Growth of Salmonella enteritidis in yolk from eggs laid by immunized hens

After hyperimmunization of laying hens with Salmonella enteritidis, antibodies can be found in egg yolks. This study was conducted to ascertain whether the growth of S. enteritidis would be suppressed in the presence of antibodies contained in egg yolk. Specifically pathogen-free (SPF)-laying hens were immunized with S. enteritidis; eggs were collected, the yolk was separated and the concentration of S. enteritidis antibodies was determined quantitatively by using the enzyme-linked immunosorbent assay (ELISA), the radial immunodiffusion and the bicinchoninic acid protein assay. Then, the yolk was inoculated with approximately 10, 100 or 1000 S. enteritidis cells/ml and incubated at 15, 20 and 30 degrees C for 0, 2, 6 and 24 h. The growth of organisms in each yolk was examined, and the generation times were calculated. The egg yolk from nonimmunized hens served as negative control. The highest level of antibody concentration was found in the hyperimmunized group. There was no difference in the generation times of S. enteritidis between the antibody-positive yolk and the negative yolk at the three different incubation temperatures. The results suggest that antibodies in the yolk do not influence the growth of S. enteritidis, even if the hens are highly immunized.     

肠炎沙门氏菌的LAMP检测方法的建立

建立肠炎沙门氏菌(Salmonella enteritidis)的环介导等温扩增(Loop-mediated isothermal amplification,LAMP)方法,实现对肠炎沙门氏菌的快速检测.通过针对肠炎沙门氏菌血清型特异性基因lygD设计LAMP内外引物对,优化LAMP扩增反应条件,采用包括肠炎沙门氏菌在内的10种不同菌株进行LAMP引物特异性检测;通过系列梯度稀释肠炎沙门氏菌菌液进行LAMP扩增,计算检出限;并对鲜鸡蛋模拟样本进行LAMP检测.结果表明LAMP法可快速特异地检测出肠炎沙门氏菌;细菌培养液检出限为2.33×101 cfu/mL,鲜鸡蛋模拟样品为2.67×l01cfu/mL.该方法反应灵敏度高,可用于食品中肠炎沙门氏菌的快速检测.     

Detection of Salmonella enteritidis in shell and liquid eggs using enrichment and plating

Detection methods using various enrichment and plating media and immunoconcentration for Salmonella enteritidis in shell and liquid eggs were evaluated. For liquid egg samples naturally contaminated with S. enteritidis, pre-enrichment in 225 ml of buffered peptone water with cysteine followed by selective enrichment in 10 ml of tetrathionate broth was the superior, resulting in the detection of S. enteritidis in all samples on six of the seven types of selective agar substrate investigated. This enrichment procedure also enabled detection of S. enteritidis in most of artificially inoculated shell egg and pasteurized liquid egg samples.     

Multiplication and motility of Salmonella enterica serovars enteritidis, infantis, and montevideo in in vitro contamination models of eggs

The invasive ability of Salmonella enterica serovars Enteritidis, Infantis, and Montevideo in eggs was examined. Strains of these serovars originating from egg contents, laying chicken houses, and human patients were experimentally inoculated (0.1-ml dose containing 78 to 178 cells) onto the vitelline membrane of eggs collected from specific-pathogen-free chickens and incubated at 25 degrees C. The test strains were detected in 25 of 138 yolk contents by day 6, indicating the penetration of Salmonella organisms through the vitelline membrane. There were no significant differences in overall rates of penetration between serovars. The organisms were also detected in the albumen from 125 of 138 eggs tested by day 6. Growth to more than 10(6) CFU/ml was observed in 48 of the 125 albumen samples. An inoculum of 1000 Salmonella cells was added to 15 ml of albumen at the edge of a petri plate. A 10-mm-diameter cylindrical well, the bottom of which was sealed with a polycarbonate membrane with 3.0-microm pores, was filled with egg yolk and placed into the albumen at the center of the dish, which was maintained at 25 degrees C. Experiments were performed in triplicate with each strain. Salmonella organisms in all the albumen samples were detected by day 11. However, motility of the organisms toward the yolk was observed in only two dishes inoculated with the Salmonella Enteritidis strain from a human patient and in one dish inoculated with the Salmonella Infantis strain from liquid egg. The albumen samples obtained from the dishes inoculated with the Salmonella Enteritidis strain had high numbers of bacteria (>10(8) CFU/ml). The present study suggests that Salmonella organisms in egg albumen are unlikely to actively move toward the yolk, although depositionon or near the vitelline membrane can be advantageous for proliferation.     

Multiplication in egg yolk and survival in egg albumen of Salmonella enterica serotype Enteritidis strains of phage types 4, 8, 13a, and 14b

Refrigeration of eggs is vital for restricting the multiplication of Salmonella enterica serotype Enteritidis contaminants, but differences between Salmonella Enteritidis strains or phage types in their survival and multiplication patterns in egg contents might influence the effectiveness of refrigeration standards. The present study compared the abilities of 12 Salmonella Enteritidis isolates of four phage types (4, 8, 13a, and 14b) to multiply rapidly in egg yolk and to survive for several days in egg albumen. The multiplication of very small numbers of Salmonella Enteritidis inoculated into yolk (approximately 10(1) CFU/ml) was monitored during 24 h of incubation at 25 degrees C, and the survival of much larger numbers of Salmonella Enteritidis inoculated into albumen (approximately 10(5) CFU/ml) was similarly evaluated during the first 3 days of incubation at the same temperature. In yolk, the inoculated Salmonella Enteritidis strains multiplied to mean levels of approximately 10(3) CFU/ml after 6 h of incubation and 10(8) CFU/ml after 24 h. In albumen, mean levels of approximately 10(4) CFU/ml or more of Salmonella Enteritidis were maintained through 72 h. Although a few differences in multiplication and survival were observed between individual isolates, the overall range of values was relatively narrow, and no significant differences (P < 0.05) were evident among phage types.     

Use of capillary tubes and plate heat exchanger to validate U.S. Department of Agriculture pasteurization protocols for elimination of Salmonella enteritidis from liquid egg products

D values for a five-strain cocktail of Salmonella Enteritidis in five different liquid egg products (whole egg, egg yolk, egg white, egg yolk + 5% sucrose + 5% NaCl, and egg yolk + 10% NaCl) were determined using 100-microl capillary tubes. The egg products were inoculated with approximately 1 X 10(10) organisms/ml and heated in capillary tubes to temperatures ranging from 51 to 68 degrees C for various time intervals. Using a pilot scale plate heat exchanger, the U.S. Department of Agriculture (USDA) protocols for pasteurization were also evaluated using egg products inoculated with approximately 1 x 10(7) Salmonella Enteritidis/ml. Results of experiments with capillary tubes suggested that almost all processes would result in less than the 9D process recommended by the USDA. However, when the egg products were pasteurized using the plate heat exchanger, a greater than 9D process was achieved for Salmonella Enteritidis in all products except egg yolk containing 5% sucrose + 5% NaCl, which received approximately a 4D process.     

Evaluation of the efficacy of Broilact in preventing infection of broiler chicks with Salmonella enteritidis PT4.

A study was conducted to evaluate treatment of day-old broiler chicks with Broilact, a live-culture preparation, for preventing intestinal colonization by a non-host-specific Salmonella (S. enteritidis PT4, with high resistance to nalidixic acid). Newly hatched broiler chicks were sprayed with Broilact at a commercial hatchery and delivered on the same day to Huntingdon Research Centre. Control chicks from the same source (i.e. chicks not treated with Broilact) were sent separately. Chicks were maintained in floor pens in groups of 40. The challenge was introduced by means of seeder birds infected with S. enteritidis PT4 (nalr) at a nominal dose level of 10(4) CFU per bird (3 seeder birds per pen of 40 contact birds). Groups of birds were killed 7, 28 and 40 days after challenge, and in each case caecal contents were examined culturally for the test organism. A total of 18 deaths occurred including 13 untreated contact birds, 3 Broilact-treated contact birds and 2 seeder birds. These were attributed to the experimental infection. Results of the examination of caecal contents from untreated control birds indicated that the challenge organism was successfully established in contact chicks via the seeder birds. The overall results for birds treated with Broilact showed a clear protective effect, with little indication of any significant infection by the challenge organism. It was concluded therefore that under the conditions of this study, Broilact was largely effective in preventing intestinal colonization by the non-host-specific s. enteritidis PT4.     

EFFECT OF RAPID COOLING ON THE GROWTH AND PENETRATION OF SALMONELLA ENTERITIDIS INTO EGG CONTENTS

Shell eggs were inoculated internally with approximately 10 cells of Salmonella enterica serovar enteritidis (S. enteritidis) and subjected to three different cooling treatments. Eggs were cooled from an initial temperature of 27C to approximately 7.2C. After cooling, eggs were stored at approximately 7.2C for 36 days, or stored at 5.7–9.5C for 30 days plus 6 days at 37C to simulate temperature abuse. Rapid cooling and subsequent storage of eggs at approximately 7.2C inhibited the growth of S. enteritidis in eggs. Slow cooling, and/or temperature abuse promoted growth of S. enteritidis in eggs. The penetration study indicated that rapid cooling and subsequent storage at 7.2C for 30 days did not affect the penetration of S. enteritidis into egg contents. The S. enteritidis isolated from the eggshell with shell membranes was significantly higher (P < 0.05) than from the internal egg contents, indicating that most of the S. enteritidis cells were trapped within the shell pores and/or shell membranes.     

Growth of Salmonella enterica serovar Enteritidis in albumen and yolk contents of eggs inoculated with this organism onto the vitelline membrane

By using an in vitro model simulating the potential opportunities for Salmonella enterica serovar Enteritidis (SE) to proliferate within eggs contaminated with this organism following oviposition, we investigated growth of SE in eggs. Seventy to 140 CFU of one of three SE strains originating either from egg contents, chicken meat, or a human infection were experimentally inoculated onto the vitelline membrane of eggs collected from specific-pathogen-free flocks of chickens and incubated at 25 degrees C. SE organisms were detected in 6 of 71 yolk contents of the eggs inoculated with any of the test strains attaining levels ranging from 2.0 x 10(2) to 4.2 x 10(8) CFU/ml by day 6. The organisms were also detected in the albumen from 38 of 55 eggs tested, growing to levels ranging from 1.0 x 10(2) to 4.3 x 10(8) CFU/ml by day 6 after inoculation. An additional three yolk contents and 15 albumen samples were culture positive for SE following enrichment. There was no correlation between the number of the organisms in the yolk contents and that in the albumen from each of the eggs. When 73 to 91 CFU of the egg strain were inoculated into samples of separated albumen obtained from eggs that were stored at 4 degrees C for 1 to 4 weeks or at 25 degrees C for 1 week, slight growth (3.0 x 10(2) to 7.4 x 10(3) CFU/ml) was found in only 3 of the 60 albumen samples by day 6 after inoculation, but the organisms were recovered from 52 samples following enrichment. The results suggest that the environment on or near the vitelline membrane can be conducive to SE proliferation over time.     

Effects of different molting procedures on incidence of Salmonella infection in flocks of naturally contaminated laying hens in a commercial egg-producing farm by detection of yolk antibodies to Salmonella in eggs

Indirect enzyme-linked immunosorbent assays (ELISAs) have been applied to detect immunoglobulin Y antibodies to different serotypes of Salmonella in the yolks of chicken eggs with heat-extracted antigens of Salmonella enterica serotypes Agona (SA), Cerro (SC), Enteritidis (SE), Montevideo (SM), and Putten (SP). The egg yolk samples examined were classified as positive if their ELISA absorbance values exceeded the value for eggs from specific-pathogen-free flocks by more than two standard deviations. Of 30 egg yolk samples from three flocks vaccinated with a killed SE vaccine, 29 were antibody positive by the ELISA assay for the SE antigen. Four to 29 of the 29 yolk samples showed positive results for the other serovars, although the absorbance values for SE were higher than those obtained for the other serotypes in each of the yolk samples. All 30 yolks from three flocks that were not administered any SE vaccines were found to be antibody negative for SE, and two samples were determined to be positive for SC. Thirty-nine or 40 eggs were obtained from each of four layer flocks in a commercial egg production farm where the laying houses were naturally contaminated with SA, SC, SM, SP, Salmonella serovar Infantis (SI), and untypeable strains. The ELISA absorbance values for SM in the egg yolks obtained from the two flocks molted through feed withdrawal when the birds restarted laying were significantly (P < 0.05) higher than those observed in the yolks obtained before the molt. In egg yolks from the two other flocks that were molted through a wheat bran diet, there was no significant difference between the absorbance values before and after the molt. The observations in the present study provide further evidence to suggest that a molt initiated through the administration of a wheat bran diet can reduce the risk for Salmonella problems in a commercial egg-producing setting.     

Eggshell factors influencing eggshell penetration and whole egg contamination by different bacteria, including Salmonella enteritidis

Trans-shell infection routes and whole egg contamination of 7 selected bacterial strains; Staphylococcus warneri, Acinetobacter baumannii, Alcaligenes sp., Serratia marcescens, Carnobacterium sp., Pseudomonas sp. and Salmonella enteritidis, recovered from egg contents, were studied. The first objective was to correlate bacterial eggshell penetration with various eggshell characteristics and bacterial strains. An agar approach was used to assess the eggshell penetration. The second objective was to assess the contamination of whole eggs with the bacterial strains; whole intact eggs were used in this case. The intact shells of agar-filled and whole eggs were inoculated with 10(3) -10(4) cfu of the selected strains. During 3 weeks storage at 20 degrees C and 60% relative humidity, the bacterial eggshell penetration was regularly monitored. The whole egg contamination was only analyzed after 3 weeks. The eggshell characteristics such as area eggshell, shell thickness and number of pores did not influence the bacterial eggshell penetration. For each individual bacterial strain the mean cuticle deposition was lower for penetrated compared to non-penetrated eggshells. For the individual strain Carnobacterium sp. and for the global results of all strains this difference was statistical significantly. The whole egg contamination was not influenced by neither the area of the eggshell nor the porosity of the eggshell. The results of the agar approach indicate that the Gram-negative, motile and non-clustering bacteria penetrated the eggshell most frequently; Pseudomonas sp. (60%) and Alcaligenes sp. (58%) were primary invaders followed by S. enteritidis (43%). All selected strains were able to penetrate; penetration was observed most frequently after ca. 4-5 days. Particularly S. enteritidis was a primary invader of whole eggs: the membranes and/or the content of 32% of the whole eggs was contaminated. The remaining bacterial eggshell contamination with the selected strain was determined after 3 weeks storage. Penetrated eggshells and contaminated whole eggs showed a significantly higher bacterial contamination on the eggshell compared to non-penetrated eggshells and non-contaminated whole eggs respectively (global results of all strains). The influence of hen age on bacterial eggshell penetration and egg content contamination was not significant. While the agar approach is suitable to study the influence of the eggshell characteristics on the bacterial eggshell penetration, the intact egg approach gives an estimation of the penetration of the shell followed by the probability of survival and migration in whole eggs.     

Prevention of colonization by Salmonella enteritidis PT4 in broiler chickens.

Field experiments in The Netherlands and in Scandinavian countries have shown that an undefined microflora originating from SPF adult poultry will reduce considerably the colonization of young chicks by Salmonella. A commercial product from this so-called Nurmi concept, Broilact, was studied for its effectiveness in preventing infection of broilers with Salmonella enteritidis PT4 (S.e.). Two trials were carried out, in which the birds were exposed to S.e. via 'seeder' birds placed among them. The trial period was 21 days and each week one third of the chicks was killed and their caecal contents examined for salmonellas. The results of the first trial can be summarized as follows. (1) After 2 weeks the number of 'seeder' birds carrying the Salmonella decreased sharply; (2) the proportion of infected chicks in the Broilact-treated group was lower than in the non-treated group; (3) Counts of S.e. in the non-treated group were higher than in the Broilact group. Results of the second trial were comparable, although no salmonellas could be isolated after the second week.     

Survey of Japanese layer farms for Salmonella enteritidis with vaccination- and infection-specific antigens for egg yolk antibodies

Japanese layer farms were surveyed for Salmonella Enteritidis vaccination and infection with specific antigens for egg yolk antibodies with the use of vaccination-specific antigen Salmonella Enteritidis FliC-specific 9-kDa polypeptide (SEP9) and infection-specific antigen deflagellated Salmonella Enteritidis whole cell (DEWC). The specific antibodies in eggs from 201 commercial layer farms throughout Japan were surveyed. The percentages of farm flocks with a mean enzyme-linked immunosorbent assay (ELISA) titer of over 0.1 were 56.2% (113 of 201) in DEWC-ELISA and 22.3% (45 of 201) in SEP9-ELISA. Flocks indicating high titers in SEP9-ELISA always showed high titers in DEWC-ELISA. Because both specific antibody titers of the vaccinated flocks monitored long term remained high throughout life, flocks with high titers of both ELISAs in this survey must be vaccinated. On the other hand, 34.3% (69 of 201) of flocks had high titers of DEWC-specific antibody alone. Because Salmonella Enteritidis infection induces the DEWC-specific antibody but not the SEP9-specific antibody, detecting only high ELISA titers of DEWC-specific antibody can be an effective monitoring tool for Salmonella Enteritidis exposure rather than vaccination. These results suggest that vaccination programs in Japanese layer farms would be insufficient to control Salmonella Enteritidis infection, and egg screening to detect specific antibodies would be valuable in obtaining the necessary information to control Salmonella Enteritidis infection.     

Growth of Salmonella enteritidis in artificially contaminated eggs: the effects of inoculum size and suspending media.

Growth profiles of two isolates of Salmonella enteritidis phage type (PT) 4 inoculated into either the albumen of whole shell eggs or into separated albumen were found to be markedly affected by the size of the inoculum and the composition of the medium used to suspend the cells prior to inoculation. Using our model with an inoculum of two cells, multiplication of the Salmonella was not seen in 93% of eggs held at 20 degrees C for 8 days. In approximately 7% of eggs, however, growth occurred during the 8 days of storage. If the inoculum equaled or exceeded 25 cells per egg when eggs were subsequently stored at 20 degrees C, or 250 cells per egg when eggs were stored at 30 degrees C, high levels of growth of Salmonella in the egg occurred significantly more frequently than when the inoculum was two cells. High levels of growth were also seen more frequently if the inoculum was suspended in buffered peptone water or maximal recovery diluent rather than in phosphate buffered saline. Growth of Salmonella in separated albumen occurred very infrequently (1.1% of samples) at low inoculum levels and did not become significant until the inoculum was 250 cells or greater. Growth in the albumen was unaffected by the composition of the suspending medium. Provided that the inoculum was approximately 2 cells per egg and the bacteria were suspended in PBS, observed growth profiles of S. enteritidis inoculated into the albumen of whole eggs resembled those in naturally contaminated eggs.     

Antimicrobial properties of lactic acid bacteria and yeast-LAB cultures isolated from traditional fermented milk against pathogenic Escherichia coli and Salmonella enteritidis strains

The survival and growth of Escherichia coli 3339 and Salmonella enteritidis 949575 isolated from human clinical samples, in milk fermented with lactic acid bacteria (LAB) and yeast strains previously isolated from Zimbabwean naturally fermented milk (NFM) was studied. The LAB starter cultures used were Lactococcus lactis subsp. lactis biovar. diacetylactis C1 alone (C1) or in combination with Candida kefyr 23 (C1/23), L. lactis subsp. lactis Lc261 alone (LC261) or in combination with C. kefyr 23 (Lc261/23). The growth of the same pathogens in milk fermented with a commercial DL culture (CH-N 22) and spontaneously fermented raw milk was also monitored. The C1 and C1/23 cultures significantly (P<0.05) inhibited the growth of both pathogens. When inoculated at the beginning of the fermentation, both E. coli 3339 and S. enteritidis 949575 counts were significantly (P<0.05) reduced by about two log cycles in C1 and C1/23 cultured milk. However, in naturally fermented milk and the DL cultured milk, both E. coli 3339 and S. enteritidis 949575 grew and reached high populations of about 9 and 8.8 log cfu ml(-1), respectively, after 18 h. When E. coli 3339 was inoculated into previously fermented milk, the viable counts were significantly (P<0.05) reduced in the presence of C1 and C1/23 from 7 log cfu ml(-1) to 3 log cfu ml(-1) after 48 h. S. enteritidis 949575 could not be recovered from these cultures after 48 h. The addition of the yeast did not enhance or diminish the inhibitory capacity of the LAB cultures. The pathogens survived in high numbers when inoculated into pre-fermented NFM and the commercial DL- (CH-N 22) cultured milk. The C1 strain, therefore, offered the best protection against the pathogens. Its inhibitory effect was mainly related to fast acid production.     

Inactivation of Escherichia coli O157:H7 and Salmonella enteritidis in Liquid Egg White Using Pulsed Electric Field

ABSTRACT: The effects of temperature and pulsed electric field (PEF) intensity on inactivation of pathogens such as Escherichia coli O157:H7 and Salmonella enteritidis in egg white was investigated. Liquid egg white inoculated with 10⁸ colony-forming units (CFU)/mL of each pathogen was treated with up to 60 pulses (each of 2 JAS width) at electric field intensities of 20 and 30 kV/cm. The processing temperatures were 10°C, 20°C, and 30°C. After treatment, uninjured and total viable cells were enumerated in selective and nonselective agars, respectively. Maximum inactivations of 3.7 and 2.9 log units were obtained for S. enteritidis and E. coli O157:H7, respectively, while injured cells accounted for 0.5 and 0.9 logs for E. coli O157:H7 and S. enteritidis , respectively. For both bacteria, increasing treatment temperature tended to increase the inactivation rate. There was synergy between electric field intensity and processing temperature. The inactivation rate constant k _T values for E. coli O157:H7 on both selective and nonselective agars were 8.2 × 10^-3 and 6.6 × 10^-3/μS, whereas the values for S. enteritidis were 16.2 × 10^-3 and 12.6 × 10^-3/μS, respectively. The results suggest that E. coli O157:H7 was more resistant to heat-PEF treatment compared with S. enteritidis.     

Modeling the thermal inactivation kinetics of heat-resistant Salmonella Enteritidis and Oranienburg in 10 percent salted liquid egg yolk

There is no suitable model for predicting thermal inactivation kinetics of Salmonella spp. for many types of liquid egg products, including salted liquid egg yolk, for use in updating U.S. Department of Agriculture (USDA) pasteurization guidelines. This is because, in part, of the variations in Salmonella strains and the changes in the processing of liquid egg products over the past 40 years. The objectives of the present study were to determine the thermal inactivation kinetics and to create a general thermal inactivation kinetics model that can be used for estimating log reductions of salmonellae in 10% salted liquid egg yolk for temperatures between 62.2 and 69°C. This model can be used by processors to help ensure adequate pasteurization. This was accomplished by studying the inactivation kinetics of a three-strain composite of heat-resistant Salmonella serovars Enteritidis and Oranienburg, inoculated into commercially processed 10% salted liquid egg yolk. The survival curves were convex, with asymptotic D-values. From these curves, a general model was developed to predict log reductions for given times at specified temperatures. For example, at a temperature of 67.3°C (153.1°F) for 3.5 min, our model predicts a 5-log reduction would be obtained, whereas with the current USDA minimum required pasteurization regimen (63.33°C [146°F] for 3.5 min), our model predicts that a reduction of only 2.7 log would be obtained. The results of this study provide information that can be used by processors to aid in producing safe, pasteurized egg yolk products, and for satisfying USDA pasteurization performance standards and developing industry guidance.     

Simple and rapid methods for detecting Salmonella enteritidis in raw eggs

The Centers for Disease Control and Prevention estimates there were 300,000 cases of Salmonella enteritidis (SE) in 1997. Egg products were associated with many of the cases. To address this problem, many producers implemented flock surveillance of the SE situation at their facilities. A rapid and simple method for detecting SE from poultry samples is critical for the effective implementation of such testing strategies. A lateral flow device for the detection of SE utilized in this study was manufactured by Neogen, Lansing, MI. The test panel is a presumptive qualitative test system that detects only members of Group D1 Salmonella species. A series of studies were conducted to optimize the test procedure for raw eggs with different sample preparations. A novel antigen extraction method was developed for use with the test panel kit. The detection limit of the test panel kit was increased approximately tenfold when the extraction method was used. Detection of SE was 100% in raw egg pools inoculated with 10 SE cells per ml of egg and incubated at a 1:10 ratio in buffered peptone water (BPW) or tetrathionate brilliant green broth (TBG) for 24 h at 37 degrees C. The developed lateral flow test kit could provide a simple, rapid, and inexpensive method for egg producers and processors to test specifically for Salmonella group D1 serovars, such as SE, in egg samples.     

Detection of Salmonella Enteriditis from Egg Components Using Different Immunomagnetic Beads and Time-resolved Fluorescence

The types of chemical linkage used to bind antibodies to magnetic beads to form immunomagnetic beads (IMB) were compared in the capture and detection of Salmonella Enteriditis from egg white, egg yolk, and whole egg. Egg components were inoculated with outbreak strains of S. Enteriditis. After incubation under different conditions, IMBs derived from linking antibodies to core magnetic beads via biotin–streptavidin interactions, Schiff-base bonds and unspecified proprietary chemistry were used to capture S. Enteriditis. Europium-labeled anti-Salmonella antibodies completed the sandwich, and time-resolved fluorescence served as the means of detection. For the Salmonella isolated in stationary phase and cultured from universal pre-enrichment broth (UPB), the detection signal intensity was affected by the chemistry utilized to link the antibodies to IMB, with results varying among the three test strains. When S. Enteriditis was cultured in egg yolk alone, plating data were similar to those of the growth of S. Enteriditis in UPB. Egg white by itself did not support the growth of S. Enteriditis. The addition of UPB to egg white restored the growth of Salmonella and yielded stronger detection signals than from cultures obtained from UPB with egg yolk. The detection signals obtained from the immunoassay were less intense for cultures grown in egg yolk + UPB than from cultures grown in UPB alone. The lower detection signals elicited by all IMBs suggest the availability of the antigenic groups recognized by the antibodies on IMBs was reduced in the presence of egg yolk.     

屠宰场生鸡肉肠炎沙门氏菌的污染途径

目的：研究屠宰场生鸡肉肠炎沙门氏菌的主要污染途径。方法：以屠宰场生鸡肉样品为研究对象,在利用多聚酶链反应(PCR)检测肠炎沙门氏菌污染的基础上,通过流行病学的方法研究生鸡肉污染与肉鸡感染的关系。结果：屠宰场生鸡肉样品肠炎沙门氏菌污染阳性率为9.03%(26/288),样品污染与样品来源屠宰场间无统计学联系,但与养殖场的肉鸡感染肠炎沙门氏菌有联系;养殖场肉鸡感染肠炎沙门氏菌与生鸡肉污染有正的统计学联系(相对危险性=18.5);肉鸡实验性感染肠炎沙门氏菌后的带菌时间可达42d,排菌达56d 以上。结论：屠宰场生鸡肉肠炎沙门氏菌的污染途径主要为内源性污染。