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Freezing Inactivation of Escherichia Coli and Enterococcus Faecalis in Water: Response of Different Strains
Author(s) -
Gao W.,
Leung K.,
Hawdon N.
Publication year - 2009
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143009x407348
Subject(s) - enterococcus faecalis , escherichia coli , microbiology and biotechnology , enterococcus , pathogenic escherichia coli , food science , log reduction , biology , chemistry , antibiotics , biochemistry , gene
The effect of freezing temperature (−7, −15, −30 and −80°C), number of freeze/thaw cycles (1 to 5 cycles) and sample volume (100 mL and 100 µL) on the viability of a pathogenic and an opportunistically pathogenic Escherichia Coli , a vancomycin‐resistant and a vancomycin‐sensitive Enterococcus Faecalis were examined. About 3.3 to 4.3 and 1.5 to 2.4 log reduction in cell density were observed in E. coli and E. faecalis , respectively, in the 100 mL samples frozen at −30°C or warmer. Freezing at −80°C was the least effective in killing the microbes, on average the log reduction at −80°C was approximately 1.0 to 1.5 units less than those achieved at the three warmer temperatures. Based on statistical analysis, cell inactivation levels achieved at −7, −15, or −30°C were not significantly different ( P‐value = 0.1648). There were no statistical difference in terms of log reduction obtained under all experimental conditions for the two E.coli strains ( P‐value = 0.46) and the two E. faecalis strains ( P‐value = 0.10). The number of freezing/thaw cycles and sample volume, however, profoundly affected inactivation capacity of freezing. Freezing could be an effective method for further reduction of E. coli and Enterococcus in municipal wastewater/sludge.