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PubMed1992

Effect of copper and cobalt addition on digestion and growth in heifers fed diets containing alfalfa silage or corn crop residues.

Copper and cobalt were added to the diet of heifers in excess of NRC recommendations for these minerals. In Experiment 1, the rate of DM disappearance from dacron bags placed in the rumen was increased by the additional dietary Cu and Co for alfalfa hay (14.6 vs. 8.4%/h) and corn cobs (5.8 vs. 3.1%/h) but did not affect the DM disappearance rate for corn crop residue silage (3.6 vs. 3.4%/h). In Experiment 2, additional Cu and Co increased DM disappearance rate of corn crop residue silage (6.2 vs. 3.4%/h) but did not influence the rate of alfalfa hay (8.6 vs. 7.6%/h). In Experiment 3, a random design with a 2 x 2 factorial arrangement was used. The diet consisted of 45% corn crop residue silage, 35% alfalfa silage containing 60 or 40% DM, 18% high moisture corn, and 2% vitamin and mineral mix with or without added Cu and Co, respectively. Each of the four diets was group-fed to 9 light and 11 heavy Holstein heifers. Growth rate was lower with Cu and Co supplementation, but DM digestibility was improved by the additional Cu and Co. These results indicate that addition of Cu and Co above the NRC requirements may aid in digestion of low quality forages.

Animals↗

PubMed1993

Effect of whole crop cereal grain silage substituted for alfalfa silage on performance of lactating dairy cows.

Barley, oats, and triticale were planted at the University of Alberta Research Station May 22 to June 1, 1990, harvested August 5 to August 19, 1990, at the early to mid-dough stage, and ensiled. Second-cutting alfalfa was harvested at midbloom and ensiled. Twenty Holstein cows in early lactation and 24 in midlactation were subjected to a 21-d standardization period (covariate) and were fed a TMR (50:50, forage: concentrate). Forage was a combination of equal portions of silage of alfalfa, barley, oats, and triticale. Following the covariate period, cows were offered TMR for ad libitum intake for 12 wk in which the forage portion of the TMR was one of the four silages. Diets based on oat and triticale silages lowered DMI, but overall milk production was not significantly different across treatments. Digestibilities of DM, OM, CP, and ADF were highest for the alfalfa silage diet, intermediate for the barley silage diet, and lowest for diets based on oat and triticale silages. The high dietary NDF concentration in oat and triticale silage limited feed intake. However, forage source had no major effect on dairy cow performance when forage was fed for ad libitum intake; therefore, barley, oat, and triticale silages harvested at an early stage of maturity can be used effectively in dairy cow rations.

Animal Feed↗

PubMed1994

Compressed baled alfalfa hay for primiparous and multiparous dairy cows.

Compressed baled alfalfa hay was fed to cows, and the effects on productivity, chewing activities, and digestion were measured using a replicated 4 x 4 Latin square design. Cows received second-cutting alfalfa hay (20% CP; 40% NDF) from either compressed or standard small rectangular bales at two forage to concentrate ratios (35:65 and 65:35, DM basis). Compressed hay did not affect milk yield, although milk fat content was higher (2.90 vs. 2.68%). Higher concentrate diets increased milk yield (32.2 vs. 28.3 kg/d), lowered milk fat (2.66 vs. 2.91%), and increased milk protein (3.16 vs. 2.99%) and lactose (5.06 vs. 4.99%) with no interaction between concentrate proportion and hay type. Cows fed compressed bales spent less time eating per kilogram of DM and NDF consumed than cows fed standard bales, but rumination time was unaffected by forage processing. For cows fed both types of hay, digestibilities of DM, ADF, and NDF were similar; ruminal liquid outflow rates also were similar, but rate of particulate passage from the reticulo-rumen was greater for cows receiving compressed hay. Compressing alfalfa hay did not adversely affect forage quality but increased the ease of shipping and handling and minimized storage space requirements. This process may be beneficial when higher milk fat content is desirable or when cows have limited time to consume forage.

Animal Feed↗

PubMed1995

Digestion and energy balance in lactating dairy cows fed varying ratios of alfalfa silage and grain.

Forty-four multiparous and 43 primiparous Holstein cows were used to study the effect of dietary alfalfa silage: grain ratio on digestion, passage of digesta, and energy balance in a complete lactation experiment. Cows were placed on one of five treatments with forage contents from 38.2 to 98.2% (DM basis) during the first 12 wk of lactation. Forage content was increased during wk 13 to 26 of lactation to give diets containing 48.2 to 98.2% forage and again during wk 27 to 44 to give diets containing 68.2 to 98.2% forage. Both DMI and DM digestibilities decreased as proportion of dietary forage increased. The DM digestibilities for multiparous and primiparous cows ranged between 69.3 and 57.3% during early lactation and 64.9 and 55.5% during late lactation. Increased percentage of forage in the diet decreased and then increased (quadratic relationship) the ruminal retention time of La, a marker applied to the alfalfa silage in early and late lactation. Time cows spent eating and ruminating per kilogram of DMI increased as proportion of forage in the diet increased. Cows fed diets with a high proportion of alfalfa silage remained in negative energy balance longer than cows fed high grain diets. Intake of NEL (calculated by either of two methods) minus NEL output (milk, maintenance, and BW change) resulted in net balances of NEL after 36 wk of lactation within 5% of NEL intake and indicated that estimates of the NEL value of feedstuffs used in this experiment were reasonably accurate.

Animal Feed↗

PubMed1998

In situ dry matter, nitrogen, and fiber degradation of alfalfa, red clover, and eastern gamagrass at four maturities.

This study compared in situ degradation characteristics of dry matter, N, and neutral detergent fiber (NDF) for alfalfa and red clover with those for eastern gamagrass, a perennial, warm season grass that is native to the Flint Hills of Kansas. Gamagrass had a high proportion of leaf tissue (> 69%) at boot and anthesis stages, at physiological maturity, and after 56 d of regrowth following clipping at boot stage. Gamagrass also had high N concentrations at boot and anthesis stages (2.82 and 2.16%, respectively). Whole-plant gamagrass tissue contained a large proportion of N that was insoluble in neutral detergent (> 51%); however, this was a characteristic only of leaf tissue and was observed on a whole-plant basis because of the large proportion of leaf tissue at all plant maturities. Degradation characteristics of dry matter and NDF generally indicated that stem and cell-wall components from gamagrass at boot and anthesis stages had large maximum extents of degradation. Nitrogen degradation rates (0.047 to 0.059/h) were slower for whole-plant gamagrass than for alfalfa (0.213/h). The most distinguishing characteristic of these findings was not that N from gamagrass degraded more slowly in the rumen than did N from alfalfa or red clover, but that this trait was coupled with N concentrations at harvestable growth stages (boot or anthesis stages) that were similar to legumes.

Animal Feed↗

PubMed1980

Gut clearance and true metabolizable energy value of dehydrated alfalfa supplemented with sodium chloride.

Dehydrated alfalfa (30 g), supplemented with .00, .15, .30, .45, or .60 g of sodium chloride, was force-fed to starved adult White Leghorn cockerels. The rate of clearance of alfalfa residues was not affected by the supplemental salt; there was a high level of variability between birds within treatment groups. The true metabolizable energy value of the alfalfa was unchanged by the salt.

Animals↗

PubMed1980

Bioavailable amino acids in corn and alfalfa as measured by applying the true metabolizable energy assay.

Amino acid (AA) availabilities were determined in three different samples of corn and one of dehydrated alfalfa using the true metabolizable cnergy (TME) assay and force-feeding the ingredients both singly and mixed with a basal diet. One of the corn samples and the alfalfa were those used in the ANRC collabortative study on metabolizable energy (Sibbald, 1978). The other two corn samples were the same cultivar but one (corn D) was afflicted with the fungal disease, "eye spot" (kabatiella zeae), and had a lower hectoliter weight than the nondiseased counterpart (corn ND). Values were calculated for both the apparent AA availability (AAAA) and true AA variability (TAAA), i.e., corrected for the metabolic and endogenous AA losses. Some of the AAAA values for corn ND and corn D varied appreciably with the method of feeding, but such variations were not reflected in the TAAA values. However, the AAAA and TAAA values of alfalfa were generally similar when fed alone or mixed with the basal diet. For the ANRC corn sample both the parameters varied substantially with generally higher AAAA and TAAA values being obtained by feeding the corn mixed with the basal diet. The AA availability values of corn D were very similar to those of its counterpart corn ND as well as the ANRC corn. Discussed are the implications of measuring AA availability in feedstuffs applying the TME assay and using the ingredients as such or as a complete diet.

Amino Acids↗

PubMed2000

Comparison of aqueous chemical treatments to eliminate Salmonella on alfalfa seeds.

Several outbreaks of salmonellosis associated with alfalfa sprouts have been documented in the United States since 1995. This study was undertaken to evaluate various chemical treatments for their effectiveness in killing Salmonella on alfalfa seeds. Immersing inoculated seeds in solutions containing 20,000 ppm free chlorine (Ca[OCl]2), 5% Na3PO4, 8% H2O2, 1% Ca(OH)2, 1% calcinated calcium, 5% lactic acid, or 5% citric acid for 10 min resulted in reductions of 2.0 to 3.2 log10 CFU/ g. Treatment with 1,060 ppm Tsunami or Vortex, 1,200 ppm acidified NaClO2, or 5% acetic acid were less effective in reducing Salmonella populations. With the exceptions of 8% H2O2, 1% Ca(OH)2, and 1% calcinated calcium that reduced populations by 3.2, 2.8, and 2.9 log10 CFU/g, respectively, none of treatments reduced the number of Salmonella by more than 2.2 log10 CFU/g without significantly reducing the seed germination percentage. Treatment with 5% acetic, lactic, or citric acids substantially reduced the ability of seeds to germinate. Treatment with 1% Ca(OH)2 in combination with 1% Tween 80, a surfactant, enhanced inactivation by 1.3 log10 CFU/g compared to treatment with 1% Ca(OH)2 alone. Presoaking seeds in water, 0.1% EDTA, 1% Tween 80, or 1% Tween 80 plus 0.1% EDTA for 30 min before treatment with water, 2,000 ppm NaOCl, or 2% lactic acid had a minimal effect on reducing populations of Salmonella. Results indicate that, although several chemical treatments cause reductions in Salmonella populations of up to 3.2 log10 CFU/g initially on alfalfa seeds when analyzed by direct plating, no treatment eliminated the pathogen, as evidenced by detection in enriched samples.

Acetic Acid↗

PubMed2000

Naturally occurring biofilms on alfalfa and other types of sprouts.

Scanning electron microscopy was used to examine the cotyledons, hypocotyls, and roots of alfalfa, broccoli, clover, and sunflower sprouts purchased from retail outlets as well as alfalfa sprouts grown in the laboratory using a tray system equipped with automatic irrigation. Biofilms were observed on all plant parts of the four types of commercially grown sprouts. Biofilms were also commonly observed on alfalfa sprouts grown in the laboratory by 2 days of growth. Rod-shaped bacteria of various sizes were predominant on all sprouts examined both as free-living cells and as components of biofilms. Occasionally, cocci-shaped bacteria as well as yeast cells were also present in biofilms. The microbes contained in the biofilms appeared to be attached to each other and to the plant surface by a matrix, most likely composed of bacterial exopolysaccharides. Biofilms were most abundant and of the largest dimensions on cotyledons, sometimes covering close to the entire cotyledon surface (approximately 2 mm in length). Naturally occurring biofilms on sprouts may afford protected colonization sites for human pathogens such as Salmonella and Escherichia coli O157:H7, making their eradication with antimicrobial compounds difficult.

Biofilms↗

PubMed2001

Efficacy of chemical treatments in eliminating Salmonella and Escherichia coli O157:H7 on scarified and polished alfalfa seeds.

Alfalfa seeds are sometimes subjected to a scarification treatment to enhance water uptake, which results in more rapid and uniform germination during sprout production. It has been hypothesized that this mechanical abrasion treatment diminishes the efficacy of chemical treatments used to kill or remove pathogenic bacteria from seeds. A study was done to compare the effectiveness of chlorine (20,000 ppm), H2O, (8%), Ca(OH)2 (1%), Ca(OH)2 (1%) plus Tween 80 (1%), and Ca(OH)2 (1%) plus Span 20 (1%) treatments in killing Salmonella and Escherichia coli O157:H7 inoculated onto control, scarified, and polished alfalfa seeds obtained from two suppliers. The influence of the presence of organic material in the inoculum carrier on the efficacy of sanitizers was investigated. Overall, treatment with 1% Ca(OH)2 was the most effective in reducing populations of the pathogens. Reduction in populations of pathogens on seeds obtained from supplier I indicate that chemical treatments are less efficacious in eliminating the pathogens on scarified seeds compared to control seeds. However, the effectiveness of chemical treatment in removing Salmonella and E. coli O157:H7 from seeds obtained from supplier 2 was not markedly affected by scarification or polishing. The presence of organic material in the inoculum carrier did not have a marked influence on the efficacy of chemicals in reducing populations of test pathogens. Additional lots of control, scarified, and polished alfalfa seeds of additional varieties need to be tested before conclusions can be drawn concerning the impact of mechanical abrasion on the efficacy of chemical treatment in removing or killing Salmonella and E. coli O157:H7.

Calcium Hydroxide↗

PubMed2001

Use of green fluorescent protein expressing Salmonella Stanley to investigate survival, spatial location, and control on alfalfa sprouts.

Laser scanning confocal microscopy (LSCM) was used to observe the interaction of Salmonella Stanley with alfalfa sprouts. The green fluorescent protein (gfp) gene was integrated into the chromosome of Salmonella Stanley for constitutive expression, thereby eliminating problems of plasmid stability and loss of signal. Alfalfa seeds were inoculated by immersion in a suspension of Salmonella Stanley (ca. 10(7) CFU/ml) for 5 min at 22 degrees C. Epifluorescence microscopy demonstrated the presence of target bacteria on the surface of sprouts. LSCM demonstrated bacteria present at a depth of 12 microm within intact sprout tissue. An initial population of ca. 10(4) CFU/g seed increased to 7.0 log CFU/g during a 24-h germination period and then decreased to 4.9 log CFU/g during a 144-h sprouting period. Populations of Salmonella Stanley on alfalfa seeds decreased from 5.2 to 4.1 log CFU/g and from 5.2 to 2.8 log CFU/g for seeds stored 60 days at 5 and 22 degrees C, respectively. The efficacy of 100, 200, 500, or 2,000 ppm chlorine in killing Salmonella Stanley associated with sprouts was determined. Treatment of sprouts in 2,000 ppm chlorine for 2 or 5 min caused a significant reduction in populations of Salmonella Stanley. Influence of storage on Salmonella Stanley populations was investigated by storing sprouts 4 days at 4 degrees C. The initial population (7.76 log CFU/g) of Salmonella Stanley on mature sprouts decreased (7.67 log CFU/g) only slightly. Cross-contamination during harvest was investigated by harvesting contaminated sprouts, then directly harvesting noncontaminated sprouts. This process resulted in the transfer of ca. 10(5) CFU/g Salmonella Stanley to the noncontaminated sprouts.

Bacterial Adhesion↗

PubMed2001

Comparison of chlorine and a prototype produce wash product for effectiveness in killing Salmonella and Escherichia coli O157:H7 on alfalfa seeds.

Outbreaks of Salmonella and Escherichia coli O157:H7 infections associated with alfalfa and other seed sprouts have occurred with increased frequency in recent years. This study was undertaken to determine the efficacy of a liquid prototype produce wash product (Fit), compared with water and chlorinated water, in killing Salmonella and E. coli O157:H7 inoculated onto alfalfa seeds. We investigated the efficacy of treatments as influenced by seeds from two different lots obtained from two seeds suppliers and by two methods of inoculation. The efficacy of treatments was influenced by differences in seed lots and amount of organic material in the inoculum. Significant (alpha = 0.05) reductions in Salmonella populations on seeds treated with 20,000 ppm of chlorine or Fit for 30 min ranged from 2.3 to 2.5 log10 CFU/g and 1.7 to 2.3 log10 CFU/g, respectively. Reductions (alpha = 0.05) in E. coli O157:H7 ranged from 2.0 to 2.1 log10 CFU/g and 1.7 to more than 5.4 log10 CFU/g of seeds treated, respectively, with 20,000 ppm of chlorine or Fit. Compared with treatment with 200 ppm of chlorine, treatment with either 20,000 ppm of chlorine or Fit resulted in significantly higher reductions in populations of Salmonella and E. coli O157:H7. None of the treatments eliminated these pathogens as evidenced by their detection on enrichment of treated seeds. Considering the human health and environmental hazards associated with the use of 20,000 ppm of chlorine, Fit provides an effective alternative to chlorine as a treatment to significantly reduce bacterial pathogens that have been associated with alfalfa seeds.

Chlorine↗

PubMed2001

Evaluation of volatile chemical treatments for lethality to Salmonella on alfalfa seeds and sprouts.

A study was done to evaluate natural volatile compounds for their ability to kill Salmonella on alfalfa seeds and sprouts. Acetic acid, allyl isothiocyanate (AIT), trans-anethole, carvacrol, cinnamic aldehyde, eugenol, linalool, methyl jasmonate, and thymol were examined for inhibitory and lethal activity against Salmonella by exposing inoculated alfalfa seeds to compounds (1,000 mg/liter of air) for 1, 3, and 7 h at 60 degrees C. Only acetic acid, cinnamic aldehyde, and thymol caused significant reductions in Salmonella populations (>3 log10 CFU/g) compared with the control (1.9 log10 CFU/g) after treatment for 7 h. Treatment of seeds at 50 degrees C for 12 h with acetic acid (100 and 300 mg/liter of air) and thymol or cinnamic aldehyde (600 mg/liter of air) significantly reduced Salmonella populations on seeds (>1.7 log10 CFU/g) without affecting germination percentage. Treatment of seeds at 50 degrees C with AIT (100 and 300 mg/liter of air) and cinnamic aldehyde or thymol (200 mg/liter of air) did not significantly reduce populations compared with the control. Seed germination percentage was largely unaffected by treatment with gaseous acetic acid, AIT, cinnamic aldehyde, or thymol for up to 12 h at 50 degrees C. The number of Salmonella on seeds treated at 70 degrees C for 80 min with acetic acid (100 and 300 mg/liter of air), AIT (100 mg/liter of air), and cinnamic aldehyde and thymol (600 mg/liter of air) at water activity (a(w)) 0.66 was not significantly different than the number inactivated on seeds at a(w) 0.49. Acetic acid at 200 and 500 mg/liter of air reduced an initial population of 7.50 log10 CFU/g of alfalfa sprouts by 2.33 and 5.72 log10 CFU/g, respectively, within 4 days at 10 degrees C. whereas AIT at 200 and 500 mg/liter of air reduced populations to undetectable levels; however, both treatments caused deterioration in sensory quality. Treatment of sprouts with 1 or 2 mg of AIT per liter of air adversely affected sensory quality but did not reduce Salmonella populations after 11 days of exposure at 10 degrees C.

Colony Count, Microbial↗

PubMed2002

Detection and elimination of Salmonella mbandaka from naturally contaminated alfalfa seed by treatment with heat or calcium hypochlorite.

In 1999, consumption of alfalfa sprouts contaminated with Salmonella Mbandaka led to a multistate outbreak of salmonellosis. In this study, the implicated alfalfa seed lot (no. 8,119) was confirmed to be contaminated with Salmonella Mbandaka at a detection frequency of approximately 72% per replicated 100 g of seed. The sensitivity of detection was improved by a combination of nonselective and selective enrichment of 5.0 ml of germination effluent, followed by immunomagnetic separation. Detection of low levels of viable cells with nonselective enrichment, employed to enhance the recovery of stressed or injured cells, was facilitated by the application of Salmonella-specific polymerase chain reaction (PCR). With PCR assays, Salmonella Mbandaka was detectable on seed stored at 5 degrees C for at least 11 months, but at an increasingly diminishing frequency. Using conventional techniques, viable populations were detected in the seed germination effluent from seeds stored for up to 8 months. Seed treatments with buffered (to pH 7) and unbuffered solutions of calcium hypochlorite, providing approximately 2,000 and 20,000 ppm of free chlorine, for 10 min were equally effective in eliminating viable populations of Salmonella Mbandaka. However, aqueous heat treatments at up to 85 degrees C for 1 min did not eliminate the naturally occurring contaminant from the seed. Reductions of > 15% in germination were observed following heat treatments of 65 degrees C for > or = 6 min or 70 degrees C for > or = 4 min. On the basis of these results, aqueous heat treatments alone do not appear to be a viable alternative to hyperchlorination as an effective method to eliminate Salmonella from alfalfa seed.

Calcium Compounds↗

PubMed2003

Efficacy of ozone in killing Listeria monocytogenes on alfalfa seeds and sprouts and effects on sensory quality of sprouts.

A study was done to determine the efficacy of aqueous ozone treatment in killing Listeria monocytogenes on inoculated alfalfa seeds and sprouts. Reductions in populations of naturally occurring aerobic microorganisms on sprouts and changes in the sensory quality of sprouts were also determined. The treatment (10 or 20 min) of seeds in water (4 degrees C) containing an initial concentration of 21.8 +/- 0.1 microg/ml of ozone failed to cause a significant (P < or = 0.05) reduction in populations of L. monocytogenes. The continuous sparging of seeds with ozonated water (initial ozone concentration of 21.3 +/- 0.2 microg/ml) for 20 min significantly reduced the population by 1.48 log10 CFU/g. The treatment (2 min) of inoculated alfalfa sprouts with water containing 5.0 +/- 0.5, 9.0 +/- 0.5, or 23.2 +/- 1.6 microg/ml of ozone resulted in significant (P < or = 0.05) reductions of 0.78, 0.81, and 0.91 log10 CFU/g, respectively, compared to populations detected on sprouts treated with water. Treatments (2 min) with up to 23.3 +/- 1.6 microg/ml of ozone did not significantly (P > 0.05) reduce populations of aerobic naturally occurring microorganisms. The continuous sparging of sprouts with ozonated water for 5 to 20 min caused significant reductions in L. monocytogenes and natural microbiota compared to soaking in water (control) but did not enhance the lethality compared to the sprouts not treated with continuous sparging. The treatment of sprouts with ozonated water (20.0 microg/ml) for 5 or 10 min caused a significant deterioration in the sensory quality during subsequent storage at 4 degrees C for 7 to 11 days. Scanning electron microscopy of uninoculated alfalfa seeds and sprouts showed physical damage, fungal and bacterial growth, and biofilm formation that provide evidence of factors contributing to the difficulty of killing microorganisms by treatment with ozone and other sanitizers.

Colony Count, Microbial↗

PubMed2003

Reduction of Salmonella enterica on alfalfa seeds with acidic electrolyzed oxidizing water and enhanced uptake of acidic electrolyzed oxidizing water into seeds by gas exchange.

Alfalfa sprouts have been implicated in several salmonellosis outbreaks in recent years. The disinfectant effects of acidic electrolyzed oxidizing (EO) water against Salmonella enterica both in an aqueous system and on artificially contaminated alfalfa seeds were determined. The optimum ratio of seeds to EO water was determined in order to maximize the antimicrobial effect of EO water. Seeds were combined with EO water at ratios (wt/vol) of 1:4, 1:10, 1:20, 1:40, and 1:100, and the characteristics of EO water (pH, oxidation reduction potential [ORP], and free chlorine concentration) were determined. When the ratio of seeds to EO water was increased from 1:4 to 1:100, the pH decreased from 3.82 to 2.63, while the ORP increased from +455 to +1,073 mV. EO water (with a pH of 2.54 to 2.38 and an ORP of +1,083 to +1,092 mV) exhibited strong potential for the inactivation of S. enterica in an aqueous system (producing a reduction of at least 6.6 log CFU/ml). Treatment of artificially contaminated alfalfa seeds with EO water at a seed-to-EO water ratio of 1:100 for 15 and 60 min significantly reduced Salmonella populations by 2.04 and 1.96 log CFU/g, respectively (P < 0.05), while a Butterfield's buffer wash decreased Salmonella populations by 0.18 and 0.23 log CFU/g, respectively. After treatment, EO water was Salmonella negative by enrichment with or without neutralization. Germination of seeds was not significantly affected (P > 0.05) by treatment for up to 60 min in electrolyzed water. The uptake of liquid into the seeds was influenced by the internal gas composition (air, N2, or O2) of seeds before the liquid was added.

Chlorine↗

PubMed2003

Survey of retail alfalfa sprouts and mushrooms for the presence of Escherichia coil O157:H7, Salmonella, and Listeria with BAX, and evaluation of this polymerase chain reaction-based system with experimentally contaminated samples.

BAX, a polymerase chain reaction (PCR)-based pathogen detection system, was used to survey retail sprouts and mushrooms for contamination with Escherichia coli O157:H7, Salmonella, Listeria spp., and Listeria monocytogenes. No Salmonella or E. coli O157:H7 was detected in the 202 mushroom and 206 alfalfa sprout samples screened. L. monocytogenes was detected in one sprout sample, and seven additional sprout samples tested positive for the genus Listeria. BAX also detected Listeria species in 17 of the mushroom samples. Only 6 of 850 PCR assays (0.7%) failed to amplify control DNA, and therefore reagent failures and the inhibition of PCR by plant compounds were rare. The sensitivity of the detection system was evaluated by assaying samples inoculated with 10 CFU of each of the pathogens. One hundred seventy-two alfalfa sprout samples were inoculated with E. coli O157:H7, and two sets of 130 samples were experimentally contaminated with Salmonella Enteritidis and L. monocytogenes. The frequency of detection depended on the protocols used for inoculation and culturing. Inoculation of samples with approximately 10 CFU from frozen stocks yielded detection rates of 87.5 and 94.5% for L. monocylogenes and Salmonella Enteritidis, respectively, in mushrooms. The corresponding rates for alfalfa sprouts were 94.5 and 76.3%. The E. coli O157:H7 detection rate was 100% for mushrooms but only 48.6% for sprouts when standard BAX culture protocols were used. The substitution of an overnight incubation in modified E. coli medium for the 3-h brain heart infusion incubation increased the rate of E. coli O157:H7 detection to 75% for experimentally contaminated sprouts. The detection rate was 100% when E. coli O157:H7 cells from a fresh overnight culture were used for the inoculation. Test sensitivity is therefore influenced by the type of produce involved and is probably related to the growth of pathogens in the resuscitation and enrichment media.

Agaricales↗

PubMed2003

Reduction of Escherichia coli O157:H7 and Salmonella on laboratory-inoculated alfalfa seed with commercial citrus-related products.

Alfalfa sprouts contaminated with the bacterial pathogens Escherichia coli O157:H7 and Salmonella have been the source of numerous outbreaks of foodborne illness in the United States and in other countries. The seed used for sprouting appears to be the primary source of these pathogens. The aim of this study was to determine whether the efficacy of commercial citrus-related products for sanitizing sprouting seed is similar to that of high levels of chlorine. Five products (Citrex, Pangermex, Citricidal, Citrobio, and Environné) were tested at concentrations of up to 20,000 ppm in sterile tap water and compared with buffered chlorine (at 16,000 ppm). Alfalfa seeds were inoculated with four-strain cocktails of Salmonella and E. coli O157:H7 to give final initial concentrations of ca. 9.0 and 7.0 CFU/g, respectively. Treatments (10 min) with Citrex, Pangermex, and Citricidal at 20,000 ppm and chlorine at 16,000 ppm produced similar log reductions for alfalfa seed inoculated with four-strain cocktails of E. coli O157:H7 and Salmonella (3.42 to 3.46 log CFU/g and 3.56 to 3.74 log CFU/g, respectively), and all four treatments were significantly (P<0.05) more effective than the control treatment (a buffer wash). Citrobio at 20,000 ppm was as effective as the other three products and chlorine against Salmonella but not against E. coli O157:H7. Environné was not more effective (producing reductions of 2.2 to 2.9 log CFU/g) than the control treatment (which produced reductions of 2.1 to 2.3 log CFU/g) against either pathogen. None of the treatments reduced seed germination. In vitro assays, as well as transmission electron microscopy, confirmed the antibacterial nature of the products that were effective against the two pathogens and indicated that they were bactericidal. When used at 20,000 ppm, the effective citrus-related products may be viable alternatives to chlorine for the sanitization of sprouting seed pending regulatory approval.

Anti-Bacterial Agents↗