Eight foodborne pathogenic and spoilage type gram-positive bacteria were evaluated for their spontaneous resistance frequencies to the peptide antimicrobial nisin. In brain heart infusion medium, spontaneous nisin resistance frequencies were in the range of 10−6 to 10−8 when exposed to nisin at concentrations 2 to 8 times the minimal inhibitory concentrations. A resistant mutant of Listeria monocytogenes Scott A (2000 U nisin per ml) was obtained by increasing stepwise exposure to nisin and was subsequently characterized. Nisin was not inactivated after exposure to mutant or parent cells growing in brain heart medium. Membrane fatty acid composition, phase transition temperature profiles (by differential scanning calorimetry), and specific growth rates of the resistant mutant and parent strain were compared. The resistant mutant had a higher phase transition temperature, higher percentage of straight-chain fatty acids, and a lower percentage of branched chain-fatty acids. The specific growth rate (k) of the resistant mutant was significantly decreased at the suboptimal temperature of 20°C where (k) was 40.9% of the parent strain k. In contrast, at 37°C, the mutant (k) was 87.6% of the parent (k). Collectively, these observations indicated that as a resistance response to nisin, fundamental changes occurred in bacterial membrane structure and function as opposed to a resistance response involving nisin degradation.

A nisin-resistant mutant of Listeria monocytogenes Scott A has been characterized by comparing its phospholipid composition with the nisin-sensitive parental strain. The total phospholipids of resistant cells were significantly (P < 0.001) decreased compared to the parental strain. The types of phospholipids isolated from nisin-resistant and sensitive cells were identical, but there was a significant decrease (P < 0.01) in the amount of three individual phospholipids. Nisin-resistant cells were found to bind less nisin and release less phospholipids than sensitive cells when treated with same concentrations of nisin. The cell surface of resistant cells was less hydrophobic compared to sensitive cells, which also may have contributed to the observed nisin resistance. The results suggest that fundamental changes occurred in the membrane structure and function of the resistant mutant as a response to nisin.

Polydioxanone suture with triclosan had activity in vitro against S. aureus, MRSA, E. coli, S. epidermidis, MRSE, and K. pneumoniae that persisted for as long as three weeks. In animal models, polydioxanone suture with triclosan inhibited in vivo colonization by S. aureus and E. coli.

Poliglecaprone 25 suture with triclosan inhibited bacterial colonization of the suture compared with untreated suture after direct in vivo challenge with S. aureus and E. coli in animal models.

Triclosan reduced in vitro colonization of poliglecaprone 25 suture by several strains of bacteria compared with untreated control sutures.

Topical absorbable hemostats are routinely utilized in surgical procedures to assist in controlling intraoperative bleeding. SURGICEL Original Absorbable Hemostat, one of the most frequently used adjunctive hemostats, is composed of oxidized regenerated cellulose (ORC). We report here that a novel powdered form of ORC, composed of aggregates of ORC fine fibers, provides additional valuable hemostatic performance characteristics and retains the biochemical and bactericidal profile of the parent ORC fabric. The ORC aggregates are more effective in promoting coagulation than their constituent ORC fine fibers because of more favorable surface energetics and surface area. Aggregates with similar particle size distributions that have higher sphericity values exhibit better coagulation efficacy. Finally, ORC aggregates more effectively promote clot formation than starch-based hemostatic particles. The results of this investigation indicate that the efficacy of this novel powdered hemostat is based on its chemical composition, morphology, and particle surface energetics.