Development of a Simple Method for Detecting Presumptive Escherichia coli on Fresh Retail Beef

ABSTRACT: A simple method of detecting Escherichia coli on retail beef was developed. Diluent used in sponge-sampling of meat was added to a tube containing double-strength lauryl sulfate tryptone broth + 5-bromo-4-chloro-3-indolyl β-D-glucuronide (X-GlcA) and a Durham tube. Tubes with blue color and gas after 24 h incubation at 35 °C were presumptive-positive. Chi-squared analysis showed a significant ( P < 0.05) relationship between the method and the Petrifilm™ E. coli /Coliform Count Plate method for E. coli in analysis of 66 retail beef samples and the 2 methods had a similar proportion of confirmed isolates (61 and 63%). The method developed is qualitatively comparable to the Petrifilm™ method and provides small-scale beef processors a simple way to monitor sanitary conditions in fabrication and grinding operations.     

Effect of chemical sanitizer combined with modified atmosphere packaging on inhibiting Escherichia coli O157:H7 in commercial spinach

Escherichia coli O157:H7 contaminated spinach has recently caused several outbreaks of human illness in the USA and Canada. However, to date, there has been no study demonstrating an effective way to eliminate E. coli O157:H7 in spinach. Therefore, this study was conducted to investigate the effect of chemical sanitizers alone or in combination with packaging methods such as vacuum and modified atmosphere packaging (MAP) on inactivating E. coli O157:H7 in spinach during storage time. Spinach inoculated with E. coli O157:H7 was packaged in four different methods (air, vacuum, N(2) gas, and CO(2) gas packaging) following treatment with water, 100 ppm chlorine dioxide, or 100 ppm sodium hypochlorite for 5 min at room temperature and stored at 7+/-2 degrees C. Treatment with water did not significantly reduce levels of E. coli O157:H7 in spinach. However, treatment with chlorine dioxide and sodium hypochlorite significantly decreased levels of E. coli O157:H7 by 2.6 and 1.1 log(10)CFU/g, respectively. Levels of E. coli O157:H7 in samples packaged in air following treatments grew during storage time, whereas levels were maintained in samples packaged in other packaging methods (vacuum, N(2) gas, and CO(2) gas packaging). Therefore there were significant differences (about 3-4 log) of E. coli O157:H7 populations between samples packed in air and other packaging methods following treatment with chemical sanitizers after 7 days storage. These results suggest that the combination of treatment with chlorine dioxide and packaging methods such as vacuum and MAP may be useful for improving the microbial safety of spinach against E. coli O157:H7 during storage.     

Specificity of a conductance assay for enumeration of Escherichia coli from broiler carcass rinse samples containing genetically similar species

Experiments were conducted to evaluate the specificity of a rapid method for enumeration of Escherichia coli from fresh broiler chicken carcasses. In three separate trials, E. coli, Citrobacter freundii, Salmonella Enteritidis, and Shigella sonnei were serially diluted and then inoculated into identical broiler chicken carcass rinses. Inoculated rinses were mixed with double-strength Coliform Medium supplemented with 2% dextrose. This mixture was placed in a Bactometer module in duplicate, and conductance was measured at 44 degrees C. Results indicated that C. freundii did not grow to an appreciable degree in the selective medium at 44 degrees C. Salmonella Enteritidis grew similarly to E. coli; however, an initial level of 10(6) Salmonella in the food product would be required for Salmonella to interfere with enumeration of E. coli using this method. S. sonnei grew at a more rapid rate than E. coli; however, there was an interaction between the regression lines formed when serial dilutions (log10 CFU/ml) were compared to E. coli detection times for these two species of bacteria. Therefore, high levels of S. sonnei in a food sample may interfere with the enumeration of E. coli. In general, Salmonella and Shigella are not found at high enough levels on poultry products to interfere with enumeration of E. coli using this method and, if found at high levels, would be detected and rejected using this procedure. Hence, the presence of organisms that are genetically and phylogenetically similar to E. coli would not preclude enumeration of E. coli using conductance under these conditions.     

3M Petrifilm大肠菌群检验方法与经典方法的比较研究

<正> 传统的大肠菌群尤其是大肠杆菌的检测方法有着检测程序比较繁琐、检测周期冗长等缺点。由北京安普生化科技有限公司提供的Petrifilm是美国3M公司发明的一种进行细菌计数的干膜,有操作简单、检测周期短等优点,它一旦投入使用,将大大缩短检测周期,简化实验操作并将取得较大的经济效益。本实验将采用Petrifilm大肠菌群计数平板(PCC)、Petrifilm大肠菌群和大肠杆菌计数平板(PEC)以及Petrifilm大肠菌群快速计数平板(RCC)进行大肠菌群计数,并将计数结果与传统方法所得结果的进行比较,来验证Petrifilm用于大肠菌群计数所得结果的准确性。     

Evaluation of Escherichia coli O157:H7 growth media for use in test-and-hold procedures for ground beef processing

Since the mid-1990s, the beef industry has used a process called test and hold, wherein beef trim and ground beef are tested to keep products contaminated with Escherichia coli O157:H7 out of commerce. Current O157:H7 detection methods rely on a threshold level of bacterial growth for detection, which is dependent on the growth medium used. Twelve media were examined for growth and doubling time: buffered peptone water (BPW), SOC (which contains tryptone, yeast extract, KCl, MgCl2, and glucose), buffered peptone water plus SOC (BPW-SOC), Bacto-NZYM, RapidChek E. coli O157:H7 medium, BioControl EHEC8 culture medium, Neogen Reveal for E. coli O157:H7--Eight Hour medium (Neogen Reveal 8), BAX System medium for E. coli O157:H7 (BAX) BAX System medium for E. coli O157:H7 MP (BAX-MP), modified E. coli broth, nutrient medium, and tryptic soy broth (TSB). All media were tested at 37 or 42 degrees C under static or shaking conditions. The eight media with the highest total CFU per milliliter and most rapid doubling times were BPW-SOC, NZYM, RapidChek, EHEC8, Neogen Reveal 8, BAX, BAX-MP, and TSB. The ability of these eight media to enrich E. coli O157:H7 in ground beef was further evaluated through time-course experiments using immunomagnetic separation. Of these media, TSB was the easiest to prepare, had a wide application base, and was the least expensive. In the test-and-hold process, the normal ratio of medium to product is 1:10. In this study, a 1:3 ratio worked as well as a 1:10 ratio. Processors using test-and-hold procedures could use 1 liter of TSB to enrich for E. coli O157:H7 in a 375-g sample instead of the usual 3.375 liters, thus saving reagents, time, and labor while maintaining accuracy.     

A new alginate-based rapid method for determining coliforms in milk

A new rapid method for monitoring coliforms was developed on the basis of the instant gelling effects of alginate and calcium. The effectiveness of this new method in the detection of coliforms was evaluated. Tests involving Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, total coliforms in milk, cold-injured coliforms, and total coliforms in raw milk were carried out. The bacterial samples were diluted in 0.2% peptone water containing 90 mM CaCl2 and added into test tubes containing modified purple broth base medium. Coliform concentrations were determined on the basis of the time of color change and gas production in the alginate tubes. All results obtained by the alginate method correlated strongly with those obtained by the conventional violet red bile agar (VRBA) plating method. The alginate method reduced detection time by 12 to 14 h compared with the conventional VRBA plating method. The alginate method can be applied in field studies more easily than melted-agar systems can. The results of this study indicate that the alginate method is an accurate, rapid, simple, and economical way to monitor and estimate concentrations of total coliforms in food.     

Development of a medium for differentiation between Escherichia coli and Escherichia coli O157:H7.

A new medium (Escherichia coli O157:H7 medium: EOH) was developed for differentiation between E. coli and E. coli O157:H7. The EOH medium was compared with sorbitol MacConkey agar (SMAC), which is the most popular medium to enumerate E. coli O157:H7. Several combinations of 35 dyes were evaluated to develop the new medium. Indigo carmine (0.03) g/liter) and phenol red (0.036 g/liter) were found as the best combination for differentiation between E. coli O157:H7 and E. coli and added to the basal agar medium (SMAC medium excluding neutral red and crystal violet) for EOH medium. On the dark blue EOH medium, E. coli produced a yellow color with clear zone, whereas E. coli O157:H7 produced a red color without clear zone. For differentiation between E. coli and E. coli O157:H7, EOH has much better potential than SMAC. Furthermore. the red color produced by normal E. coli in SMAC may mask the light gray color produced by E. coli O157: H7, whereas the yellow color with clear zone did not mask the red color without clear zone in the EOH medium. The recovery numbers of E. coli O157:H7 from inoculated ground beef, pork, and turkey were not significantly different between SMAC and EOH media (P > 0.05). The recovery rates of heat- and cold-injured E. coli O157:H7 also were not significantly different (P > 0.05).     

Cold plasma reduction of Salmonella and Escherichia coli O157:H7 on almonds using ambient pressure gases

Contamination of raw nuts, including almonds, is a food safety concern. Cold plasma is a novel antimicrobial intervention that can eliminate foodborne pathogens. The objective of this work was to evaluate the efficacy of rapid cold plasma treatments in eliminating Salmonella and Escherichia coli O157:H7 from dry almonds. Three isolates of Salmonella (S. Anatum F4317, S. Stanley H0558, and S. Enteritidis PT30) and 3 isolates of E. coli O157:H7 (C9490, ATCC 35150, and ATCC 43894) were separately grown and spot-inoculated (10 μL) onto whole almonds and allowed to dry for 10 min. Inoculated almonds were treated with a cold plasma jet, with treatment variables evaluated in a factorial design for each isolate: time, distance, and feed gas. Treatment time was 0 s (control), 10 s, or 20 s. Distance from the emitter was 2, 4, or 6 cm. Feed gas was dry air or nitrogen. After treatment, the almonds were sampled using swabs. Survivors were enumerated on tryptic soy agar (TSA) plates. Cold plasma significantly reduced both pathogens on almonds. The greatest reduction observed was 1.34 log cfu/mL reduction of E. coli O157:H7 C9490 after 20 s treatment at 6 cm spacing. The interaction of treatment time with distance from plasma emitter head was complex, and isolate-dependent. Longer duration of treatment did not always result in enhanced reductions. In general, nitrogen as a feed gas resulted in a reduced antimicrobial efficacy compared to dry air. These results indicate that short pulses of atmospheric pressure cold plasma can significantly reduce Salmonella and E. coli O157:H7 on almonds.     

Effects of using reduced volumes of nonselective enrichment medium in methods for the detection of Escherichia coli O157:H7 from raw beef

Recent work from our laboratory revealed that tryptic soy broth (TSB) was a superior enrichment medium for use in test-and-hold Escherichia coli O157:H7 methods at levels down to a ratio of three volumes of medium to one volume of sample. Lower ratios were examined for their effect on results obtained from culture isolation, the BAX E. coli O157:H7 MP assay, and the Assurance GDS E. coli O157:H7 assay. Ground beef and boneless beef trim were inoculated with a high level (170 CFU/65 g of ground beef and 43 CFU/65 g of trim) and a low level (17 CFU/65 g of ground beef and 4 CFU/65 g of trim) of E. coli O157:H7 and enriched in 3, 1, 0.5, and 0 volumes of TSB. The volume of TSB used did not affect E. coli O157:H7 detection by culture isolation, Assurance GDS detection in ground beef or trim, or the BAX MP assay detection in ground beef. However, BAX MP assay detection of E. coli O157:H7 in beef trim was 50, 42, and 33% positive when enrichment volumes of 0.5x, 1x, and 3x, respectively, were used. Optimum results with all methods were obtained using 1 volume of TSB. We concluded that detection test results can be considered valid as long as enrichment medium is used, even when it is less than the specified 3 or 10 volumes.     

简易、快速检测冷冻食品中大肠菌群、大肠杆菌的纸片荧光法

纸片荧光法是利用细菌产生某些代谢酶或化谢产物的特点,而建立的一种酶-底物反应法。该方法比AOAC规定的方法节省时间,而且将待测细菌所需的营养成分、酶促底物以及抑制杂菌的成分均固相化在纸片上,进一步简化了实验准备、便于携带,更适用于HACCP的现场监管。本实验针对纸片荧光法的灵敏度、特异性、准确性、定量反应、对受伤菌种恢复作用及对大肠杆菌的准确性进行了研究。该方法的定性、定量结果与AOAC方法无差异,检验受伤菌及大肠杆菌的结果也与AOAC法相一致,未见非特异性干扰。纸片法作为一种独特、方便、准确的快速检测法值得推广。     

PCR primers designed from malic acid dehydrogenase gene and their use for detection of Escherichia coli in water and milk samples

Escherichia coli has been the appropriate focus for monitoring of potential enteric pathogens in water and foods. Although several methods have been used for the detection or enumeration of E. coli cells in water and foods, the time and accuracy limitations of these methods suggest the need of a rapid and specific method. By comparison of the gene sequences coding for malic acid dehydrogenase (mdh) of E. coli and non-E. coli strains, two oligonucleotides were designed and their possible use as E. coli-specific PCR primers was tested. All of the 110 E. coli strains tested, including non-pathogenic and various pathogenic strains, generated the expected PCR products with Mw equal to 392 bp. On the other hand, only 97 of these 110 E. coli strains were detectable using the BAM gas production method. With the exception of Shigella strains, non-E. coli strains, including strains of the family of Enterobacteriaceae, did not generate any false positive PCR results. When this PCR system was used for the monitoring of E. coli cells inoculated into water and milk samples, as low as 10(0) cfu per 100 ml of water or per ml of milk sample could be detected if an 8 h preculture step was performed prior to the PCR. Including the preculture step, the whole PCR detection process may be completed within 12 h.     

Efficacy of aqueous ozone for the decontamination of Escherichia coli O157:H7 and Salmonella on raspberries and strawberries

The efficacy of ozone as a water additive for washing raspberries and strawberries was investigated. Pathogen-inoculated fruits were treated with aqueous ozone concentrations of 1.7 to 8.9 mg/liter at 20 degrees C for 2 to 64 min, with an aqueous ozone concentration of 21 mg/liter at 4 degrees C for 64 min, or with water as a control. Maximum pathogen reductions on raspberries were 5.6 and 4.5 log CFU/g for Escherichia coli O157:H7 and Salmonella, respectively, at 4 degrees C, whereas reductions on strawberries were 2.9 and 3.3 log CFU/g for E. coli O157:H7 and Salmonella, respectively, at 20 degrees C after 64 min. Washing with water (sparging with air as control) resulted in reductions of approximately 1 log CFU/g. The results presented here indicate that aqueous ozone may be useful as a decontaminant for small fruits.     

Monochloramine versus sodium hypochlorite as antimicrobial agents for reducing populations of bacteria on broiler chicken carcasses

Studies were conducted to compare the effect of sodium hypochlorite (SH) versus monochloramine (MON) on bacterial populations associated with broiler chicken carcasses. In study 1, nominal populations (6.5 to 7.5 log CFU) of Escherichia coli, Listeria monocytogenes, Pseudomonas fluorescens, Salmonella serovars, Shewanella putrefaciens, and Staphylococcus aureus were exposed to sterilized chiller water (controls) or sterilized chiller water containing 50 ppm SH or MON. SH at 50 ppm eliminated all (6.5 to 7.5 log CFU) viable E. coli, L. monocytogenes, and Salmonella serovars; 1.2 log CFU of P. fluorescens; and 5.5 log CFU of S. putrefaciens. MON eliminated all (6.5 to 7.5 log CFU) viable E. coli, L. monocytogenes, S. putrefaciens, and Salmonella serovars and 4.2 log CFU of P. fluorescens. In study 2, chicken carcasses were inoculated with P. fluorescens or nalidixic acid-resistant Salmonella serovars or were temperature abused at 25 degrees C for 2 h to increase the populations of naturally occurring E. coli. The groups of Salmonella serovar-inoculated or temperature-abused E. coli carcasses were immersed separately in pilot-scale poultry chillers and exposed to tap water (controls) or tap water containing 20 ppm SH or 20 ppm MON for 1 h. The P. fluorescens-inoculated group was immersed in pilot-scale poultry chillers and exposed to tap water (controls) or tap water containing 50 ppm SH or 50 ppm MON for 1 h. Carcasses exposed to the SH treatment had nominal increases (0.22 log CFU) in E. coli counts compared with controls, whereas exposure to MON resulted in a 0.89-log reduction. Similarly, average nalidixic acid-resistant Salmonella serovar counts increased nominally by 34% (41 to 55 CFU/ml) compared with controls on carcasses exposed to SH, whereas exposure to MON resulted in an average nominal decrease of 80% (41 to 8 CFU/ml). P. fluorescens decreased by 0.64 log CFU on carcasses exposed to SH and decreased by 0.87 log CFU on carcasses exposed to MON. In study 3, SH or MON was applied to the chiller in a commercial poultry processing facility. E. coli counts (for carcass halves emerging from both saddle and front-half chillers) and Salmonella prevalence were evaluated. Data from carcasses exposed to SH during an 84-day historical (Hist) and a 9-day prepilot (Pre) period were evaluated. Other carcasses were exposed to MON and tested during a 27-day period (Test). E. coli counts for samples collected from the saddle chiller were 25.7, 25.2, and 8.6 CFU/ml for Hist, Pre, and Test, respectively. E. coli counts for samples collected from the front-half chiller were 6.7, 6.9, and 2.5 CFU/ml for Hist, Pre, and Test, respectively. Salmonella prevalence was reduced from 8.7% (Hist + Pre) to 4% (Test). These studies indicate that MON is superior to SH in reducing microbial populations in poultry chiller water.     

Recovery and survival of Escherichia coli O157:H7 in reconditioned pork-processing wastewater.

The pathogen Escherichia coli O157:H7 has been recovered from various water sources and food samples. The growth potential of this bacterium in nutrient-limited, reconditioned wastewater from a pork-processing plant was determined over a temperature range of 4 to 46 degrees C. Even though the biological oxygen demand of the wastewater was <2 mg/liter, results of bioassays for assimilable organic carbon and the coliform growth response of the water suggested that sufficient nutrients were present to support limited bacterial growth. A three-strain mixture of E. coli O157:H7 grew over the temperature range of 10.2 to 29.4 degrees C. Bioassays appear to be a good indicator of the ability of this wastewater to support growth of this pathogen. Statistically higher levels of bacterial growth (P < 0.05) were detected on a nonselective medium (tryptic soy agar) than on a selective medium (sorbitol-MacConkey agar), suggesting that stress or injury of the bacterium occurs when the organism is exposed to the nutrient-limited conditions of the wastewater. These results indicate that E. coli O157:H7 can survive and grow in this particular nutrient-limited wastewater, suggesting a potential hazard if this water becomes contaminated with this pathogen.     

Effect of antemortem feeding regimes on bacterial numbers in the stomachs and ceca of pigs

Three groups, each of 45 pigs, were either not fasted, fasted for 15 h during lairage at the abattoir, or fasted for 15 h before dispatch from the piggery to the abattoir. Three subgroups, each of 15 pigs from each group, were held at the abattoir for additional times of either 0 to 1 h, 2 to 3 h, or 4 to 5 h. Immediately after slaughter, stomach and cecal contents were collected for pH measurement and enumeration of coliforms, Escherichia coli biotype 1 and lactic acid bacteria (LAB). Stomach pH changed from 4.1 to 3.1 as additional abattoir holding time increased from 0 to 1 h to 4 to 5 h but was unaffected by feed withdrawal (mean pH, 3.5). Cecal pH (range 6.4 to 7.2) increased in response to both treatments. Coliform and E. coli biotype 1 numbers in the stomach, means 4.6 and 4.5 log CFU/g, respectively, were not affected by feed withdrawal but decreased 0.8 log units as additional abattoir holding time increased from 0 to 1 to 4 to 5 h. LAB in the stomach decreased in response to both feed withdrawal and holding at the abattoir. Cecal numbers of coliforms and E. coli biotype 1 increased 0.8 and 1.0 log units to 7.8 and 7.6 log CFU/g, respectively, as a result of feed withdrawal, and 0.6 log units to 7.6 and 7.5 log CFU/g, respectively, as additional abattoir holding time increased to 4 to 5 h. The LAB in the cecum (mean 9.4 log CFU/g) increased slightly with increasing abattoir holding time. In the event of release of stomach or cecal contents onto the meat during carcass dressing, larger numbers of E. coli per g would be released from the ceca and fewer per g from the stomachs of pigs that have had feed withdrawn as compared to pigs not subjected to feed withdrawal.     

Alcoholic fermentation by 'non-fermentative' yeasts

All type strains of 'non-fermentative' yeasts, available in the culture collection of the Centraalbureau voor Schimmelcultures, were reinvestigated for their capacity to ferment glucose in the classical Durham tube test. Although visible gas production was absent, nearly all strains produced significant amounts of ethanol under the test conditions. Under conditions of oxygen-limited growth, even strong alcoholic fermentation may occur in a number of yeasts hitherto considered as non-fermentative. Thus, shake-flask cultures of Hansenula nonfermentans and Candida silvae fermented more than half of the available sugar to ethanol. It is concluded that the taxonomic test for fermentation capacity, which relies on detection of gas formation in Durham tubes, is not reliable for a physiological classification of yeasts as fermentative and non-fermentative species.     

INDICATOR AND PATHOGENIC BACTERIA IN GUACAMOLE AND THEIR BEHAVIOR IN AVOCADO PULP

The presence of some indicator microorganisms and pathogenic bacteria in guacamole sampled from restaurants and street vendors, and the behavior of Salmonella spp. , Staphylococcus aureus, and Escherichia coli O157:H7 were studied in avocado pulp. Coliform, yeast and mold populations showed a wide dispersion, in agreement with the diversity of sanitary conditions observed among places sampled. The frequency of Salmonella spp. , Listeria monocytogenes, and E. coli were 1.3, 16.0, and 60.0 %, respectively; with higher numbers among street vendors. Populations of E. coli ranged from 29 to 3800 NMP/g and S. aureus from 2.95 to 5.35 log CFU/g. Thirteen out of 16 hemolytic L. monocytogenes strains were pathogenic for mice. In avocado pulp Salmonella spp. and E. coli O157:H7 showed a lag phase close to 3 h, and a generation time of 54 min and 1.23 h, respectively. No growth of pathogens was observed in avocado pulp stored at 4-7C.     

Optimization of ferrioxamine E concentration as effective supplementation for selective isolation of Salmonella enteritidis in egg white

Utilization of ferrioxamine E (FE) as a sole source of iron distinguishes Salmonella from a number of related species, including Escherichia coli. FE is not able to serve as a source of iron for E. coli or the Proteus-Providencia-Morganella group. This confers a selective advantage on Salmonella Enteritidis in egg white supplemented with FE. The optimum concentration of FE that promoted a selective advantage for Salmonella in egg white was determined. Four supplementation concentrations were evaluated (25, 50, 200, and 500 microg/ml) in egg white artificially inoculated with proportionally mixed cultures of a rifampin-resistant strain of Salmonella Enteritidis (0.1 ml of 102 CFU/ml) and E. coli K-12 (0.1 ml of 10(1) through 10(8) CFU/ml). After a 24-h incubation at 37 degrees C, Salmonella and E. coli populations were enumerated. At higher concentrations of FE (>50 microg/ml), both Salmonella and E. coli were able to use the iron supplement (1 to 8.5 log CFU/ml and 1.8 to 8 log CFU/ml, respectively); however, lower FE concentrations (< or = 50 microg/ml) exclusively promoted Salmonella growth. Salmonella was unrecoverable without supplementation. This study indicates that optimum levels of FE supplementation in egg can improve the selective detection for Salmonella Enteritidis among other competitive organisms.     

Effect of dry air or immersion chilling on recovery of bacteria from broiler carcasses

A study was conducted to investigate the effect of chilling method (air or immersion) on concentration and prevalence of Escherichia coli, coliforms, Campylobacter, and Salmonella recovered from broiler chicken carcasses. For each of four replications, 60 broilers were inoculated orally and intracloacally with 1 ml of a suspension containing Campylobacter at approximately 10(8) cells per ml. After 1 day, broilers were inoculated with 1 ml of a suspension containing Salmonella at approximately 10(8) cells per ml. Broilers were processed, and carcasses were cooled with dry air (3.5 m/s at -1.1 degrees C for 150 min) or by immersion chilling in ice water (0.6 degrees C for 50 min). Concentrations of E. coli, coliforms, Campylobacter, and Salmonella recovered from prechill carcasses averaged 3.5, 3.7, 3.4, and 1.4 log CFU/ml of rinse, respectively. Overall, both chilling methods significantly reduced bacterial concentrations on the carcasses, and no difference in concentrations of bacteria was observed between the two chilling methods (P < 0.05). Both chilling methods reduced E. coli and coliforms by 0.9 to 1.0 log CFU/ml. Air and immersion chilling reduced Campylobacter by 1.4 and 1.0 log CFU/ml and reduced Salmonella by 1.0 and 0.6 log CFU/ml, respectively. Chilling method had no effect on the prevalence of Campylobacter and Salmonella recovered from carcasses. These results demonstrate that air- and immersion-chilled carcasses without chemical intervention are microbiologically comparable, and a 90% reduction in concentrations of E. coli, coliforms, and Campylobacter can be obtained by chilling.     

Hot water treatments to inactivate Escherichia coli O157:H7 and Salmonella in mung bean seeds

The majority of the seed sprout-related outbreaks have been associated with Escherichia coli O157:H7 and Salmonella. Therefore, an effective method is needed to inactivate these organisms on the seeds before they are sprouted. This study was conducted to assess the effectiveness of various hot water treatments to inactivate E. coli O157:H7 and Salmonella populations on mung beans seeds intended for sprout production and to determine the effect of these treatments on seed germination after the seeds were dipped in chilled water for 30 s. Mung bean seed inoculated with four-strain cocktails of E. coli O157:H7 and Salmonella were soaked into hot water at 80 and 90 degrees C with shaking for various periods and then dipped in chilled water for 30 s. The treated seeds were then assessed for the efficacy of the treatment for reducing populations of the pathogens and the effects of the treatment on germination. After inoculation and air drying, 6.08 +/- 0.34 log CFU/g E. coli O157:H7 and 5.34 +/- 0.29 log CFU/g Salmonella were detected on the seeds. After hot water treatment at 90 degrees C for 90 s followed by dipping in chilled water for 30 s, no viable pathogens were found and no survivors were found in the enrichment medium and during the sprouting process. The germination yield of the seed was not affected significantly. Therefore, hot water treatment followed by dipping in chilled water for 30 s could be an effective seed decontamination method for mung bean seeds intended for sprout production.