Journal Published Online: 01 May 1985
Volume 13, Issue 3

Poor Selectivity of Certain Lots of Commercially Available KF-Streptococcus Agar

CODEN: JTEVAB

Abstract

KF-streptococcus agar is, according to Kenner and coworkers, a selective medium for the isolation and enumeration of fecal (or Group D) streptococci in water. The selectivity is based on the presence of sodium azide in a mass concentration of 400 mg/L in the final medium. In certain lots of commercially available dehydrated medium the sodium azide amount was found to be only half of that amount. This resulted in insufficient suppression of background flora, in particular of Staphylococcus aureus, Bacillus megaterium, Bacillus coagulans, and unclassified non-Group D streptococci. Supplementary addition of sodium azide to these batches to bring the final level of this compound to about 400 mg/L resulted in the restoration of the selective properties. The results of this investigation stress the need for adequate quality control of selective media.

Author Information

Havelaar, AH
Section of Water Microbiology, Laboratory for Water and Food Microbiology, National Institute of Public Health and Environmental Hygiene, The Netherlands
van Breemen, LWCA
Brabantse Biesbosch Water Storage Corp., The Netherlands
Vessen, HAMG
Section of General Chemical Analysis, Laboratory for Chemical Analysis of Foodstuffs, National Institute of Public Health and Environmental Hygiene, The Netherlands
During, M
Section of Water Microbiology, Laboratory for Water and Food Microbiology, National Institute of Public Health and Environmental Hygiene, The Netherlands
van der List, C
Brabantse Biesbosch Water Storage Corp., The Netherlands
van Erne, EHW
Section of Water Microbiology, Laboratory for Water and Food Microbiology, National Institute of Public Health and Environmental Hygiene, The Netherlands
Pages: 4
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Stock #: JTE10785J
ISSN: 0090-3973
DOI: 10.1520/JTE10785J