Method for the Detection of Microorganisms by Fiber Optics

Abstract

The objective of the present invention is the detection / monitoring of microorganisms present in the air, water or foodstuffs through the use of a fiber optic biosensor with an evanescent-field. A first concretization of the present invention concerns a method for detection of contamination by specific microorganisms through the use of the evanescent-field of a sensitive fiber optic characterized by stages of: a) exposing the evanescent-field of the sensitive fiber optic using an appropriate technique based on physical and chemical properties; (b) permitting immediate contact of the exposed evanescent-field obtained in the stage (a) with the sample to be examined, with the aforementioned sample having a form adequate so as to obtain the generation of an optical signal in response to the presence of microorganisms in the sample; and, (c) demodulating the optical signal generated in stage (b) and using this value to quantify the microorganisms through an appropriate method. In a second concretization, the invention is directed to a composition for use in the detection of microorganisms characterized by comprising a selective culture medium for microorganisms needing to be detected and reactants capable of altering the properties of the medium to favor the interaction of the system fiber-microorganism interaction. In a third concretization the invention refers to a device for surveying microorganisms through the insertion of a sensitive fiber optic (11), with an adequately exposed evanescent-field, into a surface or volume of a biological culture medium (12) specific for the microorganism to be detected, comprising a demodulation system based on a fiber optic circuit and related components.

Description

[0001] The present invention refers to a method and device for the detection of microorganisms using a combination of microbiological procedures with devices constructed with fiber optics and related components.[0002] The microbiological procedures enable the microorganisms to be selectively cultivated and these, when in physical contact with a conveniently constructed fiber optic circuit, permit the detection and monitoring of the microorganisms in a fast and accurate way. The device overall is physically consisted of three subsystems:BACKGROUND OF INVENTION[0003] Microorganisms are life forms that despite their micrometrical size scale significantly affect human life. They may constitute viruses, bacteria, fungi, protozoa and algae. They are present in solids, liquids and air; and in all cases it may be of vital interest or importance to detect the specific presence and / or to monitor, qualitatively or quantitatively, the growth over time of one or more of these microorganisms. Man...

AI Technical Summary

Benefits of technology

[0037] This material medium may also be constituted of fluids of a corporal nature such as water, blood, urine, etc. In this last case, microorganisms may be present and reproduce throughout the volume of the fluid. The segment of sensitive optical fiber should be conveniently placed on the surface or inserted in the volume of the biological culture medium. Beforehand, however, this fiber shall have an area of its primary covering removed and will undergo a treatment employing an appropriate technique based on chemical and physical properties. This treatment aims to expose the evanescent-field of the optical fiber through etching, for instance, using, preferably, strong acids, such as hydrofluoric, hydrochloric, sulfuric acids, for instance. It is necessary that the treatment lasts for the time necessary to etch the sheath of the optic fiber to an approximate thickness of 0.5 to 1 .mu.m from the core. In this way, it is possible to expose approximately 80% of the evanescent-field. The etching is interrupted by the immersion of the fiber in deionised water and, afterwards, in a pH stable solution for an adequate time to remove any residue of water. Thus, it is possible to couple the evanescent-field of the means of guided propagation to the material medium containing the subject (microorganisms). The sensitive fiber optic, in turn, is inserted continuously in a larger fiber optic circuit, having a particular assembly with the aim of demodulating the optical signal modulated by the subject. These characteristics confer to the invention operational advantages of biological selectivity, sensitivity, resolution, response velocity, stability, possibility of miniaturization, ease of operation and easy incorporation into larger and more complex optical circuits that are destined to compose a survey network (overall survey) in a manner that microorganisms may be detected / monitored in various places simultaneously. The sensor technology described here should be employed preferably for biological detection / monitoring in a qualitative and / or quantitative manner having a specific microorganism as subject.

Problems solved by technology

Other microorganisms do not seem to serve any other practical purpose, but are, in principle, harmless to human health.

However, some of these microorganisms may become dangerous, for a series of reasons, after undergoing certain types of biological transmutations and whereupon they are termed pathogenic.

Other types of microorganisms may be intrinsically dangerous, meaning that they are naturally constituted as noxious to human health.

These techniques are reasonably complex, as they demand from the operator significant intervention and skill in order to obtain dependable results, and typically require 1 to 10 days for completion.

Apart from which, the conventional techniques use equipment that is not particularly low cost, making its employment difficult or unviable for widespread surveying, in other words, for detection / monitoring of microorganisms in more than one place simultaneously.

Concerning the techniques mentioned, there are some practical restrictions such as, for example, their success is highly dependent on the quantity of bacteria that can be concentrated in the test sample.

In molecular reactions, the test procedures are particularly liable to cross contamination by other molecules or molecular fractions.

On the other hand, the medical knowledge for fighting pathogenic microorganisms that had already infected the human body, especially those originating from hospital infection, food poisoning and water contamination, is vast but incomplete.

However, it presents the disadvantage of the analysis taking approximately 7 to 14 days, as described by Birron and Lai (B. Birron and E. Lai. "Pulsed field electrophoresis: a practical guide".

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