Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment
Reexamination Certificate
1999-11-10
2001-07-10
Wong, Edna (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
C205S692000, C606S032000, C606S122000, C606S126000
Reexamination Certificate
active
06258249
ABSTRACT:
BACKGROUND OF THE INVENTION
It has been reported that a biofilm is a conglomerate of microbial organisms embedded in a highly hydrated matrix of exopolymers, typically polysaccharides, and other macromolecules (see U.S. Pat. Nos. 5,312,813 and 5,462,644, and references cited therein). Biofilms may contain either single or multiple microbial species and readily adhere to such diverse surfaces as river rocks, soil, pipelines, teeth mucous membranes, and medical implants. By some estimates biofilm-associated cells outnumber planktonic cells of the same species by a ratio of 1000-10,000:1 in some environments.
Prevention of colonization by and eradication of biofilm-associated microorganisms is an important, and often difficult to solve, problem in medicine. Unlike planktonic organisms, which are relatively susceptible to biocides, e.g., antibiotics, the structural matrix established during biofilm formation can make the colonizing cells able to withstand normal treatment doses of a biocide. It is known that when organisms are isolated from biofilms and then grown in planktonic culture, they lose many of the characteristics associated with the progenitor cells, in particular the ability to produce a glycocalyx. In the biofilm, the glycocalyx matrix appears to serve as a barrier which protects and isolates the microorganisms from host defense mechanisms, such as antibodies and phagocytes, as well as from antimicrobial agents including surfactants, biocides and antibiotics. The aforementioned patents report that in one study, biofilm-associated bacteria were able to survive a concentration of antibiotic 20 times the concentration effective to eliminate the same species of bacteria grown in planktonic culture.
Biofilm infections can occur in a variety of disease conditions. In some tissue infections, such as prostatitis, the infective bacterium is capable of growing in the infected tissue in both biofilm (sessile) and circulating (planktonic) form. Although growth of the planktonic cells can be controlled by antibiotic treatment, the biofilm itself may be refractory to treatment, providing, in effect, a reservoir of infection which can lead to recurrence of the infection after antibiotic treatment.
Biofilm formation can also be a serious complication in bioimplants, such as bone prosthesis, heart valves, pacemakers and the like. Biofilm formation on exposed surface of a bioimplant can degrade the function of the implant, as in the case of implanted valves, lead to serious joint or bone infections, as in the case of a bone prosthesis, and in all cases, provide a source of difficult-to-treat septic infection. In the case of heart valve endocarditis cases a surgeon is forced to dissect all infected tissue, treat locally with antibiotics and antiseptics followed by valve replacement. Unfortunately, the treatment is often unsuccessful over time due to perivalvular leak caused by a continuing infection. If the surgeon had a more effective method of treating the infection during surgery, valve replacement outcomes could be improved.
While U.S. Pat. No. 5,312,813 discloses in vivo treatment of a urinary tract infection, for example, there is no mention of the treatment of an infection during the course of surgery. U.S. Pat. No. 5,462,644 is similar in this regard. In both these patents, in vivo treatment may instead be accomplished by administering a biocide orally with electrical current then being applied across the area to be treated. Thus, the in vivo treatment in these cases is accomplished by non-invasive means and outside of the context of surgery.
The present inventor has recognized that a need exists to enable surgeons to treat infected areas during surgery to thereby enhance probabilities for success of re-implant of a bio-prosthesis. The present invention provides a solution to one or more of the disadvantages and deficiencies described above.
SUMMARY OF THE INVENTION
The present invention provides a method of killing microorganisms in a biofilm within a human body that has been exposed during the course of surgery. In general, this method may be accomplished by surrounding the area to be treated that has been exposed to surgery with a composition containing a biocide and then providing an electrical current across the biocide composition. The biocide composition may be thickened or in the form of a gel.
In one broad respect, the invention comprises a method for the treatment of an infected area within a body, comprising applying an electrically conductive biocide composition to an infected area within a body that has been exposed during surgery, and applying an electric field to the biocide composition, wherein the electric field strength and duration of application are sufficient to produce killing of microorganisms in the infected area. In one embodiment, the source of electric field may be remote from the infection. That is, the infectious biofilm need not be in direct contact with the electrodes or source of the electric current. Preferable, the electric field strength and duration of application are sufficient to essentially eliminate the microorganisms of the infection or biofilm. As used herein, electrically conductive biocide composition refers to an aqueous composition typically containing an electrolyte, a buffer and one or more biocides. By biocides it is meant antibiotics, antiseptics, anti-fungal agents, disinfectants and sterilants. Alternatively, the biocide may be generated in situ upon application of an electric field to the electrically conductive medium.
The invention further provides a method for disinfecting or sterilizing devices infected with biofilms, wherein the device is implanted in a body, comprising applying an electrically conductive biocide composition to a device within a body that has been exposed during surgery, and applying an electric field to the biocide composition, wherein the electric field strength and duration of application are sufficient to produce killing of the microorganisms in the biofilm. In one embodiment, the biocides are present in a concentration which is less than effective to kill the biofilm microorganisms in the absence of the electric field. The electric field is preferably generated by currents between the electrodes of at least about 1 to about 200 milliamps, most preferably between about 1 and about 50 milliamps.
An alternative embodiment of this invention includes encapsulation of the surgical site between plates thereby creating a chamber which is filled with the electrically conductive biocide composition. An electrical current could then be applied to the plates, thereby providing current across the biocide composition.
REFERENCES:
patent: 4419248 (1983-12-01), Costerton
patent: 4542169 (1985-09-01), Costerton
patent: 4800959 (1989-01-01), Costerton et al.
patent: 5174378 (1992-12-01), Costerton et al.
patent: 5312813 (1994-05-01), Costerton et al.
patent: 5462644 (1995-10-01), Woodson
patent: 0 147 970 A1 (1985-10-01), None
Scott Timothy L.
Sulzer Carbomedics Inc.
Wong Edna
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