Salmonella enteritidis in chicken eggs

After an outbreak caused by salmonella enteritidis (SE) of which home-made mayonnaise and remoulade sauce were found to be the cause, SE was detected in ten of the remaining eggs. Subsequently 409 eggs of the next shipment from the same outlet were examined bacteriologically. Of 70 of the eggs examined, SE was found in 5 egg yolk samples and in 3 egg white samples as well as in 2 of 7 pooled shell samples. Five out of 35 pooled whole egg samples comprising a total of 349 eggs were likewise positive for SE. The isolates belonged to the phage types 4 and 7 carried the virulence plasmid pRQ29.     

鸡沙门菌恩诺沙星耐药性风险评估

采用世界动物卫生组织(OIE)通用的方法,建立动物模型,对鸡沙门菌恩诺沙星耐药性进行释放评估和暴露评估.通过释放评估证实,防突变浓度与最小抑菌浓度相比增高4～16倍.说明细菌极易发生突变产生耐药性,细菌在体外诱导容易产生耐药性.耐药基因可通过接合的方式进行转移.暴露评估中,感染耐药菌的小鼠与未感染小鼠接触,未经感染小鼠暴露于动物垫料及未处理的粪便中,未感染小鼠分离的沙门菌也出现耐药性,说明细菌耐药性可在动物之间、动物与环境之间转移.耐药菌易在小鼠结肠中定植.耐药菌存在扩散的风险.     

Salmonella enteritidis clearance and immune responses in chickens following Salmonella vaccination and challenge

Our previous work showed that the cell-mediated immunity (CMI) was enhanced by live Salmonella vaccine (LV). The objective of this study was to evaluate the impact of live and killed Salmonella vaccines on Salmonella enteritidis (SE) clearance and to determine if the clearance was mediated by cell-mediated and/or humoral immunity. Chickens were first immunized at 2 weeks of age followed by a booster dose at 4 weeks, challenged with live SE 2 weeks later (6-week-old) and tested for CMI, antibody response and SE clearance 1-week post SE-challenge (7-week-old). Spleen cell proliferation induced by SE-flagella and Concanavalin A (Con A) were significantly higher and SE shedding was significantly lower in the LV group. The splenic CD3 population was significantly lower and B cells were higher in the control group compared to all the SE-challenged groups (with and without vaccination). Serum antibody to SE-flagella and envelope were significantly higher in the KV group compared to all the other groups. These results suggest that LV protects against SE infection, probably by enhancing the CMI.     

柔嫩艾美尔球虫与肠炎沙门菌混合感染对雏鸡盲肠菌群的影响

为探讨柔嫩艾美尔球虫与肠炎沙门菌单独感染及混合感染对盲肠肠道菌群的影响,12日龄莱航鸡口服单独或混合感染柔嫩艾美尔球虫或肠炎沙门菌,18日龄通过16SrRNA Miseq高通量测序检测鸡盲肠菌群组成。结果表明,18日龄莱航鸡盲肠内主要菌群为厚壁菌门和拟杆菌门。与柔嫩艾美尔球虫或肠炎沙门菌单独感染相比,混合感染导致肠杆菌科明显增加,毛螺菌科明显减少;因此,柔嫩艾美尔球虫与肠炎沙门菌混合感染对盲肠肠道菌群的影响与两者单独感染明显不同。     

Duration of immunity induced in chickens by an attenuated live Salmonella enteritidis vaccine and an inactivated Salmonella enteritidis/typhimurium vaccine

The aim of this study was to examine the duration of immunity of different vaccination schemes using the S. enteritidis live vaccine Gallivac Se and the S. enteritidis-S. typhimurium inactivated vaccine Gallimune Se+St. Three groups of Lohman Brown chickens were used. Group one was vaccinated three times orally with Gallivac Se at weeks one, seven and 13 of age. Group two was vaccinated twice orally with Gallivac Se in weeks one and seven and once i.m. with Gallimune Se+St in week 14 of age. A third group was not vaccinated and served as the control group. Eight randomly selected chickens from each of the three groups were challenged with a nalidixic acid resistant S. enteritidis PT4 strain in weeks 24, 51 and 71 of age and the same number of animals were challenged with a S. typhimurium DT 104 strain in weeks 26, 54 and 73 (75) of age.The chickens were euthanised seven days post challenge and the number of challenge strain organisms (log10 cfu) in the liver and on caecal mucosa was determined.The quantitative investigation of the challenge strain in the liver and caecal mucosa revealed a statistically significant (p < 0.05) lower challenge strain burden in the vaccinated groups compared with the non-vaccinated control group up to week 71 (73) of age. The protective effects were demonstrated for both challenge strains.     

Dynamics of lymphocyte subpopulation changes in the cecal tonsils of chickens infected with Salmonella enteritidis

Salmonella enteritidis (SE)-induced changes in various T and B lymphocyte subpopulations in the cecal tonsils of chickens were analyzed using flow cytometry. At 1 day post-SE inoculation, the percentages of CD3(+) and CD8(+) T lymphocytes were significantly decreased in the group inoculated with 1x10(9) SE colony-forming units (CFU) (SE high) and in the group inoculated with 1x10(6) SE CFU (SE low) compared with the uninfected control group. The percentage of CD4(+) T lymphocytes was significantly increased in the SE high group compared to the uninfected and the SE low groups at 4 days after SE inoculation. The percentage of IgG(+) B lymphocytes was also significantly increased in both SE high and low groups compared to the uninfected control at 6 days post-SE inoculation. In contrast, the SE low group showed significantly fewer IgM(+) B lymphocytes compared to the uninfected and SE high groups. These results show that SE infection induces significant changes in the cecal tonsil lymphocytes subpopulations shortly following SE inoculation.     

鸡体内减毒鼠伤寒沙门氏菌的繁殖和免疫反应

初步研究了cya和crp双基因突变减毒鼠伤寒沙门氏菌(Salmonella typhimurium)在鸡体内的繁殖和免疫反应。1、4或7日龄肉鸡分别经口感染10^8或10^9CFU减毒S．typhimurium X4550，接种后3—4周鸡体内特异性细胞和体液免疫达到最高峰。4日龄口服10^9CFu组免疫效果最佳，但1日龄高剂量组表现增重降低及免疫抑制。28日龄每鸡口服攻击10^10CFU强毒S．typhimurium 50333，各免疫组保护率为100％。同时免疫鸡还能全部或部分阻止沙门氏菌在肝脏和脾脏的繁殖。接种后病毒S．typhimurium在泄殖腔的检出时间为4周左右。     

噬菌体对鸡肠炎沙门氏菌的防治研究

肠炎沙门氏菌是全球食源性疾病暴发的主要病原菌之一,可引起禽类发病死亡,造成巨大的经济损失.噬菌体是一种细菌病毒,具有严格的宿主特异性.在耐药菌日益增长、抗生素使用受限的情况下,可考虑将噬菌体作为消除病原体的替抗药物.因此,文章就噬菌体对肠炎沙门氏菌的防控及其应用前景展开综述,同时为其他耐药菌的治疗防控提供新的策略.     

Mucosal humoral immunity to experimental Salmonella enteritidis infection in the chicken crop

In this report, we show that chickens, infected with Salmonella enteritidis (SE) by oral gavage, produce secretory immunoglobulin As (sIgAs) that specifically bind to numerous SE antigens. Chickens infected with SE showed strong sIgA response against flagella in both bile and crop. The optical density values of enzyme-linked immunosorbent assay (ELISA) tests in positive bile and crop were 1.17 and 0.38, respectively, and were significantly different from those of negative samples. Western immunoblotting revealed that approximately 13.5-, approximately 56-, approximately 62-, approximately 80-, and approximately 143-kD polypeptides were immunodominant proteins in bile, whereas approximately 56-, approximately 62-, and approximately 80-kD polypeptides were found to be strong antigens in crop. These results indicate that the crop may function as another site for mucosal immunity, and the SE flagella-based ELISA of crop samples can provide a useful screening test of SE exposure in chickens.     

Use of a live attenuated Salmonella typhimurium vaccine to protect hens against Salmonella enteritidis infection while undergoing molt

Previous studies demonstrated that Salmonella enteritidis infections in hens undergoing molt via feed withdrawal were more severe than in full fed hens. We conducted two trials to determine if immunizing specific-pathogen-free, Salmonella-culture-negative hens via aerosol exposure to MeganVacl, a commercially available attenuated Salmonella typhimurium vaccine, would reduce transmission of S. enteritidis from infected hens to uninfected but contact-exposed hens during a molt. In trial 1, one group of hens received two aerosol doses of vaccine 2 wk apart whereas a second group of hens remained nonvaccinated. In trial 2, the vaccinated group received only one dose of vaccine. Two weeks after the final immunization, feed was removed from all the hens, and on day 4, the center hen in rows of 11 hens received a dose of 3 x 10(5) (trial 1) or 1.3 x 10(6) (trial 2). Transmission to the unchallenged hens was followed 3, 10, 17, and 24 days later. Vaccination reduced the horizontal spread of S. enteritidis in vaccinated hens compared with their nonvaccinated counterparts, with vaccinated hens shedding significantly less S. enteritidis on day 10 postchallenge in trial 1 and on days 3, 10, 17, and 24 in trial 2. Recovery of S. enteritidis from ovaries was significantly reduced in the vaccinated hens in trial 1 and from livers/spleens, ovaries, and cecum in trial 2. These studies indicate that immunization of hens with a live S. typhimurium vaccine could help reduce S. enteritidis problems during a molt situation.     

Infection of laying hens with Salmonella enteritidis PT4 by conjunctival challenge.

The direct administration of either 103 or 108 cells of Salmonella enteritidis phage type 4 on to the conjunctiva of laying hens resulted in systemic infection. The bacterium was isolated from a variety of tissues, including the ovary and oviduct, and it was excreted in faeces for at least 27 days after infection.     

Effect of nitrofurazone or novobiocin on Salmonella enteritidis cecal colonization and organ invasion in Leghorn hens.

Nitrofurazone (433 mg/liter drinking water) administration to leghorn laying hens for 72 hours with a 48-hour withdrawal period before nitrofurazone-sensitive Salmonella enteritidis challenge resulted in a S. enteritidis culture-positive rate significantly (P less than 0.05) higher than that of unmedicated controls when hens were cultured 6 days following challenge. In a similar experiment, simultaneous nitrofurazone administration and S. enteritidis challenge resulted in no significant differences in S. enteritidis isolation frequency. However, unchallenged nitrofurazone-medicated contact control hens showed a significantly higher S. enteritidis culture-positive rate than the unchallenged unmedicated controls. This increase in apparent S. enteritidis susceptibility was associated with significantly lower cecal propionic acid and fewer anaerobic colony-forming units (CFU). In a third experiment, nitrofurazone treatment had no effect when the antibiotic was withdrawn 72 hours before S. enteritidis challenge. In a subsequent experiment, novobiocin (385 mg/kg) or nitrofurazone (300 mg/kg) was administered to adult hens for 7 days before challenge with nitrofurazone and novobiocin-resistant S. enteritidis. Both nitrofurazone and novobiocin administration resulted in a significantly higher S. enteritidis culture-positive rate than unmedicated controls at end of the experiment 7 days post-challenge. Results indicate that administration of some antibiotics may enhance susceptibility to S. enteritidis in leghorn hens.     

Intestinal carriage of Campylobacter jejuni and Salmonella by chicken flocks at slaughter.

Campylobacter jejuni were isolated in large numbers from the majority of birds sampled in colonic swabs from 28 of 60 flocks at slaughter. By contrast only small numbers of birds from 11 of the same 60 flocks yielded Salmonella enteritidis serotypes. Three C. jejuni isolates from each flock were serotyped on the basis of their heat-stable antigens, using antisera prepared against 16 serotypes common in Campylobacter diarrhea in man. The majority (72 of 83) of the chicken isolates could be serotyped.     

Cytokine gene expression in chicken cecal tonsils following treatment with probiotics and Salmonella infection

Probiotics are currently employed for control of pathogens and enhancement of immune response in chickens. In this study, we investigated the underlying immunological mechanisms of the action of probiotics against colonization of the chicken intestine by Salmonella enterica subsp. enterica serovar Typhimurium (Salmonella serovar Typhimurium). Birds received probiotics by oral gavage on day 1 of age and, subsequently, received Salmonella serovar Typhimurium on day 2 of age. Cecal tonsils were removed on days 1, 3 and 5 post-infection (p.i.), RNA was extracted and subjected to real-time quantitative RT-PCR for measurement of interleukin (IL)-6, IL-10, IL-12 and interferon (IFN)-gamma gene expression. There was no significant difference in IL-6 and IL-10 gene expression in cecal tonsils of chickens belonging to various treatment groups. Salmonella serovar Typhimurium infection resulted in a significant increase in IL-12 expression in cecal tonsils on days 1 and 5p.i. However, when chickens were treated with probiotics prior to experimental infection with Salmonella, the level of IL-12 expression was similar to that observed in uninfected control chickens. Treatment of birds with probiotics resulted in a significant decrease in IFN-gamma gene expression in cecal tonsils of chickens infected with Salmonella compared to the Salmonella-infected birds not treated with probiotics. These findings reveal that repression of IL-12 and IFN-gamma expression is associated with probiotic-mediated reduction in intestinal colonization with Salmonella serovar Typhimurium.     

Effect of anaerobic cecal microflora and dietary lactose on colonization resistance of layer chicks to invasive Salmonella enteritidis.

The effect of oral inoculation with anaerobic cultures of cecal microflora and providing lactose in the feed on colonization resistance to invasive Salmonella enteritidis was evaluated in newly hatched leghorn chicks. Salmonella colonization of the ceca, tissue invasion and organ colonization, horizontal transmission, and seroconversion were significantly decreased (P less than 0.01) in chicks inoculated with cecal flora. The addition of lactose to the feed, in the absence of cecal microflora, failed to provide protection. Dietary lactose enhanced colonization resistance in chicks that were inoculated with anaerobic cultures of cecal flora. The results indicated that establishment of normal cecal flora in layer chicks together with the addition of lactose to the diet markedly increases resistance to cecal colonization and organ invasion, and decreases horizontal transmission of S. enteritidis.     

Occurrence of Salmonella enteritidis in pooled table eggs and market-ready chicken carcasses in Zambia.

The level of Salmonella enteritidis contamination in Zambian table eggs and ready market chicken carcasses was studied. Nine of the 240 (3.8%) pooled samples of table eggs and 18 of 382 (4.7%) chicken carcasses were contaminated with S. enteritidis. All the isolates from the table eggs belonged to the enteropathogenic invasive phage type 4, whereas seven isolates from the chicken carcasses belonged to phage type 4, three were phage type 7, and eight were untypable (rough type). All the isolates were sensitive to gentamycin, ampicillin, tetracycline, cotrimoxazole, amoxycillin, furazolidone, and chloramphenicol.     

Effects of vaccination and other preventive methods for Salmonella enteritidis on commercial laying chicken farms

The effect of introducing vaccinated commercial laying chickens on to farms, which previously had laying flocks that were infected with Salmonella Enteritidis, was investigated by sampling faeces and environmental samples, and in some cases spent hens. In 15 of 17 free-range flocks vaccination eliminated any evidence of infection. In 11 barn egg production flocks, vaccination produced similar results in four flocks on one farm but infection persisted in seven flocks on other farms. Vaccination of two consecutive cage layer flocks led to a gradual disappearance of the infection, but in 18 other flocks there was evidence of infection after vaccination. In one continuously occupied cage layer house, treatment by competitive exclusion was followed by a gradual disappearance of S Enteritidis in faeces and a substantial reduction in its levels in the environment. On four barn egg production sites disinfection with a formaldehyde, glutaraldehyde and quaternary ammonium compound disinfectant eliminated Salmonella species even though birds housed subsequently were not vaccinated. In three flocks that had been vaccinated for four years, S Enteritidis was still present. In most cases the poor performance of the vaccine was associated with severe rodent control problems and a poor standard of cleaning and disinfection.