• Korean Journal of Microbiology
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• v.31 no.3
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• pp.245-254
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• 1993

Distribution and variation of bacterial densities of heterotrophic plate count (HPC) and Enterobacteriaceae in the water supply systems comprising raw, treated, and three tap water samples of a water treatment plant in Seoul were studied 23 times from 1991 to 1992. HPC bacteria of raw. treated, and tap waters on $R_{2}A$ agar media were at a density of $1.22{\times}10^{3} to 3.05{\times}10^{5}$, $1.50{\times}10^{1} to 4.29{\times}10^{3}$ and 2 to $5.41{\times}10^{3}$ cfu/ml, respectively. Densities of Enterobacteriaceae in raw, treated, and tap waters on mENDO-LES agar media ranged from 0.] to 8200 cfu/ml, 0 to 17.5 cfu/JOO mI. and 0 to 47.5 cfu/IOO ml, respectively. Injured Enterobacteriaceae of treated and tap waters on m-T7 agar media were at a density of o to 27 and 0 to 35 cfu/100 mI. These results showed that the density of bacteria in the treated water outflowing from the water plant significantly increased as the water flowed along the distribution sytems, which is so-called bacterial regrowth. The predominant bacteria] types in the water supply system were Pw'udomonas and Acinerobacter. In raw water, the ratio of Pseudomonas was higher than that of Acinetobaeter, but in treated and tap waters. both ratios were reversed. The most predominant species of Enterobacteriaceae was Enterobacter agglomerans. Some species such as Citrobacter freundii. Escherichia coli. Klebsiella pneumoniae. and Shigella dysenteriae which are opportunistic pathogens or pathogens were not found in the treated water but additionally detected in tap waters.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.7
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• pp.1025-1031
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• 2011

The objective of this study was to compare the performances of conventional microbiological media used in isolation of Shigella spp. from foods. Total of six selective media, including MacConkey agar (MAC), Salmonella Shigella agar (SSA), desoxycholate citrate agar (DCA), xylose lysine desoxycholate agar (XLD), hektoen enteric agar (HEA), and CHROMagar, were tested. MAC showed almost the same colony numbers as compared to tryptic soy agar (TSA) while DCA showed significantly lower colony numbers when cultivated Shigella spp. was counted in each medium. In a food recovery test with beef, pork and shrimp, S. sonnei recovered well on CHROMagar (p<0.05). With lettuce and cabbage, S. sonnei displayed significantly significant recovery (p<0.05) on SSA in comparison with other selective media. Heat-injured cells recovered well on MAC and SSA. In a specificity test using Enterobacteriaceae strains, HEA was identified as having the highest specificity among the tested media. However, Morganella spp. could not be differentiated from Shigella spp. on any of the tested selective media. Shigella spp. precluded the possibility of isolation from foods by a single 'best' selective medium. Consequently, a combination of complementary selective media or selection of appropriate media according to cell conditions must be considered for comprehensive isolation.