Bacteria detection methods

Abstract

1. A method for detecting fluorescence from bacteria suitable for determining the presence of feces or other fluorophores, the method comprising the steps of irradiating a target with fluorescence excitation light having an excitation wavelength and monitoring emission of fluorescence light from the target at a wavelength longer than the excitation wavelength.

Description

[Technical field]

[0001] The present invention relates to a method for detecting fluorescence from bacteria, in particular detecting bacterial fluorescence in incontinence pads, diapers or nappies, a fiber optic cable or other form of light guide for use in the method, and an apparatus for carrying out the method of the invention. [Background technology]

[0002] Fecal incontinence (inability to control bowels) is a tremendous social and hygienic problem, affecting 2-3% of adults. There is a particularly high prevalence in frail older adults in nursing home or hospital settings. Individuals with reduced sensation (e.g., neurological conditions) or consciousness (e.g., dementia) often do not know if they have accidentally deposited feces in their incontinence pads, or cannot distinguish between passing feces or flatus, and therefore may make unnecessary repeated trips to the bathroom. This can be a burden for some patients, for example those who are wheelchair bound and must find an accessible toilet to transfer and remove clothing and incontinence pads. Caregivers, whether in a hospital, nursing home, or private home, often need to check as well, but there is no practical way to do this without removing clothing, which can be difficult with frail individuals.

[0003] Existing urinary incontinence products incorporate a hydrophobic layer and are specifically designed to absorb and contain urine. However, they are unable to absorb feces. Modern wet-retention surfaces and superabsorbent pads can accommodate large volumes of urine without damaging delicate skin or unpleasant odors. Thus, if only urine enters the pad, changing can be delayed until the pad approaches capacity. However, upon defecation, the product must be changed immediately and the skin must be washed as soon as possible to prevent skin damage. Thus, a rapid and accurate signal is needed when the patient has defecate. Summary of the Invention

[0004] According to a first aspect of the present invention there is provided a method of detecting fluorescence from bacteria suitable for determining the presence of feces or other fluorophores, the method comprising the steps of irradiating a target with excitation light having an excitation wavelength and monitoring emission of fluorescent light from the target at a wavelength longer than the excitation wavelength.

[0005] The wavelength of the excitation light may be within a range of 420 nm to 645 nm, and more specifically, the wavelength of the excitation light may have a central wavelength of substantially 635 nm. The fluorescent light may have a wavelength of 650 nm or more. The excitation wavelength may include a plurality of wavelengths corresponding to one or more porphyrin Q bands.

[0006] The target may be a receptacle for receiving bodily fluids or bodily exudates, and more specifically, the receptacle may be an incontinence pad, a diaper, or a nappy, or a receptacle for receiving a sample of bodily fluids or bodily exudates outside the body.

[0007] The method according to the first aspect may further comprise the steps of modulating the intensity or frequency of the excitation light, optionally detecting a corresponding modulation of light emitted by the target, and filtering out emitted light without said modulation.The method may further comprise detecting a fluorescence lifetime associated with the sample fluorescence, the lifetime being detected using a time-resolved or phase-resolved detection technique.

[0008] The method may further include providing a light source and coupling light output from the light source into a light guide, and the illuminating step is performed with light emitted from a light guide, optionally the light guide being an optical fiber. The monitoring step may include monitoring light coupled from the target into the light guide at a wavelength greater than a wavelength of the excitation light.

[0009] The light source and / or detector may be provided in an incontinence pad, nappy or diaper.

[0010] The method may further comprise the steps of measuring the emission of the fluorescent light and comparing the emission to a predefined threshold.The method may further comprise the steps of detecting a wavelength spectrum and / or a fluorescence lifetime of the fluorescent light.

[0011] Optionally, a signal is generated to notify a user of the presence of bacteria.

[0012] According to a second aspect of the present invention, there is provided a detection system for detecting the presence of feces, comprising: a light source; a light source optical fiber, the light source optical fiber being optically coupled to the light source; a receiver optical fiber; and a detector, the detector being optically coupled to the receiver optical fiber. A detection system is provided comprising:

[0013] The source optical fiber and the receiver optical fiber may be the same fiber or optical fibers or may be different optical fibers. The source optical fiber may be a fiber optic cable comprising a core and a cladding, and the cladding may comprise a number of discontinuities that provide optical paths for light coupled into or out of the fiber. The discontinuities may be arranged in a non-linear pattern with adjacent gaps positioned increasingly farther from each other to maintain a certain degree of light leakage along the cable.

[0014] The source optical fiber and the receiver optical fiber may be the same optical fiber, the optical fiber may be optically coupled to the detector and the light source, and the detector and the light source may be coupled to the optical fiber at the same end of the optical fiber or at opposite ends of the optical fiber.

[0015] The system may further comprise a pad, with the source optical fiber and / or the receiver optical fiber attached to or integrally formed with the pad. The system may further comprise a communications module for transmitting and / or receiving data to one or more external devices. The system may further comprise an alarm, with the alarm being one of an optical alarm, an audible alarm, or a tactile alarm.

[0016] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0017] [Figure 1] 1 illustrates a typical porphyrin excitation spectrum, showing a strong Soret excitation band and several weak Q bands. [Diagram 2] 1 is a graph of spectral measurements of fluorescence emission from several stool samples. [Diagram 3] 1 shows an example of a "leaky" light guide. [Figure 4] 1A-1C are schematic diagrams illustrating several configurations of leaky optical fibers within a target sensing area. [Diagram 5] 13A and 13B show schematic diagrams of a configuration using an engineered diffuser positioned at the target sensing area. [Figure 6] 13 shows an example of coupling and detection of fluorescent light into and from a single detection fiber. [Figure 7] 1 shows an example of the coupling and detection of fluorescent light into and from two fibers used for fluorescence detection. [Figure 8] FIG. 8 shows a block diagram for processing an optical signal in the fluorescence detection system shown in any of FIGS. 4 to 7. [Figure 9] Here's how. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Disclosed herein are methods and systems for detecting the presence of bacteria in stool. The challenge of detecting the presence of bacteria in stool can be addressed by taking advantage of the fact that certain bacteria prevalent in stool have characteristic fluorescent properties. Normal stool contains a very large number of bacteria, with 25-54% of their mass being bacterial biomass. Fluorescence from feces appears to result from conversion to protoporphyrin IX, coproporphyrin, and pepto- and deuteroporphyrins, but is not limited to these moieties.

[0019] Fluorescent species such as porphyrins typically exhibit a large Stokes shift, and therefore the presence of the porphyrin, and therefore the presence of bacteria, can be detected by exciting the porphyrin with light of a given wavelength band ("excitation light") and monitoring the fluorescence emission at wavelengths longer than the wavelength of the excitation light ("fluorescence light").

[0020] The absorption (excitation) spectrum of porphyrins shows a strong so-called "Soret band" in the blue region of the visible spectrum, as shown by reference number 1 in Figure 1. This intense Soret band is due to the S0 to S2 electronic state / energy transition. The position of this band has an absorption maximum below 430 nm, typically in the range of 400-420 nm.

[0021] However, the absorption spectrum of porphyrins is not limited to the Soret band, but there is another weaker absorption band called the "Q band", which is shown in FIG. 1 with reference number 2. In porphyrins, the Q band is split due to vibrational excitation, which generates two bands due to the transition from the ground state to two excited vibrational states (Q(0,0) and Q(1,0)). Furthermore, the presence of NH protons breaks the symmetry, resulting in further splitting of these bands into two bands each. Thus, four Q bands (Qx(0,0), Qy(0,0), Qx(1,0) and Qy(1,0)) can be observed. Therefore, excitation of porphyrins at peak absorbance wavelengths corresponding to the Soret or Q band peaks is possible.

[0022] Generally, as shown in FIG. 1, the four porphyrin Q bands have absorption peaks at about 505 nm ("Q-IV"), about 535 nm ("Q-III"), about 575 nm ("Q-II"), and about 635 nm ("QI"). The excitation light may be selected to have a wavelength that substantially corresponds to the peak absorption wavelengths of the porphyrin Q-IV, Q-III, Q-II, and QI bands. By "substantially corresponding" it is meant that the excitation light may have an optimal wavelength within ±10 nm, preferably ±5 nm, of the peak absorption wavelength of each Q band. The width of the excitation spectrum may be smaller or larger than the width of the illustrated absorption peaks.

[0023] By using excitation light having a wavelength in the range of about 500-645 nm, one or more of the Q bands of bacterial porphyrins can be excited, thereby leading to the production of fluorescent emission. Alternatively, due to the strong Soret band absorption, radiation in the blue or UV region of the spectrum, for example at about 415-420 nm or below about 400 nm, can be used to excite the porphyrins. The use of such excitation wavelengths results in correspondingly strong fluorescent emission, thus allowing easy detection of the presence of bacteria. When excitation is performed in the porphyrin Soret band, for example using wavelengths below about 430 nm, fluorescent emission is generally observed above about 650 nm.

[0024] Soret band excitation wavelengths can be used, for example, to detect feces in incontinence pads. However, prolonged or long-term exposure to light in the blue and / or UV regions of the spectrum is considered potentially toxic to skin and other tissues. Such wavelengths are not readily absorbed by DNA, but may induce DNA damage indirectly through other cellular structures with the formation of reactive oxygen species that can transfer photon energy to DNA via mutagenic oxidative intermediates such as 8-hydroxydeoxyguanosine (8-OHdG). Therefore, it is preferable that detection methods avoid the long-term use of such wavelengths.

[0025] Furthermore, traces of grease (creams, ointments, etc.) on the skin and optical whiteners (as found in some types of incontinence pads and diapers) can also fluoresce under blue or UV light, so false positive detection of bacteria may occur if fluorescence detection is performed using Soret band excitation light in incontinence pads or diapers.

[0026] However, the inventors have realized that Q-band excitation light (i.e., excitation light having a wavelength between 500 nm and 645 nm) can be safely used. Figure 2 shows the spectra obtained from several fecal samples illuminated with light in the range of 500-645 nm, as indicated by reference numeral 3. As shown in Figure 2, the resulting Stokes shift results in fluorescence at wavelengths of about 650 nm and above. The emission spectrum shows a main emission peak from about 675 nm to about 735 nm. These wavelengths depend on the excitation wavelength and porphyrin species used.

[0027] There are other advantages to using longer wavelength Q-band excitation light for the purpose of detecting the presence of stool. Stool samples can be optically dense, especially if the volume is large. This can result in significant self-absorption (inner filter effect). Rayleigh scattering of excitation and fluorescence emission light is inversely proportional to the fourth power of the wavelength, and Mie scattering also decreases as the wavelength is increased. These effects can increase the intensity of the fluorescence emission light that can be detected, thereby facilitating detection. Longer wavelengths of excitation light greatly reduce the degree of self-absorption and can illuminate deeper samples, thus improving detection.

[0028] Therefore, despite weaker absorption in the longer wavelength Q bands, exciting the QI or Q-II bands has certain advantages over exciting the Q-III or Q-IV bands.

[0029] Thus, in the present method, detection of bacteria may be performed by illuminating a target with excitation light having a wavelength in the range of 500 nm to 645 nm while simultaneously monitoring for the presence of fluorescent light having a wavelength of 650 nm or greater. The target may be a soiled incontinence pad, diaper, or nappy worn by a user. Alternatively, the target may be a sample of an external bodily fluid or other sample suspected of containing bacteria.

[0030] Certain bacteria associated with urinary tract infections may also contain porphyrins and therefore undergo a similar fluorescence process as outlined above, so if the target to be illuminated as described above is an incontinence pad, diaper or nappy, detection of bacteria may also correspond to detection of urine associated with urinary tract infections.

[0031] If the irradiation target is an incontinence pad, diaper or nappy, the detection of bacteria is preferably carried out while a user is wearing said incontinence pad, diaper or nappy.

[0032] Various methods can be used to separate the excitation light from the fluorescence emission, so that only the pure fluorescence emission is detected. For example, the fluorescence signal can be detected using an optical detector or using a spectrometer. Alternatively, the fluorescence lifetime information can be extracted using frequency modulated or pulsed excitation followed by fluorescence phase or lifetime detection, respectively. In most cases, it is desirable to separate the fluorescence emission from the excitation light using one or more filters.

[0033] Excitation light having a wavelength substantially corresponding to the peak absorption wavelength of the porphyrin QI band (e.g., 635±10 nm, particularly 635±5 nm) provides superior performance in light source and detector detection capabilities, emission efficiency, minimal scattering, and low cost.

[0034] Typically, it is necessary to convert the collected fluorescence light into a meaningful output. This conversion step may include determining the fluorescence emission by various detection approaches and comparing it with a predetermined threshold value. If the level of fluorescence exceeds the threshold value, a positive identification indicating the presence of bacteria, and thus the presence of feces, may be made.

[0035] If fluorescence is detected, the method may further include generating a signal (e.g., for notifying the user of the presence of bacteria, such as for notifying the user of the presence of feces). The signal may be, for example, a sound or a visual display (e.g., a light or a message on a screen such as the screen of a computer or a handheld device).

[0036] Irradiating the target with excitation light and collecting the fluorescence emission may include transmitting the excitation light along a light guide to the target. In the vicinity of the target, the light guide is intentionally made "leaky". Figure 3 shows an example of an optical fiber cable 30 that operates as a light guide suitable for irradiating the target. The optical fiber cable 30 includes a core 31 having a refractive index n1 and a cladding 32 having a refractive index n2, where n2 < n1 in this case. The core 30 and the cladding 32 may be made of any material known in the art for optical fiber cables, such as silica, glass, or a polymer, or other forms of light guides.

[0037] When the target is an incontinence pad, diaper, or nappy, it is desirable to illuminate multiple locations within the target to optimize detection of bacteria. To illuminate the target area, various means can be used to distribute the excitation light over a wide area and collect the fluorescent emission from said area. Some approaches use a "leaky" fiber optic cable. The cladding 32 comprises multiple discontinuities 33. These discontinuities 33 ("gaps" or "discontinuities") in the cladding 32 expose the core 31. In such a "leaky" cable, the excitation light can "leak" out of the core 31 through the gaps 33 in the cladding 32, thereby illuminating multiple locations within the target adjacent to the gaps 33. Fluorescent light resulting from any bacteria present at such locations can also enter the fiber optic cable through the gaps 33 in the cladding (i.e., the fluorescent light is "collected" by the cable).

[0038] By providing multiple discontinuities 33 along the length of the fiber optic cable 30 or other type of light guide, the total internal reflectance of the light transmitted by the fiber optic cable 30 is partially suppressed at these portions, and the light percolates along the length of the fiber optic cable 30. Compared to a fiber optic cable with a single "open" end, this increases the area over which the fiber optic cable 30 can detect the presence of bacteria in a target, such as fecal bacteria in a pad. The gaps 33 may extend around all or a portion of the circumference of the fiber optic cable 30. The gaps 33 may take the form of pin pricks, slits, scratches, or notches in the cladding, and may extend around the circumference of the fiber optic cable 30 or only a portion of the circumference. The gaps 33 may be one or more spiral cuts along the length of the fiber optic cable 30. The gaps 33 may be formed by engraving, etching, laser cutting, drilling, sanding, sandblasting, or any other suitable technique.

[0039] The gaps 33 in the fiber cladding 32 may be positioned and dimensioned such that light leakage from the core 31 is substantially uniform at each gap. This also ensures that a substantially uniform amount of fluorescent light per unit length (e.g., per mm or per cm) is collected by the optical fiber. This can be achieved by arranging similar gaps 33 in a nonlinear pattern, as shown in FIG. 3, where adjacent gaps 33 are positioned increasingly closer to each other toward the distal end of the optical fiber to maintain a constant degree of light leakage.

[0040] In adult pads or diapers the target area may cover a maximum of 10-15cm in length and typically 5-10cm in width. In infant diapers or nappies this length may be correspondingly shorter.

[0041] Light exiting fiber optic cable 30 scatters when it encounters a target material, such as an incontinence pad, diaper, or diaper material. In this manner, the portion of the target that is illuminated is increased beyond just the portion immediately adjacent gap 33 in cladding 32. Preferably, fiber optic cable 30 has a diameter of less than 1 mm, such as 0.75 mm ±0.25 mm or less, although other readily available fiber optic cables 30 are readily available and particularly suitable for use as described herein.

[0042] Fiber optic cables may be made "leaky" in other ways. For example, the cable may be bent to form multiple curves, e.g., in a wave-like shape. The curves increase the angle of incidence of the light traveling within the fiber to the interface between the core and the cladding, thereby decreasing the amount of internal reflection. When the fiber is woven into a material, multiple curves can be included to create corresponding regions where emitted and absorbed light can be coupled into or out of the fiber.

[0043] Instead of a single fiber optic cable, multiple cables can be used. The cables may be arranged in the form of a fiber bundle, or may be parallel to each other or at an angle (e.g. perpendicular to each other). In such cases, the technical difficulty of manufacturing multiple fibers is compensated by having a very thin sensor that may be of acceptable sensitivity even when using less efficient fibers, and by further increasing the sensing area. The fibers can also be arranged in a mesh-type arrangement relative to each other if woven into the fabric of the pad.

[0044] Depending on the optical configuration used to deliver the excitation light and collect the fluorescent emission light, one or more leaky fibers can be used, and one or more leaky fibers can be arranged in a number of configurations as shown in Figure 4. As shown in Figure 4A, when a single fiber is used, fiber 42 operates as a conventional light guide, but is made leaky at section 41 and terminates in connector 43. The leaky section meanders across target area 45 where fecal material is expected to be present.

[0045] An alternative arrangement is shown in Figure 4B, where two fibers 42 are made leaky at section 41 and terminated in a dual fiber connector 44. The fibers are placed adjacent to each other, with one fiber transmitting the excitation light and the other fiber collecting the fluorescence emission light. The leaky section 41 meanders throughout the target area 45. The leaky sections of the fiber optic cables must be close enough to each other to allow the two cables to illuminate / receive light from the target 45 and interact with the same sensing area.

[0046] An alternative approach is shown in Figure 4C, which again uses a dual fiber connector 44, but which terminates the two ends of a single optical fiber. The fiber has a leaky portion 41 with a non-leaky portion 42. The fiber thus delivers excitation light across the target area and collects fluorescent emission from the target area 45.

[0047] The serpentine portions of fiber 41 in Figure 4 may be attached to a highly porous flexible substrate that allows the passage of urine to the underlying absorbent region of the pad. The leaky portions may run parallel to one another and may be knotted, glued, woven into the sensor pad, or otherwise attached in place.

[0048] Yet another approach is shown in FIG. 5. Here, a non-leaky fiber 53 is used to transmit the excitation light and collect the fluorescent emission between a leaky fiber 52 and a flexible diffuser 51 similar to those used in LED backlight panels. Such an engineered diffuser can be made of flexible PDMS / PMMA. These or other forms of light guide plates can be connected to a detection unit using one or more fiber optic cables. In this example, the fibers 52 are made leaky only where they are in contact with the flexible diffuser 51. Other similar approaches to distribute light over a large area are also suitable. The diffuser 51 acts as a large light guide operating by total internal reflection. Total internal reflection is disrupted at intervals by incorporating dips or bumps across the sheet to form a side-illuminated diffuser, as shown in the enlarged portion 54.

[0049] It can therefore also act as a collector of light across a large target area. There must be a large number of holes in the diffuser 51 to allow the passage of urine.

[0050] Alternatively, the light source and detector may be placed near the target area and the signal information brought into the signal processing unit by electrical rather than optical means. The simplicity of using electrical rather than optical connections is balanced by the challenge of developing ultra-thin, flexible optical filters to remove the excitation light from the detected signal.

[0051] The fiber optic cable (or cables) described above may form part of a fluorescence detection system comprising one or more light guides, a light source, and a photodetector, with further details regarding these components (and other optional components) described below.

[0052] The light source and detector are typically incorporated into a unit that can be selectively connected to fiber optic delivery and sensing cables. The light source may be coherent or incoherent and may operate continuously, modulated or pulsed during the sensing period.

[0053] Red (630-640 nm) laser sources may be preferred. Such sources combine the conflicting requirements of low cost, low optical etendue (a term in the art that indicates the ability to focus a beam; it is the product of the source area and the solid angle emitted by the source), and low operating power, all of which are essential for long-term, reliable operation. The brightness and low etendue allow for easy light launch in fibers. In particular, a wavelength of 635 nm can be used.

[0054] Optionally, the output power of the light source can be sensed by a photodiode inside the light source (e.g., a laser) to maintain the average output power at a user-defined value. Optionally, temperature control of the light source may be necessary to stabilize the emission wavelength. Optionally, the light source is switched on only intermittently to conserve power, for example in short pulses every 10 seconds, or every 30 seconds, or every minute, or any other convenient period.

[0055] The detector may be a photodiode or an avalanche photodiode. Silicon photodiodes or silicon avalanche photodiodes are particularly suitable due to their high optical-to-electrical quantum efficiency and responsivity, which are particularly good in the wavelength range corresponding to the fluorescence wavelengths associated with Q-band excitation of porphyrins.

[0056] Alternatively, the detector may be a spectrometer or a time-resolved detector, such as a single photon avalanche diode (SPAD).A number of fluorescence detection techniques known to those skilled in the art of fluorescence detection can be used.

[0057] The light delivery and sensing fiber optic cables are generally disposable because they become contaminated, but the unit containing the light source and detector along with other signal processing electronics is reusable. Disposable parts are intended for single use, and the cost of those parts is preferably minimized.

[0058] The fluorescence emission detector may be configured to detect only light in the wavelength range corresponding to the fluorescence emission band to be detected, and not the excitation wavelength.

[0059] The configuration shown in Figure 4A may be coupled to a typical fluorescence excitation and detection system shown in Figure 6A or 6B. A conventional fluorescence detection system based on a long-pass dichroic reflector 64 is shown in Figure 6A. A single fiber 61 is connected to the fluorescence detection system via connector 62 and its output is collimated by lens 63. The collimated fluorescence output is transmitted by dichroic filter 64 through a long-pass or notch filter 67 to a detector 68. Detector 68 may require the use of a focusing lens 68a.

[0060] Dichroic reflector 64 reflects excitation light from light source 66. This light may require a collimating lens 66a and low pass filter 65 to remove longer wavelength emission sidebands from the fluorescence excitation source 66. The collimated fluorescence excitation light is focused onto fiber 61 by lens 63.

[0061] Alternatively, a short-pass dichroic reflector 65 may be used, and the positions of the detector 68 and its filter 67 and lens 68a may be swapped with the light source 66, its collimating lens 66a and sideband rejection filter 65. The angle between the excitation and emission optical axes does not need to be 90 degrees, but can be any angle dictated by the design of the dichroic reflector 64.

[0062] Alternatively, the dichroic reflector may be replaced by a 50:50 beam splitter cube or plate, in which case approximately 50% of the excitation light is lost and 50% of the emission light is lost. However, dichroic reflectors with a sharp transition between transmitted and reflected wavelengths are difficult to fabricate, so operation at close Stokes shifts is possible.

[0063] A configuration that provides a similar level of loss while eliminating the need for a dichroic reflector entirely is shown in FIG. 6B. Here, light from a light source 68, which may require collimation by lens 68a, is filtered by a short pass filter 67 and directed by lens 66 to optical fiber 64b, which is part of a fiber splitter / combiner configuration with three ports 64a, 64b, 61a. Approximately 50% of the light entering fiber 64b is transmitted to port 61a. Similarly, approximately 50% of the fluorescent light emission present at port 61a is present at the output of port 64a. This light is collimated by lens 63 and passed through a long pass filter 65 to a detector 69, which may also require a focusing lens 69a. As before, the filter removes the excitation light from reaching the detector 69.

[0064] In the exemplary system shown in Figures 6A and 6B, the excitation light and emission light are delivered to the target area by a single fiber. The connector 62 may allow free rotation of the cable. Preferably, the connector uses both rotational and axial latches.

[0065] Although conventional lenses and filters are shown in Figures 6A and 6B, a range of other optical components may be used, such as gradient index lenses, Fabry-Perot filters and other all-fiber components.

[0066] A typical fluorescence excitation and detection system with dual fiber ports, as required by the configuration shown in FIGS. 4B and 4C, is shown in FIG.

[0067] Excitation light from light source 78, associated collimating lens 78a, and sideband rejection filter 77 is focused by lens 76 into excitation optical fiber 71b which is used to connect to dual fiber connector 72. Similarly, light from fluorescence emission optical fiber 71a is collimated by lens 73, and any excitation light present is rejected by long pass or notch filter 75. Light thus filtered is focused by lens 79a onto detector 79.

[0068] In this exemplary system, the connector 72 must not allow free rotation of the cable. Preferably, the connector uses an axial latching mechanism.

[0069] Steady-state excitation and detection, operating continuously or in short bursts, is the simplest to use, although other detection techniques may be envisaged in the exemplary configurations shown in Figures 6 and 7. These include the use of a spectrometer replacing the detector, in which case the spectrometer may detect the wavelength emission spectrum of the emitted light. Alternatively, a fluorescence lifetime measurement technique may be used in which the light source output is pulsed or modulated at one or more frequencies appropriate to the fluorescence lifetime of the sample. The detector may then be a time-resolved or phase-demodulated detector. Spectral information may be useful to identify spectral peaks (as shown in Figure 2), in which case dispersion information may potentially provide insight into other aspects of the patient's health. Similarly, time-resolved information may provide similar information, with the added advantage of being insensitive to attenuation changes in optical fibres. Any suitable optical arrangement known to those skilled in the art may be used.

[0070] If the level of processed and detected fluorescent information exceeds a predefined threshold, a positive identification of bacteria (e.g., in fecal form) is made. Preferably, this involves sending an alert to a user (e.g., a wearer of an incontinence pad with a light-guiding device as shown in Figures 4 and 5, or a caregiver such as a nurse or doctor). If detection is performed to detect the presence of stool, this alert may prompt the replacement of the soiled incontinence pad / diaper with a clean one.

[0071] The bacteria detection system may further comprise a signal processing unit that receives electronic signals from the detector, processes them, and determines whether the optical detector detects fluorescence information of the object that exceeds a predetermined threshold. The predetermined threshold may be set to eliminate "false positive" detections of bacteria that arise from unavoidable background noise inherently generated by any of the optical components of the device or from fluorescence from other light sources.

[0072] Detection of bacteria may be performed continuously (i.e. by continuously generating excitation light and monitoring fluorescence) or may be performed at discrete time intervals separated by periods during which detection is not performed. Detection at discrete time intervals may help to conserve power (e.g., extend the life of the device if it is battery-powered). Also, particularly in the case of stool detection, continuous monitoring may not be necessary because the patient does not pass stool frequently. Detection may therefore be performed at regular intervals, for example at intervals of 20 minutes or less, preferably 5 to 15 minutes. If detection is performed, it is sufficient that this detection is performed for a time long enough to be able to detect the presence or absence of fluorescence. Therefore, during each detection interval, excitation light is preferably provided for a period of a few seconds or less.

[0073] The excitation light may be modulated and the signal processing unit may be configured to detect only the corresponding modulation in the fluorescence. The intensity and / or frequency of the excitation light may be modulated. Such synchronous detection techniques are known to those skilled in the art of signal processing. Light sources that are not related to the excitation / emission process, such as ambient light, are not modulated in the same way and therefore may be filtered out. The modulation waveform may be sinusoidal or square shaped or other shapes known to those skilled in the art of synchronous demodulation.

[0074] The above-mentioned fluorescent detection system may be incorporated into an incontinence pad, diaper, or nappy. Pads, nappies, and nappies are well known in the art, and their exact structure is not essential to the practice of the present invention. However, they generally include an elongated absorbent portion that generally contains an odor control agent. In the following description, the term "pad" is used for brevity, but should be understood to encompass nappies and nappies as well as incontinence pads. Pads can also refer to separate inserts with leaky optical fibers or other light diffusing configurations, whereby the pad is inserted into the nappy, thus eliminating the need to change the design of the nappy.

[0075] A distributed sensing device as described above may be integrally formed within the pad (i.e., both the cable and pad are disposable as a unit) or the fiber optic cable may be removable from the pad, in which case it can be sterilized after use and reused.

[0076] The pad may include means for positioning the distributed sensing device, particularly the portion of the cable that includes multiple discontinuous portions, substantially centrally within the pad. As used herein, the term "central" should be understood as central with respect to the longer dimension of the pad (i.e., with respect to the longer dimension of the pad, in which the cable extends back and forth relative to the user of the pad). Since soiling (e.g., from feces, urine or other excretions) typically occurs centrally within the pad, central placement of the sensor provides a more reliable method of detecting bacteria. The central location may be achieved, for example, by the presence of a sleeve to hold the cable in place or by a loop of material through which the cable can be routed. In certain embodiments, the cable may be woven into the fabric of the pad.

[0077] It will be appreciated that the light source, detector and further processing system require a power source. The power source may be integrated within the detection system (i.e. a cell or battery), or (e.g. in a clinical setting) the system may include a connection (e.g. via a power connection on a USB connector) to an external low voltage power source that is also used to charge the cell or battery.

[0078] The fluorescence detection system may include a compact housing for containing the reusable components (light source, detector, communication module, signal processing unit, etc.), which may fit into a pocket of a diaper or the like. The housing may have an opening therein that defines an optical port, as outlined below.

[0079] The housing may comprise a means for resetting the system when the incontinence pad is replaced, such as a push button or switch. Alternatively, the system may be reset via an external data link, as described below. The housing may further comprise an indicator configured to alert the user when a positive identification of bacteria occurs. The indicator may be a visible light, a sounder, a buzzer. A vibration alert system may be preferred if the fluorescence detection system is to be worn by a wheelchair-bound user, for example.

[0080] The fluorescence detection system may further comprise an optical port for receiving an end of a connecting fiber. The connecting fiber may further comprise a magnetic portion at one end configured to magnetically lock onto a magnet on or in the port. Thus, the connecting fiber can be selectively attached (e.g., plugged / unplugged) to the optical port, thereby allowing a leaky fiber optic cable to be integrally formed into a disposable part (such as an incontinence pad, diaper, or disposable test probe) while allowing the remaining components in the housing to be reused.

[0081] The optical port may further comprise a sensor 85 for detecting whether the connecting fiber is properly inserted into the port or whether the connecting fiber has been cut. The sensor 85 may be configured to transmit this "fiber connect / disconnect" signal to the processing and communication units as shown in Figure 8 and described below. Alternatively, cable sensing may be performed by sensing the reflection from an open connector.

[0082] Figure 8 includes an optical path 81 (or electrical connections if the light source and detector are located within the pad) connected to an optical detection subsystem 82, such as the systems or configurations described in connection with any of Figures 4-7. The optical detection subsystem 82 provides electrical signals 82a, 82b corresponding to the fluorescence excitation and emission signals, respectively. These signals are processed by electronic amplifiers, filters, and / or driver circuitry 83 using designs well known to those skilled in the art of processing electrical signals, and are used to drive electrical signals from the light source and optoelectronic devices using synchronous detection techniques, fluorescence lifetime detection, or using an optical spectrometer.

[0083] The data stream 83a may be passed to a digital processing unit 84 to process the data and determine a positive or negative identification of the feces. The digital processing unit may perform further functions such as detecting if the light guide is plugged in, via a link 85a to a sensor 85, to detect if the fluorescence exceeds a preset baseline threshold. The system may include a light source 84c and / or an audible sounder 84d that illuminates or emits a sound to indicate a positive identification of the feces. The sounder 84d may also be a vibration signaling device such as those used in mobile phones. The system may also include a push button or switch 84b to reset the system to a state of negative identification, i.e. no bacteria detected.

[0084] Additionally, the digital processing unit 84 may provide information 84a to a system control unit 86 which logs the acquired information and provides this information to an optional data link 89 via connector 89a to an optional external data bus (e.g., Universal Serial Bus, USB) and / or to an optional wireless transceiver unit 87, such as a wireless modem or other wireless transceiver, which links to other devices via radio frequency 87a.

[0085] The control unit 86 may include power distribution from a battery 89 and a system for charging the battery either from a USB port or a wireless charging device 88a.

[0086] The data may include information indicating that the bacteria was positively identified and / or a timestamp indicating the time the positive identification was made. Upon a positive identification, the transmitted data may trigger an external device alert to be generated, such as an audio, buzzer, light, text message, or other notification to a user. Additionally, the transmitted data may include status information of the detection system, such as battery level, and / or a "fiber connect / disconnect" signal (as described below).

[0087] A user may use one or more external devices to transmit to the communication module to configure the detection system. For example, if the external device is a smartphone or computer, the user may use an installed software application for configuration. Configuration may include identifying the patient and resetting the detection system to a state of negative identification, i.e., no bacteria were detected. If periodic detection is performed, configuration may include selecting a time interval and duration for detection, as outlined above.

[0088] Multiple detection systems may communicate with a single external device, for example, a nurse or doctor may monitor data for multiple patients.

[0089] 9 shows a method comprising a first step S1 of illuminating a target with light, and a second step S2 of monitoring the target for fluorescence. Optional further steps of this general method are described above.

[0090] Although the present invention has been described with respect to the above preferred embodiments, it should be understood that these embodiments are merely exemplary and the claims are not limited to these embodiments. Those skilled in the art can make modifications and alternatives in light of the disclosure that are believed to fall within the scope of the appended claims. Each feature disclosed or illustrated in this specification may be incorporated into the present invention alone or in any suitable combination with any other feature disclosed or illustrated in this specification.

Claims

1. 1. A method for determining the presence of human feces using fluorescence from bacteria prevalent in human feces, comprising: irradiating the target with excitation light having an excitation wavelength in the range of 500 nm to 645 nm; monitoring emission of fluorescent light from said target having an emission peak within the range of 675 nm to 735 nm; The method includes:

2. The method of claim 1 , wherein the illumination is performed using a source light guide, the source light guide being positioned to include a plurality of leaks along a length of the source light guide.

3. The method of claim 1 , wherein the wavelength of the excitation light has a central wavelength of substantially 635 nm.

4. 4. The method of claim 1, wherein the excitation wavelengths include a plurality of wavelengths corresponding to one or more porphyrin Q bands.

5. 5. The method of claim 1, wherein the target is a container for receiving bodily fluids or bodily exudates.

6. 6. The method of claim 5, wherein the container is an incontinence pad, a diaper or nappy, or a container for receiving a sample of a body fluid or body waste outside the body.

7. The method of claim 1 , further comprising modulating the intensity or frequency of the excitation light.

8. 8. The method of claim 7, further comprising the steps of detecting a corresponding modulation in light emitted by the target and filtering out emitted light without the modulation.

9. 8. The method of claim 7, further comprising the step of detecting a fluorescence lifetime associated with the sample fluorescence, said lifetime being detected using a time-resolved or phase-resolved detection technique.

10. 10. The method of claim 1, further comprising the steps of providing a light source and coupling light output from the light source into a light guide, and wherein the irradiating step is performed by light emitted from the light guide, optionally the light guide being an optical fiber.

11. The method of claim 10 , wherein the step of monitoring comprises monitoring light coupled from the target into the light guide.

12. 12. The method according to claim 10 or 11, further comprising the step of providing the light source and / or detector in an incontinence pad, nappy or diaper.

13. measuring the emission of fluorescent light; comparing said luminescence to a predetermined threshold; The method of claim 1 , further comprising:

14. 14. The method of claim 1, further comprising detecting a wavelength spectrum of the fluorescent light.

15. 15. The method of claim 1, further comprising detecting a fluorescence lifetime of the fluorescent light.

16. 16. The method of claim 1, further comprising the step of generating a signal to notify a user of the presence of bacteria.

17. 1. A detection system configured to determine the presence of human feces using fluorescence from bacteria prevalent in human feces, comprising: a light source configured to emit light in the range of 500 nm to 645 nm; a light source optical fiber optically coupled to the light source; a receiver optical fiber; a detector configured to detect light in a range of 675 nm to 735 nm, the detector being optically coupled to the receiver optical fiber; a signal processing unit configured to determine a positive identification of human feces based on a plurality of electronic signals, the plurality of electronic signals indicating that the light detected by the detector has an emission peak in a range of 675 nm to 735 nm; A detection system comprising:

18. 20. The detection system of claim 17, wherein the source optical fiber and the receiver optical fiber are the same optical fiber or are different optical fibers.

19. 20. The detection system of claim 17, wherein the light source optical fiber is a fiber optic cable comprising a core and a cladding, the cladding comprising a plurality of discontinuous portions that provide optical paths for light coupled to or from the light source optical fiber.

20. 20. The detection system of claim 19, wherein the fiber optic cable is configured to transmit light from a proximal end to a distal end, and the discontinuities are arranged in a non-linear pattern in which adjacent gaps are positioned increasingly closer to each other toward the distal end of the fiber optic cable to maintain a constant degree of light leakage along the cable.

21. 21. The detection system of claim 17, 19 or 20, wherein the light source optical fiber and the receiver optical fiber are the same optical fiber, the optical fiber optically coupled to the detector and the light source, and the detector and the light source coupled to the optical fiber at the same end of the optical fiber or at opposite ends of the optical fiber.

22. 22. The detection system of claim 17, further comprising a pad, the source optical fiber and / or the receiver optical fiber being attached to or integrally formed with the pad.

23. 23. The detection system of any one of claims 17 to 22, further comprising a communication module for transmitting and / or receiving data from one or more external devices.

24. 24. The detection system of any one of claims 17 to 23, further comprising an alarm, the alarm being one of an optical alarm, an acoustic alarm, or a tactile alarm.

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