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.
Aims: Clostridium perfringens is recommended as a suitable indicator bacterium for human enteric viruses, Giardia cysts and Cryptosporidium oocysts in finished water and in the assessment and evaluation of water treatment. Several agars and confirmation procedures were evaluated in parallel with the Australian/New Zealand Standard (AS/NZ) Method for the enumeration of Cl. perfringens from treated and untreated sewage samples.
Methods and Results: The current AS/NZ method utilizes tryptose sulfite cycloserine agar (TSC), lactose gelatin medium (LG) and nitrate motility medium (NM) at an incubation temperature of 37°C. Sixty treated and untreated sewage samples were used to evaluate TSC agar, membrane Cl. perfringens agar (mCP), Perfringens agar (OPSP) and Perfringens agar with 4‐methylumbelliferyl phosphate (OPSP–MUP) for enumeration of Clostridium. An incubation temperature of 44°C for 24 h was used for comparison. Confirmation procedures were also evaluated using 103 isolates and included LG and NM, ortho‐nitrophenyl‐β‐d‐galactopyranoside (ONPG) with MUP (ONPG–MUP) and phosphatase reagent (PR). OPSP compared favourably with TSC agar. One false negative result was obtained from each of the LG/NM and ONPG–MUP procedures. No false results were obtained using the PR confirmation procedure.
Conclusions: OPSP agar and PR were determined as suitable replacements for the AS/NZ Standard procedure with no interference from spreading organisms.
Significance and Impact of the Study: This is a simple and rapid method for isolating and enumerating Cl. perfringens from sewage samples and confirmed results can be reported more quickly due to shorter analytical turnaround times.
Aims: The equivalence of Oxoid (CM 1046) Brilliance(TM)E. coli/coliform selective agar to mFC agar, as used in the Australian/New Zealand Standard Method to detect thermotolerant coliforms and Escherichia coli in water samples, was assessed.
Methods and Results: A total of 244 water samples were analysed in parallel over a 5‐month period. Sewage effluent samples (n = 131, sites = 43), freshwater (n = 62, sites = 18) and marine/brackish water samples (n = 51, sites = 23) were analysed. The Wilcoxon matched‐pairs signed‐ranks test showed a varying degree of statistical difference between the two methods. All matrices had a higher recovery in the trial method. Enterococci faecalis, Aeromonas spp. and Vibrio spp. did not grow on the CM1046 agar, and Pseudomonas aeruginosa and Enterobacter aerogenes were inhibited.
Conclusions: The use of CM 1046 for the detection and enumeration of E. coli and thermotolerant coliforms in water samples is a suitable alternative to the AS/NZS Standard Method.
Significance and Impact of the study: The use of CM1046 agar was less labour intensive and time consuming, as no secondary confirmation steps were required. Confirmed results could be reported within 24 h of sample analysis, as compared to 48 h with the reference method. Public health concerns can be addressed in a more efficient manner.
Aims: To evaluate and review two methods for enumeration of E. coli bacteria in surface water samples.Methods and results: Filtration using membrane faecal coliform (mFC) agar and a defined substrate technology Y method (Colilert-18 w ) was evaluated. E. coli BioBall Y bacteria were seeded into autoclaved surface water samples. In addition, 266 surface water samples from South East Queensland were analysed in parallel using both mFC and Colilert-18 w .Conclusions: E. coli is the bacterium of choice when analysing water samples for faecal contamination. An overall lower mean recovery was demonstrated using mFC agar than Colilert for both seeded surface water and in parallel testing of surface water samples. There was a statistically significant difference between BioBall bacteria on mFC agar and values on the QA certificate ( p # 0.0001) but there was no significance difference between Colilert for E. coli using the BioBall ( p ¼ 0.8488). There was a significant difference between mFC agar and Colilert in parallel testing of surface water samples ( p # 0.0001) with greater sensitivity demonstrated by the Colilert procedure.This data confirms the conclusions of other researchers that Colilert is a suitable substitute for membrane filtration for surface water analysis for the detection of E. coli as faecal indicator bacteria.
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