Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Wearing apparel – fabric – or cloth
Reexamination Certificate
2001-06-07
2003-07-15
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Wearing apparel, fabric, or cloth
C424S402000, C424S422000, C424S423000, C424S449000, C424S443000, C424S484000
Reexamination Certificate
active
06592885
ABSTRACT:
BACKGROUND OF THE INVENTION
Any penetration of the skin carries with it the risk of potential infection. This risk pertains to simple wounds incurred by accident or negligence; to surgical procedures performed under controlled conditions which utilize different biomaterials for the closure and dressing of incisions and/or wounds; and to a diverse range of in-vivo implantable textile fabrics, configured textile articles, and textile-containing mechanical appliances and devices which are surgically introduced into the body for diagnostic, therapeutic and/or prosthetic purposes.
The rational use of antimicrobial agents against infection, particularly for simple wound treatment, has been advocated generally and has been previously reviewed in detail [Rodgers, K. G.,
Emer. Med. Clin. N. Am
. 10: 753 (1992)]. Similarly, the major concerns regarding the ever-growing incidence of infections resulting from biocompatible textiles, articles and devices implanted in the body—espite recent advances in sterile procedures used in the clinical/surgical setting—have been considered and reviewed as the primary purpose and focus of a FDA/EPA/CDC/AAMI joint conference [Proceedings, Infection Control Symposium: Influence Of Medical Device Design, U.S. Dept. of Health and Human Services, Bethesda, Md., January 1995]. Moreover, the use of antibiotics and of mechanisms for delivering antimicrobial agents generally, particularly via slow-release delivery systems over time, to prevent or reduce severity of infection for implanted biodegradable materials has been reviewed [Sasmor et al.,
J. Vasc. Sur
. 14: 521 (1993)]. All of these considerations lead to the same conclusion: Infection, with or without the use of antibiotics, must be prevented or be controlled for all implantable biomaterials (including textiles, articles and devices) regardless of need or medical purpose.
Infection of Implantable Biomaterials
Infection of implantable biomaterials, specifically prosthetic vascular grafts, is an ever-growing problem and concern. For example, prosthetic vascular grafts, which are composed primarily of either polyester or polytetrafluoroethylene (PTFE), are a source of significant clinical morbidity and mortality upon infection [Goldstone, J. and W. S. Moore,
Am. J. Surg
. 128: 225 (1974); Liekweg et al.,
Surgery
81: 335 (1977); Bunt, T. J.,
Surgery
93: 733 (1983); Golan, J. F.,
Infect. Dis. Clin. N. Am
., 3: 247 (1989); Sugarman, B. and E. J. Young,
Infect. Dis. Clin. N. Am
. 3: 187 (1989)], significantly impacting patient quality of life. Graft infection occurs in 2-6% of all clean cases performed [Hoffert et al.,
Arch. Surg
. 90: 427 (1965); Fry, W. L. and S. M. Lindenauer,
Arch. Surg
. 94: 600 (1966); Rittenhouse et al.
Ann. Surg
. 170: 87 (1969); Drapanas et al.,
Ann. Surg
. 172: 351 (1970); Szilagyi et al.,
Ann. Surg
. 176: 321 (1972)], with morbidity and mortality related to the anatomic position of the graft. Infectious inoculation of the biomaterial presumably occurs at the time of implantation or as a result of transient bacteremia in the immediate post-operative period [Cheri et al.,
J. Vasc. Surg
. 14: 521 (1991)]. Peri-operative parental antibiotics, while having a defined role in wound infection prophylaxis, often fail to permeate the avascular spaces immediately around prosthetic grafts as well as the carbohydrate-rich bacterial biofilm once pathogens have adhered [Gristina, A. G., Science 237: 1585 (1987); Kaiser et al.,
Ann. Surg
. 188: 283 (1978); Greco, R. S.,
J. Vasc. Surg
. 13: 5 (1991); Bandyk et al.,
J. Vasc. Surg
. 13: 575 (1991)].
The two main types of bacteria responsible for graft infection are the coagulase negative
Staphylococcus aureus
(
S. aureus
) and
Staphylococcus epidermidis
(
S. epidermidis
).
S. aureus
has been shown to be responsible for 65-100% of acute (days to weeks) infections (3,14). Typically, these infections develop rapidly and generate an intense response by the host defense mechanisms. An ever-increasing problem (which has been documented both in animal models and in humans) is the susceptibility of vascular prostheses to later (months to years) infection.
S. epidermidis
has emerged as the leading isolate from infection vascular conduits (20-60%) with infection appearing late after implantation. Both of these instances are clearly not affected by low level antibiotic transiently occurring at the time of surgery. A decreased amount of antibiotic may also play a role in the development of resistant organisms.
Health care costs for graft infection should also be considered since the onset of this complication results in elevated patient care costs. In 1989, approximately $150M was spent on the implantation of synthetic arterial grafts in the United States. Using the estimated infection rates, approximately $3 to $9 million has been spent to implant another vascular graft external of the infection site, a procedure required to prevent subsequent infection and failure of the replacement graft. The cost of treating infection, the mortality that occurs in some 25% of infected cases and inflation also must be included. Thus, the overall total impact of graft infection on health care costs can only be estimated, however, the magnitude of the problem is extremely significant, driving the research to develop infection-resistant biomaterials.
Conventional Efforts To Combat Graft Surface Infections
Numerous strategies have been attempted in order to create an infection-resistant graft surface for biomaterials. Chelating agents have been evaluated as a release system for antibiotics from a biomaterial surface. One approach which has been the subject of numerous investigations was the ionic binding of antibiotics by surfactants. Cationic surfactants such as tridodecylmethyl ammonium chloride and benzalkonium chloride were sorbed at the anionic surface potential of a polymeric material, thereby permitting weak adhesion of anionic antibiotics to the surface [Harvey et al.,
Ann. Surg
. 194: 642 (1981); Harvey et al.,
Surgery
92: 504 (1982); Harvey et al.,
Am. J. Surg
. 147: 205 (1984); Shue et al.,
J. Vasc. Surg
. 8: 600 (1988); Webb et al.,
J. Vasc. Sur
. 4: 16 (1956)]. The selected antibiotic was then released upon contact with blood. Silver was also examined as a release system for various antibiotics from graft surfaces, applied either as a chelating agent [Modak et al.,
Surg. Gynecol. Obstet
. 164: 143 (1987); Benvenisty et al.,
J. Surg. Res
. 44: 1 (1988); White et al.,
J. Vasc. Surg
. 1: 372 (1984)] or alone due to its antimicrobial properties.
Binding agents have also been employed in order to create localized concentrations of antibiotic on the graft surface. These agents, which were either protein or synthetic-based, were embedded within the biomaterial matrix thereby either “trapping” or ionically binding the antibiotic. The basement membrane protein collagen has served as a release system for rifampin, demonstrating antimicrobial efficacy in a bacteremic challenge dog model [Krajicek et al.,
J. Cardiovasc. Surg
. 10: 453 (1969)] as well as in early European clinical trials [Goeau-Brissonniere, O.,
J. Mal. Vasc
. 21: 146 (1996); Strachan et al.,
Eur. J. Vasc. Surg
. 5: 627 (1991)]. Fibrin, either as a pre-formed glue or in pre-clotted blood, has been utilized as a binding agent for various antibiotics including gentamycin, rifampin and tobramycin [Haverich et al.,
J. Vasc. Surg
. 14: 187 (1992); McDougal et al.,
J. Vasc. Surg
. 4: 5 (1986); Powell et al.,
Surgery
94: 765 (1983); Greco et al.,
J. Biomed. Mater. Res
. 25: 39 (1991)].
Levofloxacin has been incorporated in an albumin matrix and gelatin has been used as the release system for the antibiotics rifampin and vancomycin, with animal studies also showing efficacy in acute bacteremic challenges [Muhl et al.,
Ann. Vasc. Surg
. 10: 244 (1996); Sandelic et al.,
Cardiovasc. Surg
. 4: 389 (1990)].
Synthetic binders have also been evaluated for
Bide Martin J.
LoGerfo Frank W.
Phaneuf Matthew D.
Quist William C.
Ghali Isis
Page Thurman K.
Prashker David
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