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At least 163 records · Page 9Linked to original sources
PubMed2005

Pre-existing immunity to pathogenic Listeria monocytogenes does not prevent induction of immune responses to feline immunodeficiency virus by a novel recombinant Listeria monocytogenes vaccine.

Listeria monocytogenes is an attractive biologic vaccine vector against HIV because it induces a strong cell mediated immune response, can be delivered by mucosal routes, can be readily manipulated to express viral antigens, and is easy and inexpensive to produce. Proof of concept studies have been performed using HIV Gag expressing recombinant L. monocytogenes in the mouse. Here we report the development and validation of recombinant L. monocytogenes to be evaluated in the FIV/cat model of HIV. Using a simplified approach to introduce individual and polyprotein FIV gag genes, we show that recombinant L. monocytogenes containing the entire gag expresses the full-length Gag polyprotein in a soluble secreted form. A DNA vaccine plasmid (pND14-Lc-env) that replicates in Gram positive bacteria and contains the FIV SU (gp100) and the ectodomain of TM (gp40) in a eukaryotic expression cassette was transfected into LM-gag to create LM-gag/pND14-Lc-env. After infection of target cells with LM-gag/pND14-Lc-env in vitro, both FIV Gag and Env proteins were detected in soluble cell lysates. Whether previous exposure to L. monocytogenes affects the immunogenicity of LM-gag/pND14-Lc-env was determined in cats infected with wild-type L. monocytogenes orally and/or subcutaneously. After a single oral dose of LM-gag/pND14-Lc-env, cats with existing anti-L. monocytogenes immune responses developed anti-FIV Gag IgA titers in vaginal secretions, saliva, and feces. Similarly, FIV Gag and Env specific IFN-gamma ELISPOT responses were measurable in spleen and lymph node but at a statistically higher frequency in cats exposed to a single subcutaneous dose of wild-type L. monocytogenes versus cats exposed both subcutaneously and orally. The FIV/cat model will provide a useful challenge system to determine whether recombinant L. monocytogenes can protect against a lentivirus in its natural host after challenge by the routes common to HIV transmission.

Animals↗
PubMedDate not supplied

CT features of early Listeria monocytogenes cerebritis.

Listeria monocytogenes is a relatively uncommon pathogen affecting infants or adults with predisposing conditions, such as cirrhosis, diabetes mellitus, autoimmune disease, renal transplants, and solid and lymphoreticular malignancies. Cerebral parenchymal involvement is rare and consists of focal cerebritis, which may progress to abscess formation. This article presents three cases of early Listeria monocytogenes cerebritis, two of which demonstrated ill-defined superficial areas of low attenuation with curvilinear gyral enhancement and one of which demonstrated a deep, low-attenuation lesion with faint surrounding enhancement. Although these findings are nonspecific, their early recognition in the proper clinical setting may help institute early antibiotic therapy, which appears to be successful without surgical intervention.

Adult↗
PubMed2004

Incidence of Listeria monocytogenes in two milk processing environments, and assessment of Listeria monocytogenes blood agar for isolation.

A year-long survey of two Northern Ireland milk processing plants for Listeria monocytogenes was carried out. Sample sites included the milk processing environment (walls, floors, drains, and steps), processing equipment, raw and pasteurised milk. The FDA listeria-selective enrichment procedure was used to process samples and an additional agar medium, L. monocytogenes Blood Agar (LMBA), was utilized as part of the isolation procedure in order to compare its performance to that of the recommended Oxford and Palcam agars. LMBA proved to be a very useful tool and was able to detect L. monocytogenes from 94.1% of sites compared to the 76.5% and 79.4% detection rate displayed by Oxford and Palcam agars, respectively. The overall incidence of listeria on equipment was 18.8% (6.3% L. monocytogenes), in the environment was 54.7% (40.6% L. monocytogenes) and in raw milk 44.4% (22.2% L. monocytogenes). On one occasion, L. welshimeri was isolated from pasteurised milk, probably demonstrating post-pasteurisation contamination of product. The main environmental sources of L. monocytogenes were considered to be a floor drain and stainless steel steps.

Agar↗
PubMed1981

T cell-mediated cytotoxicity induced by Listeria monocytogenes. I. Activation of Listeria antigen-responsive T cells.

Soon after rats are infected with Listeria monocytogenes (LM), Listeria antigen- (LMA) responsive lymphocytes are delivered to the animal's thoracic duct. These LM-responsive lymphocytes can be restimulated in vitro by LMA to generate cells that have a potent cytolytic capability. The activation of LMA responsive lymphocytes is immunologically specific and dependent upon the activity of histocompatible accessory cells. Neither cell-free LMA nor LMA-pulsed allogeneic accessory cells can promote a significant cytotoxic response by negatively selected responder lymphocytes. LM-dependent cytolytic lymphocytes differ from natural killer (NK) cells inasmuch as their activation is not facilitated by interferon (IF). Likewise, supernatants from cultures containing specifically sensitized thymus-derived (T) lymphocytes and histocompatible LMA-pulsed accessory cells fail to augment (day 2 and day 3 supernatants actually inhibit) the activation process. The results imply that the successful activation of LM dependent cytolytic lymphocytes requires the cooperative interplay of responder T cells and specific-antigen-pulsed accessory cells.

Animals↗
PubMed2004

CpG oligodeoxynucleotides improve the survival of pregnant and fetal mice following Listeria monocytogenes infection.

Listeria infection during pregnancy can cause the death of both mother and fetus. Previous studies established that immunostimulatory CpG oligodeoxynucleotides (ODN) increase the resistance of healthy adult mice to many infectious pathogens, including Listeria monocytogenes. This study examines whether the innate immune response elicited by CpG ODN can reduce the susceptibility of pregnant mice to lethal listeria challenge. The results indicate that CpG ODN treatment significantly improves maternal survival and reduces pathogen transmission to offspring. CpG ODN administered during pregnancy did not induce abortion, birth defects, or reduce the size or health of litters. These findings suggest that CpG ODN may provide a safe and effective means of improving the health of mothers and fetuses during pregnancy.

Adjuvants, Immunologic↗
PubMed1995

Differential regulation of TNF-alpha production by listeriolysin-producing versus nonproducing strains of Listeria monocytogenes.

Only Listeria monocytogenes that produce listeriolysin O (LLO) elicit protective immunity. Given the importance of tumor necrosis factor alpha (TNF-alpha) in anti-Listeria immunity, we have investigated TNF-alpha production by macrophages after they ingested live LLO-producing compared to LLO-non-producing bacteria. We used two genetically engineered strains of Listeria that differed only in their ability (Ly+) or inability (Ly-) to produce LLO. Ly+ and Ly- caused the same kinetics of increased mRNA abundance for TNF-alpha during the first 90 min after phagocytosis. However, only Ly+ caused sustained transcription of TNF-alpha mRNA, and this may account for the increased release of TNF-alpha. The transcriptional inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) prevented the sustained abundance of cytokine mRNA 20 h after ingestion of Ly+. In addition, nuclear run-on assays indicated sustained transcription of TNF-alpha genes only after ingestion of Ly+. LLO itself was not responsible for the ability of Ly+ to stimulate the sustained transcription of the TNF-alpha genes. Instead, LLO may allow Listeria to survive within macrophages so that other bacterial products cause sustained TNF-alpha gene transcription. Both Ly+ and Ly- produced molecules, isolated by 50% ammonium sulfate, that induced cytokine production. In conclusion, we now report that Ly+ causes sustained transcription of the TNF-alpha gene and production of TNF-alpha by macrophages in vitro. We speculate that the TNF-alpha may activate endothelium and thus allow the recruitment of T cells to sites of infection. This may contribute to the ability of only LLO-producing Listeria to induce protective immunity.

Animals↗
PubMed2006

Compartmentalization of the broad-range phospholipase C activity to the spreading vacuole is critical for Listeria monocytogenes virulence.

Listeria monocytogenes is a bacterial pathogen that multiplies in the cytosol of host cells and spreads directly from cell to cell by using an actin-based mechanism of motility. The broad-range phospholipase C (PC-PLC) of L. monocytogenes contributes to bacterial escape from vacuoles formed upon cell-to-cell spread. PC-PLC is made as an inactive proenzyme whose activation requires cleavage of an N-terminal propeptide. During infection, PC-PLC is activated specifically in acidified vacuoles. To assess the importance of compartmentalizing PC-PLC activity during infection, we created a mutant that makes constitutively active PC-PLC (the plcBDelta pro mutant). Results from intracellular growth and cell-to-cell spread assays showed that the plcBDelta pro mutant was sensitive to gentamicin, suggesting that unregulated PC-PLC activity causes damage to host cell membranes. This was confirmed by the observation of a twofold increase in staining of live infected cells by a non-membrane-permeant DNA fluorescent dye. However, membrane damage was not sufficient to cause cell lysis and was dependent on bacterial cell-to-cell spread, suggesting that damage was localized to bacterium-containing filopodia. Using an in vivo competitive infection assay, we observed that the plcBDelta pro mutant was outcompeted up to 200-fold by the wild-type strain in BALB/c mice. Virulence attenuation was greater when mice were infected orally than when they were infected intravenously, presumably because the plcBDelta pro mutant was initially outcompeted in the intestines, reducing the number of mutant bacteria reaching the liver and spleen. Together, these results emphasize the importance for L. monocytogenes virulence of compartmentalizing the activity of PC-PLC during infection.

Animals↗
PubMed2003

Efflux pump Lde is associated with fluoroquinolone resistance in Listeria monocytogenes.

Five Listeria monocytogenes isolates (CLIP 21369, CLIP 73298, CLIP 74811, CLIP 75679, and CLIP 79372) were found to be resistant to fluoroquinolones during the screening for antibiotic resistance of 488 L. monocytogenes isolates from human cases of listeriosis in France. On the basis of a fourfold or greater decrease in the ciprofloxacin MIC in the presence of reserpine, fluoroquinolone resistance was attributed to active efflux of the drugs. The lde gene (Listeria drug efflux; formerly lmo2741) encodes a 12-transmembrane-segment putative efflux pump belonging to the major facilitator superfamily of secondary transporters that displayed 44% identity with PmrA from Streptococcus pneumoniae. Insertional inactivation of the lde gene in CLIP 21369 indicated that the corresponding protein was responsible for fluoroquinolone resistance and was involved in the level of susceptibility to dyes such as ethidium bromide and acridine orange.

Amino Acid Sequence↗
PubMed2004

Molecular determinants of Listeria monocytogenes virulence.

Listeria monocytogenes is the etiological agent of listeriosis, a severe human foodborne infection characterized by gastroenteritis, meningitis, encephalitis, abortions, and perinatal infections. This gram-positive bacterium is a facultative intracellular pathogen that induces its own uptake into nonphagocytic cells and spreads from cell to cell using an actin-based motility process. This review covers both well-established and recent advances in the characterization of L. monocytogenes virulence determinants and their role in the pathophysiology of listeriosis.

Bacterial Adhesion↗
PubMed2006

Acute symptomatic hydrocephalus in Listeria monocytogenes meningitis.

Listeria monocytogenes meningitis appears to have increased in incidence. Although most reported cases of listeriosis involve the central nervous system, brain computed tomography is usually normal. Hydrocephalus is a common complication of tuberculous meningitis, which has a high prevalence in Taiwan. However, patients with L. monocytogenes meningitis rarely develop the complication of symptomatic hydrocephalus. We report a patient with L. monocytogenes meningitis who presented with persistent alteration of consciousness after appropriate antimicrobial therapy. Follow-up brain computed tomography revealed acute hydrocephalus. An Ommaya reservoir was implanted, and daily drainage of the cerebrospinal fluid was performed. The patient improved gradually and his mental status recovered completely 4 days later. This case should remind physicians to be aware of the possible occurrence of hydrocephalus in L. monocytogenes meningitis and that prompt cerebrospinal fluid drainage may achieve a good outcome.

Adult↗
PubMedDate not supplied

Antibiotic therapy for Listeria monocytogenes bacteremia.

Listeria monocytogenes has been recognized as an important pathogen in immunocompromised patients, but it has been rarely reported in Taiwan. We reviewed 13 cases of L. monocytogenes bacteremia at National Taiwan University Hospital over a 12-year period. All of the patients had underlying diseases. Fever was the most common presenting symptom, and neurologic signs were found in 6 patients. Most of the patients received penicillin G, ampicillin or piperacillin with an aminoglycoside. Corticosteroids were used in 9 of 13 patients. The overall mortality directly due to L. monocytogenes bacteremia was 31%. However, patients treated with cephalosporins or oxacillin had higher mortality than those treated with penicillin G, ampicillin or piperacillin (p = 0.05). Given the increasing number of immunosuppressed patients in Taiwan, it is likely that more cases will be encountered. Physicians in Taiwan should be aware of L. monocytogenes bacteremia and its treatment.

Adolescent↗
PubMed2000

LaXp180, a mammalian ActA-binding protein, identified with the yeast two-hybrid system, co-localizes with intracellular Listeria monocytogenes.

The Listeria monocytogenes surface protein ActA is an important virulence factor required for listerial intracellular movement by inducing actin polymerization. The only host cell protein known that directly interacts with ActA is the phosphoprotein VASP, which binds to the central proline-rich repeat region of ActA. To identify additional ActA-binding proteins, we applied the yeast two-hybrid system to search for mouse proteins that interact with ActA. A mouse cDNA library was screened for ActA-interacting proteins (AIPs) using ActA from strain L. monocytogenes EGD as bait. Three different AIPs were identified, one of which was identical to the human protein LaXp180 (also called CC1). Binding of LaXp180 to ActA was also demonstrated in vitro using recombinant histidine-tagged LaXp180 and recombinant ActA. Using an anti-LaXp180 antibody and fluorescence microscopy, we showed that LaXp180 co-localizes with a subset of intracellular, ActA-expressing L. monocytogenes but was never detected on intracellularly growing but ActA-deficient mutants. Furthermore, LaXp180 binding to intracellular L. monocytogenes was asymmetrical and mutually exclusive with F-actin polymerization on the bacterial surface. LaXp180 is a putative binding partner of stathmin, a protein involved in signal transduction pathways and in the regulation of microtubule dynamics. Using immunofluorescence, we showed that stathmin co-localizes with intracellular ActA-expressing L. monocytogenes.

Actins↗
PubMed2001

Comparison of sludge and clinical isolates of Listeria monocytogenes.

AIMS: Listeria monocytogenes strains isolated in the same geographical area from sewage sludge and from patients presenting with listeriosis were compared. METHODS AND RESULTS: All isolates were typed by serotyping, phage typing and SmaI/ApaI pulsed-field gel electrophoresis (PFGE). Among the sludge isolates (n=32), 22 subtypes could be distinguished by the combination of all typing methods. The human isolates (n=11) were distributed into 10 subtypes which clearly differed from those observed among sludge isolates, except for one cluster formed by two related human isolates which showed high similarity in PFGE patterns (SmaI: 92%; ApaI: 89.5%) with one sludge isolate. CONCLUSION: These results suggest the existence of an epidemiological link between sludge and human isolates, but they may also be reflecting the distribution of L. monocytogenes types within the environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Sludge and human L. monocytogenes may be related but further epidemiological studies are necessary to elucidate this point.

Bacterial Typing Techniques↗
PubMedDate not supplied

[Brain abscesses due to Listeria monocytogenes].

INTRODUCTION: Listeria monocytogenes is a gram-positive bacillus which causes sporadic infections in immunocompromised humans, with a special propensity for the central nervous system, in the form of acute, subacute or chronic meningitis, rhombencephalitis or abscesses in the brain or spinal cord. The final diagnosis is established by germ culture in blood or in cerebrospinal fluid (CSF). Preferred treatment is ampicillin in association with aminoglycosides. CASE REPORT: We report the case of a 70-year-old male patient with a history of arterial hypertension and chronic lymphatic leukaemia with no specific treatment, who suffered meningoencephalitis and brain abscesses caused by L. monocytogenes. Symptoms were a 48-hour history of headache and a febrile condition. The CSF showed lymphocytic pleocytosis with hypoglycorrhachia. Magnetic resonance scans of the brain revealed areas of cerebritis and multiple brain abscesses in the right frontal lobe. Specific treatment was established with ampicillin for 13 weeks, associated with gentamicin and vancomycin during the first few weeks, until x-rays showed the lesions to be resolved. CONCLUSIONS: L. monocytogenes infections must be investigated in all patients with cellular immunosuppression who present febrile symptoms. The central nervous system may be the only area of the body infected. Moreover, this site will need studying in patients who present neurological focus data or an alteration in the state of consciousness and bacteraemia due to L. monocytogenes. Establishing suitable treatment as early as possible can improve the prognosis.

Aged↗
PubMed1977

Listeria monocytogenes endophthalmitis.

Listeria monocytogenes and a staphylococcus organism caused a catastrophic endophthalmitis in a patient despite appropriate local and systemic antimicrobial chemotherapy. Although L monocytogenes is widespread in nature and has produced a variety of clinical illnesses, it has only one previously been reported to cause endophthalmitis. If appropriate microbiologic techniques are not employed, the organism may go unrecognized as an ocular pathogen.

Ampicillin↗
PubMed2004

Molecular aspects of Listeria monocytogenes infection.

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.

Bacterial Toxins↗