Richard A. Harvey

The role of antibiotic bonding in the prevention of vascular prosthetic infections.

Oxacillin, a negatively charged antibiotic, was bonded to polytetrafluoroethylene (PTFE) grafts using the cationic surfactant, benzalkonium chloride. Control PTFE grafts and bonded grafts prepared at room temperature and at 90 C were placed in the infrarenal aorta of dogs and challenged by local contamination with Staphylococcus aureus. Bonded grafts were superior to controls in negative cultures, patency, and survival. The possible role of antibiotic bonding in the prevention of vascular prosthetic infection is discussed.

Prevention of vascular prosthetic infection with an antibiotic-bonded Dacron graft***★

Surfactant-mediated antibiotic bonding was used in an animal model of aortic prosthetic infection. Control grafts, control plus parenteral oxacillin, and oxacillin-bonded Dacron grafts were challenged by local inoculation with Staphylococcus aureus. Ninety percent of controls, 80% of parenteral antibiotic recipients, and only 30% of antibiotic-bonded Dacron grafts became infected (p less than 0.01, p less than 0.03). Antibiotic-bonded grafts were also superior in terms of suture line cultures and patency. In separate experiments in a subcutaneous pouch model, antibiotic bonding significantly improved the median infective dose of Dacron over that of controls and Dacron soaked in cephalosporin. These studies demonstrate that antibiotic-bonded Dacron implants are highly resistant to infection. A multicenter clinical trial is planned.

The noncovalent bonding of antibiotics to a polytetrafluoroethylene-benzalkonium graft.

This study evaluates the noncovalent bonding of anionic antibiotics to polytetrafluoroethylene grafts using hciual-konium chloride as u cationic anchor. The binding of radiolabeled surfactants and antibiotics was evaluated by liquid scintillation and in an in vitro microbiologic assay against Staphylococcus aureus. Significant quantities of antibiotic were bound when the grafts were pretreated with benzalkonium in ethanol or aqueous solution at elevated temperature. Bound antibiotic is stable in aqueous salt solutions, but slowly dissociates in the presence of blood or serum. The ionic nature of the bonding process is clarified by the use of a variety of antibiotics and surfactants with complementary charges. The ability of the bcn/.alkonium treated grafts to adsorb antibiotic from blood is, likewise, demonstrated and the possibility of concomitantly binding heparin and antibiotic simultaneously is evaluated. These studies support the ability to noncovalently bond antibiotics to polytetrafluoroethylene surfaces and form the basis for eventually utilizing these surfaces in the prevention of vascular prosthetic infections

Infection-Resistant Continuous Peritoneal Dialysis Catheters

The techniques of bonding of anionic antibiotics by treatment with cationic surfactants were applied to continuous ambulatory peritoneal dialysis (CAPD) catheters. The elution of 14C-penicillin from tridodecylmethylammonium chloride (TDMAC) treated silicone elastomer catheters in dialysis solution was biphasic, with 95% dissociated from the catheter by 48 h. Forty percent of the TDMAC left the catheter surface during the initial 2 days. The ability of the surfactant TDMAC to bind antibiotics after incubation in dialysis solution correlated directly with the amount of surfactant remaining. Rats with intraperitoneal dialysis catheters were inoculated with exit site and intraluminal bacterial challenges. Intraperitoneal catheter tips treated with TDMAC-penicillin were rendered more resistant to colonization after exit site and intraluminal bacterial challenges.

Noncovalent bonding of penicillin and cefazolin to dacron

Dacron grafts treated with the surfactant, benzalkonium chloride or TDMAC bind significant quantities of penicillin-14C or cefazolin-14C. The treated grafts showed strong antibacterial activity which indicated that bound radioactivity corresponds to the reversible adsorption of biologically active molecules. Bound penicillin-14C or cefazolin-14C slowly dissociates when the grafts are placed in a surgically prepared muscle pouch in the rat. This slow release of antibiotic produces therapeutic levels of antibiotic in the adjacent tissue. Binding can also be achieved by in situ irrigation of surfactant treated grafts with antibiotic or by injection of the antibiotic.

The biochemical bonding of cefoxitin to a microporous polytetrafluoroethylene surface

Cefoxitin was bound to a microporous polytetrafluoroethylene (PTFE) surface with tridodecylmethylammonium chloride (TDMAC). Bactericidal concentrations of cefoxitin were achieved with very small doses of the antibiotic. Elution of cefoxitin from microporous PTFE occurs by two concurrent first-order processes, each occurring at a different rate constant. Bound cefoxitin inhibits the growth of Staphylococcus aureus in a bioassay. Finally, cefoxitin can be adsorbed to TDMAC-treated microporous PTFE in vivo when the antibiotic is administered locally or intravenously. The application of antibiotic bonding to the prevention of vascular prosthetic infections is discussed.

A simple stopped-flow photometer

Abstract A stopped-flow photometer is described which is simple enough for teaching applications yet sufficiently versatile to serve as a nucleus for a research instrument. The rapid mixing device employs small sample volumes (typically 20 μl of each reactant) and features a mixing time of 4 milliseconds, a pneumatic drive mechanism, and temperature control for the reactants. Rapid reactions can be monitored by changes in transmittance or fluorescence or by measuring simultaneous changes in transmittance and fluorescence. A photometric system with all solidstate electronic components is described along with an oscilloscope triggering circuit.

Antibiotic bonded nephrostomy catheters for percutaneous nephrostomies

A prospective controlled trial of the effectiveness of a cefoxitin-bonded nephrostomy catheter was undertaken to determine the effectiveness of an antibiotic bonded catheter in decreasing the infectious complications of percutaneous nephrostomy. The study concludes that bonding of the antibiotic cefoxitin to percutanoeus nephrostomy catheters did not influence the incidence of bacteriuria or urinary tract infection. In addition, observations on the overall incidence of complications from percutaneous nephrostomy are made.

Patency of a Small Vessel Prosthesis Bonded to Tissue Plasminogen Activator and Iloprost

To test the thrombosis resistance of a vascular prosthesis coated with antithrombogenic agents, we evaluated a small vessel prosthesis of expanded polytetrafluoroethylene (ePTFE) implanted in the rat aorta and removed 1 week following surgery. Control grafts consisted of 1 mm internal diameter ePTFE. Experimental grafts consisted of 1 mm internal diameter ePTFE noncovalently bonded to tissue plasminogen activator (tPA) and iloprost using the surfactant tridodecylmethylammonium chloride. After 1 week the grafts were harvested, patency was determined, and histologic specimens were prepared for electron microscopy. Six of 10 control grafts were thrombosed, whereas 9 of 10 tPA-iloprost-bonded grafts were patent (p<0.03). Of concern, there was an unexpectedly high mortality rate in the tPA-iloprost group compared to the control group among animals that died before completion of the study. Evaluation of the safety of these drugs must, therefore, be an early component of future experiments. Nevertheless, these studies indicate that a small vessel prosthesis bonded to tPA and iloprost may ameliorate some of the complications associated with early graft failure.

Heterogeneity in the rapidly exchanging metals of horse liver alcohol dehydrogenase

Abstract Substitution of the two rapidly exchanging zinc atoms of liver alcohol dehydrogenase by cobalt is biphasic; replacement by the first cobalt occurs at a rate ( t 1 2 = 15 minutes ) approximately ten times faster than substitution by the second cobalt atom. The hybrid enzyme containing one gram atom of cobalt has a characteristic visible absorption spectrum which is not perturbed by NADH or 1,10-phenanthroline. The fluorescence of NADH or e-NAD bound to the hybrid is not quenched. These data indicate a previously unrecognized heterogeneity in the rapidly exchanging zinc atoms; one of the exchange labile zinc atoms is located at a structural metal binding site rather than an active site.