Construction and characterization of vaccine strains of Salmonella harboring mutations in two different aro genes

Derivatives of the mouse-virulent Salmonella typhimurium strain SL1344 were constructed harboring stable mutations in aroC alone or in aroC and aroA together. Fifty percent lethal doses after intravenous inoculation of the mutants into BALB/c mice were determined, and the mutants were as highly attenuated as were SL1344 aroA derivatives. All aro-dependent derivatives persisted in vivo at similar levels and for similar intervals in the livers and spleens of BALB/c mice infected intravenously. Mice vaccinated orally with 10(10) live organisms of the different derivatives survived and were well protected against oral challenge with virulent S. typhimurium. A Salmonella typhi Ty2 derivative, designated WBL2000, was constructed that harbors well-defined, stable mutations in both aroA and aroC.     

Salmonella serotype Typhimurium infection of bovine Peyer's patches down-regulates plasma membrane calcium-transporting ATPase expression

To identify host genes differentially expressed during Salmonella enterica serotype Typhimurium infection, an RNA differential display was made with total RNA extracted from ileal loops that were infected with Salmonella Typhimurium 2.5 h after infection. Down-regulated cDNA was identified in bovine Peyer's patches after infection that was highly homologous to a human plasma membrane calcium-transporting ATPase (PMCA). Differential expression of PMCA, evaluated by Northern analysis, was found to have more than a 4.6-fold decrease in expression of mRNA (size, approximately 5.1 kb). PMCA mRNA was detected by in situ hybridization exclusively within epithelial cells in the Peyer's patches. cDNA (4.4 kb) was amplified by rapid amplification of cDNA ends, cloned, and sequenced and showed a high homology to hPMCA. Bovine PMCA is down-regulated in epithelial cells of Peyer's patches after infection with Salmonella Typhimurium and, subsequently, may influence cellular calcium levels that contribute to the inflammatory processes in the pathogenesis of diarrhea.     

A cytolysin encoded by Salmonella is required for survival within macrophages.

A Salmonella gene encoding a cytolysin has been identified by screening for hemolysis on blood agar. DNA sequence analyses together with genetic mapping in Salmonella suggest that it is unrelated to other toxins or hemolysins. The gene (slyA) is present in every strain of Salmonella examined, in Shigella, and in enteroinvasive Escherichia coli but not in other Enterobacteriaceae. SlyA (salmolysin) purified from a derivative of the original clone has hemolytic and cytolytic activity and has a molecular weight predicted by the DNA sequence. The median lethal dose and infection kinetics in mice suggest that the toxin is required for virulence and facilitates Salmonella survival within mouse peritoneal macrophages.     

Salmonella serotypes identified in Mexican health services

OBJECTIVE: To identify the different Salmonella strain serotypes isolated at public and private laboratories in Mexico and at the Institute for Epidemiologic Diagnosis and Referral (InDRE). MATERIAL AND METHODS: A total of 24,394 Salmonella strains collected from 1972 to 1999 in public and private health laboratories of Mexico were analyzed with the Kauffmann-White method, using antisera produced by InDRE, according to Centers for Disease Control and Prevention (CDC, Atlanta, GA) standards; 15,843 (64.9%) samples were from human sources and 8,551 (35.1%) from non-human sources. RESULTS: One hundred ninety nine different serotypes were identified. The most frequent serotype in human beings was S. Typhimurium (20.4%), followed by S. Enteritidis (18.3%). In the past few years, the frequency of S. Enteritidis has been increasing, surpassing that of S. Typhimurium since 1991. Presently S. Enteritidis is the most frequently isolated serotype. In non-human sources, S. Derby (13.8%) and S. Anatum (8.5%) are the most frequent strains. CONCLUSIONS: Salmonella serotypes most frequently isolated in Mexico are: S. Typhimurium, S. Enteritidis, S. Derby, S. Agona y S. Anatum. From the epidemiologic standpoint, it is necessary to identify circulating and emerging Salmonella serotypes in order to target pertinent preventative interventions.     

Multiplex polymerase chain reaction assay for selective detection of Salmonella enterica serovar typhimurium

A multiplex polymerase chain reaction (PCR) assay was developed for the identification of Salmonella enterica serovar Typhimurium. Three sets of primers were designed for detecting O4, H:i, and H:1,2 antigen genes from the antigen-specific genes rfbJ, fliC, and fljB, respectively. These were evaluated in a multiplex PCR assay by using DNAs from S. enterica serovar Typhimurium, 15 other Salmonella serovars, and 8 non-Salmonella enteric pathogens. Multiplex PCR proved to be capable of identifying S. enterica serovar Typhimurium specifically and differentiating it from other Salmonella serovars in addition to non-Salmonella enteric pathogens. Thus, this multiplex PCR assay can be practically applied to the identification of S. enterica serovar Typhimurium.     

基于RNA-Seq的羊种布鲁氏菌新转录本与非编码RNA鉴定

目的 对羊种布鲁氏菌的转录本进行测序,鉴定基因组中新的转录本和非编码RNA。方法 提取羊布鲁氏菌的总RNA,去除rRNA后连接接头逆转录成cDNA,PCR扩增后进行测序,以羊布鲁氏菌16M的基因组序列为参照对测序得到的reads进行比对作图,通过生物信息学方法进行新转录本和非编码RNA的鉴定。结果 测序数据分析显示,reads在基因组上覆盖度较好。与现有注释基因相比,有773个基因的5'或3'端在基因组的原有位置基础上发生了延伸,并发现了16个新的转录本。根据测序结果,共鉴定出241条候选的非编码RNA(sRNA),进一步的RT-PCR验证结果显示,预测的sRNA在体外条件下有表达。结论 布鲁氏菌基因组中存在除了预测以外的新的转录本,布鲁氏菌中存在非编码RNA且在不同条件下有差异表达。     

A second trans-spliced RNA leader sequence in the nematode Caenorhabditis elegans.

In the nematode Caenorhabditis elegans, the 22-nucleotide RNA sequence called the spliced leader (SL) is trans-spliced from the 100-nucleotide-long SL RNA to some mRNAs. We have identified a trans-spliced leader (SL2) whose sequence differs from that of the original spliced leader (SL1), although both are 22 nucleotides long. By primer-extension sequencing, SL2 but not SL1 was shown to be present at the 5' end of the mRNA encoded by one of the four glyceraldehyde-3-phosphate dehydrogenase genes. The other three glyceraldehyde-3-phosphate dehydrogenase genes encode mRNAs that have the SL1 but not the SL2 sequence at their 5' ends. Therefore, the trans-splicing process can discriminate the transfer of SL1 from that of SL2 in a gene-specific manner.     

Salmonella serovars isolated from humans in São Paulo State, Brazil, 1996-2003

Salmonellosis remains an important cause of diarrheal illness in humans in S?o Paulo State, Brazil. In this study were identified 3554 Salmonella isolates from human infections, during the period 1996-2003. Among 68 different serovars determined, S. Enteritidis was the most frequent one in gastrointestinal and extra-intestinal infections accounting for 67.4% of all isolates. S. Typhimurium and S. enterica subsp. enterica (4,5,12:i:-) were most frequently isolated from children aged < 1-4 year-old, in contrast, people with S. Enteritidis infections were most likely to be 20-50 year-old. In our geographic area the continued laboratorial surveillance of salmonellosis, including serotyping, has showed the trends in Salmonella serovars causing infections in humans throughout the time.