[Show abstract][Hide abstract] ABSTRACT: Cryptosporidium parvum oocysts may reach soil through direct deposition of human or animal fecal material, irrigation with raw wastewater or untreated
effluents, and contaminated runoff. Examination of soil samples for oocyst presence is of primary importance in order to prevent
secondary contamination of crops and groundwater. Several methods were proposed for oocyst recovery from soil samples; however,
their efficiency was very low. In the present study, four known methods used to recover oocysts from water and fecal samples
(sedimentation, sedimentation with reduced water content, sucrose floatation, water–ether separation) were compared to a method
used in the past to recover bacterial spores from bottom sediments (two-phase separation). The two-phase separation technique
proved to be the best method of choice resulting in a recovery average of 61.2 ± 15.6%. According to this method, the lowest
and highest recoveries were 37% to 95%, respectively. Two other important outcomes were observed with the soil experimental
set-up: (1) recovery efficiency is influenced by oocyst viability (high viability was directly correlated with increased recovery
efficiency) and (2) high sand content of soil samples reduced oocyst recovery by its detrimental effect on oocyst viability.
Water Air and Soil Pollution 10/2009; 203(1):325-334. DOI:10.1007/s11270-009-0015-y · 1.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Deliberate or accidental contamination of foods such as milk, soft drinks, and drinking water with infectious agents or toxins is a major concern to health authorities. There is a critical need to develop technologies that can rapidly and efficiently separate and concentrate biothreat agents from food matrices. A key limitation of current centrifugation and filtration technologies is that they are batch processes with extensive hands-on involvement and processing times. The objective of our studies was to evaluate the continuous flow centrifugation (CFC) technique for the rapid separation and concentration of bacterial spores from large volumes of milk. We determined the effectiveness of the CFC technology for concentrating approximately 10(3) bacterial spores in 3.7 liters (1 gal) of whole milk and skim milk, using Bacillus subtilis, Bacillus atrophaeus, and Clostridium sporogenes spores as surrogates for biothreat agents. The spores in the concentrated samples were enumerated by using standard plating techniques. Three independent experiments were performed at 10,000 rpm and 0.7 liters/min flow rate. The mean B. subtilis spore recoveries were 71.3 and 56.5% in skim and whole milk, respectively, and those for B. atrophaeus were 55 and 59.3% in skim and whole milk, respectively. In contrast, mean C. sporogenes spore recoveries were 88.2 and 78.6% in skim and whole milk, respectively. The successful use of CFC to concentrate these bacterial spores from 3.7 liters of milk in 10 min shows promise for rapidly concentrating other spores from large volumes of milk.
Journal of food protection 04/2009; 72(3):666-8. · 1.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In the present study, during a period of 16months Colilert 3000 was validated in laboratory and field tests and compared
to standard laboratory methods for monitoring of coliforms and E. coli. No false positive/negative results for coliforms/E. coli were found in 80 potable well water samples monitored with the Colilert 3000 and compared to standard methods. Although usage
of Colilert 3000 to monitor raw water is not recommended by the manufacturer, the E. coli results of 100 samples were 100% positive by membrane filtration, Colilert 18 and MPN and only 80% positive by the Colilert
3000. In addition, in all positive samples, Colilert 3000 and Colilert 18 showed higher results of two to three orders of
magnitude compared to MF and MPN. This significant difference was probably due to the presence of Aeromonas spp. and Vibrio spp. (natural inhabitants of the raw surface water) known to interfere with the Colilert test. Treated surface water was
monitored by Colilert 3000 for the presence of coliforms and E. coli. Among the 100 samples tested in parallel by membrane filtration all were negative, while with Colilert 3000 only 76% were
negative. Post-test identification of the positive samples did not reveal the presence of E. coli but interfering microorganisms. The last application was to evaluate Colilert 3000 to monitor accidental or deliberate pollution
of drinking water with sewage sources. Among 20 samples spiked with raw sewage (0.1 and 1%) all results were positive for
both coliforms and E. coli. The time span required for Colilert 3000 to detect positive samples was 6–10h compared to 24h with the standard membrane
Water Air and Soil Pollution 02/2008; 188(1):3-8. DOI:10.1007/s11270-007-9421-1 · 1.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aims of this study were to validate a portable continuous flow centrifuge (PCFC) as an alternative concentration step of US-EPA Method 1623 and to demonstrate it's efficacy for recovery of low numbers of protozoa from large volumes of various water matrices.
Recoveries of Cryptosporidium parvum oocysts, Giardia intestinalis cysts and Encephalitozoon intestinalis spores spiked into 10-1000 l volumes of various water matrices were evaluated during in-house and collaborative trials. Spiked protozoa were either approved standards or diluted stock samples enumerated according to USEPA Method 1623. Cryptosporidium recoveries exceeded method 1623 criteria and substantially high recoveries were observed for Giardia and E. intestinalis.
Portable continuous flow centrifuge methodology exceeded method 1623 acceptance criteria for Cryptosporidium and could be easily adopted for other protozoa.
The PCFC could be adopted as an alternative user-friendly concentration method for Cryptosporidium and for monitoring of large volumes of source and tap water for accidental or deliberate contamination with protozoa and potentially with other enteric pathogens. It is anticipated that PCFC would also be equal or superior to filtration for protozoa monitoring in wastewater and effluents.
[Show abstract][Hide abstract] ABSTRACT: A portable device was developed and assembled from a stationary differential continuous flow centrifuge usually employed for blood cell separation, for the purpose of concentrating Cryptosporidium and Giardia from large volumes of water. Following compaction onto the wall of the disposable plastic centrifuge bowl and aspiration of residual water, the oocysts and cysts were dislodged by injection of a 20 ml solution containing 0.01% Tween-80 and 1% SDS and vigorous shaking. Following aspiration, the oocysts were pelleted, reacted with specific FITC-conjugated monoclonal antibodies, and enumerated via fluorescence microscopy. The entire procedure required about 2 h. Initially, 55% and 87% of Cryptosporidium oocysts and Giardia cysts, respectively, were recovered from 45 litres of tap water, and 27% and 57%, respectively, from river water. Adjustments in centrifuge speed and flow rates improved recovery to about 90% for Cryptosporidium oocysts and hence, this method compared favourably with the recently developed calcium carbonate flocculation method. It was superior in time requirement and volume flexibility, and showed a distinct advantage over the standard cartridge filtration method in all respects. The continuous flow centrifugation equipment is compact, mobile, flexible, and yields reproducibly high recovery rates. The ease of handling, speed of performance and minimal requirements for post-concentration equipment, reagents and labour make the system highly cost-effective. It appears to offer an improved method, well suited for use by water utilities for monitoring the burden of water-borne protozoan pathogens.
[Show abstract][Hide abstract] ABSTRACT: During a period of 9 months (May 1995–January 1996), various environmental sources were investigated for the presence of Giardia and Cryptosporidium in Israel. Out of 15 samples from five streams, 12 were positive for Cryptosporidium (80%) with an average concentration of 0.04–1.9 oocysts/l and 8 were positive for Giardia (53.3%) with 0.05–0.78 cysts/l. Two springs were also tested and found positive for Cryptosporidium and (0.54 oocysts/l) only. The main drinking water reservoir of Israel, Lake Kineret, was also sampled 6 times at two sites. Cryptosporidium was isolated in 4/6 samples (66.6%) at an average concentration of 0.3–1.09 oocysts/l while Giardia was present in 5/6 samples (83.3%), 0.135–16.2 cysts/l. Drinking water entering a filtration pilot plant was also tested and found positive for Cryptosporidium in 23/35 samples (0–317 oocysts/l) and 8/35 for Giardia (0–16.7 cysts/l). In order to evaluate some potential inputs of contamination of the drinking water sources, two possible contributors were tested: domestic sewage and cowshed effluents. In sewage effluents, 3/3 samples were positive for both Cryptosporidium and Giardia. The oocysts and cysts were present at 8.3–8.05/l and 5–27.3/l respectively. In cowshed effluents, 1/6 samples was positive for Cryptosporidium at a high concentration (3,630 oocysts/l) but no Giardia cysts were found. The levels of Cryptosporidium and Giardia oocysts and cysts isolated from these environmental samples may present a public health hazard although no major outbreaks have so far been reported in Israel.