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Giardia and Cryptosporidium levels were determined by using a combined immunofluorescence test for source waters of 66 surface water treatment plants in 14 states and 1 Canadian province. The results showed that cysts and oocysts were widely dispersed in the aquatic environment. Giardia spp. were detected in 81% of the raw water samples. Cryptosporidium spp. were found in 87% of the raw water locations. Overall, Giardia or Cryptosporidium spp. were detected in 97% of the raw water samples. Higher cyst and oocyst densities were associated with source waters receiving industrial or sewage effluents. Significant correlations were found between Giardia and Cryptosporidium densities and raw water quality parameters such as turbidity and total and fecal coliform levels. Statistical modeling suggests that cyst and oocyst densities could be predicted on the basis of watershed and water quality characteristics. The occurrence of high levels of Giardia cysts in raw water samples may require water utilities to apply treatment beyond that outlined in the Surface Water Treatment Rule of the U.S. Environmental Protection Agency.

Coagulase-positive Staphylococcus aureus was isolated from over 6% of 320 rural drinking water specimens. Well water was the most common source examined. The presence of S. aureus was not found to correlate with the presence of coliform bacteria. Strains of Staphylococcus that produced enterotoxin A were found in 40% of the samples containing S. aureus. Additional studies showed that faucet aerator screens were common sources of high cell densities of S. aureus.

On six occasions during a 15-month period, the private well and spring water supplies in a modern rural neighborhood of 78 households were examined for total coliforms, fecal coliforms, Staphylococcus aureus, and standard plate count bacteria. More than one-third of the water supplies were unsatisfactory on at least one occasion as judged by standard plate counts over 10(3)/ml and the presence of coliforms, fecal coliforms, and/or S. aureus. Citrobacter freundii, Klebsiella pneumoniae, and Escherichia coli were the most frequently isolated total coliforms. At least 12 other genera of bacteria were identified from standard plate count agar. Coliform contamination was found to be higher after periods of rainfall, and high standard plate counts were more prevalent during warmer weather. These observations probably reflect leakage of surface water into improperly sealed wells or aquifer contamination during winter and the lack of chlorination to control microbial regrowth during the warm season. An inverse correlation was found between the presence of high standard plate counts and incidence of coliforms. Consumer education and at least a twice yearly monitoring of private water supplies (winter and summer) are suggested methods to signal that treatment may be necessary to reduce the risk of waterborne disease.

Examination of naturally occurring C. parvum oocysts from environmental water samples has previously been hampered by the inability to determine the public health significance of detected organisms. As a result the safety of drinking water supplies was in question. These limitations have been resolved through the development and application of a method that incorporates immunomagnetic separation (IMS) and an infectivity determination using an integrated cell culture, polymerase chain reaction assay (CC-PCR). Briefly, the method concentrates water samples by filtration or centrifugation and isolates oocysts by IMS. An acidified Hank's balanced salt solution (HBSS) containing 1% trypsin was used for the dissociation of captured oocysts from the IMS beads. In vitro HCT-8 cell culture of purified oocysts was performed in 96-well microtiter plates and infected cells were detected using PCR primers specific for C. parvum. A total of 242 raw source waters or filter backwash water samples from twenty five sites in the U.S. were analyzed to validate the procedure. Oocyst seeded in raw and filter backwash water samples were used to evaluate recovery efficiencies and performance of the CC-PCR protocol with different water quality matrices. The CC-PCR detected infectious Cryptosporidium parvum in 6 of 121 (5.0%) raw and 9 of 122 (7.4%) filter backwash water samples. All CC-PCR positive samples were confirmed by cloning and DNA sequence analysis of the PCR products. Isolates were shown to originate from human and animal sources. Grouping of genotypes permitted evaluation of strain diversification and variation. Current studies are using this technique to examine oocysts in various watersheds and in the finished drinking water of over 80 surface water treatment plants. [ABSTRACT FROM AUTHOR]