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Prions cause various transmissible spongiform encephalopathies. They are highly resistant to the chemical and physical decontamination and sterilization procedures routinely used in healthcare facilities. The decontamination procedures recommended for the inactivation of prions are often incompatible with the materials used in medical devices. In this study, we evaluated the use of low-temperature hydrogen peroxide gas plasma sterilization systems and other instrument-processing procedures for inactivating human and animal prions. We provide new data concerning the efficacy of hydrogen peroxide against prions from in vitro or in vivo tests, focusing on the following: the efficiency of hydrogen peroxide sterilization and possible interactions with enzymatic or alkaline detergents, differences in the efficiency of this treatment against different prion strains, and the influence of contaminating lipids. We found that gaseous hydrogen peroxide decreased the infectivity of prions and/or the level of the protease-resistant form of the prion protein on different surface materials. However, the efficiency of this treatment depended strongly on the concentration of hydrogen peroxide and the delivery system used in medical devices, because these effects were more pronounced for the new generation of Sterrad technology. The Sterrad NX sterilizer is 100% efficient (0% transmission and no protease-resistant form of the prion protein signal detected on the surface of the material for the mouse-adapted bovine spongiform encephalopathy 6PB1 strain and a variant Creutzfeldt-Jakob disease strain). Thus, gaseous or vaporized hydrogen peroxide efficiently inactivates prions on the surfaces of medical devices.

Objective: To determine the susceptibilities of vancomycin-resistant and -sensitive enterococci (VRE and VSE) to various concentrations of commonly used, commercial, hospital-grade disinfectants., Design: A microbial suspension test using inocula of 10(8) cells per mL in a disinfectant test dilution was used to determine inactivation kinetics of the test strains. In each test, 1-mL aliquots were removed from the cell-disinfectant mixtures at 15 and 30 seconds and then at 1-minute intervals for 5 minutes and neutralized. Appropriate serial dilutions were plated on agar medium for enumeration of survivors., Results: VRE and VSE challenge inocula (in the absence of any additional protein or serum challenge) were below the limit of detection (5 colony-forming units/mL) after 15 seconds' exposure to the manufacturers' suggested use-dilutions of quaternary ammonium, phenolic, or iodophor germicidal detergents. In subsequent tests, when the disinfectants were diluted far beyond-the recommended use-dilutions (extended dilution), no differences were demonstrated between the susceptibilities of VRE and VSE., Conclusions: VRE and VSE are sensitive to a spectrum of commonly used environmental disinfectants and have parallel inactivation rates when challenged with extended dilutions of these products. Our findings did not demonstrate a relationship between antibiotic and germicide resistance. Routine disinfection and housekeeping protocols presently used in hospitals need not be altered due to concerns about the potential for environmentally mediated transmission of antibiotic-resistant microorganisms.

Objective: In this study, we measured microbial growth and endotoxin production in the intravenous anesthetic propofol using 10 different microbial strains; 6 isolated from outbreak cases and 4 from laboratory stock cultures., Design: In each trial, endotoxin-free glass tubes containing 10 ml propofol were inoculated with 10(0)-10(3) CFU/ml of the test organism and incubated at 30 degrees C for 72 hours., Setting: In May and June 1990, the Centers for Disease Control received reports of 5 outbreaks in 5 states of postsurgical patient infections and/or pyrogenic reactions. Epidemiologic and laboratory investigations implicated extrinsic contamination of an intravenous anesthetic, propofol, as the probable source of these outbreaks., Results: After 24 hours, 9 of the 10 cultures increased in viable counts by 3 to 6 logs. At least 1 ng/ml of endotoxin was produced within 24 hours by Escherichia coli, Enterobacter cloacae, and Acinetobacter calcoaceticus subspecies anitratus., Conclusions: Propofol can support rapid microbial growth and endotoxin production. To avoid infectious complications, scrupulous aseptic technique should be used when preparing or administering this anesthetic.

Objective: Laboratory investigations were initiated with a povidone-iodine antiseptic solution that was intrinsically contaminated with Pseudomonas cepacia. These investigations were helpful in understanding the microbicidal and chemical properties of iodophor solutions and the mechanism by which P cepacia can survive in iodine-containing antiseptics., Design: Included in these studies were: prolonged survival of P cepacia; available and free iodine determinations; microbial challenge studies; and scanning electron microscopic examination of contaminated antiseptic., Results: P cepacia survived in this iodophor antiseptic up to 68 weeks from the date of manufacture. A uniform concentration of 1% available iodine was found in all lots of povidone-iodine tested as specified on the product label, but free iodine (I2) values varied greatly. Low free iodine levels of 0.23 to 0.46 ppm were associated with the contaminated lot of povidone-iodine. Solutions of povidone-iodine with varying levels of free iodine were rapidly microbicidal when challenged with cells of P cepacia derived from culture broth and washed or adapted to growth in water. P cepacia cells taken directly from contaminated povidone-iodine survived for significantly longer periods of time. Large numbers of P cepacia were found embedded in extracellular material and among strands of glycocalyx between cells as shown by scanning electron microscopy., Conclusions: The physical thickness of cellular and extracellular material that forms on surfaces could protect embedded organisms from the microbicidal action of disinfectants and antiseptics and subsequently allow for extended microbial survival times. Manufacturers should be aware that distribution piping surfaces colonized with bacteria may be a source of product contamination and resistant organisms.

Objective: To test the utility of a newly developed multilocus enzyme electrophoresis typing method for Xanthomonas maltophilia., Design: Isolates were first screened by slide agglutination, which served as the standard to characterize the outbreak strains. All isolates were then subjected to multilocus enzyme electrophoresis and the results analyzed based on epidemiological data., Setting: This outbreak occurred in a shock-trauma intensive care unit of a large general community hospital., Patients: Patients admitted to the shock-trauma intensive care unit who had X maltophilia isolated from any site greater than or equal to 24 hours after admission met the case definition. Specimens from patients who fit the case definition were characterized, as were specimens from other patients that were used as controls for nonoutbreak isolates. Environmental samples were also evaluated for X maltophilia., Results: Most of the 64 isolates received during this outbreak were serotype 10, and when they were subjected to multilocus enzyme electrophoresis, one electrophoretic type predominated and correlated to most outbreak isolates. Unrelated isolates of serotype 10 from other institutions all exhibited unique electrophoretic types., Conclusion: Application of multilocus enzyme electrophoresis to X maltophilia outbreaks is a valuable addition to the characterization of suspected outbreak strains.