Antimicrobial activity of Ti-ZrN/Ag coatings for use in biomaterial applications

Severely broken bones often require external bone fixation pins to provide support but they can become infected. In order to reduce such infections, novel solutions are required. Titanium zirconium nitride (Ti-ZrN) and Ti-ZrN silver (Ti-ZrN/Ag) coatings were deposited onto stainless steel. Surface microtopography demonstrated that on the silver containing surfaces, Sa and Sv values demonstrated similar trends whilst the Ra, average height and RMS value and Sp values increased with increasing silver concentration. On the Ti-ZrN/Ag coatings, surface hydrophobicity followed the same trend as the Sa and Sv values. An increase in dead Staphylococcus aureus and Staphylococcus epidermidis cells was observed on the coatings with a higher silver concentration. Using CTC staining, a significant increase in S. aureus respiration on the silver containing surfaces was observed in comparison to the stainless steel control whilst against S. epidermidis, no significant difference in viable cells was observed across the surfaces. Cytotoxicity testing revealed that the TiZrN coatings, both with and without varying silver concentrations, did not possess a detrimental effect to a human monocyte cell line U937. This work demonstrated that such coatings have the potential to reduce the viability of bacteria that result in pin tract infections

Relationship between the virulence and inert surface adhesion of Listeria monocytogenes

International audienc

Reassessing the risk of microbial contamination from roosting cormorants in source water supply reservoirs

A previous water quality risk assessment of source water supply reservoirs in subtropical southeast Queensland (Australia) evaluated little black cormorants (Phalocrocorax sulcirostris) roosting on intake infrastructure as potentially posing an extreme risk of microbial contamination through direct deposition of fecal matter to the aquatic environment. To evaluate this risk rating, we assessed populations of little black cormorants occupying 3 intake structures across 2 reservoirs, enumerated Escherichia coli (E. coli) levels collected from fecal matter, and estimated a daily E. coli load to the reservoir for each population. Concurrently, we supplemented the existing routine monthly water quality monitoring program with targeted water sampling to measure E. coli concentrations in water at the 3 water intake points and at 2 sites without extant cormorant populations. Up to 3.9 × 10 E. coli organisms were estimated to be produced per day by the largest population surveyed. Cormorants were present at intake sites and absent from reference sites; however, concentrations of E. coli were not significantly higher in water at intake sites compared with reference sites (p = 0.793 vs. p = 0.1069, respectively), and there was no significant relationship (p = 0.9671) between cormorant numbers and water column concentrations of E. coli. The inability to quantify significant differences in microbial concentrations among sites suggests a more intensive sampling regime is required to clarify the relative contribution of contamination sources. Populations of roosting cormorants in our study reservoirs are unlikely to pose an extreme risk to source water quality when compared to other catchment-based inputs that dominate microbial pollution