Spent Irrigation Water Research Articles

Enhancement of a Spent Irrigation Water Recycling Process: A Case Study in a Food Business

Food operations use vast amounts of water. To reduce utility costs as well as concerns regarding water depletion in ecosystems, food businesses usually try to reuse their water. However, this often needs a recycling process to ensure the water is of good quality and safe to reuse in a food environment. This paper presents a case study of a grower of beansprouts and other varieties of sprouted seeds that uses six million litres of water weekly. Approximately 60% of their spent irrigation water is recycled using both 50 µm and 20 µm drum filtration. In addition, chlorine dioxide is used as part of the recycling process as a disinfectant. Our analysis demonstrated that the size of suspended solid particles in over 90% of the cumulative sample tested was smaller than the current 20 µm filter in place, highlighting that the existing system was ineffective. We, then, explored options to enhance the water recycling system of the company. After careful analysis, it was proposed to install a membrane-filtration system with ultraviolet technology to increase the finest level of filtration from the existing 20 µm to 0.45 µm absolute and sterilize any remaining bacteria. This not only improved water quality, but also allowed for the removal of chemicals from the recycling system, delivering both financial and technical improvements.

Water Microbiota from a Commercial Alfalfa Sprout Crop over 4 Days of Growth.

Sprouts have been implicated in numerous foodborne illness outbreaks. To better understand baseline microbial profiles of irrigation water and subsequent spent irrigation water of alfalfa sprouts, DNA from water was extracted, sequenced, and annotated with CosmosID and a custom pipeline to provide bacterial, fungal, protist, and antimicrobial resistance gene profiles.

The value of a complex unit for the simultaneous use of a transverse surface and a longitudinal ridge when irrigating cotton

The article provides data on the development of a complex Palodelatel unit without damaging growing plants, the simultaneous rate of a transverse surface and a longitudinal ridge in saline, sloping uneven soils in the Bukhara region, also taking into account the slope and unevenness of the soil relief, in a scientifically based form it is stated about the uniform provision of irrigation water and reduction of manual labor, working time, duration and distance between irrigation days, saving spent irrigation water and elimination of salt spots and reducing the cost of irrigation water by 25%, irrigation duration by 1.5-2 days, crop addition by 5-4.2 c / ha.

Assessing the Public Health Impact and Effectiveness of Interventions To Prevent Salmonella Contamination of Sprouts

Sprouts have been a recurring public health challenge due to microbiological contamination, and Salmonella has been the major cause of sprout-associated outbreaks. Although seed treatment and microbiological testing have been applied as risk reduction measures during sprout production, the extent to which their effectiveness in reducing the public health risks associated with sprouts has not been well investigated. We conducted a quantitative risk assessment to measure the risk posed by Salmonella contamination in sprouts and to determine whether and how mitigation strategies can achieve a satisfactory risk reduction based on the assumption that the risk reduction achieved by a microbiological sampling and testing program at a given sensitivity is equivalent to that achieved by direct inactivation of pathogens. Our results indicated that if the sprouts were produced without any risk interventions, the health impact caused by sprouts contaminated with Salmonella would be very high, with a median annual estimated loss of disability-adjusted life years (DALYs) of 691,412. Seed treatment (with 20,000 ppm of calcium hypochlorite) or microbiological sampling and testing of spent irrigation water (SIW) alone could reduce the median annual impact to 734 or 4,856 DALYs, respectively. Combining seed treatment with testing of the SIW would further decrease the risk to 58 DALYs. This number could be dramatically lowered to 3.99 DALYs if sprouts were produced under conditions that included treating seeds with 20,000 ppm of calcium hypochlorite plus microbiological testing of seeds, SIW, and finished products. Our analysis shows that the public health impact due to Salmonella contamination in sprouts could be controlled if seeds are treated to reduce pathogens and microbiological sampling and testing is implemented. Future advances in intervention strategies would be important to improve sprout safety further.

Outbreaks Caused by Sprouts, United States, 1998–2010: Lessons Learned and Solutions Needed

After a series of outbreaks associated with sprouts in the mid-1990s, the U.S. Food and Drug Administration (FDA) published guidelines in 1999 for sprouts producers to reduce the risk of contamination. The recommendations included treating seeds with an antimicrobial agent such as calcium hypochlorite solution and testing spent irrigation water for pathogens. From 1998 through 2010, 33 outbreaks from seed and bean sprouts were documented in the United States, affecting 1330 reported persons. Twenty-eight outbreaks were caused by Salmonella, four by Shiga toxin-producing Escherichia coli, and one by Listeria. In 15 of the 18 outbreaks with information available, growers had not followed key FDA guidelines. In three outbreaks, however, the implicated sprouts were produced by firms that appeared to have implemented key FDA guidelines. Although seed chlorination, if consistently applied, reduces pathogen burden on sprouts, it does not eliminate the risk of human infection. Further seed and sprouts disinfection technologies, some recently developed, will be needed to enhance sprouts safety and reduce human disease. Improved seed production practices could also decrease pathogen burden but, because seeds are a globally distributed commodity, will require international cooperation.

Evaluation of PCR Detection of Salmonella in Alfalfa Sprouts and Spent Irrigation Water Collected during Sprouting of Naturally Contaminated Seed

This study evaluated the efficacy of a PCR-based system (DuPont Qualicon BAX) for detection of Salmonella in sprouts and spent irrigation water collected during sprouting of seeds naturally contaminated with Salmonella. Alfalfa seeds were grown in Mason jars at 20 and 30°C for 3 days. Levels of Salmonella present in the water and sprouts were determined by most-probable-number (MPN) analysis. Background microflora levels were also determined. Samples of spent irrigation water and sprouts were enriched overnight individually in tetrathionate broth and in buffered peptone water with novobiocin at 42°C and then run in the BAX system. Samples were also enriched according to the U.S. Food and Drug Administration's Bacteriological Analytical Manual (FDA BAM) method for Salmonella as a comparison. Salmonella levels were lower at 20°C compared with 30°C for some trials, and background microflora levels ranged from 10(7) to 10(8) CFU/g or ml at 20°C and 10(8) to 10(9) CFU/g or ml at 30°C. In trials with a Salmonella level >1.1 MPN/g or ml, both the BAX and FDA BAM methods were able to detect Salmonella in all samples. In trials with lower levels (0.21 MPN/g or ml or lower) of Salmonella, BAX was able to detect more positive samples than FDA BAM. For one trial with <0.003 MPN/g or ml of Salmonella, the presence of the pathogen was not indicated by either the BAX or the FDA BAM method. The results suggest that PCR detected low levels of Salmonella in sprouts or spent irrigation water collected from sprouting of naturally contaminated seeds.

VIDAS Salmonella (SLM) Assay Method EasySLM with ChromID Salmonella (SM2) Agar

A method modification study was conducted for the VIDAS Salmonella (SLM) assay (AOAC Performance Tested Method 020901) using the EasySLM method to validate a matrix extension for peanut butter. The VIDAS EasySLM method is a simple enrichment procedure compared to traditional Salmonella methods, requiring only pre-enrichment and a single selective enrichment media, Salmonella Xpress 2 (SX2) broth. SX2 replaces the two selective broths in traditional methods and eliminates the M broth transfer, incubation, and subsequent pooling of M broths prior to VIDAS assay. The validation study was conducted under the AOAC Research Institute Emergency Response Validation program. VIDAS SLM was compared to the U.S. Food and Drug Administration's Bacteriological Analytical Manual (FDA-BAM) method for detection of S. enterica ser. Typhimurium in peanut butter. All peanut butter samples were prepared, blind-coded, and shipped to the method developers' laboratory by Q Laboratories. In addition, Q Laboratories performed most probable number and reference method analyses on peanut butter samples. The VIDAS EasySLM ChromID Salmonella (SM2) Agar was previously validated in the Performance Tested Methods program for the detection of Salmonella in roast beef, raw ground pork, turkey, pork sausage, raw chicken breast, dry pet food, whole milk, ice cream, bagged spinach, shrimp (raw, peeled), raw cod, spent irrigation water, pecans, peanut butter, dry pasta, cake mix, ground black pepper, nonfat dry milk, liquid eggs, cantaloupe, and orange juice. In the matrix extension study for peanut butter, the VIDAS EasySLM method was shown to be equivalent to the appropriate reference culture procedure using both buffered peptone water pre-enrichment and the FDA-BAM lactose pre-enrichment in the two-step enrichment method with SX2 media. The current study extends the validation to include peanut butter.

Concentration and detection of Salmonella in mung bean sprout spent irrigation water by use of tangential flow filtration coupled with an amperometric flowthrough enzyme-linked immunosorbent assay.

The development of a culture-free method for Salmonella screening of spent irrigation water derived from sprouting mung bean beds is described. The system used tangential flow filtration (TFF) to nonspecifically concentrate cells from large (2- to 10-liter) sample volumes. The retentate (100 ml) from the TFF was then flowed over an anti-Salmonella antibody-modified cellulose acetate membrane. The captured Salmonella was detected by reacting with a secondary anti-Salmonella and goat anti-rabbit biotin labeled antibody, followed by avidin-tagged glucose oxidase. The hydrogen peroxide generated from the enzymic oxidation of glucose was amperometrically detected at an underlying platinum electrode. It was found that 10 liters of Salmonella suspensions of 2 log CFU/ml could be concentrated to 4 log CFU/ml with 60% recovery regardless of the flow rate (112 to 511 ml/min) or transmembrane pressure (0 to 20 lb/in2) applied. The solids content of spent irrigation water negatively affected the filtration rate of TFE. This was most evident in spent irrigation water collected in the initial 24 h of the sprouting period, where the solids content was high (4,170 mg/liter) compared with samples collected at 96 h (560 mg/ liter). Trials were performed using mung bean beds inoculated with different Salmonella levels (1.3 to 3.3 log CFU/g). By using the optimized TFF and flowthrough immunoassay it was possible to detect Salmonella in spent irrigation water at levels of 2.43 log CFU/ml within 4 h. The integrated concentration and detection system will provide a useful tool for sprout producers to perform in-house pathogen screening of spent irrigation water.

Composite versus single sampling of spent irrigation water to assess the microbiological status of sprouting mung bean beds

AbstractBACKGROUND: Spent irrigation water testing has been recommended in sprouted seed production to detect the presence of pathogens. However, because of the heterogeneous distribution of contamination within batches of sprouted seed, taking single samples of spent irrigation water may return false‐negative results. The following evaluated whether spent irrigation water collected from multiple points provided a more representative assessment of the microbiological status of the sprouting mung bean bed compared to when single samples were taken.RESULTS: Generic Escherichia coli or Aeromonas was recovered in one and 10 of the 160 sprout samples taken from 32 sprouting mung bean batches, respectively. Composite spent irrigation water samples tested positive for generic E. coli on 19 occasions compared to 12 when single samples were taken. Mesophilic Aeromonas was detected in 13 composite spent irrigation water samples which compared to eight single samples. The prevalence of either target bacterium in composite spent irrigation water samples was not significantly (P &gt; 0.05) different compared to when a single sample was collected.CONCLUSIONS: Sampling spent irrigation water from multiple points under sprouting mung bean beds does not significantly increase the probability of detecting contamination, if present. The findings of the study should be considered when devising sampling plans for spent irrigation water testing in bean sprout production. Copyright © 2008 Society of Chemical Industry

Factors Influencing the Growth of Salmonella during Sprouting of Naturally Contaminated Alfalfa Seeds

In this study, the factors that affect Salmonella growth during sprouting of naturally contaminated alfalfa seeds associated with two previous outbreaks of salmonellosis were examined. A minidrum sprouter equipped with automatic irrigation and rotation systems was built to allow sprouting to be conducted under conditions similar to those used commercially. The growth of Salmonella during sprouting in the minidrum was compared with that observed in sprouts grown in glass jars under conditions commonly used at home. The level of Salmonella increased by as much as 4 log units after 48 h of sprouting in jars but remained constant during the entire sprouting period in the minidrum. The effect of temperature and irrigation frequency on Salmonella growth was examined. Increasing the sprouting temperature from 20 to 30°C increased the Salmonella counts by as much as 2 log units on sprouts grown both in the minidrum and in the glass jars. Decreasing the irrigation frequency from every 20 min to every 2 h during sprouting in the minidrum or from every 4 h to every 24 h during sprouting in the glass jars resulted in an approximately 2-log increase in Salmonella counts. The levels of total aerobic mesophilic bacteria, coliforms, and Salmonella in spent irrigation water closely reflected those found in sprouts, confirming that monitoring of spent irrigation water is a good way to monitor pathogen levels during sprouting.

Salmonella infections associated with mung bean sprouts: epidemiological and environmental investigations

We investigated an outbreak of Salmonella Enteritidis (SE) infections linked to raw mung bean sprouts in 2000 with two case-control studies and reviewed six similar outbreaks that occurred in 2000-2002. All outbreaks were due to unusual phage types (PT) of SE and occurred in the United States (PT 33, 1, and 913), Canada (PT 11b and 913), and The Netherlands (PT 4b). PT 33 was in the spent irrigation water and a drain from one sprout grower. None of the growers disinfected seeds at recommended concentrations. Only two growers tested spent irrigation water; neither discarded the implicated seed lots after receiving a report of Salmonella contamination. We found no difference in the growth of SE and Salmonella Newport on mung beans. Mung bean sprout growers should disinfect seeds, test spent irrigation water, and discontinue the use of implicated seed lots when pathogens are found. Laboratories should report confirmed positive Salmonella results from sprout growers to public health authorities.

Mathematical Modeling and Assessment of Microbial Migration during the Sprouting of Alfalfa in Trays in a Nonuniformly Contaminated Seed Batch Using Enterobacter aerogenes as a Surrogate for Salmonella Stanley

Raw seed sprouts have been implicated in several food poisoning outbreaks in the past 10 years. The U.S. Food and Drug Administration recommends that sprout growers use interventions (such as testing of spent irrigation water) to control the presence of pathogens in the finished product. During the sprouting process, initially low concentrations of pathogen may increase, and contamination may spread within a batch of sprouting seeds. A model of pathogen growth as a function of time and distance from the contamination spot during the sprouting of alfalfa in trays has been developed with Enterobacter aerogenes. The probability of detecting contamination was assessed by logistic regression at various time points and distances by sampling from sprouts or irrigation water. Our results demonstrate that microbial populations and possibility of detection were greatly reduced at distances of ≥20 cm from the point of contamination in a seed batch during tray sprouting; however, the probability of detecting microbial contamination at distances less than 10 cm from the point of inoculation was almost 100% at the end of the sprouting process. Our results also show that sampling irrigation water, especially large volumes of water, is highly effective at detecting contamination: by collecting 100 ml of irrigation water for membrane filtration, the probability of detection was increased by three to four times during the first6hof seed germination. Our findings have quantified the degree to which a small level of contamination will spread throughout a tray of sprouting alfalfa seeds and subsequently be detected by either sprout or irrigation water sampling.

Quantitative Analysis of the Growth of Salmonella Stanley during Alfalfa Sprouting and Evaluation of Enterobacter aerogenes as Its Surrogate

Raw seed sprouts have been implicated in several food poisoning outbreaks in the last 10 years. Few studies have included investigations of factors influencing the effectiveness of testing spent irrigation water, and in no studies to date has a nonpathogenic surrogate been identified as suitable for large-scale irrigation water testing trials. Alfalfa seeds were inoculated with Salmonella Stanley or its presumptive surrogate (nalidixic acid–resistant Enterobacter aerogenes) at three concentrations (∼3, ∼30, and ∼300 CFU/g) and were then transferred into either flasks or a bench top–scale sprouting chamber. Microbial concentrations were determined in seeds, sprouts, and irrigation water at various times during a 4-day sprouting process. Data were fit to logistic regression models, and growth rates and maximum concentrations were compared using the generalized linear model procedure of SAS. No significant differences in growth rates were observed among samples taken from flasks or the chamber. Microbial concentrations in irrigation water were not significantly different from concentrations in sprout samples obtained at the same time. E. aerogenes concentrations were similar to those of Salmonella Stanley at corresponding time points for all three inoculum concentrations. Growth rates were also constant regardless of inoculum concentration or strain, except that lower inoculum concentrations resulted in lower final concentrations proportional to their initial concentrations. This research demonstrated that a nonpathogenic easy-to-isolate surrogate (nalidixic acid–resistant E. aerogenes) provides results similar to those obtained with Salmonella Stanley, supporting the use of this surrogate in future large-scale experiments.

Direct Quantitation and Detection of Salmonellae in Biological Samples without Enrichment, Using Two-Step Filtration and Real-Time PCR

A new two-step filtration protocol followed by a real-time PCR assay based on SYBR green I detection was developed to directly quantitate salmonellae in two types of biological samples: i.e., chicken rinse and spent irrigation water. Four prefiltration filters, one type of final filter, and six protocols for recovery of salmonellae from the final filter were evaluated to identify an effective filtration protocol. This method was then combined with a real-time PCR assay based on detection of the invA gene. The best results were obtained by subsequent filtration of 100 ml of chicken rinse or 100 ml of spent irrigation water through filters with pore diameters of >40 mum to remove large particles and of 0.22 microm to recover the Salmonella cells. After this, the Salmonella cells were removed from the filter by vortexing in 1 ml of physiological saline, and this sample was then subjected to real-time quantitative PCR. The whole procedure could be completed within 3 h from sampling to quantitation, and cell numbers as low as 7.5 x 10(2) CFU per 100-ml sample could be quantified. Below this limit, qualitative detection of concentrations as low as 2.2 CFU/100 ml sample was possible on occasion. This study has contributed to the development of a simple, rapid, and reliable method for quantitation of salmonellae in food without the need for sample enrichment or DNA extraction.

Spatial Distribution of Salmonella, Escherichia coli O157:H7, and Other Bacterial Populations in Commercial and Laboratory-Scale Sprouting Mung Bean Beds

The reliability of testing spent irrigation water to assess the microbiological status of sprouting mung bean beds has been investigated. In commercial trials, the distribution of opportunistic contaminants within 32 bean sprout beds (25 kg of mung beans per bin) was assessed 48 h after germination. The prevalence of generic Escherichia coli, thermotolerant coliforms, and Aeromonas in sprouts (n = 288) was 5, 11, and 39%, respectively, and 57, 70, and 79% in the corresponding spent irrigation water samples (n = 96). Contamination was heterogeneously distributed within the seedbed. In laboratory trials, beans inoculated with a five-strain cocktail of either Salmonella or E. coli O157:H7 (103 to 104 CFU/g) were introduced (1 g/500 g of noninoculated seeds) at defined locations (top, middle, or base), and the beans were then sprouted for 48 h. When seeds inoculated with pathogens were introduced at the base or top of the seedbed, the pathogens were typically restricted to these sites and resulted in 44% of the spent irrigation water samples returning false-negative results. Introducing inoculated beans into the middle or at the presoak stage enhanced the distribution of both pathogens within the subsequent sprout bed and resulted in comparable levels recovered in spent irrigation water. The study demonstrated that even though screening a single sample of spent irrigation water is more reliable than testing sprouts directly, it does not provide an accurate assessment of the microbiological status of sprouting mung bean beds. Such limitations may be addressed by ensuring that bean batches are mixed prior to use and by taking spent irrigation water samples from multiple sites at the latter stages of the sprouting process.

A Simple Method for the Direct Detection of Salmonella and Escherichia coli O157:H7 from Raw Alfalfa Sprouts and Spent Irrigation Water Using PCR

The U.S. Food and Drug Administration recognizes that raw seed sprouts are an important cause of foodborne disease and is now recommending that either spent irrigation water or final product be screened for Salmonella and Escherichia coli O157:H7 as a means of assuring the safety of product intended for consumption. In an effort to streamline such testing efforts, a simple method to preconcentrate pathogens from sprouts and spent irrigation water was investigated to facilitate the direct (without prior cultural enrichment) detection of pathogens using the PCR technique. Alfalfa sprouts and spent irrigation water were seeded with Salmonella enterica serovar Typhimurium and E. coli O157:H7 at 10−1 to 106 CFU/g or CFU/ml, respectively. Samples were blended (sprouts only) and then centrifuged at high speed to sediment the total bacterial population. The precipitate was processed for DNA isolation, PCR amplification, and amplicon confirmation by Southern hybridization. Mean pathogen recoveries after centrifugation ranged from 96 to 99% for both pathogens in both matrices. Using primers targeting the invA gene for Salmonella Typhimurium and the stx genes of E. coli O157:H7, it was possible to detect both pathogens in alfalfa sprouts at seeding concentrations as low as 10 CFU/g. PCR detection limits for both pathogens from spent irrigation water were 10−1 CFU/ml, the equivalent of 100 CFU/liter of water. Because spent irrigation water is constitutionally simple, it is particularly well suited for bacterial concentration by simple centrifugation steps. In this study, progress was made toward development of a rapid, inexpensive, and sensitive method for the detection of sprout-associated pathogens that is relevant to current industrial practices and needs.

A Rapid and Automated Fiber Optic–Based Biosensor Assay for the Detection ofSalmonella in Spent Irrigation Water Used in the Sprouting of Sprout Seeds

Recent outbreaks of foodborne illness have been linked to the consumption of contaminated sprouts. The spent irrigation water used to irrigate sprouts can carry many microorganisms, including pathogenic strains ofEscherichia coli andSalmonella enterica. These pathogens are believed to originate from the seeds. The U.S. Food and Drug Administration recommends that sprout producers conduct microbiological testing of spent irrigation water from each production lot at least 48 h after seeds have germinated. Microbial analysis for the detection ofSalmonella is labor-intensive and takes days to complete. A rapid and automated fiber-optic biosensor assay for the detection ofSalmonella in sprout rinse water was developed in this study. Alfalfa seeds contaminated with various concentrations ofSalmonella Typhimurium were sprouted. The spent irrigation water was assayed 67 h after alfalfa seed germination with the RAPTOR (Research International, Monroe, Wash.), an automated fiber optic–based detector.Salmonella Typhimurium could be positively identified in spent irrigation water when seeds were contaminated with 50 CFU/g. ViableSalmonella Typhimurium cells were also recovered from the waveguides after the assay. This biosensor assay system has the potential to be directly connected to water lines within the sprout-processing facility and to operate automatically, requiring manual labor only for preventative maintenance. Therefore, the presence ofSalmonella Typhimurium in spent irrigation water could be continuously and rapidly detected 3 to 5 days before the completion of the sprouting process.

RAPID DETECTION OF OUTBREAK ESCHERICHIA COLI O157 AND SALMONELLA ON ALFALFA SPROUTS BY IMMUNOMAGNETIC CAPTURE AND TIME‐RESOLVED FLUORESCENCE1

ABSTRACTCommercially available alfalfa seeds were inoculated with low levels (∼ 4 CFU/g) of pathogenic bacteria and sprouted at 25C. At 48 h, the spent irrigation water and sprouts were separately transferred to brain heart infusion (BHI) broth and enriched for 4 h at 37C and 160 rpm. Specific immunomagnetic beads (IMB) were then applied to capture the E. coli O157 or Salmonella in the enriched media. Separation and concentration of captured pathogens were achieved using magnetic particle concentrators (MPC). IMB captured E. coli O157:H7 and Salmonella spp. then formed sandwiched complexes with europium (Eu) labeled anti‐E. coli O157 antibodies and samarium (Sm) labeled anti‐Salmonella antibodies, respectively. After washing the complexes, the lanthanide labels were extracted out from the complexes by specific chelators to form strongly fluorescent Eu‐ and Sm‐chelates. The specific time‐resolved fluorescence (TRF) associated with Eu or Sm was measured to estimate the extent of capture of the E. coli O157 and Salmonella, respectively. The results indicated that the approach could detect E. coli O157 and many Salmonella spp. from spent irrigation water or sprouts grown from contaminated seeds. Nontargeted bacteria, e.g., native microflora present on the untreated seeds and inoculated Aeromonas and Citrobacter, exhibited no crossreactivity and counts were not significantly different from background fluorescence of the IMB alone. Since pathogen detection was achieved within 6 h, the assay could detect contamination levels as low as 4 CFU/g of seeds and it showed no cross‐reactivity with nonpathogenic microflora present on the sprouts, the developed methodology could be used as a rapid, sensitive and specific screening process for E. coli O157 and Salmonella spp. in sprouts and their irrigation water.

Industry Practices and Compliance with U.S. Food and Drug Administration Guidelines among California Sprout Firms

Since 1995, raw vegetable sprouts have been implicated as the vehicle of infection in 15 foodborne outbreaks involving Salmonella and 2 foodborne outbreaks involving Escherichia coli O157:H7. To reduce the numbers of sprout-related outbreaks, the U.S. Food and Drug Administration (FDA) published Guidance for Industry: Reducing Microbial Food Safety Hazards for Sprouting Seeds in 1999. Between October 2000 and April 2001, 61.5% (16 of 26) of the known commercial sprout firms in California were enrolled in a survey to evaluate the industry practices of California sprouting operations and to determine compliance with FDA guidelines. A standardized questionnaire was used to collect data on firm demographics and seed disinfection practices. Additionally, free chlorine levels in seed disinfection solutions were measured, and 48-h spent irrigation water samples were collected from each firm. The irrigation water was screened for Salmonella and E. coli O157:H7 with FDA-recommended test kits. Free chlorine levels in the treatment solutions ranged from 50 to 35,000 mg/liter (ppm), with a median of 14,000 mg/liter (ppm). Free chlorine levels were higher for firms producing alfalfa sprouts than for those producing only mung bean or soybean sprouts (P = 0.03). Levels of free chlorine tended to be higher for firms using a calcium hypochlorite treatment solution than for firms using a sodium hypochlorite treatment solution (P = 0.067). All 32 irrigation water samples screened for Salmonella tested negative. Of the irrigation water samples tested for E. coli O157:H7, 75% (24 of 32) tested negative, and 25% (8 of 32) tested presumptive positive. The eight presumptive positive samples were found to be negative after further testing. These results indicate that producers of alfalfa sprouts are generally achieving the FDA-recommended calcium hypochlorite level of 20,000 mg/liter (ppm), whereas mung bean sprout producers are not.

Microbiological analysis of seed sprouts in Norway

As part of larger survey of microbial contamination of fruits and vegetables in Norway, four different sprouted seed products were analysed for bacterial and parasitic contaminants ( n=300 for bacterial analyses and n=from 17 to 171 for parasite analyses, depending on parasite). Escherichia coli O157, Salmonella, Listeria monocytogenes, Cyclospora oocysts, Ascaris eggs and other helminth parasites were not detected in any of the sprout samples. Thermotolerant coliform bacteria (TCB) were isolated from approximately 25% of the sprout samples, with the highest percentage of TCB positive samples in alfalfa sprouts. Most TCB were Enterobacter spp. and Klebsiella. E. coli was isolated from 8 of 62 TCB positive mung bean sprout samples. Cryptosporidium oocysts were detected in 8% of the sprout samples and Giardia cysts were detected in 2% of the samples. All the Cryptosporidium positive samples, and most of the Giardia positive samples, were mung bean sprouts. Parasite concentrations in positive samples were low (between 1 and 3 oocysts/cysts per 50 g sprouts). Sprout irrigation water was also analysed for microbial contaminants. E. coli O157 and L. monocytogenes were not detected. TCB were isolated from approximately 40% of the water samples. Salmonella reading was isolated from three samples of spent irrigation water on 3 consecutive days. Cryptosporidium and Giardia were also isolated from spent irrigation water. Additionally, eight samples of unsprouted mung bean seed were analysed for Cryptosporidium oocysts and Giardia cysts. One or both of these parasites were detected in six of the unsprouted seed samples at concentrations of between 1 and 5 oocysts/cysts per 100 g unsprouted seed. Whilst our results support spent irrigation water as the most suitable matrix for testing for bacteria, unsprouted seed is considered the more useful matrix for analysing for parasite contaminants.