Ultrastructural analysis of an infected collagen-coated vascular graft.

The incidence of infection following arterial reconstruction using synthetic graft materials varies from less than 1 to 5%. One of three mechanisms is thought to be responsible: 1. intraoperative contamination, 2. extension from adjacent infected or colonized tissue, or 3. hematogenous or lymphogenous seeding. We present ultrastructural data of a patient with a polymicrobial graft infection due to a prostheto-enteric fistula 16 years after reconstruction of an aortobifemoral graft. The polymer surface showed signs of biodegradation and was completely covered with a layer of plasma proteins. Disrupted fibroblasts on the intersegmental graft surface were surrounded by bundles of collagen. Gram-negative rods and grampositive cocci were embedded in an extracellular EPS matrix. Bacterial culture confirmed growth of Eikenella corrodens, Fusobacterium nucleatum and Peptostreptococcus species. Fibrin and granulation tissue from the neoadventitia started to mark off the inflammatory process. Transmission electron microscopy is a valuable tool for the investigation of alloplastic arterial devices. After 16 years of implantation the graft shows different signs of biodegradation.

[Experimental investigations onto the biocompatibility of coated vascular grafts as a function of the primary disease in various patients groups]. / Experimentelle Untersuchungen zur Biokompatibilität beschichteter Gefässprothesen in Abhängigkeit von der Grundkrankheit verschiedener Patientenkollektive.

INTRODUCTION: This work presents initial experimental results obtained with co-incubation of human neutrophilic granulocytes from patients with various diseases (5 patients each group) and collagen- or silver-coated polyester grafts (25 patients each graft). METHODS: After two-hour co-cultivation of the graft with human granulocytes of different patients (normal controls; peripheral occlusive vascular disease; diabetes mellitus; carcinoma/chemotherapy; sepsis), the following parameters were determined by flow cytometry: CD11b, CD62L, fMLP, CXCR2. RESULTS: The change in the receptor expression was taken as a measure of responsiveness, with statistically significant differences seen within and between the groups. For the silver-coated graft, such differences were mainly noted for the fMLP receptor (p=0.01). For the two-hour incubation with collagen coating, the receptors CD62L and CXCR2 were indicative of differences between the various diseases (CD62L p=0.01; CXCR2 p=0.01). Comparison between the grafts revealed statistically significant differences for the CXCR2 and the fMLP receptors (CXCR2 p=0.00; fMLP p=0.03). CONCLUSIONS: The differences noted between the grafts and between the patients groups are suggestive of an altered responsiveness of the granulocytes to the grafts. This enables new aspects with respect to the genesis of accompanying clinical symptoms.

Prolonged application of closed in-line suction catheters increases microbial colonization of the lower respiratory tract and bacterial growth on catheter surface.

BACKGROUND: Microorganisms become attracted to polymer surfaces for a number of reasons including positive charge of biomaterial or concentration of nutrients on the biomaterial surface. Many bacteria additionally possess specific receptors for the interaction with extracellular host protein components that adhere on the biomaterial surface. Several authors suggest that application of closed in-line polypropylene suction catheters (CISC) in intubated patients for more than 24 h is safe and can reduce the costs associated with mechanical ventilation. Therefore, we evaluated the possible role of prolonged application of CISC to cause enhanced colonization of both the biomaterial and the lower respiratory tract. MATERIALS AND METHODS: The prospective, randomized study included 23 mechanically ventilated patients. The CISC tips, adjacent segments and tracheobronchial aspirates of each patient were examined for microbial growth. RESULTS: Application for 72 h significantly enhanced the microbial growth on the CISC tips and on the adjacent catheter segment. Usage for 3 days led to a significant increase in colonization in the lower respiratory tract. CONCLUSION: Normal saline instillation in conjunction with endotracheal suctioning may lead to a dispersion of microorganisms into the lower respiratory tract. More effective self-cleaning mechanisms are necessary to decontaminate the CISC surface after suctioning.