Inactivation of micro-organisms isolated from infected lower limb arthroplasties using high-intensity narrow-spectrum (HINS) light

High-Intensity Narrow-Spectrum (HINS) light is a novel blue light inactivation technology which kills bacteria through a photodynamic process, and has been shown to have bactericidal activity against a wide range of species. Specimens from patients with infected hip and knee arthroplasties were collected over a one year period (1 May 2009 – 30 April 2010). A range of these microbial isolates was tested for sensitivity to HINS-light. During testing, suspensions of the pathogens were exposed to increasing doses of HINS-light (of 123mW/cm2 irradiance). Non-light exposed control samples were also used. The samples were then plated onto agar plates and incubated at 37°C for 24 hours before enumeration. Complete inactivation (greater than 4-log10 reduction) was achieved for all of the isolates. The typical inactivation curve showed a slow initial reaction followed by a rapid period of inactivation. The doses of HINS-light required ranged between 118 and 2214 J/cm2. Gram-positive bacteria were generally found to be more susceptible than Gram-negative. As HINS-light uses visible wavelengths, it can be safely used in the presence of patients and staff.This unique feature could lead to its possible use in the prevention of infection during surgery and post-operative dressing changes.