Comparative tissue response to a bovine peritoneum matrix and UltraPro mesh under experimental Acinetobacter...

Biologic extracellular matrix (ECM) implants are investigated for abdominal wall reconstruction because they may support tissue remodeling while limiting persistent foreign-body reactions. However, their response to contamination with multidrug-resistant pathogens remains insufficiently characterized. This exploratory study compared a bovine-derived peritoneum ECM scaffold with UltraPro mesh in a rat model of Acinetobacter baumannii contamination.

Thirty outbred rats were included. Twenty-four animals underwent ECM or UltraPro implantation and were evaluated on postoperative days 10 and 20 (n = 6 per subgroup); six non-implanted animals receiving sterile saline served as a non-implanted reference group. Abdominal wall defects were reconstructed and inoculated with 200 µL of an A. baumannii suspension at 10⁹ CFU/mL. Tissue responses were assessed using semi-quantitative histological scoring based on ISO 10993-6 principles. Conventional microbiological culture was also performed.

All animals survived, and no clinically evident wound infection, dehiscence, or abscess formation was observed. On day 10, ECM demonstrated greater necrosis and polymorphonuclear-cell infiltration than UltraPro. By day 20, ECM showed reduced necrosis, increased cellular colonization, and greater reticulin fiber deposition, consistent with early tissue organization. UltraPro demonstrated increasing multinucleated giant-cell activity, fibrosis, granulomatous inflammation, and capsule formation. Conventional culture did not recover viable A. baumannii from ECM specimens, whereas the organism was recovered from 2 of 12 UltraPro specimens.

Under experimental A. baumannii contamination, ECM and UltraPro demonstrated distinct early patterns of tissue response. ECM showed a more pronounced acute inflammatory response followed by histological changes consistent with early tissue organization, whereas UltraPro demonstrated progressive foreign-body and fibrotic changes during the observation period. Because of the small subgroup size, short follow-up, absence of concurrent sterile implant controls, semi-quantitative histological assessment, and lack of quantitative microbiological and biomechanical evaluation, these findings should be considered exploratory and do not establish superior functional or clinical performance of either material. Longer-term microbiological, mechanical, and functional studies are required.