Relationships of salmonellae to fecal coliforms in bottom sediments

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THE use of bottom sampling in water quality investigations is generally limited to observations on the benthic fauna. There have been recurring indications, however, that bottom sediments may also furnish considerable information from a microbiol standpoint--that the mud may serve as a concentrated and stable index of the quality of the overlying water, particularly where there is great variability in the bacterial quality of the water. In 1905, SAVAGE (1905) examined estuarine mud for coliforms and streptococci to determine the usefulness of mud as an index of shellfish sanitation. Bacteriological results correlated closely with a sanitary survey, and sampling of the same areas during different seasons showed considerable uniformity. Coliform survival in different mud samples was also quite uniform, and Salmonella typhi was found to survive for extended periods in sterilized mud. ALLEN et al. (1953) examined the chemical and bacterial characteristics of mud from polluted and unpolluted lakes and estuaries. Although they found no relationship between the degree of pollution and the sulfide, organic carbon, or organic nitrogen content in the mud samples, there was a relationship between pollution and the concentration of fecal coliforms and fecal streptococci in the upper 2 in. of mud. RIa-IEtCBERG et al. (1958) investigated coliform distribution in bottom sediments around California marine sewage outfalls. High coliform levels were found in mud extending several miles from outfalls discharging primary effluent. In contrast, very low levels were found around an outfall discharging chlorinated secondary effluent. The distribution in mud reflected the effluent flow pattern in the overlying water. Much higher densities, however, were found in the mud than in the water, suggesting prolonged survival after sedimentation. BONDE (1967) examined the sediments of the Ore Sound qualitatively for coliforms and fecal coliforms, and found that percent recovery was related to the degree of pollution and the depth of the overlying water; recovery decreased with depth. Clostridium perfringens counts in sediments were also proportional to the pollution, and the ratio of spores to vegetative cells increased with distance from the source of pollution. GELD~ICrI and CLARKE (1966) indirectly showed the effect of bottom sediments on the intestinal contents of freshwater fish. Bottom-feeding fish, such as catfish, carp, and suckers, had higher levels of coliforms, fecal coliforms, and fecal streptococci than did surface-feeding and predaceous fish taken from the same point. Since fish lack an indigenous intestinal flora (MARGOLIS, 1935) and (BELL, 1941), these high numbers of organisms in bottom-feeders probably originated from ingestion of heavily contaminated bottom materials. The purpose of this study was to compare the relationship of indicator organisms