Fingerprinting of Salmonella enterica subsp. enterica serovar Enteritidis by ribotyping

Objective: To carry out an epidemiologic evaluation of Salmonella enterica subsp. enterica serovar Enteritidis outbreaks in households and small communities by means of rRNA gene restriction pattern analysis (ribotyping).
Method: One hundred Enteritidis isolates dating from 1989 to 1994 which could be allocated epidemiologically to different sources or to small community outbreaks were investigated with ribotyping, a fingerprinting method in which bacterial DNA is hybridized with the biotin-labeled plasmid pKK 3535 containing a ribosomal RNA operon of Escherichia coli to determine the ribosomal RNA gene restriction patterns.
Results: Four different ribotyping patterns were found with the restriction endonuclease Sma I and nine with Sph I. Ribotypes of isolates which could be allocated epidemiologically to a common source usually corresponded. Almost 60% of the Enteritidis infections had the ribotyping pattern Sph I-A. In contrast, this pattern was not found in any of the five Enteritidis strains isolated in 1989. The suspicion that Enteritidis phage type 4 infections are caused by consumption of insufficiently heated eggs is supported by the fact that the ribotyping pattern Sph 1-A was found in isolates from eggs and from human specimens.
Conclusions: As patterns Sph I-A and Sma I-J appeared in 58% and 75% of the isolates, respectively, ribotyping cannot be used for the differentiation between various outbreaks with these two patterns. In cases where the Enteritidis strains showed less frequent patterns, ribotyping seems to be a practical tool for the identification of infection chains. In addition newly appearing ribotyping patterns can give information about the epidemiologic development of Enteritidis infection.     

Prevention and identification of Salmonella Enteritidis infection via novel diagnostic stained antigens and polyclonal antibodies

Analysis of Salmonella Enteritidis with specific antisera and stained antigen helps to reduce the identification time of the infection and offers clinical and epidemiological advantages both for poultry health and food industry for the control of salmonellosis. In this study, S. Enteritidis O and H specific antisera were obtained from rabbits immunised subcutaneously using formalin-treated whole bacterial cells as antigens. S. Enteritidis specific stained O and H antigens were prepared and tested for their diagnostic usefulness. In order to eliminate cross reactivity, Salmonella Adeyo was used as an antigen for the production of H specific polyclonal antibody and stained H antigen. Enzyme-linked immunosorbent assay results of antisera were obtained, ranging from 273,300±0.041–312,200±0.028 A492 nm. Stained O and H antigen preparations were achieved with a stronger binding degree to the hyperimmune rabbit sera and without being shown cross-reactivity between O and H antigens.     

Salmonella enterica Serovar Enteritidis,England and Wales, 1945–2011

In England and Wales, the emergence of Salmonella enterica serovar Enteritidis resulted in the largest and most persistent epidemic of foodborne infection attributable to a single subtype of any pathogen since systematic national microbiological surveillance was established. We reviewed 67 years of surveillance data to examine the features, underlying causes, and overall effects of S. enterica ser. Enteritidis. The epidemic was associated with the consumption of contaminated chicken meat and eggs, and a decline in the number of infections began after the adoption of vaccination and other measures in production and distribution of chicken meat and eggs. We estimate that >525,000 persons became ill during the course of the epidemic, which caused a total of 6,750,000 days of illness, 27,000 hospitalizations, and 2,000 deaths. Measures undertaken to control the epidemic have resulted in a major reduction in foodborne disease in England and Wales.     

The impact of Salmonella Enteritidis on lipid accumulation in chicken hepatocytes

Salmonella enterica serovar Enteritidis (SE) is a public health concern and infected chickens serve as a reservoir that potentially transmits to humans through food. Although SE seldom causes systemic disease in chickens, virulent SE strains can colonize in intestines and lead a persistent infection of the liver. The liver is the primary organ for lipid metabolism in chickens and the site for production and assembly of main components in yolk. We performed a time-course experiment using LMH-2A cells that were infected with SE and co-incubated with β-oestradiol to evaluate if SE infection affected lipid metabolism and subsequently changed lipoprotein formation for egg yolk. The results indicated that lipid accumulation significantly increased in infected LMH-2A cells while the viability of these cells was only slightly decreased. The mRNA expressions of lipid transportation and most lipogenetic genes including sterol regulatory element binding protein 1, acetyl-CoA carboxylase, fatty-acid synthase, long-chain-fatty-acid-CoA ligase 1, peroxisome proliferator-activated receptor-γ, and very-low-density lipoproteins (VLDLs) II were significantly up-regulated while the expression of lipogenetic-related stearoyl-CoA denaturase 1 was down-regulated. Moreover, decline in lipid transportation of hepatocytes was evidenced by the down-regulation of oestrogen receptor α which promotes VLDLy formation, an increase of intra-cellular accumulation of Apoprotein B (ApoB) protein, and a decrease of cellular excretion of VLDL protein. Conclusively, SE infection could elevate lipid synthesis and reduce lipid transportation in the chicken hepatocytes. These changes may lead excessive lipid accumulation in liver and slower lipoprotein deposition in yolk.     

Estimate of illnesses from Salmonella enteritidis in eggs, United States, 2000

Results from our model suggest that eating Salmonella enterica serovar Enteritidis-contaminated shell eggs caused 182,060 illnesses in the United States during 2000. Uncertainty about the estimate ranged from 81,535 (5th percentile) to 276,500 illnesses (95th percentile). Our model provides but 1 approach for estimating foodborne illness and quantifying estimate uncertainty.     

Ethidium bromide efflux by Salmonella: modulation by metabolic energy, pH, ions and phenothiazines

The main efflux pump of Salmonella enterica serotype Enteritidis, which obtains its energy for the extrusion of noxious agents from the proton-motive force, was studied with the aid of an ethidium bromide (EtBr) semi-automated method under conditions that define the role of metabolic energy, ions and pH in the extrusion of the universal substrate EtBr. The results obtained in this study indicate that in minimal medium containing sodium at pH 5 efflux of EtBr is independent of glucose, whereas at pH 8 metabolic energy is an absolute requirement for the maintenance of efflux. In deionised water at pH 5.5, metabolic energy is required for the maintenance of efflux. The inhibitory effect of the ionophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) on efflux is shown to be minimised by low pH, and at high pH by metabolic energy. Similarly, thioridazine, an inhibitor of metabolic enzymes, inhibits efflux of EtBr only at pH 8 and the degree of inhibition is lessened by the presence of metabolic energy.     

Importance of subunit vaccine antigen of major Fli C antigenic site of Salmonella Enteritidis II: A challenge trial

Salmonella enterica subsp. enterica serovar Enteritidis (SE) infection in chickens shows a mild pathogenicity except for young ages, compared with other animals, and laying hens sometimes produce SE-contaminated eggs leading to public health concerns. To reduce the problem, SE bacterin in poultry farms has been applied. We previously demonstrated that a subunit antigen, g.m. part polypeptide in SE-Fli C (SEp 9), could be a candidate subunit antigen of SE vaccine which may show less side effects in chickens. In this study, we used SEp 9 along with an adjuvant to inoculate chickens, then the chickens were orally challenged with SE, and suppression of the SE count in the cecum was investigated. Chickens inoculated with a commercial SE vaccine were prepared as positive controls (vaccine group), and those with physiological saline (control group) for comparison of the bacterial count after challenge. Employing two types of antibody-detection ELISA coated with either de-flagellated SE or SEp 9, specific antibody levels in blood and the intestine were determined.     

复合PCR鉴定沙门菌的方法

沙门菌属于肠杆菌科，是具有鞭毛、能运动的革兰阴性杆菌，而且它是导致食源性疾病的主要病原菌之一。为了加强口岸执法管理、缩短检验检疫流程和提高检验检疫工作效率，本实验拟建立复合聚合酶链反应快速检验鼠伤寒沙门菌的方法，以求提高检验工作准确性和速度。本实验在参考国内外文献的基础上，设计了两对引物，建立了较稳定的PCR检测系统。本实验中，使用了不同的菌株作为比较，证实了系统特异性良好，并且从不同的食品来源检出的沙门菌，皆能被本实验系统鉴定检出。使用复合PCR技术，能快速、准确的鉴定肠炎沙门菌和鼠伤寒沙门菌，并且较之经典的鉴定方法，时间上提前了2—3d。     

Potential international spread of multidrug-resistant invasive Salmonella enterica serovar enteritidis

In developing countries, Salmonella enterica serovar Enteritidis causes substantial illness and death, and drug resistance is increasing. Isolates from the United Kingdom containing virulence-resistance plasmids were characterized. They mainly caused invasive infections in adults linked to Africa. The common features in isolates from these continents indicate the role of human travel in their spread.