[Examinations on the behaviour of grampositive and gramnegative bacteria in aqua bidest and tap-water at different initial colony counts and different temperatures (author's transl)].

Abstract

Experiments were done about the behaviour of 5 different strains of Staph. aureus, Strept. faecalis, E. coli, Ser. marcescens and P. aeruginosa in aqua bidest and sterile tap water at 20 degrees C, 30 degrees C and 40 degrees C. The behaviour of 3 different initial colony counts in each case was examined. Colony forming units (CFU) were evaluated at the beginning and after 1, 2, 4, 6 and 24 h. CFU were reduced at Staph. aureus and E. coli in aqua bidest and tap water not earlier than after 4 h, but mostly after 24 h. In Strept. faecalis CFU were reduced in aqua bidest at 40 degrees C after 24 h, in tap water at 40 degrees C after 4 h, but there were no changes of CFU in both media at 20 degrees C or 30 degrees C. Ser. marcescens strains were growing in aqua bidest and tap water after 24 h at 20 degrees C. P. aeruginosa strains were reduced in aqua bidest at all temperatures but they were growing in tap water after 24 h. Reduction or growth of all strains did not depend on initial colony count during examination time, changing of CFU turned out to be quicker at 40 degrees C than at 20 degrees C. It is the conclusion that in humidifiers and nebulizers CFU will be different from initial colony count not earlier than after 6 h. Growth will be seen after 6 until 24 h if there are no particular nutritive organic compounds.