Assessment of the pathogenic potential of two Listeria monocytogenes human faecal carriage isolates (original) (raw)
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Pathogenic potential of Listeria monocytogenes isolated from cattle faeces in Adoekiti
African Journal of Clinical and Experimental Microbiology, 2018
Listeria monocytogenes is an opportunistic food-borne pathogen causing listeriosis especially among immune-compromised persons. Its high rate of morbidity and mortality has classed the organism among the top watch list in foods. It is known to produce several virulence factors which aid its survival in harsh conditions and its dissemination within host cells. The pathogenicity of L. monocytogenes, isolated from cattle faeces in Ado-Ekiti, was determined in Wister albino rats for two weeks and the relative virulence was calculated. Rats were challenged with isolates producing listeriolysin O and phospholipase orally, intraperitoneally and subcutaneously. Biochemical parameters and haematoxylin and eosin (H and E) stained sections of selected organs were examined for significant changes (p < .05) and histopathological effects post-experiment. Relative virulence was recorded at 0% with rats showing no signs of infection or death. However, significant changes in total protein, lipid profile and some selected antioxidant enzymes, as well as cytological changes in the examined H and E sections of organs showed that an infection had occurred. Bacteria may have however been eradicated by the immune-competent rats. This study therefore concludes that isolates may be pathogenic especially for persons tagged 'high risk' due to low immunity.
Pathogenic potential of Listeria monocytogenes isolated from cattle faeces in Adoekiti
African Journal of Clinical and Experimental Microbiology
Listeria monocytogenes is an opportunistic food-borne pathogen causing listeriosis especially among immune-compromised persons. Its high rate of morbidity and mortality has classed the organism among the top watch list in foods. It is known to produce several virulence factors which aid its survival in harsh conditions and its dissemination within host cells. The pathogenicity of L. monocytogenes, isolated from cattle faeces in Ado-Ekiti, was determined in Wister albino rats for two weeks and the relative virulence was calculated. Rats were challenged with isolates producing listeriolysin O and phospholipase orally, intraperitoneally and subcutaneously. Biochemical parameters and haematoxylin and eosin (H and E) stained sections of selected organs were examined for significant changes (p < .05) and histopathological effects post-experiment. Relative virulence was recorded at 0% with rats showing no signs of infection or death. However, significant changes in total protein, lipid profile and some selected antioxidant enzymes, as well as cytological changes in the examined H and E sections of organs showed that an infection had occurred. Bacteria may have however been eradicated by the immune-competent rats. This study therefore concludes that isolates may be pathogenic especially for persons tagged 'high risk' due to low immunity.
FEMS Immunology & Medical Microbiology, 2005
We analyzed 27 Listeria monocytogenes strains of serotypes 1/2b and 4b, from invasive and gastroenteric listeriosis, for molecular and experimental virulence. Molecular virulence was tested by PCR for the presence of 8 major virulence-associated genes and genetic polymorphisms through restriction enzyme analysis; genomic DNA typing using pulsed-field gel electrophoresis was also performed. Experimental virulence was evaluated through intra-peritoneal and intra-gastric mouse virulence assays. Our results showed no significant differences in the virulence-related molecular properties of the strains analyzed. All strains were equally pathogenic following intra-peritoneal inoculation of mice. In mice inoculated intra-gastric with 4 representative strains of the 2 types of listeriosis, there were no significant differences in the bacterial count when comparing invasive and gastroenteric strains, suggesting that the strains were comparable in terms of mean oral infectivity.
Acta biochimica et biophysica Sinica, 2006
A low-pathogenicity isolate of Listeria monocytogenes from cow's milk, as screened in mouse and chicken embryonated egg models, was examined for virulence-related phenotypic traits. Corresponding virulence genes (iap, prfA, plcA, hly, mpl, actA, plcB, InlA and InlB) were compared with L. monocytogenes reference strains 10403S and EGD to elucidate the possible molecular mechanisms of low virulence. Although L. monocytogenes H4 exhibited similar patterns to strain 10403S in terms of hemolytic activity, in vitro growth and invasiveness and even had higher adhesiveness, faster intracellular growth and higher phospholipase activity in vitro, it was substantially less virulent than the strain 10403S in mouse and chicken embryo models (50% lethal dose: 10(8.14) vs. 10(5.49) and 10(6.73) vs. 10(1.9), respectively). The genes prfA, plcA and mpl were homologous among L. monocytogenes strains H4, 10403S and EGD (>98%). Genes iap, hly, plcB, InlA and InlB of L. monocytogenes 10403S had h...
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.
Infection and Immunity, 1990
We identified nonhemolytic mutants of Listeria monocytogenes that were severely deficient in their ability to invade mammalian nonprofessional phagocytes. These mutants were generated spontaneously or by means of transposon Tn916 mutagenesis. In terms of their extracellular proteins, the noninvasive mutants were deficient not only in the sulfhydryl-activated hemolysin (listeriolysin) but also in an antigenically unrelated extracellular protein with an apparent molecular weight of 32,000 which could induce opacity in egg yolk and is considered to be a phospholipase. Our results suggest the existence of a common genetic control between the expression of listeriolysin and that of other determinants, including a phospholipase and determinants involved in the ability of L. monocytogenes to enter mammalian cells.
Molecular aspects of Listeria monocytogenes infection
Polish journal of microbiology / Polskie Towarzystwo Mikrobiologów = The Polish Society of Microbiologists, 2004
Listeria monocytogenes, a food-borne intracellular animal and human pathogen, interacts with infected host cells both prior to entry and during the intracellular phase of infection. This review is focused on the role of secreted proteins, including listeriolysin O and two distinct phospholipases C, in modulating the signal transduction of infected cells.