Chemistry: molecular biology and microbiology – Apparatus – Including measuring or testing
Reexamination Certificate
2000-09-15
2001-09-11
Beisner, William H. (Department: 1744)
Chemistry: molecular biology and microbiology
Apparatus
Including measuring or testing
C435S030000, C435S287600, C435S287700, C435S287900, C435S297200
Reexamination Certificate
active
06287849
ABSTRACT:
This invention relates to microbiological testing of a liquid sample. In particular, it relates to a culture monitor and to a kit for microbiological testing of a liquid sample, and to a method of microbiologically testing a liquid sample.
The Applicant is aware of WO 91/18085 which discloses a device for culturing and identifying microorganisms in a liquid sample. The device includes a dry nutrient which is rehydrated during filtration of the liquid sample. The Applicant is also aware of WO 96/37600 which comprises an absorbent support placed under a membrane filter on which microorganisms are retained during filtration. A liquid nutrient medium is supplied to the microorganisms by absorbing the nutrient medium in the absorbent support. The Applicant is further aware of U.S. Pat. No. 4,777,137 which discloses a device which includes a sealed container holding liquid culture medium which is applied directly to a membrane filter with microorganisms.
According to a first aspect of the invention, there is provided a culture monitor for microbiological testing of a liquid sample, the culture monitor including
a housing having a liquid inlet and a liquid outlet;
liquid sample filtration means inside the housing between the liquid inlet and the liquid outlet, the liquid sample filtration means including a filter medium so that a liquid sample entering the housing through the liquid inlet passes through the filter medium, with microorganisms present in the liquid sample being retained on the filter medium and spent liquid or filtrate passing through the filter medium; and
a reservoir in the housing downstream of the liquid sample filtration means relative to the liquid inlet, with a volume of a rehydration agent for the dehydrated culture medium being provided in the reservoir or the reservoir being adapted to retain during filtration, as a rehydration agent, a portion of the filtrate, the dehydrated culture medium being located such that it is sealed or separated from the spent liquid or filtrate during filtration at least until immediately after filtration of a liquid sample and such that it can be brought into contact with the rehydration agent, after filtration, to form a rehydrated culture medium for the microorganisms retained on the filter medium.
The housing may be adapted to allow the insertion of a dehydrated culture medium into the housing, between the filtration means and the liquid outlet.
The culture monitor may include a cold water soluble gelling agent in the housing between the filtration means and the liquid outlet such that, the gelling agent can be brought into contact with the rehydration agent and the dehydrated culture medium. Instead, the gelling agent may be supplied separately, being insertable into the culture monitor prior to the culture monitor being used to test a liquid sample.
The liquid outlet of the housing may be configured to allow only an excess portion of the filtrate to drain from the reservoir and to retain during filtration, as the rehydration agent, a portion of the filtrate. Thus, an inlet end of the liquid outlet may be raised above a floor of the reservoir, thereby to retain during filtration, as the rehydration agent, a portion of the filtrate. Typically, in one embodiment of the invention, the reservoir retains a 5-20 mi portion of the filtrate.
The housing may define a chamber, which functions as the reservoir. Typically, the housing is modular, comprising at least two separable sections, each section typically being of a synthetic plastics or polymeric material. The sections may be fitted together in a fluid tight manner, e.g. with an interference fit. It is to be appreciated that, by separating the sections of the housing, the dehydrated culture medium and the gelling agent can be inserted into the housing. Typically, the housing is circular cylindrical in outline in plan view.
The reservoir chamber may be a first chamber, the housing including or defining a second chamber downstream of the first chamber relative to the liquid inlet. The second chamber may be defined by a third section of the housing, which may be separable from the rest of the housing. In the same fashion, more chambers downstream of the second chamber may be defined by the housing.
The outlet may extend through the second chamber. Thus, at least until immediately after the monitor has been used to filter the liquid sample, the first chamber and the second chamber of the monitor may be sealed from each other. The outlet may be a two part outlet, comprising an upper section and a lower section, the two sections being displaceable relative to each other. In one embodiment of the invention, the upper section fits in a fluid tight manner in male-female fashion in the lower section, and is axially displaceable relative to the lower section.
The monitor may include removable closure members for the liquid inlet and the liquid outlet respectively. In one embodiment of the invention, the closure members are interchangeable and are in the form of plugs having elongate plug stems which fit spigot-socket fashion into the liquid inlet and outlet, thereby closing off the inlet and outlet, with one of the plugs having a longer plug stem than the other plug.
The culture monitor may be configured to establish contact between the dry culture medium and the rehydration agent. In one embodiment of the invention, a floor of the first chamber has a zone of weakness surrounding the liquid outlet, and in particular the inlet end of the liquid outlet. Thus, in this embodiment, axial displacement of the upper section of the outlet away from the lower section leads to failure of the zone of weakness and allows the rehydration agent in the reservoir or first chamber to be contacted with the dry culture media in the second chamber. Displacement of the upper section of the outlet may be effected by inserting an object, such as the stem of the long stemmed plug, into the lower section of the outlet and exerting a force or a load on the upper section of the outlet, thereby axially to displace the upper section away from the lower section to effect failure of the zone of weakness.
In another embodiment of the invention, the second chamber and the first chamber are each defined by a housing section, the housing sections being screw-threadedly attached or attachable to each other, with a sealed flow passage being provided between the chambers. The seal of the flow passage may be configured to be pierced or broken when the chambers are advanced towards each other by rotating their housing sections relative to each other, thus establishing flow communication between the two chambers.
The second chamber may include or may be defined by one or more compartments, e.g. 2-8 compartments. The or each compartment may be sealed from the rest of the second chamber, and/or the compartments may be sealed from each other. The compartment(s) may be annular or circular. The or each compartment may be configured to release its contents when so required. Thus, the compartments may hold the rehydration agent, which may be deionised sterilized water; the dehydrated culture medium; the gelling agent; a supplementary growth nutrient; and/or a non-target bacterial growth inhibitor. The compartments may also hold separated constituents of the dehydrated culture media, thus advantageously prolonging the shelf life of the monitor. It is to be appreciated that, if the monitor stores a volume of rehydration agent, then there is no need to retain a portion of the filtrate, and the reservoir or first chamber does not need being adapted to retain during filtration, as the rehydration agent, a portion of the filtrate.
In one embodiment of the invention, a single compartment is provided in the second chamber, the compartment being in the form of an annular channel formed between the floor of the first chamber and a floor of the second chamber with the channel being sealed from the rest of the compartment by complementary annular male and female formations on the floors of the chambers. Release of the contents of the channel is thus
McNerney Michael James
Pigott Eugene
Amanzi Technologies Limited
Beisner William H.
Johnson Kenneth H.
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