We evaluated the efficiency of five membrane filters for recovery of Cryptosporidium parvum oocysts and Giardia lamblia cysts. These filters included the Pall Life Sciences Envirochek (EC) standard filtration and Envirochek high-volume (EC-HV) membrane filters, the Millipore flatbed membrane filter, the Sartorius flatbed membrane filter (SMF), and the Filta-Max (FM) depth filter. Distilled and surface water samples were spiked with 10 oocysts and 10 cysts/liter. We also evaluated the recovery efficiency of the EC and EC-HV filters after a 5-s backwash postfiltration. The backwashing was not applied to the other filtration methods because of the design of the filters. Oocysts and cysts were visualized by using a fluorescent monoclonal antibody staining technique. For distilled water, the highest percent recovery for both the oocysts and cysts was obtained with the FM depth filter. However, when a 5-s backwash was applied, the EC-HV membrane filter (EC-HV-R) was superior to other filters for recovery of both oocysts (n ‫؍‬ 53 ؎ 15.4 per 10 liters) and cysts (n ‫؍‬ 59 ؎ 11.5 per 10 liters). This was followed by results of the FM depth filter (oocysts, 28.2 ؎ 8, P ‫؍‬ 0.015; cysts, 49.8 ؎ 12.2, P ‫؍‬ 0.4260), and SMF (oocysts, 16.2 ؎ 2.8, P ‫؍‬ 0.0079; cysts, 35.2 ؎ 3, P ‫؍‬ 0.0079). Similar results were obtained with surface water samples. Giardia cysts were recovered at higher rates than were Cryptosporidium oocysts with all five filters, regardless of backwashing. Although the time differences for completion of filtration process were not significantly different among the procedures, the EC-HV filtration with 5-s backwash was less labor demanding.

Aims:  To use BioBallTM cultures as a precise reference standard to evaluate methods for enumeration of Escherichia coli and other coliform bacteria in water samples. Methods and Results:  Eight methods were evaluated including membrane filtration, standard plate count (pour and spread plate methods), defined substrate technology methods (ColilertTM and ColisureTM), the most probable number method and the Petrifilm disposable plate method. Escherichia coli and Enterobacter aerogenes BioBallTM cultures containing 30 organisms each were used. All tests were performed using 10 replicates. The mean recovery of both bacteria varied with the different methods employed. Conclusions:  The best and most consistent results were obtained with Petrifilm and the pour plate method. Other methods either yielded a low recovery or showed significantly high variability between replicates. Significance and Impact of the Study:  The BioBallTM is a very suitable quality control tool for evaluating the efficiency of methods for bacterial enumeration in water samples.

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