Thesis (Ph. D.)--University of Hong Kong, 1987.

Infection by <I>Salmonella enteritidis </I>and <I>S. typhimurium</I> has been studied in the rat (Hooded Lister) model <I>in vivo</I>. Salmonellosis in the Hooded Lister rat has many similarities with the disease in humans. <I>Salmonellae</I> associated with the small intestinal epithelium as early as 4 h after intragastric intubation. Therefore, reinfection from the large intestine initially may not play a significant role in the infection process. Both <I>Salmonella</I> serotypes colonised, persisted and proliferated in the gastrointestinal tract and invaded sub-epithelial tissues, mainly via the ileum, leading to the systemic distribution of these pathogens. Coincidental with the infection, polyamine levels and crypt cell proliferation rates in the small intestine increased resulting in substantial growth of the tissue. This growth was particularly dramatic in the ileum where there was also some disruption of the villous epithelium. It is possible that these effects of the infection on the metabolism and morphology of the small bowel, which strongly resembles the changes induced by some plant lectins, may facilitate the colonisation and invasion of the gut by <I>Salmonella sp.</I> It was shown for the first time, that <I>S. enteritidis</I> and <I>S. typhimurium</I> strains expressing type 1 fimbriae closely associated with the rat ileal epithelium <I>in vivo</I>. Moreover, orally administered purified type 1 fimbriae also associated with the ileal surface. Thus, type 1 fimbriae alone or in combination with other fimbriae may play an important role in the early stages of infection with these pathogenic bacteria. This was further supported by the finding that deletion of the type 1 fimbriae from a strain of <I>S. enteritidis</I> led to a reduction in the numbers of <I>Salmonella </I>present in the distal ileum 6 h post-dosing. The deletion of type 1 fimbriae did not however affect the long-term progression of infection, suggesting that type 1 fimbriae do not play a prominent role in persistence.

Typescript (photocopy) / xiv, 203 leaves, [2] leaves of col. plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology, 1983

M.Tech. (Biotechnology) / Please refer to full text to view abstract

Bibliography: leaves 197-274. / 274, [146] leaves, [9] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Aims to characterize the cell-mediated immune response to Salmonella infection in mice, by comparing the antigen presenting cell activity of peritoneal cells (PCs) obtained from infected mice with that of PCs from normal mice and analysing the T cell subsets induced by primary and secondary Salmonella infections. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1993?

Thesis (Ph. D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1988. / Includes bibliographical references (leaves 126-171).

Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 96-114).

As bactérias do gênero Salmonella, especialmente S. Enteritidis e S. Typhimurium, são responsáveis por imensos prejuízos econômicos ao setor avícola, uma vez que produtos como carne de frango e ovos são apontados como a principal fonte desse patógeno em surtos de salmonelose humana. Perdas econômicas na avicultura também estão relacionadas à infecção em aves jovens devido ao desenvolvimento de doença clínica e ao aumento da mortalidade. A patogenicidade de Salmonella é considerada complexa e multifatorial necessitando de estudos que possam esclarecer a interação entre patógeno e hospedeiro. O presente trabalho teve por objetivo avaliar a virulência de 130 isolados de S. Enteritidis e 70 de S. Typhimurium, inoculadas em pintos de um dia de idade através do estabelecimento de um índice de patogenicidade. Para cada cepa, foram utilizados 10 pintos comerciais da linhagem Cobb provenientes de matrizes de corte com idade superior a 58 semanas. As aves foram inoculadas com 0,2 mL de uma solução contendo aproximadamente 2x108 UFC de S. Enteritidis ou S. Typhimurium, através da via intraperitoneal. A mortalidade e a presença de lesões associadas à septicemia foram observadas diariamente durante sete dias. As aves encontradas mortas durante esse período foram necropsiadas e observadas quanto à presença de aerossaculite (A), perihepatite (Ph), pericardite (Pc), peritonite (Pt), onfalite (O) e celulite (C). Para cada lesão foi atribuído o valor de “0,833” se presente e o valor “0” quando ausente. Animais mortos nas primeiras 24 horas pósdesafio receberam a pontuação 10, o que representa o índice máximo. Do segundo ao sétimo dia, houve uma diminuição proporcional da pontuação no tempo de morte (TM) a cada dia em que o animal sobrevivia. O cálculo do índice de patogenicidade de cada pintinho inoculado (IP) obedeceu a seguinte fórmula: IP = (TMx5) + A + Ph + Pc + Pt + O + C. Para obtenção do IP de cada amostra foi realizada a média do IP obtido com as 10 aves inoculadas. A partir dos resultados do trabalho, foi possível atribuir um valor de patogenicidade a cada uma das cepas permitindo classificá-las em grupos de baixa, intermediária e de alta patogenicidade. Os sorotipos analisados neste estudo não diferiram na capacidade de induzir a formação de lesões septicêmicas e elevada mortalidade. Desta forma conclui-se que, tanto S. Enteritidis quanto S. Typhimurium, são potencialmente capazes de causar doença clínica e mortalidade de forma semelhante aos sorovares adaptados às aves. / Bacterials of the Salmonella genus, particularly Salmonella (S.) Enteritidis and S. Typhimurium, are responsible for serious economic loss on the poultry industry, once eggs and meat chicken are the principle sources of the pathogens on outbreak of salmonellosis in human. Economic loss on the poultry industry, also is related infection in young chicks due to development clinical disease and increased mortality. The pathogenicity of Salmonella is complex and multifactorial which requires studies that elucidate the interaction between pathogen and host. The present study, was conducted to evaluate the virulence of 130 isolate of S. Enteritidis and 70 of S. Typhimurium, inoculated in 01 day old chicks, through establishment of one index of pathogenicity. For each strain was used 10 commercial lineage Cobb chicks older than 58 weeks old. Chickens were inoculated with 0,2 mL containing approximately 2 x 108 CFU of S. Enteritidis or S. Typhimurium by route intraperitoneal. Mortality and lesions associated septicemia were observed daily for seven days. Dead chicks during this period were necropsied and observed as the presence of airsaculitis (A), perihepatitis (Ph), pericarditis (Pc), peritonitis (Pt), omphalitis (O) and cellulitis. For each lesion was attributed the value “0,833” when present and “0”when absent. Dead animals on first 24 hours post-challenge received the punctuation 10. The second to seventh day, there was a proporcional decrease of punctuation on time of death (TM) each day that the chickens survived. The calculation of the index of pathogenicity obeyed the following formula: IP = (TMx5) + A + Ph + Pc + Pt + O + C. For obtainment IP of each strain was realized the average IP obtained with 10 inculated chickens. Based on results this study, was possible to assign a value of pathogenicity for each isolated allowing to classify them on groups of low, intermediate and high pathogenicity. The sorovars analyzed did not differ on ability to induce septicemic lesions and high mortality. Therefore it is concluded that, such S. Enteritidis as S. Typhimurium, are potencially capable to cause clinical disease and mortality similar to serotypes poultry adapted.

The role of neutrophils in the pathogenesis of Salmonella typhimurium-induced ruminant and human enteritis and diarrhea remains incompletely understood. To address this question, the in vivo bovine ligated ileal loop model of non-typhoidal salmonellosis was used in calves with the naturallyoccurring Bovine Leukocyte Adhesion Deficiency (BLAD) mutation whose neutrophils are unable to extravasate and infiltrate the extravascular matrix. Data obtained from BLAD calves were compared to those from genetically normal calves negative for the BLAD mutation. Morphologic studies showed that the absence of significant tissue influx of neutrophils in intestine infected by S. typhimurium resulted in less tissue damage, reduced luminal fluid accumulation, and increased bacterial invasion compared to regular calves. Study of gene expression profile of cytokines by quantitative Real-Time PCR (qRTPCR) revealed that the massive tissue influx of neutrophils during acute infection is mainly driven by the CXC chemokine GRO- α especially in the last stages of acute infection and to a lesser extent, IL-8. In contrast, the pro-inflammatory cytokines IL-1 β and TNF- α were not significantly correlated with the presence or absence of tissue neutrophils. The precise in situ localization of gene expression of these major cytokines and chemokines was investigated by qRTCPR from specific groups of intestinal cells captured by Laser Capture Microdissection in S. typhimuriuminfected ileal loops from BLAD animals. Our data confirmed that gene expression of IL-8, GRO- α, and IL-1 β was predominantly localized to enterocytes of crypts with less expression in enterocytes of villi tips and cells that form the domed villi were not an important source of TNF- α gene expression. Microarray technology was used to determine the global transcriptional profile of bovine intestinal loops inoculated with S. typhimurium. The host samples were hybridized on a 13K bovine-specific oligoarray and microarray data was analyzed using a suite of gene expression analysis and modeling tools. Analysis of our data revealed that the tissue influx of neutrophils in ileal loops greatly influenced the host gene expression. Major differences in gene expression in relevant fields of Salmonella research including inflammation and immune response, Toll-like receptor signaling, cytokine profiles, apoptosis, and intracellular defense against infection are discussed.

Salmonella is a common enteric pathogen and is the most frequently reported bacterial infection in the United States. The two most commonly reported serotypes causing human illness in the United States are Salmonella serotype Typhimurium and Salmonella serotype Enteritidis (SE). The incidence and number of foodborne outbreaks of SE started to increase in the 1970s and by 1994, SE was the most common Salmonella serotype reported to the Centers for Disease Control and Prevention (CDC). SE has been most commonly associated with consumption of shell eggs. Outbreak reports were obtained from the Foodborne Disease Outbreak Surveillance System (FDOSS) and analyzed. The number of outbreaks of SE has declined by 67% since 1990, likely as a result of the combined effect of on-farm interventions, public health policies, and food safety education messages. In addition to the decline in SE outbreaks, study findings demonstrate that there have been changes in the geographical distribution of SE outbreaks in the US. “Simple egg” foods and retail food settings have been the most commonly and consistently associated vehicles and food consumption and preparation settings with SE outbreaks in the US from 1973 to 2008.