recited in claim 11 wherein said agitation is effected by gently shaking said container.

Claim 14

A method as recited in claim 11 wherein said agitation is effected by a magnetic stirring bar in said container, said stirring bar being subjected to the field of a rotating magnet outside said container.

Claim 15

A method as recited in claim 1 wherein said container and its contents are maintained at temperatures lying in the range between about 35° and about 37° C.

Claim 16

A method as recited in claim 14 wherein said container and its contents are maintained at a constant temperature.

Claim 17

A method as recited in claim 14 wherein the temperature of said container and its contents is brought to within the range from about 35° to about 37° C. prior to inoculation of the test container.

Claim 18

A method as recited in claim 1 wherein the references standard is established by providing an identical second sterile container containing culture medium and gas, maintaining the sterility of said container, subjecting said sterile container to the same conditions to which the inoculated container is subjected, monitoring the sterile container for the production of a vacuum.

Claim 19

A method as recited in claim 17 wherein the temperature of said test container and the temperature of said reference container are brought to within the range from about 35° to about 37° C. prior to inoculating said test container.

Claim 20

A method as recited in claim 17 wherein the initial pressure in said inoculated container and the initial pressure in said reference container are equilibrated prior to subjecting the containers to conditions conductive to bacterial growth.

Claim 21

A method as recited in claim 19 wherein the equilibration of pressures in said containers is effected by venting both containers to the atmosphere.

Claim 22

A method as recited in claim 1 wherein the pH of said culture medium is buffered to a pH between about 6 and about 8.

Claim 23

A method as recited in claim 21 wherein the pH of said culture medium is buffered to a pH between about 6.9 and 7.4.

Claim 24

In the identification of unknown microorganisms, the steps of, providing a sealable sterile container containing a sterile culture medium and a quantity of oxygen containing gas in the head space above said medium, inoculating said culture medium in said container with a sample of the organism to be identified and sealing the container, said container being connected to means for sensing the production of a vacuum in said container, subjecting the sealed, inoculated container to conditions conducive to bacterial growth for a period of time sufficient for growth of bacteria to consume some of the oxygen from the oxygen containing gas in said container, retaining in the head space gas any gases evolved from the culture medium into the head space gas, monitoring said container for the production of a vacuum due to consumption of oxygen, recording the result of the monitoring step and comparing the recorded pattern of vacuum production to known patterns of vacuum production for known categories of microorganisms.

Claim 25

In the identification of unknown microorganisms, the steps of, providing a sealable sterile container containing a sterile culture medium and a quantity of oxygen containing gas in the head space above said medium, inoculating said culture medium in said container with a sample of the organism to be identified and sealing the container, said container being connected to means for sensing the production of a vacuum in said container, subjecting the sealed, inoculated container to conditions conducive to bacterial growth for a period of time sufficient for growth of bacteria to consume some of the oxygen from the oxygen containing gas in said container, retaining in the head space gas any gases evolved from the culture medium into the head space gas, monitoring said container for the production of a vacuum due to consumption of oxygen, recording the result of the monitoring step and comparing the recorded pattern of vacuum production to known patterns of vacuum production for known categories of microorganisms.

Claim 26

In a method for detecting bacteria by providing a sealable sterile container containing a culture medium and a quantity of gas in the head space of said container above said culture medium, inoculating said culture medium in said container with a sample of material to be tested for the presence of bacteria and sealing the container, said container being connected to means for sensing the pressure of the gas within said container, subjecting the container and its contents to conditions conducive to bacterial growth for a predetermined period of time and monitoring the container during subjection to conditions conducive to bacterial growth for increases in the pressure of the gas within the container, the improvement comprising said container being connected to means for measuring reductions in the pressure of the gas in said container, said gas in said container comprising oxygen and being substantially free of hydrocarbon, establishing a reference standard representing the initial pressure of the gas in the container, retaining in said head space gas any gases evolved from the culture medium into the head space gas, measuring any reduction in the pressure of the gas in said container to a valve less than said reference standard, comprising the measured pressure to said reference standard and determining whether there has occurred a reduction in pressure exceeding a predetermined threshold decrease indicating the presence of oxygen consuming bacteria; said threshold decrease being greater than any reduction attributable to measurement deviations or variations in experimental conditions.

Claim 27

In a method for detecting bacteria by providing a sealable sterile container containing a culture medium and a quantity of gas in the head space of said container above said culture medium, inoculating said culture medium in said container with a sample of material to be tested for the presence of bacteria and sealing the container, said container being connected to means for sensing the pressure of the gas within said container, subjecting the container and its contents to conditions conducive to bacterial growth for a predetermined period of time and monitoring the container during subjection to conditions conducive to bacterial growth for increases in the pressure of the gas within the container, the improvement comprising said container being connected to means for measuring reductions in the pressure of the gas in said container, said gas in said container comprising oxygen and being substantially free of hydrocarbon, establishing a reference standard representing the initial pressure of the gas in the container, retaining in said head space gas any gases evolved from the culture medium into the head space gas, measuring any reduction in the pressure of the gas in said container to a valve less than said reference standard, comprising the measured pressure to said reference standard and determining whether there has occurred a reduction in pressure exceeding a predetermined threshold decrease indicating the presence of oxygen consuming bacteria; said threshold decrease being greater than any reduction attributable to measurement deviations or variations in experimental conditions.

Claim 28

A method as recited in claim 19 wherein the equilibration of pressure in said containers is effected by venting the containers to each other through a submicron filter.

Claim 31

A method as recited in claim 26 wherein the pattern of vacuum production for a sample containing known numbers of the same bacteria is determined by parallel treatment of an identical culture medium containing vial inoculated with a known number of the same bacteria.

Claim 32

A method as recited in claim 26 wherein said container and its contents are maintained at temperatures lying in the range between about 35° and about 37° C.

Claim 33

A method as recited in claim 26 wherein said gas in said test container is air.

Claim 34

A method as recited in claim 26 wherein said vacuum sensing means is a continuously operating analog pressure transducer connected to recording means.

Claim 35

A method as recited in claim 26 wherein said culture medium in said container is agitated during the period of time the container and its contents are subjected to conditions conducive to bacterial growth.

Claim 36

A method as recited in claim 26 wherein the pH of said culture medium is buffered to a pH between about 6.9 and about 7.4.

Claim 37

A method according to claim 1 further comprising generating an output signal indicating when a reduction in pressure exceeding said threshold decrease has occurred.

Claim 38

A method according to claim 1 wherein said material to be tested for the presence of bacteria is a body fluid.

Claim 39

A method according to claim 34 wherein said body fluid is urine.