Antibacterial action of copper in respiratory therapy apparatus

The effects of copper in heated nebulizers

The antibacterial potential of copper mesh in heated nebulizers was evaluated by simulating clnical usage in the laboratory and comparing the relationship between the copper levels achieved in nebulizer water and the growth of Pseudomonas aeruginosa organisms. Mesh size, length of immersion, temperature, water replacement, and nebulization all affected copper concentration. Antibacterial acitivity was demonstrated over a wide range of copper levels for as long as three weeks. Nebulizers driven for one hour by 10 L/min of gas flow and containing 8 gm of copper mesh were inoculated with more than 31,000 organisms and became sterile within 60 minutes of inoculation. Units without copper showed a much slower decline in colony counts. Solutions of copper salts also proved to be effective antibacterial substances but only in much higher concentrations than those achieved with copper mesh. It it is concluded that metallic copper mesh is an effective antibacterial substance when used in water-containing heated nebulizers. Attempts to quantitate aerosolization of copper were not sucessful, and potential upper-airway deposition and human toxicity with this technique remain to be defined.

Outbreaks of Serratia marcescens infections in a cardiothoracic surgical intensive care unit

An outbreak of infections with pigmented Serratia marcescens involving 3 patients in a cardiothoracic surgical intensive care unit is reported. A respirator is thought to have been the source of pneumonia in 2 patients, and fomite spread from 1 of these is considered responsible for the induction of fatal endocarditis in the third patient. This outbreak demonstrates the rapid dissemination of a bacterial strain within the unit, several methods of dissemination, the wide variation in apparent virulence of the organism, the alterations of antibacterial host defense which made bacterial disease possible and which determined the site of infection, and the difficulties of adequate therapy. The third patient is the seventh reported with serratia infection of a prosthetic heart valve.