Abstract
In vitro pure culture studies were conducted on three different strains of Escherichia coli (K-12, EPA 00244, and SWEI) to determine the effect of chlorination on catalase activity. In each case, stationary-phase cells exhibited significant (P less than 0.001) reductions in enzyme activity following exposure to chlorine. Mean differences in activity between control and chlorine-stressed cells ranged from 8.8 to 20.3 U/mg of protein for E. coli SWEI and EPA 00244, respectively. Following initial enzyme studies, resuscitation experiments utilizing the membrane filtration technique were conducted on chlorinated sewage effluent. Five different amendments, including catalase (1,000 U per plate), heat-inactivated catalase (1,000-U per plate), sodium pyruvate (0.05%), a catalase-sodium pyruvate combination (1,500 U/0.01%), and acetic acid (0.05%), were tested for the ability to enhance detection of chlorine-stressed cells on M-fecal coliform (M-FC), mT7, M-Endo, and tryptone-glucose-yeast extract (TGY) media. Significant (P less than 0.001) increases in recovery of fecal coliforms on M-FC, total coliforms on mT7 and M-Endo, and total heterotrophs on TGY were obtained on plates containing catalase, pyruvate, or the combination of these compounds. Supplementation with heat-inactivated catalase and acetic acid did not improve recovery of chlorine-stressed cells compared with recovery on nonamended media. Subsequent analysis of colonies from plates containing compounds which enhanced recovery indicated coliform verification percentages of greater than 80% on M-FC, greater than 90% on mT7, and greater than 94% on M-Endo media. These data suggest that the addition of peroxide-degrading compounds to various standard recovery media may improve detection of both coliform and heterotrophic bacteria in chlorinated waters.
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