Piglet endocarditis

A total of 36 newly weaned piglets (16 to 20 days old, weighing 4.5 to 6.8 kg) were purchased from the Swine Research and Education Center at Auburn University for use in model development [bioluminescence imaging (BLI) only], fluorescence probe colocalization, and clinical PET/MRI studies. The animals were acclimated for 5 to 7 days before central-line implantation surgery. Piglets were sedated with dexmedetomidine (DEXDOMITOR, Zoetis) and butorphanol. An intravenous catheter was placed, and anesthesia was induced using a combination of ketamine (10 mg/kg; KETASET, Zoetis), dexmedetomidine (20 μg/kg), and butorphanol (0.4 mg/kg). A line block of 0.5% lidocaine (Xylocaine-MPF, Fresenius Kabi, USA) was placed before making a 3- to 4-cm incision just lateral to the midline. A combination of sharp and blunt dissection was used to identify and isolate the left jugular vein and then to create a subcutaneous pocket for the vascular access port (VAP; 5 Fr ClearPort, Access Technologies). The vascular port consisted of a titanium outlet with a silicone septum and catheter. A small jugular venotomy was made, and a 0.6-mm guide wire was introduced into the vascular lumen. The polyurethane VAP catheter was placed over the guide wire and advanced into the right ventricle under fluoroscopic guidance. Correct positioning of the catheter was confirmed using multiple injections of radiopaque contrast under fluoroscopic observation. Ports were implanted in the front right region of the neck. Once the desired catheter positioning was confirmed, the VAP catheter was secured within the jugular vein with several circumferential sutures of 3-0 polypropylene (PROLENE, Ethicon). The catheter tubing was cut to an appropriate length and connected to the VAP that was then secured within the subcutaneous pocket with multiple polypropylene sutures. The surgical site was lavaged with saline and closed with 3-0 poliglecaprone 25 (MONOCRYL, Ethicon) in the subcutaneous and intradermal layers. A 22-gauge Posigrip Huber point needle was placed into the VAP, continued patency was confirmed, and the VAP was heparin-locked. The VAP site was marked with a permanent skin marker for ease of injection. The piglets then recovered from anesthesia. Analgesia was provided with carprofen (2.2 mg/kg per os every 12 hours; RIMADYL, Zoetis) and butorphanol (0.2 to 0.4 mg/kg, intramuscularly every 4 to 6 hours). At 6 to 8 hours after surgery, piglets were injected with 4 × 10⁸ to 8 × 10⁸ CFU of S. aureus Xen36 (PerkinElmer Inc.) through the VAP using a Huber needle. Thereafter, the port was flushed with 5 ml of sterile PBS.

For aortic valve endocarditis, piglets were similarly prepared, but the aorta was accessed via the left carotid artery. Aortic valve damage was induced by repeated passing of a 2.5-mm diameter cytology brush (Endoscopy Support Services) through the valve. The brush was positioned under fluoroscopy guidance aided by repeated contrast injection. A venous leg catheter was used to administer anesthesia and the S. aureus Xen36 inoculum (5 × 10⁸ to 8 × 10⁸ CFU), followed by a bolus 60-ml sterile saline flush.

For optical studies, piglets were injected with 0.4 μmol of DAB-VT680XL in 2 ml of sterile PBS via the ear vein using a 25-gauge butterfly. Animals were euthanized 10 to 12 hours later and, BLI and fluorescence reflectance imaging (FRI) were performed immediately after necropsy using an IVIS Lumina XRMS imaging system (PerkinElmer Inc.). For PET/MRI, piglets were transferred to Mt. Sinai Hospital. All experimentation and the transport were approved by the Institutional Animal Care and Use Committee for Auburn University under protocol no. 2016-2860.