A simple apparatus for the determination of the resistance of bioindicators to saturated steam at temperatures less than 100 degrees C., tested with Enterococcus faecium as test microbe
Spicher, G.; Borchers, U.; Peters, J.
Zentralblatt für Hygiene und Umweltmedizin 192(1): 33-44
1991
ISSN/ISBN: 0934-8859 PMID: 1953932 Document Number: 378814
An apparatus is described by means of which the resistance of microbiological indicators to water vapor at temperatures below 100 degrees C can be determined. The apparatus can be assembled from parts generally available in laboratories. The principle of the apparatus consists in the production of water vapor of the desired temperature under conditions of reduced pressure and its recondensation to water after having passed a special chamber. Accordingly, the device consists of a heated round-bottom flask serving as steam generator, an exposure chamber (B), and a condenser (D) attached to a receiver (E). The bioindicators are exposed to the water vapor in the exposure chamber. A bypass located between the steam generator and the condenser allows for continuous operation even when the exposure chamber is opened. The reduced pressure was achieved by means of a waterjet pump and adjusted by two tandem-joined pressure-regulating valves as needed. The apparatus was tested using water vapor of 73, 75 and 77 degrees C, respectively, and bioindicators containing Enterococcus faecium as test organism. In the range of exposure periods in which bioindicators change from the status "all indicators having surviving test organisms" to the status "all indicators free from surviving test organisms" the bioindicators showed D values of 5.7, 4.4 and 2.9 min, respectively. For the temperature dependence of resistance a z value of 12.5 Kelvin resulted.