Pathogenicity test for Listeria monocytogenes using immunocompromised mice (original) (raw)
Related papers
Journal of Medical Microbiology, 1991
The virulence of 74 Listeria monocytogenes isolates from clinical cases and food products and of 11 isolates of other Listeria species was tested in mice immunocompromised with carrageenan. Isolates of species other than L. monocytogenes were not lethal to such mice. All 29 clinical isolates of L. monocytogenes (serotypes 1/2a, 1/2b, 4b) and 33 of 42 isolates of various serotypes isolated mainly from dairy products killed all test mice (100% lethality) at an inoculum of 104cfu/mouse. All lethal strains of L. monocytogenes were haemolytic and possessed the 58-Kda band specific for listeriolysin 0 as demonstrated by SDS-PAGE immunoblotting. The nine avirulent strains of L. monocytogenes had detectable haemolytic activity, but in six of them this activity was significantly weaker than in virulent strains and the 58-Kda band was not detected. The other three avirulent strains were highly haemolytic and possessed the 58-Kda band, which suggests that other factor(s) could be involved in the virulence of L. monocytogenes.
Comparison of Listeria monocytogenes Virulence in a Mouse Model
Journal of Food Protection, 2006
Listeriosis results from exposure to the foodborne pathogen Listeria monocytogenes. Although many different strains of L. monocytogenes are isolated from food, no definitive tests currently predict which isolates are most virulent. The objectives of this study were to address two major data gaps for risk assessors, variability among L. monocytogenes strains in pathogenicity and virulence. Strains used in our monkey clinical trial or additional food isolates were evaluated for their virulence and infectivity in mice. All strains were equally pathogenic to immunocompromised mice, causing deaths to 50% of the population 3 days after exposure to doses ranging from 2 to 3 log CFU. Doses resulting in 50% deaths on the fifth day after administration were 1 to 2 log lower than those on the third day, indicating that the full course of pathogenicity exceeds the 3-day endpoint in immunocompromised mice. Three strains were chosen for further testing for their virulence and infectivity in liver...
Some Aspects of Murine Experimental Listeriosis
Acta Veterinaria Scandinavica, 1985
A set of experiments was carried out in order to approach the complex nature of L. monocytogenes infections from different aspects. Experiment 1 showed that Listeria are able to gain admission to body by numerous ways and both subcutaneous and oral entry can lead to fatal septicemia. It also gave slight support to the theory of direct neural transmission of Listeria to the brain and indicated the possibility that intestinal absorption after oral exposition at least partly occurs via lymphatic vessels. No inflammatory reaction could be caused to mice by ocular flushing with Listeria suspension.The second trial proved that there are vast differences in the animal pathogenecity of Listeria strains — even among those of the same serotype. In experiment 3A the abolishing effect of dextran sulfate on the early resistance of mice to Listeria was confirmed and it turned out that cortisone at a therapeutic dose level did not bring about that phenomenon. Levamisole granted no conspicuous enhancement of resistance in this acute challenge; however, the results of the immunity test (3B) suggested that levamisole may be beneficial during the induction phase. On the other hand, starvation appeared to impair long-term immunity. Likewise, in experiment 4 starved mice were quite susceptible to acute challenge with Listeria. Raised ambient temperature, on the contrary, prominently increased the survival rate of the animals.Owing to the fairly small number of animals these results should be regarded as preliminary starting points to further studies.
FEMS Microbiology Letters, 2009
Three different Listeria monocytogenes strains, LO28 (a laboratory strain with truncated InlA), 4446 (a clinical isolate) and 7291 (a food isolate), were compared in a guinea-pig model designed to mimic food-borne exposure. The objectives were (1) to verify the applicability of the animal model for distinguishing between Listeria with different virulence properties and (2) to explore whether it was possible to reduce the required number of animals by dosing with mixed cultures instead of monocultures. Consistent with in vitro observations of infectivity in Caco-2 cells, faecal densities and presence in selected organs were considerably lower for LO28 than for the other two strains. Additionally, the animal study revealed a difference in prevalence in faeces as well as in internal organs between the clinical isolate and the food isolate, which was not reproduced in vitro. Dosage with monocultures of Listeria strains gave similar results as dosage with a mixture of the three strains; thus, the mixed infection approach was a feasible way to reduce the number of animals needed for determination of listerial virulence.
Virulencia de cepas de Listeria monocytogenes procedentes de cabras y sus derivados
Revista Mexicana de Ciencias Pecuarias
Se evaluó la virulencia de cepas de Listeria monocytogenes todas de serotipo 4b procedentes de cabras y susderivados. Se observaron niveles de virulencia variables cuando se comparó la virulencia relativa (porcentaje deletalidad) en ratones BALB/c inoculados vía intravenosa o intragástrica y su capacidad para infectar macrófagos J774A.1, y células epiteliales Caco-2. Dos cepas obtenidas de alimento de cabras produjeron 100 % de letalidad por ambas vías de inoculación y no mostraron diferencia significativa con la cepa testigo (P>0.05) respecto al porcentajede invasión y a los parámetros de la cinética de crecimiento cuadrática observada en ambas líneas celulares. Si bien todas las cepas lograron invadir las células Caco-2, solamente algunas consiguieron invadir el bazo después de la inoculación por vía intragástrica. Las dos cepas provenientes de alimento de cabras fueron las más virulentas, representando un riesgo para la salud humana y animal, ya que pueden ser diseminadas en e...
Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes
Journal of Visualized Experiments, 2011
Listeria monocytogenes (Listeria) is a Gram-positive facultative intracellular pathogen 1. Mouse studies typically employ intravenous injection of Listeria, which results in systemic infection 2. After injection, Listeria quickly disseminates to the spleen and liver due to uptake by CD8α + dendritic cells and Kupffer cells 3,4. Once phagocytosed, various bacterial proteins enable Listeria to escape the phagosome, survive within the cytosol, and infect neighboring cells 5. During the first three days of infection, different innate immune cells (e.g. monocytes, neutrophils, NK cells, dendritic cells) mediate bactericidal mechanisms that minimize Listeria proliferation. CD8 + T cells are subsequently recruited and responsible for the eventual clearance of Listeria from the host, typically within 10 days of infection 6. Successful clearance of Listeria from infected mice depends on the appropriate onset of host immune responses 6. There is a broad range of sensitivities amongst inbred mouse strains 7,8. Generally, mice with increased susceptibility to Listeria infection are less able to control bacterial proliferation, demonstrating increased bacterial load and/or delayed clearance compared to resistant mice. Genetic studies, including linkage analyses and knockout mouse strains, have identified various genes for which sequence variation affects host responses to Listeria infection 6,8-14. Determination and comparison of infection kinetics between different mouse strains is therefore an important method for identifying host genetic factors that contribute to immune responses against Listeria. Comparison of host responses to different Listeria strains is also an effective way to identify bacterial virulence factors that may serve as potential targets for antibiotic therapy or vaccine design. We describe here a straightforward method for measuring bacterial load (colony forming units [CFU] per tissue) and preparing single-cell suspensions of the liver and spleen for FACS analysis of immune responses in Listeria-infected mice. This method is particularly useful for initial characterization of Listeria infection in novel mouse strains, as well as comparison of immune responses between different mouse strains infected with Listeria. We use the Listeria monocytogenes EGD strain 15 that, when cultured on blood agar, exhibits a characteristic halo zone around each colony due to β-hemolysis 1 (Figure 1). Bacterial load and immune responses can be determined at any time-point after infection by culturing tissue homogenate on blood agar plates and preparing tissue cell suspensions for FACS analysis using the protocols described below. We would note that individuals who are immunocompromised or pregnant should not handle Listeria, and the relevant institutional biosafety committee and animal facility management should be consulted before work commences.
Cell Wall-deficient Forms (L-Forms) of Listeria monocytogenes in Experimentally Infected Rats
Zentralblatt für Bakteriologie, 1997
Experimental infections were induced with different bacterial forms of Listeria monocy togenes: parental (S-forms), protoplastic (L-forms) and combined inoculum of both forms by i. p. injection of rats. The parental bacterial forms (S-forms) were isolated up to 7 days after challenge from the peritoneal cavity and the liver, while the L-forms were isolated up to 60 days from the peritoneal cavity. Continuous adhesion of L-forms on the peritoneal macrophage surface was found by scanning-electron microscopy. Erythrocyte and leucocyte count as well as some clinical chemistry parameters were measured during infections. They showed different dynamics in the three experimental groups. Histomorphological changes in the liver (microabscesses and mononuclear cellular granulomas) of infected animals were observed. They were less intensive and appeared later in rats infected with L-forms. The ex periments demonstrated that infections caused by parental bacterial forms and by combined inoculum took an acute course, while the infection caused by L-forms could be distin guished as a prolonged and persistent one.
Assessment of the pathogenic potential of two Listeria monocytogenes human faecal carriage isolates
Microbiology (Reading, England), 2002
Two human faeces carriage isolates of Listeria monocytogenes (H1 and H2) were compared to reference strains (ScottA and LO28) with regard to their lethality in 14-day-old chick embryos, their haemolytic and phospholipase (phosphatidylcholine-phospholipase C and phosphatidylinositol-phospholipase C) activities and their invasiveness towards Caco-2 cells. Experimental infection of chick embryos allowed discrimination of the strains into those exhibiting high virulence (ScottA and H2), those exhibiting slightly attenuated virulence (LO28) and those exhibiting low virulence (H1). A similar percentage mortality and time to death for embryos was observed when they were infected with H2 as was seen with infection by the reference strain ScottA. Therefore, human carriage strain H2 was considered potentially pathogenic. In contrast to H2 and ScottA, H1 exhibited low virulence. Using the tissue-culture cell-line model, it was found that carriage strain H1 was unable to enter Caco-2 cells effi...
Rabbit listeriosis is one of the major diseases problems that facing rabbit breeding and industry in Egypt. Listeria monocytogenes is the main responsible food borne pathogen for listeriosis in humans, rabbits and many animal species. The scope of the present study was to discuss the phenotypic and genotypic characterization of some virulence genes (16s rRNA, hlyA and iap) of L. monocytogenes isolates in rabbits and to show the correlation between the intensity of the experimental infection and hematological, biochemical changes and their effects on the immune status of the animal. Conventional bacteriological examination for isolation of L. monocytogenes was applied for all collected samples including culturing on specific media and biochemical identification test. Samples were collected from suspected cases of rabbit farms in Ismailia Governorate. Moreover, an oral experimental trial for induction of listeriosis in two groups of rabbits (1 st was the infected group and 2 nd was the control) was also, done. L. monocytogenes was isolated from rabbit farms in a percentage of 21.8% (12/55) however; experimentally it was reisolated from all rabbits of the 1 st group. Microcytic hypochromic anaemia, leukocytosis associated with neutrophilla, lymphopenia and monocytosis were observed in experimentally infected rabbits at 7 days p.i. and leukocytosis with neutrophilia and monocytosis in 15 days p.i. A highly significant elevation in the activities of ALT and AST, hypocalcemia associated with significant increase in uric acid, creatinine and inorganic phosphorus were observed in infected group. Meanwhile, highly significant decrease in total proteins associated with decrease of total globulins especially alpha and beta-globulin and hypoalbuminemia but increased gamma globulin in 15 days p.i. were recorded. PCR analysis of 16S rRNA gene was applied for the molecular identification and differentiation of L. monocytogenes from other Listeria species. 16S rRNA gene was found in all the recovered isolates (100%). Also, the genotypic detection of some virulent genes with PCR revealed that hly A gene was detected in (11/12) of L. monocytogenes isolates (91.7%) meanwhile, iap gene gave clear bands at 193 bp in all isolates (100%) confirming more virulence and pathogencity of these isolates. Recommendation of successful preventive, good sanitation programs and control measures in rabbit farms should be implemented. Also, further in vitro and in vivo studies for the role and mechanism of other