A swine model for the evaluation of efficacy of anti-microbial catheter coatings

A swine model was developed to investigate the efficacy of percutaneous venous catheters with anti-microbial coatings. The catheters used in the study consisted of silver-coated and uncoated catheters, both designed for percutaneous venous access. Five commercial pigs were each implanted with three venous catheters and followed for a period of 90 days. Two of the three catheters were coated and one was uncoated. To evaluate the percutaneous aspects of the catheters in the model, two venous access catheters were implanted percutaneously, parallel to the dorsal midline. These catheters were just caudal to the region that is dorsal to the scapula in each animal. In each case, the catheter to the left of the dorsal midline was silver-coated while the catheter to the right of the dorsal midline was uncoated. A silver-coated catheter was also implanted in the left external jugular vein of each animal and buried subcutaneously in order to evaluate the elution of the coating through the body under venous contact. Over the 90 day period, the concentration of silver in the blood rose to a mean peak level of 23.2 ppb following implantation of the catheters and then decreased after the second post-surgery week. The histological evaluation and macroscopic inspection at necropsy revealed minimal tissue response to both coated and uncoated materials. Data on bacterial growth indicated that bacteria were present at the terminal subcutaneous end of two of the uncoated percutaneous catheters. Based upon serum silver levels, exudate formation, histological examination, and bacterial growth information, the swine model was deemed to be suitable for testing the efficacy of catheters containing anti-microbial coatings.