Control of respirator-associated infection due to Pseudomonas aeruginosa

Epidemiology and prevention of pseudomonas aeruginosa chest infection in an intensive care unit

An epidemiological investigation of Pseudomonas aeruginosa in an Intensive Care Neurosurgical Unit has shown that there were epidemic, endemic and endogenous types present simultaneously. These pseudomonads were cultured from purulent sputa postoperatively and sometimes caused systemic disease. The epidemic type was traced to a ventilator and a nebulizer whilst the endemic and endogenous types were not found in environmental sites. Effective decontamination of equipment and the use of bacterial filters where possible are essential in preventing the spread of infection. Staff hygiene remains important, particularly hand washing with antiseptic soap preparations.

Epidemiological patterns of Klebsiella colonization and infection in an intensive care ward

Twenty-four per cent of 2315 patients admitted to the intensive care unit of St Thomas's Hospital in the 4 year period from November 1969 became colonized or infected with Klebsiella species. Capsular typing of 986 klebsiella isolates from 551 patients showed that there were 695 patient-isolates, mostly derived from the respiratory tract. Capsular types 47 and 21 were the commonest types and together accounted for 19.9% of the patient-isolates. The 14 commonest types accounted for 47.3% of all patient-isolates and all these strains showed clustering, strongly suggesting a changing common source, cross infection, or both.

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.