[Leaflet on the prevention of intestinal diseases through food infections (Salmonella infections)].
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Germany, West↗
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Immunity to systemic Salmonella infections.
Salmonella infections are a serious public health problem in developing countries and represent a constant concern for the food industry. The severity and the outcome of a systemic Salmonella infection depends on the "virulence" of the bacteria, on the infectious dose as well as on the genetic makeup and immunological status of the host. The control of bacterial growth in the reticuloendothelial system (RES) in the early phases of a Salmonella infection relies on the NADPH oxidase-dependent anti-microbial functions of resident phagocytes and is controlled by the innate resistance gene Nramp1. This early phase is followed by the suppression of Salmonella growth in the RES due to the onset of an adaptive host response. This response relies on the concerted action of a number of cytokines (TNFalpha, IFNgamma, IL12, IL18, and IL15), on the recruitment of inflammatory phagocytes in the tissues and on the activation of the recruited cells. Phagocytes control bacterial growth in this phase of the infection by producing reactive nitrogen intermediates (RNI) generated via the inducible nitric oxide synthase (iNOS). Clearance of the bacteria from the RES at a later stage of the infection requires the CD28-dependent activation of CD4+ TCR-alphabeta T-cells and is controlled by MHC class II genes. Resistance to re-infection with virulent Salmonella micro-organisms requires the presence of Th1 type immunological memory and anti-Salmonella antibodies. Thus, the development of protective immunity to Salmonella infections relies on the cross-talk between the humoral and cellular branches of the immune system.
Animals↗
Effects of splenectomy on the retention of Salmonella enteritidis and on the hemopoietic response to Salmonella infection.
Salmonella infection induces a marked increase in the splenic granulopoiesis, but causes a reduction in hemopoiesis in the bone marrow. In this study, effects of Salmonella enteritidis infection on hemopoietic stem cells were examined in splenectomized (SX-) mice. Splenectomy emphasized hemopoietic damage in the bone marrow caused by Salmonella infection. Total nucleated cells, pluripotent stem cells (CFUs) and granulocyte-macrophage progenitor cells (GM-CFC) in the bone marrow of SX-mice all decreased markedly compared with sham-splenectomized (NX-) mice, and the recovery from the decline was also delayed. Thus, neither enhancement of the granulopoiesis nor granulopoietic recovery in the bone marrow was observed to compensate the granulopoietic response in the spleen. Splenectomy also resulted in a longlasting retention of Salmonella in the liver. The observations indicate that the spleen is the major organ to respond to bacterial invasion in regard to enhanced granulopoiesis and hence enhanced bacterial clearance.
Animals↗
[Host defense mechanisms against Salmonella infection].
Salmonella is one of the gram negative intracellular pathogens. The immune response to Salmonella includes innate immunity and adaptive immunity. The intestinal epithelium, neutrophil, macrophage, dendritic cell, NK cell, NK T cell and gammadelta T cell take important part in former process, and antigen specific T cell and B cell take part in the later process. Macrophages and dendritic cells increase in number early after Salmonella infection and produce variety of cytokines. Especially, IL-12, IL-15 and IL-18 play important roles in protection against Salmonella infection, proliferation of NK cell, NKT cell and gammadelta T cell, producing IFN-gamma, in addition, IL-12 and IL-18 induce IFN-gamma production by Th1 cells and adaptive immune response.
Animals↗
Inducible nitric oxide synthase and Salmonella infection.
Salmonella infection is associated with the increased expression of inducible nitric oxide synthase in macrophages and other cells. This review summarizes current knowledge of the molecular mechanisms involved in the induction process, and discusses the functional significance of nitric oxide production in the context of host defense against Salmonella.
Animals↗
A lethal role for lipid A in Salmonella infections.
Salmonella infections in naturally susceptible mice grow rapidly, with death occurring only after bacterial numbers in vivo have reached a high threshold level, commonly called the lethal load. Despite much speculation, no direct evidence has been available to substantiate a role for any candidate bacterial components in causing death. One of the most likely candidates for the lethal toxin in salmonellosis is endotoxin, specifically the lipid A domain of the lipopolysaccharide (LPS) molecule. Consequently, we have constructed a Salmonella mutant with a deletion-insertion in its waaN gene, which encodes the enzyme that catalyses one of the two secondary acylation reactions that complete lipid A biosynthesis. The mutant biosynthesizes a lipid A molecule lacking a single fatty acyl chain and is consequently less able to induce cytokine and inducible nitric oxide synthase (iNOS) responses both in vivo and in vitro. The mutant bacteria appear healthy, are not sensitive to increased growth temperature and synthesize a full-length O-antigen-containing LPS molecule lacking only the expected secondary acyl chain. On intravenous inoculation into susceptible BALB/c mice, wild-type salmonellae grew at the expected rate of approximately 10-fold per day in livers and spleens and caused the death of the infected mice when lethal loads of approximately 10(8) were attained in these organs. Somewhat unexpectedly, waaN mutant bacteria grew at exactly the same rate as wild-type bacteria in BALB/c mice but, when counts reached 10(8) per organ, mice infected with mutant bacteria survived. Bacterial growth continued until unprecedentedly high counts of 10(9) per organ were attained, when approximately 10% of the mice died. Most of the animals carrying these high bacterial loads survived, and the bacteria were slowly cleared from the organs. These experiments provide the first direct evidence that death in a mouse typhoid infection is directly dependent on the toxicity of lipid A and suggest that this may be mediated via pro-inflammatory cytokine and/or iNOS responses.
Acyltransferases↗
[Salmonella infections in swine. Salmonella infections in swine in meat hygiene].
Salmonella is considered one of the most important food borne pathogens that has potential implications for human health. In Germany, Salmonella monitoring is being used in swine farms as a predictor for Salmonella infection and to implement control measures directed to minimise cross-contamination at the slaughter plant. An research project was established in order to gain experience with the eradication of Salmonella in German swine herds.
Abattoirs↗
[Protagonists of innate immunity during in Salmonella infections].
Salmonella are facultative intracellular Gram-negative bacteria that are found ubiquitously in nature and have the ability to infect a wide range of hosts including humans, domesticated, wild mammals, and birds. The principal clinical manifestations associated with Salmonella infection in humans are enteric fever (typhoid and paratyphoid) and a self-limiting gastroenteritis (salmonellosis). Additionally, silent carriage of this bacterium is frequent and contributes to disease dissemination. Typhoid fever still represents a major public health problem in many developing countries. On the other hand, industrialized countries experience an increased incidence of nontyphoidal Salmonella infections with most cases tracing back to food contamination. Studies using mouse model of infection with a highly virulent Salmonella typhimurium serotype have provided important insight into the complexity of the innate immune response to infection. The players are numerous but emphasis was placed on the genes that were discovered using genetic approaches and in vivo assay with live pathogen and include positional cloning of mouse mutations and manipulation of genes in the context of whole animal either by transgenesis or knockout technologies. Some of the critical genes include those known to play a role in the detection of the bacteria (Cd14, Lbp, Tlr4 and Tlr5) and in microbicidal activity (Slc11a1, Nos2, NADPH oxidase and cryptdins). These discoveries have already initiated the search for the contribution of particular genetic pathways in the innate immune response of humans to infection with Salmonella and other intracellular microorganisms.
Animals↗
[Immunologic status of patients with Salmonella infections].
Salmonella typhimurium infection was diagnosed in 186 patients aged 18-56. The clinical picture was that of gastroenteritis (73.1%), enteritis (14.0%), gastritis (6.45%), gastroenterocolitis (6.45%). Salmonellosis of moderate severity presented in 88.7% of patients, a severe course occurred in 11.3%. Concomitant disorders arose in 22.6% of cases. Immunological investigation disclosed T-lymphopenia, reduced number of multireceptor RFC, both T-helpers and T-suppressors. The levels of 0-lymphocytes and CIC were on the increase. Salmonellosis of long duration was characterized by hyperactivity of autoimmune reactions.
Adolescent↗
Effect of bovine virus diarrhoea-mucosal disease virus infection on salmonella infection in calves.
The possibility that bovine virus diarrhoea virus (BVDV) infection could aggravate concurrent salmonella infections was investigated in two series of experiments with Salmonella dublin and S typhimurium. In both series of experiments the clinical signs tended to be more severe in dual infections than in those with salmonella alone. Faecal excretion of S dublin was similar in both single and dual infected calves. A protracted bacteraemia occurred only in two dual infected calves, one of which died from suppurative meningitis. In the case of S typhimurium, body temperatures, passage of abnormal faeces and isolation rates of salmonella from faeces were significantly increased. The results suggest that BVDV infection may indeed exacerbate the effects of salmonella infection and the aetiological relationship of the two agents should be considered during outbreaks of bovine salmonellosis.
Animals↗
The spectrum of Salmonella infection.
Salmonellae have demonstrated an extraordinary capacity to adapt to a wide range of ecologic niches and to the peculiarities of modern society, such as the mass production of food products. The vast majority of infections in the United States are caused by serotypes not specifically adapted to human or animal hosts, whereas the most frequent isolate in developing countries is S. typhi, which is highly adapted to human hosts. The number of isolates reported in the United States has been increasing steadily since 1975, largely a result of outbreaks associated with the mass production of food products, particularly poultry, which is frequently contaminated. Salmonella infection occurs when ingested organisms bypass gastric defenses, multiply within the intestinal lumen, penetrate the intestinal mucosa, and multiply within macrophages of the reticuloendothelial system. They may then disseminate via the systemic circulation. Several virulence factors have been identified. The wide range of pathologic and clinical manifestations are subdivided into four syndromes, each requiring a distinct diagnostic and therapeutic approach: (1) gastroenteritis, (2) enteric fever, (3) bacteremia with or without metastatic disease, and (4) asymptomatic carriage. Although any serotype can cause any of these syndromes, certain serotypes are associated with specific presentations. Serious complications of bacteremic infection include infections of the aorta, endocardium, bone, and meninges. Salmonella infection is particularly severe in patients who have AIDS, leukemia, lymphoma, immunodeficiency of other causes, inflammatory bowel disease, schistosomiasis, and macrophage dysfunction. Diagnosis is based on culture of the organism from appropriate sites. Several serologic tests have been developed that warrant further evaluation. Chloramphenicol, ampicillin, amoxicillin, and trimethoprimsulfamethoxazole have clearly established efficacy. Experience with third generation cephalosporins and quinolones is preliminary and fragmentary, but results suggest that they may prove to be efficacious in certain clinical circumstances. Antibiotic resistance has become a major problem in certain geographic areas. The three vaccines for S. typhi that are currently in use internationally provide only moderate protection for short periods of time.
Humans↗
The role of host cell death in Salmonella infections.
Salmonella enterica is an important enteric pathogen of humans and a variety of domestic and wild animals. Infection is initiated in the intestinal tract, and severe disease produces widespread destruction of the intestinal mucosa. Salmonella strains can also disseminate from the intestine and produce serious, sometimes fatal infections with considerable cytopathology in a number of systemic organs. A combination of bacterial genetic and cell biology studies have shown that Salmonella uses specific virulence mechanisms to induce host cell death during infection. Salmonella produces one set of virulence proteins to promote invasion of the intestine and a different set to mediate systemic disease. Significantly, each set of virulence factors mediates a distinct mechanism of host cell death. The Salmonella pathogenicity island-1 (SPI-1) locus encodes a type III protein secretion system (TTSS) that delivers effector proteins required for intestinal invasion and the production of enteritis. The SPI-1 effector SipB activates caspase-1 in macrophages, releasing IL-1beta and IL-18 and inducing rapid cell death by a mechanism that has features of both apoptosis and necrosis. Caspase-1 is required for Salmonella to infect Peyer's patches and disseminate to systemic tissues in mice. Progressive Salmonella infection in mice requires the SPI-2 TTSS and associated effector proteins as well as the SpvB cytotoxin. Apoptosis of macrophages in the liver is found during systemic infection. In cell culture, Salmonella strains induce delayed apoptosis dependent on SPI-2 function in macrophages from a variety of sources. This delayed apoptosis also requires activation of TLR4 on macrophages by the bacterial LPS. Downstream activation of kinase pathways leads to balanced pro- and antiapoptotic regulatory factors in the cell. NF-kappaB and p38 mitogen-activated protein kinase (MAPK) are particularly important for the induction of antiapoptotic factors, whereas the kinase PKR is required for bacterial-induced apoptosis. The Salmonella SPI-2 TTSS is essential for altering the balance in favor of apoptosis during intracellular infection, but the effectors involved remain poorly characterized. The SpvB cytotoxin has been shown to play a role in apoptosis in human macrophages by depolymerizing the actin cytoskeleton. A model for the role of bacteria-induced host cell death in Salmonella pathogenesis is proposed. In the intestine, the Salmonella SPI-1 TTSS and SipB mediate macrophage death by caspase-1 activation, which also releases IL-1beta and IL-18, promoting inflammation and subsequent phagocytosis by incoming macrophages and leading to dissemination to systemic tissues. Intracellular secretion of virulence effector proteins by the SPI-2 TTSS facilitates growth of Salmonella in these macrophages and the delayed onset of apoptosis in extraintestinal tissues. These infected, apoptotic cells are targeted for engulfment by incoming macrophages, thus perpetuating the cycle of cell-to-cell spread that is the hallmark of systemic Salmonella infection.
Animals↗
TREATMENT OF ACUTE CASES OF SALMONELLA INFECTION AND SALMONELLA CARRIERS WITH AMPICILLIN AND NEOMYCIN.
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Ampicillin↗
Diverse virulence traits underlying different clinical outcomes of Salmonella infection.
Salmonella strains have evolved to infect a wide variety of reptiles, birds, and mammals resulting in many different syndromes ranging from colonization and chronic carriage to acute fatal disease. Adaptation to a large number of different evolutionary niches has undoubtedly driven the high degree of phenotypic and genotypic diversity in Salmonella strains. Differences in LPS and flagellar structure generate the antigenic variation that is reflected in the more than 2,000 known serotypes. Moreover, variations of LPS structure affect the virulence of the strain. The differential expression of various fimbriae by Salmonella is likely to be due to the wide variety of mucosal surfaces that are encountered by various strains, and the host immune response may select for a different expression pattern. As with these surface structures, a variety of other important virulence determinants show a variable distribution in Salmonella strains and also serve to delineate the divergence of the Salmonella lineage from E. coli. The acquisition of the SPI-1 region may have represented the defining genetic event in the separation of the Salmonella and E. coli lineages. The SPI-1 cell invasion function allowed Salmonella to establish a separate niche in epithelial cells. The mgtC locus on SPI-3 is also present in all lineages and facilitates the adaptation of the bacteria to the low Mg2+, low pH environment of the endosome that results from SPI-1-mediated invasion. Subsequent acquisition of SPI-2 allowed Salmonella to manipulate the sorting of the endosome or phagosome, altering the intracellular environment and facilitating bacterial growth within infected cells. The ability to disseminate from the bowel and establish extraintestinal niches is promoted by the spv locus. Since Salmonella proliferates within macrophages and must avoid phagocytosis by neutrophils to establish a systemic infection, the spv genes appear to promote the macrophage phase of the disease process. Here the polymorphism of the spv locus is clearly demonstrated, since the serovars that cause most cases of nontyphoid bacteremia contain the spv genes. The absence of the spv genes from S. typhi is particularly puzzling and is a strong indication that the pathogenesis of typhoid fever is fundamentally different from that of bacteremia due to nontyphoid Salmonella. There is currently no genetic explanation for the phenotype of host adaptation or for the finding that only a few serovars cause the majority of human infections. Based on recent findings that multiple individual virulence genes have a variable distribution in Salmonella, it is unlikely that a single locus will be found to be responsible for these complex biological traits. Instead, a complicated combination of genes are likely to contribute to the overall virulence phenotype.
Animals↗
Dynamics of bacterial growth and distribution within the liver during Salmonella infection.
Salmonella enterica causes severe systemic diseases in humans and animals and grows intracellularly within discrete tissue foci that become pathological lesions. Because of its lifestyle Salmonella is a superb model for studying the in vivo dynamics of bacterial distribution. Using multicolour fluorescence microscopy in the mouse typhoid model we have studied the interaction between different bacterial populations in the same host as well as the dynamic evolution of foci of infection in relation to bacterial growth and localization. We showed that the growth of Salmonella in the liver results in the spread of the microorganisms to new foci of infection rather than simply in the expansion of the initial ones. These foci were associated with independently segregating bacterial populations and with low numbers of bacteria in each infected phagocyte. Using fast-growing and slow-growing bacteria we also showed that the increase in the number of infected phagocytes parallels the net rate of bacterial growth of the microorganisms in the tissues. These findings suggest a novel mechanism underlying growth of salmonellae in vivo with important consequences for understanding mechanisms of resistance and immunity.
Animals↗
Salmonella infections in finishing pigs in The Netherlands: bacteriological herd prevalence, serogroup and antibiotic resistance of isolates and risk factors for infection.
Salmonellae are wide spread in man and animals world wide and are of increasing significance as causative agents of foodborne diseases in man. The European Union, national authorities and the pig industry are therefore more and more interested in the Salmonella status of the pig population. The aim of this study was to estimate the bacteriological prevalence of Salmonella in finishing pig herds, the serogroup and the resistance to antibiotics of the isolated Salmonellae and a preliminary risk analysis of factors associated with infection. For this, 317 finishing pig herds were randomly selected from a database containing 1500 herds in the southern part of the Netherlands. In each herd 24 samples of fresh faeces were collected from two compartments with pigs close to market weight. Per compartment 12 samples of faeces were pooled into one pooled sample. Pooled samples were cultured in duplicate. Salmonella spp. were recovered from 71 out of 306 herds (23%) in which two compartments could be sampled. A total of 108 isolated Salmonella's were serotyped: 71 serogroup B, 3 serogroup C1, 6 serogroup C2, 22 serogroup D1, and 6 isolates neither serogroup B, C or D1. Of a total of 115 Salmonella isolates tested, none were resistant to colistin, enrofloxacin, flumequin or gentamicin. Automated liquid feeding of by-products, and membership of an Integrated Quality Control (IQC) production group were associated with a decreased risk of infection, while use of trough feeding was associated with an increased risk of infection. It is necessary to test these presumed risk factors in intervention studies to evaluate their potency to reduce the Salmonella prevalence in finishing pigs and thereby reduce the risk of Salmonellosis in people consuming pork.
Animals↗
Epidemiology of Salmonella infection in calves: the source of calfhood infection by Salmonella dublin.
Investigation of the source of neonatal Salmonella dublin infection of calves was undertaken by carrying out caesarean section of cows with a history of excretion of S dublin following either S dublin enteritis or S dublin abortion. No evidence of transplacental infection was detected but six of 10 animals showed evidence of excretion of the organism in the faeces, vaginal discharge or milk in the period immediately following parturition. The strong probability of early infection as a result of contamination of the environment is therefore suggested.
Animals↗
Pancreatic involvement in Salmonella infection.
CONTEXT: Salmonella has been identified as a causative agent of acute pancreatitis. OBJECTIVE: We prospectively evaluated the frequency of acute pancreatitis, pancreatic enzyme elevation and morphological pancreatic abnormalities in patients with Salmonella infection. SUBJECTS: Thirty consecutive patients with salmonellosis (Salmonella enterica serovar Enteritidis: n=25; Salmonella enterica serovar Typhimurium: n=5) and 30 sex- and age-matched healthy subjects were studied. MAIN OUTCOME MEASURES: All subjects underwent serum amylase and lipase determination and ultrasonography. RESULTS: None of the subjects developed acute pancreatitis. Two patients (6.7%) and two controls showed serum amylase activity above the upper reference limit whereas, in five patients (16.7%) and one control subject (3.3%), the serum lipase activity appeared above the upper reference limit. Salmonella infection significantly increased serum activity of lipase (P<0.001) while it did not significantly affect serum amylase levels (P=0.204). Serum lipase activity was significantly higher in patients infected by Salmonella enterica serovar Typhimurium than in those infected by Salmonella enterica serovar Enteritidis (P=0.012). Ultrasonography did not show pancreatic abnormalities in any of the subjects. CONCLUSIONS: Our data demonstrated an elevation of serum lipase activity in gastroenteritis due to Salmonella infection, but this elevation does not seem to have clinical significance. The elevation of serum lipase seems to be particularly related to infection from Salmonella enterica serovar Typhimurium.
Acute Disease↗