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H Kator

Publications and source records attributed to H Kator.

4 recordsLinked to original sources
PubMed1997

Enumeration of Enterococcus sp. using a modified mE method.

A modified mE medium (mEI) containing the chromogenic substrate indoxyl-beta-D-glucoside to detect beta-D-glucosidase activity was evaluated with respect to specificity and recovery of enterococci from environmental waters. Extending incubation from 24 to 48 h improved enterococci recovery but 77% of the colonies classified as non-target were confirmed as enterococci. Randomly chosen enterococcal isolates from sewage, exposed in microcosms containing 0.22 micron membrane filtered fresh or estuarine water, exhibited differences in persistence as a function of exposure treatment. Decreasing the concentration of or eliminating indoxyl-beta-D-glucoside from mE did not significantly affect recovery of purified isolates.

Bacteriological Techniques↗
PubMed1988

Survival of Escherichia coli and Salmonella spp. in estuarine environments.

Survival of Escherichia coli and Salmonella spp. in estuarine waters was compared over a variety of seasonal temperatures during in situ exposure in diffusion chambers. Sublethal stress was measured by both selective-versus-resuscitative enumeration procedures and an electrochemical detection method. E. coli and Salmonella spp. test suspensions, prepared to minimize sublethal injury, were exposed in a shallow tidal creek and at a site 7.1 km further downriver. Bacterial die-off and sublethal stress in filtered estuarine water were inversely related to water temperature. Salmonella spp. populations exhibited significantly less die-off and stress than did E. coli at water temperatures of less than 10 degrees C. Although the most pronounced reductions (ca. 3 log units) in test bacteria occurred during seasonally warm temperatures in the presence of the autochthonous microbiota, 10(2) to 10(4) test cells per ml remained after 2 weeks of exposure to temperatures of greater than 15 degrees C. Reductions in test bacteria were associated with increases in the densities of microflagellates and plaque-forming microorganisms. These studies demonstrated the survival potential of enteric bacteria in estuarine waters and showed that survival was a function of interacting biological and physical factors.

Escherichia coli↗
PubMed1979

Sublethal stress in Escherichia coli: a function of salinity.

Sublethal stress in Escherichia coli was detected in various test media after exposure (in vitro) to seawater of various salinites. Stress was measured with an electrochemical detection technique and a beta-galactosidase assay. Test media included EC medium, medium A-1, and tryptic soy broth modified to contain lactose for beta-galactosidase assay experiments. Stress was defined as the difference between a predicted electrochemical response time calculated for unstarved cells from a standard curve and the observed electrochemical response time for cells starved in seawater. The higher the salinity, the greater the stress for all test media examined. Stress was most pronounced in EC and was attributed primarily to initial die-off of starved cells exposed to the test medium at the elevated temperature of 44.5 degrees C. Lag time and growth rates in test media were not significantly affected by salinity. beta-Galactosidase specific activity, assayed in starved cells after transfer to an induction medium at 44.5 degrees C for 150 min, was inversely related to the salinity of the starved cell suspension. The consequences of these observations with respect to coliform enumeration methods are discussed.

Bacteriological Techniques↗