EXAMINATIONS ON THE BEHAVIOR OF GRAM-POSITIVE AND GRAM-NEGATIVE BACTERIA IN AQUA BIDEST AND TAP-WATER AT DIFFERENT INITIAL COLONY COUNTS AND DIFFERENT TEMPERATURES

Abstract

Experiments were done on the behavior of 5 different strains of Staphylococcus aureus, Streptococcus faecalis, Escherichia coli, Serratia marcescens and Pseudomonas aeruginosa in aqua bidest and sterile tap water at 20, 30 and 40.degree. C. The behavior 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 S. aureus and E. coli in aqua bidest and tap water not earlier than after 4 h, but mostly after 24 h. In S. faecalis CFU were reduced in aqua bidest at 40.degree. C after 24 h and in tap water at 40.degree. C after 4 h, but there were no changes of CFU in both media at 20 or 30.degree. C. S. marcescens strains grew in aqua bidest and tap water after 24 h at 20.degree. C. P. aeruginosa strains were reduced in aqua bidest at all temperatures but they grew in tap water after 24 h. Reduction or growth of all strains did not depend on initial colony count during examination time; change of CFU was quicker at 40 than at 20.degree. C. In humidifiers and nebulizers CFU are different from initial colony count no earlier than after 6 h. Growth is seen from 6-24 h if there are no particular nutritive organic compounds.