Method and apparatus for sensing the presence of microbes

• US 5,968,766 A
• Filed: 03/31/1998
• Issued: 10/19/1999
• Est. Priority Date: 03/31/1998
• Status: Expired due to Term

• Current Assignee: Microbiosystems, LP
• Original Assignee: Be Safe
• Inventors: Powers, Linda
• Primary Examiner(s): Leary, Louise N.
• Application Number:
  US09/052,460
• Time in Patent Office: 567 Days
• Field of Search: 435/29, 435/4, 435/283.1, 435/285.2
• US Class Current: 435/29
• CPC Class Codes: G01N 21/6486 Measuring fluorescence of biological material, e.g. DNA, RNA, cells G01N21/6428 takes precedence
• CPC Class Codes: G01N 21/94 Investigating contamination, e.g. dust G01N21/85 takes precedence

Abstract

Method and apparatus for the detection of aerobic microbes on non-living surfaces in which electromagnetic radiation having a wavelength greater than 350 nm is directed onto the surface to cause excitation of pyridine nucleotides present in microbial cells to emit radiation having a higher wavelength. That higher wavelength radiation and reflected radiation is then sensed as a measure of the amount of microbial cells on the surface.

Claims

1. A method for the detection of microbes in an environment comprising the steps of:

(a) directing electromagnetic waves into an environment, said electromagnetic radiation having a wavelength greater than 350 nm, whereby any microbial cells present in the environment and containing nicotinamide adenine pyridine nucleotides are excited to emit fluorescence having an energy less than the excitation energy and whereby some of said electromagnetic radiation is reflected in said environment, and

(b) sensing the fluorescence and the reflected electromagnetic radiation as a measure of the amount of microbes present in said environment.

2. The method is defined in claim 1 wherein the electromagnetic radiation having a wavelength within the range of about 350 to 400 nm.

3. The method is defined in claim 1 wherein the electromagnetic radiation having a peak wavelength of about 366 nm.

4. The method is defined in claim 1 which includes the step of filtering the electromagnetic radiation emitted by the microbial cells to isolate a narrow band of wavelengths.

5. The method is defined in claim 1 wherein the electromagnetic radiation emitted by the microbial cells is filtered to provide a peak wavelength of about 440 nm.

6. The method as defined in claim 1 wherein the electromagnetic radiation has a wavelength greater than about 350 nm to cause fluorescence of microbes in said environment and wherein the fluorescence exhibits a wavelength greater than about 400 nm.

7. The method as defined in claim 1 which includes the steps of directing electromagnetic radiation having two wavelengths, one of said wavelengths being greater than about 350 nm and the other of said wavelengths being less than about 340 nm, whereby the higher wavelength excites fluorescence of microbial cells and the lower wavelength excite fluorescence of another component present in the environment.

8. The method as defined in claim 1 wherein the environment is a meat or poultry surface and the electromagnetic radiation directed thereto have one wavelength greater than about 350 nm to cause fluorescence of microbial cells present on the surface and another wavelength less than about 340 nm to excite fluorescence of fat, cartilage or bone present on the surface of the sample.

9. The method as defined in claim 1 which includes the step of sensing the fluorescence of microbial cells and sensing the electromagnetic radiation reflected by said environment and determining the difference or ratio therebetween as a measure of the amount of microbes present in said environment.

10. The method as defined in claim 1 which includes the step of filtering the electromagnetic radiation directed into the environment to provide a narrow band of wavelengths of said electromagnetic radiation directed into the environment.

11. The method as defined in claim 1 wherein the electromagnetic radiation directed into the enviroment is filtered to provide a peak wavelength of about 366 nm.

12. The method as defined in claim 1 which includes the step of rotating a rotary filter to filter the electromagnetic radiation directed into the environment to generate timed pulses of electromagnetic radiation directed into the environment having two discrete bands of wavelengths, one of said bands having wavelengths predominantly greater than 350 nm and the other of said bands having wavelengths predominantly less than 340 nm whereby said one band excites the fluorescence of microbial cells present in the environment and said other band excites the fluorescence other substances present.

13. The method as defined in claim 1 which includes the step of rotating a rotary filter to filter the electromagnetic radiation emitted from said environment to receive timed pulses of electromagnetic radiation having two discrete bands of wavelengths, one of said bands having wavelengths predominantly above about 400 nm as a measure of the fluorescence of microbial cells and the other of said bands having energies near that of the excitation radiation as a measure of electromagnetic radiation reflected by said environment.

21. The method as defined in claim 1 wherein the electromagnetic waves are directed into the environment in time-modulated pulses.

14. Apparatus for the detection of microbes on a non-living environment comprising:

(a) means for directing electromagnetic radiation toward an environment, said means adapted to emit radiation having wavelengths greater than 350 nm and excite microbial cells in the environment to emit fluorescence;

(b) a detector for electromagnetic radiation capable of converting the radiation into an electrical signal, said detector adapted to detect electromagnetic radiation at wavelengths above about 400 nm as a measure of microbial cells present in the environment and to detect electromagnetic radiation having energies near that of the excitation radiation as a measure of the electromagnetic radiation reflected by the environment; and

(c) means for receiving electrical signals corresponding to the fluorescence of the microbial cells and electrical signals corresponding to the electromagnetic radiation reflected by the environment and determining the amount of microbes in the environment.

15. The apparatus as defined in claim 14 wherein the means for directing electromagnetic radiation is adapted to direct electromagnetic radiation of at least two discrete bands of wavelengths, one of the bands having wavelengths above 350 nm to excite the fluorescence of microbial cells and the other of the bands having wavelengths below about 340 nm as a measure of another characteristics of the environment.

16. The apparatus as defined in claim 15 wherein the means for directing electromagnetic radiation includes at least two excitation filters, one of the filters passing electromagnetic radiation having wavelengths predominantly above 350 nm and the other of the filters passing electromagnetic radiation having wavelengths predominantly below 340 nm.

17. The apparatus is defined in claim 16 wherein said filters are in the form of two arcuate segments mounted for rotation, one segment adapting to pass electromagnetic radiation having wavelengths predominantly above 350 nm and the other segment adapted to pass electromagnetic radiation having wavelengths predominantly below 340 nm whereby rotation of the filter generates timed pulses of electromagnetic radiation having wavelengths predominantly above 350 nm and electromagnetic radiation having wavelengths predominantly below 340 nm.

18. The apparatus is defined in claim 14 which includes a probe, said probe including fiber optic elements adapted to transmit excitation electromagnetic radiation from the means for directing electromagnetic radiation and fiber optic elements attached to transmit emission electromagnetic radiation from the sample to the detector.

19. The apparatus is defined in claim 14 which includes means for scanning the fluorescence signals, including means for moving said means for directing electromagnetic radiation along an X and Y axes to provide a raster illumination of the sample.

20. The apparatus as defined in claim 19 which includes at least two emission filters, one filter adapted to pass electromagnetic radiation having wavelengths predominantly above 400 nm and the other of said filters adapted to pass electromagnetic radiation having energies near that of the excitation radiation whereby the electromagnetic radiation passed through the filter having wavelengths above 400 nm corresponds to the microbial content of the environment and the electromagnetic radiation passed through the filter having energies near that of the excitation radiation corresponds to the amount of light reflected by the environment.

22. The apparatus as defined in claim 17 wherein the means for directing electromagnetic radiation includes means for time-modulating the electromagnetic radiation as pulses.