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1.
Internal contamination of eggs laid by hens infected with Salmonella enteritidis has been a prominent international public health issue since the mid-1980s. Considerable resources have been committed to detecting and controlling S. enteritidis infections in commercial laying flocks. Recently, the Centers for Disease Control and Prevention also reported a significant association between eggs or egg-containing foods and S. heidelberg infections in humans. The present study sought to determine whether several S. heidelberg isolates obtained from egg-associated human disease outbreaks were able to colonize reproductive tissues and be deposited inside eggs laid by experimentally infected hens in a manner similar to the previously documented behavior of S. enteritidis. In two trials, groups of laying hens were orally inoculated with large doses of four S. heidelberg strains and an S. enteritidis strain that consistently caused egg contamination in previous studies. All five Salmonella strains (of both serotypes) colonized the intestinal tracts and invaded the livers, spleens, ovaries, and oviducts of inoculated hens, with no significant differences observed between the strains for any of these parameters. All four S. heidelberg strains were recovered from the interior liquid contents of eggs laid by infected hens, although at lower frequencies (between 1.1% and 4.5%) than the S. enteritidis strain (7.0%). 相似文献
2.
Experimental infection models are useful tools for understanding how Salmonella enteritidis is deposited in eggs and for testing potential strategies to control eggborne transmission of disease to humans. Oral inoculation of laying hens is presumed to provide the closest simulation of naturally occurring infections, but alternatives such as intravenous or aerosol inoculation have sometimes been recommended as options to induce higher incidences of egg contamination. The present study compared the frequency, level, and location of S. enteritidis deposition in egg contents after experimental inoculation by three different routes. In two replicate trials, specific-pathogen-free laying hens were infected with an S. enteritidis culture mixture prepared to optimize invasive behavior. Groups of hens received either an oral dose of 10(9) S. enteritidis, an aerosol dose of 10(9) S. enteritidis, or an intravenous dose of 10(5)-10(7) S. enteritidis. Oral inoculation led to the highest incidence of fecal shedding of S. enteritidis, whereas intravenous inoculation produced the highest specific antibody titers. Eggs laid during the first 21 days postinoculation were cultured to detect and enumerate S. enteritidis in the yolk and albumen. No significant differences were observed among the three inoculation routes in the frequencies of isolation of S. enteritidis from either yolk or albumen. For all three routes of administration, S. enteritidis was recovered more often from yolk (at frequencies ranging from 4% to 7%) than from albumen (0 to 2%). Over 73% of contaminated eggs harbored fewer than 1 colony-forming unit (CFU) of S. enteritidis per milliliter, and only 3% of such eggs contained more than 100 CFUs/ml. Significantly higher levels of S. enteritidis contaminants were associated with intravenous inoculation than with the other routes. No advantage of using aerosol or intravenous administration of S. enteritidis as an alternative to oral inoculation for inducing the production of contaminated eggs was evident in this study. 相似文献
3.
Salmonella enteritidis and other Salmonella in laying hens and eggs from flocks with Salmonella in their environment. 总被引：2，自引：1，他引：1 
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下载免费PDF全文 C Poppe R P Johnson C M Forsberg R J Irwin 《Canadian journal of veterinary research》1992,56(3):226-232
Seven Canadian layer flocks with Salmonella enteritidis in their environment were investigated to determine the numbers of hens infected with S. enteritidis, the localization of S. enteritidis in organs of infected hens and the numbers of S. enteritidis-infected eggs produced by two affected flocks. By a microagglutination test (MAT) using S. pullorum antigens, these flocks had more seropositive hens (mean 51.9 +/- 16.9%) than two Salmonella-free flocks (mean 13.0 +/- 4.2%). Culture of tissues of 580 hens (433 seropositive) from the seven flocks detected 26 (4.5%) S. enteritidis-infected hens from two flocks. In one flock, 2/150 hens were infected with S. enteritidis phage type (PT) 8, which was confined to the ceca, and no Salmonella spp. were isolated from 2520 eggs (one day's lay). In the second flock, where 24/150 hens were infected with S. enteritidis PT13, extraintestinal infection was found in nine hens and involved the ovaries and/or oviduct in two hens. Salmonella enteritidis PT13 was isolated from one sample of egg contents and from one sample of cracked shells from among 14,040 eggs (one day's lay) from this flock. The overall prevalence of S. enteritidis-contaminated eggs from the two flocks with infected hens was less than 0.06%. Other Salmonella spp. isolated were S. heidelberg from 58 hens (10%), and S. hadar, S. mbandaka and S. typhimurium from one hen (0.2%) each. The MAT with antigens of S. pullorum had a sensitivity of 81% and a specificity of 24% for detecting S. enteritidis-infected hens.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
Because egg yolk and albumen differ substantially in their abilities to support bacterial growth, the initial level and location of Salmonella enteritidis deposition are critical for determining whether proposed standards for refrigerating eggs are likely to protect public health by preventing extensive microbial multiplication. In the present study, three groups of laying hens were infected with oral doses of approximately 10(9) cells of different S. enteritidis strains (two were phage type 4 and one was phage type 13a) in two replicate trials. For all three S. enteritidis strains, the incidence of yolk contamination (approximately 2.5% overall) was significantly greater than the incidence of albumen contamination (approximately 0.5% overall). The phage type 13a strain was less often isolated from fecal samples at 2 wk post-inoculation than were the phage type 4 strains, but no significant differences between strains were observed in the incidence of egg contamination. Most freshly laid contaminated eggs contained fewer than 1 S. enteritidis cell/ml of egg yolk or albumen, and no sample contained more than 67 S. enteritidis cells/ml. 相似文献
5.
Salmonella enterica serovar Enteritidis (S. Enteritidis) is one of the most prevalent causes for human gastroenteritis and is by far the predominant Salmonella serovar among human cases, followed by Salmonella Typhimurium. Contaminated eggs produced by infected laying hens are thought to be the main source of human infection with S. Enteritidis throughout the world. Although previous studies have looked at the proportion of infected eggs from infected flocks, there is still uncertainty over the rate at which infected birds produce contaminated eggs. The aim of this study was to estimate the rate at which infected birds produce contaminated egg shells and egg contents. Data were collected from two studies, consisting of 15 and 20 flocks, respectively. Faecal and environmental sampling and testing of ovaries/caeca from laying hens were carried out in parallel with (i) for the first study, testing 300 individual eggs, contents and shells together and (ii) for the second study, testing 4000 eggs in pools of six, with shells and contents tested separately. Bayesian methods were used to estimate the within‐flock prevalence of infection from the faecal and hen post‐mortem data, and this was related to the proportion of positive eggs. Results indicated a linear relationship between the rate of contamination of egg contents and the prevalence of infected chickens, but a nonlinear (quadratic) relationship between infection prevalence and the rate of egg shell contamination, with egg shell contamination occurring at a much higher rate than that of egg contents. There was also a significant difference in the rate of egg contamination between serovars, with S. Enteritidis causing a higher rate of contamination of egg contents and a lower rate of contamination of egg shells compared to non‐S. Enteritidis serovars. These results will be useful for risk assessments of human exposure to Salmonella‐contaminated eggs. 相似文献
6.
Production of Salmonella enteritidis-contaminated eggs by experimentally infected hens 总被引：9，自引：0，他引：9
Laying hens of three different ages were experimentally infected with a strain of Salmonella enteritidis by either oral inoculation or contact transmission. Total egg production was depressed in exposed hens of all three age groups. Persistent intestinal shedding was observed in a small number of hens. Eggs with contents contaminated by S. enteritidis were produced by exposed hens at a high frequency, but only during a fairly short period of time that extended through approximately 1 week postinoculation for older hens and through 2 weeks for younger hens. S. enteritidis was recovered from whole yolks and albumen of these eggs at similar frequencies, but not from the content of yolks. Eggs with contaminated shells were also produced, but at a lower frequency. Contaminated eggs were produced by orally inoculated and contact-exposed hens at similar frequencies. S. enteritidis was not isolated from the contents of eggs laid by hens infected with other S. enteritidis strains. 相似文献
7.
Experimental infection models are valuable tools for understanding and preventing the deposition of Salmonella enteritidis inside eggs. Oral inoculation is believed to closely simulate naturally occurring S. enteritidis infections of chickens, but oral infection studies have often generated relatively low frequencies of egg contamination. The present study assessed whether repeated in vivo passage of an S. enteritidis strain could affect its ability to cause egg contamination in experimentally infected hens. The incidence of egg contamination was determined in groups of hens inoculated orally with either a phage type 13a S. enteritidis strain or derivatives of this parent strain that were obtained by three successive rounds of passage and reisolation from tissues of infected hens. Passaged S. enteritidis isolates recovered from ovaries and oviducts induced a significantly higher incidence of egg contamination (16.97%) than was attributed to the parent strain (8.27%). However, passaged S. enteritidis isolates recovered from livers and spleens were not associated with a significantly increased frequency of deposition in eggs. By either inducing or selecting for the expression of relevant microbial properties, passage of S. enteritidis through reproductive tissues of chickens may be useful for improving the efficiency at which experimental infection models produce egg contamination. 相似文献
8.
Bacteriologic culturing of environmental samples taken from sources such as manure pits and egg belts has been the principal screening tool in programs for identifying commercial laying flocks that have been exposed to Salmonella enteritidis and are thus at risk to produce contaminated eggs. Because airborne dust and aerosols can carry bacteria, air sampling offers a potentially efficient and inexpensive alternative for detecting S. enteritidis in poultry house environments. In the present study, an electrostatic air sampling device was applied to detect S. enteritidis in a room containing experimentally infected, caged laying hens. After oral inoculation of hens with a phage type 13a S. enteritidis strain, air samples were collected onto agar plates with the electrostatic sampling device, an impaction air sampler, and by passive exposure to the settling of aerosols and dust. Even though the floor of the room was cleaned once per week (removing most manure, dust, and feathers), air samples were positive for S. enteritidis for up to 4 wk postinoculation. On the basis of both the number of S. enteritidis colonies observed on incubated agar plates and the frequency of positive results, the efficiency of the electrostatic device was significantly greater than that of the passive exposure plates (especially at short collection intervals) and was similar to that of the far more expensive impaction sampler. The electrostatic device, used for a 3-hr sampling interval, detected airborne S. enteritidis on 75% of agar plates over the 4 wk of the study. 相似文献
9.
In Experiment 1, mature laying hens were inoculated intravaginally with 10(6) colony-forming units of Salmonella enterica serovar enteritidis (S. enteritidis), Salmonella typhimurium, Salmonella infantis, Salmonella hadar, Salmonella heidelberg, or Salmonella montevideo to compare their abilities to colonize the reproductive organs of chickens and to contaminate eggs. Salmonella enteritidis was more frequently recovered (from 11 of 40 eggs, 27.5%) than the other serovars, and especially the inner shell was contaminated with these organisms in 10 of 40 eggs (25.0%). The contamination rates and the viable counts in cloaca were significantly (P < 0.05) higher in hens inoculated with S. enteritidis than in those inoculated with the other serovars at 4 days postinoculation (PI). In the vagina, the positive rates were 90%-100% in hens inoculated with S. enteritidis, and the viable counts of the organisms in this portion were significantly (P < 0.05) higher than those of the other serovars at 2, 4, and 7 days PI. The ceca were colonized similarly by each serovar at 7 days PI. The spleen and ovary were infected with S. enteritidis in three and one hen, respectively. No Salmonella was recovered from liver and peripheral blood in any hen. Salmonella enteritidis was recovered from other oviductal portions than the vagina (10%-20%), whereas no forming egg was contaminated in the oviduct. In Experiment 2, the in vitro adherence of these six serovars to the vaginal epithelium was compared with vaginal explants. The mean number of S. enteritidis attaching to the secondary villi in the vaginal lumen was significantly (P < 0.05) higher than those of the other serovars. These results suggest that S. enteritidis has a specific advantage over the other Salmonella serovars by its capacity to colonize the vaginal tissues of hens, and this higher affinity of S. enteritidis to the vagina may play a significant role in the production of many S. enteritidis-contaminated eggs. 相似文献
10.
Contamination of eggs by Salmonella Enteritidis has been a prominent cause of human illness for several decades and is the focus of a recently implemented national regulatory plan for egg-producing flocks in the United States. Salmonella Heidelberg has also been identified as an egg-transmitted pathogen. The deposition of Salmonella strains inside eggs is a consequence of reproductive tract colonization in infected laying hens, but prior research has not determined the relationship between the numbers of Salmonella that colonize reproductive organs and the associated frequency of egg contamination. In the present study, groups of laying hens in two trials were experimentally infected with large oral doses of strains of Salmonella Enteritidis (phage type 13a), Salmonella Heidelberg, or Salmonella Hadar. Reproductive tissues of selected hens were cultured to detect and enumerate Salmonella at 5 days postinoculation, and the interior contents of eggs laid between 6 and 25 days postinoculation were tested for contamination. Significantly more internally contaminated eggs were laid by hens infected with Salmonella Enteritidis (3.58%) than with strains of either Salmonella Heidelberg (0.47%) or Salmonella Hadar (0%). However, no significant differences were observed between Salmonella strains in either isolation frequency or the number of colony-forming units (CFU) isolated from ovaries or oviducts. Salmonella isolation frequencies ranged from 20.8% to 41.7% for ovaries and from 8.3% to 33.3% for oviducts. Mean Salmonella colonization levels ranged from 0.10 to 0.51 log CFU/g for ovaries and from 0.25 to 0.46 log CFU/g for oviducts. Although parallel rank-orders were observed for Salmonella enumeration (in both ovaries and oviducts) and egg contamination frequency, a statistically significant relationship could not be established between these two parameters of infection. 相似文献
11.
A W vd Giessen R Peters P A Berkers W H Jansen S H Notermans 《The Veterinary quarterly》1991,13(1):41-46
The contamination of poultry in the Netherlands with Salmonella enteritidis was tested. For this, different methods (detection of S. enteritidis in faecal samples of 25 g; detection of S. enteritidis in cloacal swabs; detection of S. enteritidis by serological testing of antibodies in serum) were compared for their efficiency to detect S. enteritidis in flocks of poultry. Testing of faecal samples clearly yielded the best results. This method was used in a transmission study, in which 14 flocks descending from a contaminated primary mother flock were screened for the presence of S. enteritidis. The method was also used for screening 49 flocks of laying hens and 52 flocks of broiler chickens throughout the Netherlands. From the transmission study it became clear that S. enteritidis, phage type 2 (Dutch phage set) was isolated both from the mother flock and from five of the descendent flocks. Screening of poultry flocks for the presence of salmonella revealed that salmonella was present in 47% of the layer flocks and in 94% of the broiler flocks. S. enteritidis was isolated from 15% of the flocks screened. 相似文献
12.
Detection of antibody to Salmonella enteritidis and S typhimurium in the yolk of hens' eggs 总被引：2，自引：0，他引：2
Enzyme-linked immunosorbent assays (ELISAs) have been developed to detect IgG antibodies to Salmonella enteritidis and S typhimurium in the yolk of hens' eggs. Better discrimination and more consistent results were obtained between eggs from experimentally infected and uninfected hens by using saline-dilution of yolk rather than chloroform extraction. Threshold absorbance values were determined in three salmonella-free flocks, and on the basis of these results ELISA optical density values greater than 0.25 were considered to be positive for antibodies to salmonella. Four flocks with a history of salmonella infection were examined; three contained birds which were seropositive for S enteritidis by ELISA and from which S enteritidis was isolated, and a large proportion of eggs from these birds contained antibody to S enteritidis. Eggs from the fourth flock had no detectable antibody, although serum antibody was detected in some birds. No salmonellae were isolated from the yolks of the eggs from any of the four flocks. 相似文献
13.
Internal contamination of eggs by Salmonella Enteritidis has been a significant source of human illness for several decades and is the focus of a recently proposed U.S. Food and Drug Administration regulatory plan. Salmonella Heidelberg has also been identified as an egg-transmitted human pathogen. The deposition of Salmonella strains inside eggs is apparently a consequence of reproductive tissue colonization in infected laying hens, but the relationship between colonization of specific regions of the reproductive tract and deposition in different locations within eggs is not well documented. In the present study, groups of laying hens were experimentally infected with large oral doses of Salmonella Heidelberg, Salmonella Enteritidis phage type 13a, or Salmonella Enteritidis phage type 14b. For all of these isolates, the overall frequency of ovarian colonization (34.0%) was significantly higher than the frequency of recovery from either the upper (22.9%) or lower (18.1%) regions of the oviduct. No significant differences were observed between the frequencies of Salmonella isolation from egg yolk and albumen (4.0% and 3.3%, respectively). Some significant differences between Salmonella isolates were observed in the frequency of recovery from eggs, but not in the frequency or patterns of recovery from reproductive organs. Accordingly, although the ability of these Salmonella isolates to colonize different regions of the reproductive tract in laying hens was reflected in deposition in both yolk and albumen, there was no indication that any specific affinity of individual isolates for particular regions of this tract produced distinctive patterns of deposition in eggs. 相似文献
14.
Differences among six Salmonella serovars in abilities to colonize reproductive organs and to contaminate eggs in laying hens 总被引：3，自引：0，他引：3
The abilities of Salmonella serovars to colonize the reproductive organs of chickens and to contaminate eggs were compared. Mature laying hens were inoculated intravenously with 10(5) colony-forming units of Salmonella enteritidis, Salmonella typhimurium, Salmonella infantis, Salmonella hadar, Salmonella heidelberg, or Salmonella montevideo to cause the systemic infection. Salmonella enteritidis was recovered from three yolks of the laid eggs (7.0%), suggesting egg contamination from the transovarian transmission of S. enteritidis. The liver, spleen, and cecum were colonized by each serovar similarly at 4 or 7 days postinoculation (PI), whereas the ovary and preovulatory follicles were colonized by S. enteritidis with significantly (P < 0.05) higher levels than by the other serovars at 4 and 7 days PI. Salmonella enteritidis was recovered from the cloaca and vagina at 2, 4, and 7 days PI and from the other portions of the oviduct at 4 and 7 days PI. In addition, S. enteritidis had been persistent in the peripheral blood for 7 days PI. These results suggest that S. enteritidis is the predominant serovar to colonize the reproductive organs of mature laying hens among six serovars used in this study, reflecting the field situatibn in which the predominant outbreaks of human salmonellosis were caused by S. enteritidis-contaminated eggs recently. The ability of S. enteritidis to colonize the reproductive organs may be one of the reasons that egg contamination with S. enteritidis has increased. 相似文献
15.
肠炎沙门氏菌污染饲料对鸡蛋安全的影响 总被引：2，自引：0，他引：2
本研究选用160只60周龄白来航蛋鸡,随机分为4组,分别一次性采食30g添加了0、4.7×102、4.7×105、4.7×108cfu肠炎沙门氏菌(SE)的饲料,然后用特异性PCR法对试验鸡所产鸡蛋的不同部位进行SE检测,并观察记录生产性能。结果显示,对照组鸡蛋各部位均为阴性,试验组的蛋壳、壳膜、蛋黄、蛋白均能检测到SE,且随染菌量的增大,检出率增高。当摄入108cfu的SE时,会降低产蛋率,但对鸡蛋的表观性状没有显著影响,成为危害人类健康的潜在隐患。 相似文献
16.
Egg contamination by Salmonella Enteritidis has remained a significant public health problem for nearly two decades, and Salmonella Heidelberg has also been recently implicated in egg-transmitted human illness. Colonization of the intestinal tract is a necessary precursor to the invasion of reproductive organs and subsequent deposition inside eggs laid by infected hens, but the relationship between the persistence of Salmonella in the intestinal tract and the likelihood of egg contamination has been uncertain. In this study, groups of laying hens were inoculated with large oral doses of strains of Salmonella Enteritidis and Salmonella Heidelberg, including variants of the original parent strains that had been reisolated from eggs laid by infected hens in a prior study. The shedding of Salmonella in voided feces was monitored for 6 wk postinoculation, and all eggs laid by infected hens between 5 and 22 days postinoculation were cultured for Salmonella in their contents. The mean duration of fecal shedding was significantly longer for the previously passaged Salmonella strains (26.7 days) than for the original parent strains (17.5 days), and the passaged strains caused a significantly higher frequency of egg contamination (6.4%) than did the parent strains (3.3%). However, the duration of fecal shedding and the frequency of egg contamination were not correlated for any of the Salmonella Enteritidis or Salmonella Heidelberg strains. 相似文献
17.
Detection of infected poultry flocks is essential for controlling eggborne transmission of Salmonella enteritidis to humans. The present study evaluated the detection of antibodies in the sera of experimentally infected chickens by a fluorescence polarization assay with a tracer prepared from the O-polysaccharide of S. enteritidis and an enzyme-linked immunosorbent assay (ELISA) with an S. enteritidis flagellin antigen. In two trials, groups of specific-pathogen-free laying hens were infected orally with either 10(6) or 10(8) colony-forming units (CFU) of S. enteritidis (phage type 13a) or with 10(8) CFU of Salmonella typhimurium. Serum samples were collected before inoculation and at five subsequent weekly intervals. Both assays successfully detected the majority of hens infected with S. enteritidis at either dose level, but they also identified a substantial number of hens infected with S. typhimurium as seropositive. The fluorescence polarization test detected S. enteritidis infection significantly more often and cross-reacted with sera from hens infected with S. typhimurium significantly less often than the ELISA. The fluorescence polarization assay also offered advantages in terms of speed and methodologic simplicity. 相似文献
18.
Two small free range flocks with 32 hens, whose Salmonella enteritidis contaminated eggs caused salmonellosis in man, were investigated for localisation of the agent. Salmonella enteritidis phage type 4 was isolated from 12 of 32 hens (37.5%). Eight hens (25%) harbored the bacterium in the ovary and/or the oviduct. The rapid slide agglutination test with Salmonella pullorum-antigen revealed 21 positive hens (66%). All eight hens with Salmonella enteritidis phage type 4 in the reproductive tract were seropositive. The significance of these findings for the control of Salmonella enteritidis phage type 4-infections in poultry is discussed. 相似文献
19.
Effects of administering killed Salmonella enterica serovar enteritidis (SE) vaccines to laying hens prior to induced molting on egg production and on shedding of SE were investigated. Forty hens were vaccinated with one of two SE vaccines available commercially in the United States and Japan. Twenty-five days after vaccination, feed was withdrawn for 2 wk from 20 vaccinated plus 10 unvaccinated hens to induce molt. Four days after molt induction, all hens were challenged with a dose of 2.4 X 10(9) of SE. For the 25 days following administration of the SE bacterins, egg production in vaccinated hens showed approximately a 15% decrease. After molt induction, egg production in molted hens ceased and then returned to normal levels 8 or 9 wk postvaccination. Through the 3-mo experimental period, the decreases in numbers of eggs laid in the unvaccinated/molted group and two vaccinated/molted groups were 225 (26.2%), 245 (28.4%), and 274 (31.9%), respectively, compared with 860 in the unvaccinated/unmolted group. There was no significant difference in egg lay at the P < 0.05 level among the former three groups. Hens in the vaccinated/molted groups shed about two logs less SE than hens in the unvaccinated/molted group 3 14 days postchallenge (P < 0.05 or 0.01). These results indicate that vaccination prior to induced molting might be effective in preventing the exacerbation of SE problems within flocks in which the potential for SE contamination may exist. 相似文献
20.
1. An experiment that included 1440 caged laying hens in 24 experimental units was conducted to determine the effect of differences in excreta moisture on the proportion of dirty eggs and the microbial contamination of eggs that were ostensibly uncontaminated by excreta. Excreta moisture contents were changed by giving the hens diets that contained 4 different concentrations of sodium. 2. Diets containing 1.6, 5, 10 or 15 g/kg dietary sodium were fed ad libitum to 1140 laying hens for a 12-week feeding period. A sample of excreta was collected from each experimental unit each week and its moisture content determined. All eggs produced were classified as clean or dirty according to the European Community Egg Marketing Regulations. A sample of eggs were collected from each experimental unit on 4 separate occasions in the last 4 weeks of the feeding period and the total bacterial numbers on ostensibly clean egg shells were determined. 3. Increasing dietary sodium concentration gave linear (P<0.01) increases in excreta moisture. Each 100 g/kg increase in excreta moisture increased (P<0.001) dirty egg numbers by 0.52% of the total eggs produced. Increasing excreta moisture gave a linear increase (P<0.001) in the (log-transformed) numbers of microorganisms that contaminated ostensibly clean egg shells. 相似文献