Gary C. du Moulin

Concentration of Mycobacterium avium by hospital hot water systems.

Water from 34 sites on two temporarily vacant hospital floors was analyzed for the presence of mycobacteria. These sites included 18 cold water taps and 16 hot water taps, including shower heads. A total of 14 sites (41%) demonstrated the presence of Mycobacterium avium as confirmed by biochemical characterization, DNA/rRNA probe analysis, and seroagglutination. Of positive sites, 11 were hot water sources with an average temperature of 55 degrees C and yielding up to 500 colony-forming units per 100 mL. Seven of 11 strains analyzed for glycolipid antigens were identified with the type 4 serovar, the preponderant serovar of M avium in patients with acquired immunodeficiency syndrome from the Boston area. Potable hot water systems, particularly those that generate aerosols, may contain concentrations of M avium greater than those found in cold water systems and could serve as an environmental source for colonization and infection of immunocompromised persons.

E. coli peritonitis and bacteremia cause increased blood-brain barrier permeability

Impaired mental status is a poorly understood manifestation of sepsis and may be associated with altered permeability of the blood-brain barrier. To examine the possibility that sepsis affects permeability of the blood-brain barrier, rats were infected with a peritoneal implant consisting of sterilized feces, barium sulfate, and 10(8) colony forming units (CFU) of Escherichia coli. Using this model, reproducible episodes of peritonitis with bacteremia resulted. Rats were sacrificed hourly after 5 min circulation of 100 mg horseradish peroxidase. Animals were perfused-fixed and the brains removed. Representative coronal sections were stained for peroxidase reaction product and cerebral blood vessels were examined microscopically for evidence of HRP staining and extravasation. The number of stained cerebral vessels from infected rats was increased at all times compared to uninfected control rats. Extravasation of horseradish peroxide within neuropil was significantly higher in hours 1, 4 and 5 as compared to controls. The lack of significant increase in hours 2 and 3 may suggest transient closing or repair of the tight junctions. We conclude that peritonitis and bacteremia are associated with increased permeability of the blood-brain barrier.

The Anesthesia Machine and Circle System Are Not Likely to be Sources of Bacterial Contamination

Patients who had upper respiratory tract gram-negative bacillary colonization and noncolonized patients were followed through surgical procedures to determine what bacterial organisms would be deposited in anesthesia apparatus. Anesthesia machines were cultured for bacteria in many locations before and after each surgical procedure. Six machines in routine operating room use were studied after use on six colonized patients and nine uncolonized patients. Sixteen corrugated tubes from unopened packages served as controls. The results indicated that the machines remained free of bacteria of patient origin. Levels of contamination were only slightly higher in the expiratory tubing, and the bacterial species most commonly recovered were environmental in origin. Even after periods of anesthetic administration as long as six hours in patients heavily colonized with gram-negative bacilli, contamination of the anesthesia apparatus with the colonizing organisms did not occur. Intentional contamination of a sterilized anesthesia machine with two gram-negative organisms confirmed the clinical observations. Analysis of oxygen and nitrous oxide gas sources for bacteria had negative results. Basic hygienic management of anesthesia machines will ensure safety from the standpoint of cross-infection.

Contamination of Medical Gas and Water Pipelines in a New Hospital Building

Medical gases and water were sampled and tested for purity prior to the opening of a 176-bed addition to a 450-bed general hospital. Contamination was found. In delivered oxygen, compressed air, and nitrous oxide, this consisted of a volatile hydrocarbon at an initial concentration of 10 parts per million and a dust of fine gray particulate matter. In water from new taps bacterial contamination with as many as 400,000 organisms per 100 ml was present. All these contaminants were considered potential hazards to patient safety. Studies were done to help delineate the nature and origin of these contaminants. Each contaminant was eventually largely eliminated by purging the respective pipeline systems with continuous flows. Planners, builders, and responsible medical personnel must be aware of the potential for such hazards in a new hospital building.