The immune response of human neonates to Listeria monocytogenes infection

Infection with Listeria monocytogenes during pregnancy has a high fetal and neonatal mortality. In rodents, it has been shown that resistance to Listeria infection is dependent upon a T cell-mediated immune response to the bacteria. The immune humoral and cell-mediated response to L. monocytogenes was studied in seven mother infant pairs who had documented evidence of L. monocytogenes sepsis. All studies were carried out 1 year following the initial infection as part of a clinical and immunological follow-up, and compared to an appropriate control group. The microagglutination titre and opsonizing activity of mothers previously infected with Listeria was significantly greater than that of the control mothers or their infected infants. There was no difference between the babies previously infected with L. monocytogenes when compared to control infants. The in vitro lymphoblastogenic response to Listeria, staphylococci, tetanus toxoid, and phytohemagglutinin was assessed. Infected mothers had a significantly greater proliferative response in the presence of Listeria than the control mothers, while the response of the previously infected infants was not different from that of the control infants. The response to the other antigens and PHA was similar in all groups. In conclusion, infants infected with L. monocytogenes during the perinatal period demonstrated neither a specific antibody response nor exhibited a cell-mediated immune response to this bacteria. These data support the idea that perinatally-infected infants have a markedly impaired immune response to L. monocytogenes and may, thus, explain their increased susceptibility to this infection.     

Antibiotic synergism against Listeria monocytogenes

The effectiveness of ampicillin, penicillin, streptomycin, and gentamicin against 20 strains of Listeria monocytogenes was studied in vitro. For all strains, the minimal bactericidal concentration (MBC) of both ampicillin and penicillin was much higher than the minimal inhibitory concentration (MIC). The MBC of both streptomycin and gentamicin was close to the MIC, but relatively high concentrations of these antibiotics were necessary to inhibit the growth of most of the strains of Listeria. The combination of penicillin plus streptomycin was synergistic against 19 of 20 strains and in the remaining strain produced enhanced killing (but of less magnitude than our criterion for synergism). Combinations of penicillin plus gentamicin, ampicillin plus streptomycin, and ampicillin plus gentamicin produced enhanced killing against all strains tested. No antagonism was observed when ampicillin or penicillin was combined with streptomycin or gentamicin.     

Lymphocytes are detrimental during the early innate immune response against Listeria monocytogenes

Mice deficient in lymphocytes are more resistant than normal mice to Listeria monocytogenes infection during the early innate immune response. This paradox remains unresolved: lymphocytes are required for sterilizing immunity, but their presence during the early stage of the infection is not an asset and may even be detrimental. We found that lymphocyte-deficient mice, which showed limited apoptosis in infected organs, were resistant during the first four days of infection but became susceptible when engrafted with lymphocytes. Engraftment with lymphocytes from type I interferon receptor-deficient (IFN-alphabetaR(-/-)) mice, which had reduced apoptosis, did not confer increased susceptibility to infection, even when the phagocytes were IFN-alphabetaR(+/+). The attenuation of innate immunity was due, in part, to the production of the antiinflammatory cytokine interleukin 10 by phagocytic cells after the apoptotic phase of the infection. Thus, immunodeficient mice were more resistant relative to normal mice because the latter went through a stage of lymphocyte apoptosis that was detrimental to the innate immune response. This is an example of a bacterial pathogen creating a cascade of events that leads to a permissive infective niche early during infection.     

Listeria monocytogenes infection in patients with cancer

Listeriosis (LT) is an important infection in immunocompromised patients, but no large series of LT in cancer patients have been recently described. We reviewed the records of 34 cancer patients with LT at our institution (1990-2001). Twenty patients (59%) had an underlying hematologic malignancy. In 11 patients, LT complicated bone marrow transplantation. Lymphocytopenia was observed in 62% of the patients. Twenty-six patients (76%) received prior corticosteroids. Bacteremia was the most common presentation of LT (74%) followed by meningoencephalitis (21%). The most common treatment of LT was ampicillin with or without gentamicin (68%). The median duration of treatment was 26 days (range, 8-74 days). The rate of response to antimicrobial therapy was 79%. No relapses were identified. LT contributed to death in 9 (75%) of the 12 patients who died. Meningoencephalitis had the worst prognosis (3 of 6 cases were fatal). Treatment of central nervous system LT continues to have a high failure rate.     

Listeria monocytogenes causing endovascular infection.

Listeria monocytogenes is an uncommon cause of mycotic aneurysms, endocarditis, and other endovascular infections. When they occur, these infections usually involve patients with relatively normal host defenses, but with abnormal vascular intima or cardiac valves. We have reported a Listeria monocytogenes infection at the site of a posttraumatic aortic aneurysm.     

胶体金标记单克隆抗体测定单增李斯特菌试剂盒制备

目的制备单增李斯特菌54001、54002型的单克隆抗体（McAb）,制备胶体金标记单增李斯特菌抗体免疫层析检测试剂板。方法以纯化单增李斯特菌为抗原,免疫Balb／c小鼠,制备单克隆抗体,鉴定其特性,建立并验证胶体金标记单增李斯特菌抗体免疫层析试剂板的检测方法。结果筛选出2株单抗杂交瘤细胞株F5、F9,免疫球蛋白亚类均为IgM。通过选用柠檬酸钠法制备胶体金,测定其最适结合蛋白浓度为28g/ml,制备胶体金标记单增李斯特菌抗体免疫层析检测板。结论为产单核李斯特菌提供了一个方便、快捷、切实有效的检测技术。     

Determination of the effect of antimicrobics in combination against Listeria monocytogenes

The in vitro activity of selected penicillins, extended spectrum cephalosporins, vancomycin, gentamicin, erythromycin, tetracycline, rifampin, and trimethoprim and sulfamethoxazole (alone and in combination) was determined by microtiter technique for 20 isolates of Listeria monocytogenes. The activity of selected combinations of antimicrobics was determined by the microtiter checkboard technique. Trimethoprim-sulfamethoxazole (1:20 ratio) was the most active agent in inhibitory tests and also showed bactericidal activity. The combinations of gentamicin with either ampicillin or vancomycin and that of erythromycin with tetracycline showed bactericidal effect in synergy studies. Combining ampicillin with an extended spectrum cephalosporin showed no antagonism, whereas, combining rifampin with trimethoprim or with trimethoprim/sulfamethoxazole led only to indifference or antagonism. These observations may have importance in selection of therapy in animal models or in selected clinical situations.     

Intracerebral activity of antibiotics against Listeria monocytogenes during experimental rhombencephalitis

We used a model of rhombencephalitis in gerbils to test the efficacy of various antibiotics against Listeria monocytogenes. Gerbils were inoculated in the middle ear with strain EGD and treated subcutaneously with various antibiotics alone or in combination. We found that the most active antibiotics on intracerebral bacteria were amoxycillin, co-trimoxazole, rifampicin and imipenem. Vancomycin, gentamicin and ciprofloxacin were weakly or not active. The combinations amoxycillin-co-trimoxazole, amoxycillin-gentamicin and co-trimoxazole-rifampicin were highly active against intracerebral bacteria.     

In-vitro synergy testing of nine antimicrobial combinations against Listeria monocytogenes

In-vitro antimicrobial synergy against Listeria monocytogenes was assessed using nine combinations in chequerboard (bacteriostatic) tests and time-kill (bactericidal) studies. Ampicillin/gentamicin and trimethoprim/sulphamethoxazole were the most synergistic combinations in bacteristatic tests, whereas gentamicin with ampicillin, trimethoprim or vancomycin and trimethoprim/sulphamethoxazole were the most synergistic in bactericidal tests. Gentamicin-containing combinations were most effective at killing L. monocytogenes and those containing rifampicin least effective.     

In vitro activities of trimethoprim and sulfamethoxazole against Listeria monocytogenes

The in vitro activities of trimethoprim and sulfamethoxyazole against clinical isolates of Listeria monocytogenes were examined separately and in combination with a microtiter broth dilution system. Sulfamethoxazole demonstrated variable activity and was generally bacteriostatic. Trimethoprim alone was bactericidal against 96% of isolates at less than 0.5 microgram/ml. The bactericidal action of trimethoprim against L. monocytogenes was generally potentiated by sulfamethoxyazole even when isolates were relatively resistant to sulfamethoxyazole alone.     

Peritoneal exudation of macrophages by irritants and its effect on immune responses against sheep erythrocytes and Listeria monocytogenes

Relation between the degradation of antigenic substances by peritoneal exudate macrophages induced by different irritants and subsequent induction of immune responses against SRBC or Listeria monocytogenes were studied. Delayed footpad reaction and antibody production to SRBC were both suppressed by pretreatment with thioglycollate or with killed Corynebacterium parvum. In contrast, delayed footpad reaction and acquired cellular resistance to Listeria were augmented by pretreatment with thioglycollate. When pretreated with C. parvum, however, such augmentations in immune responses to Listeria were not observed but these responses were suppressed. It was suggested that the amount of antigenic stimuli was determined by the mutual relationship between the level of macrophage activity as scavenger cells and the susceptibilities of the antigenic substances to degradation by macrophages, and that induction of immune responses were affected by this mutual relationship.     

Memory CD8+ T cells provide innate immune protection against Listeria monocytogenes in the absence of cognate antigen

Interferon (IFN)-gamma plays an important role in the innate immune response against intracellular bacterial pathogens. It is commonly thought that natural killer cells are the primary source of this cytokine that is involved in activating antibacterial effects in infected cells and polarizing CD4+ T cells toward the Th1 subset. However, here we show that both effector and memory CD8+ T cells have the potential to secrete IFN-gamma in response to interleukin (IL)-12 and IL-18 in the absence of cognate antigen. We demonstrate that memory CD8+ T cells specific for the ovalbumin protein secrete IFN-gamma rapidly after infection with wild-type Listeria monocytogenes (LM). Furthermore, small numbers of ovalbumin-specific, memory CD8+ T cells can reduce spleen and liver bacterial counts in IFN-gamma-deficient mice 3 d after LM infection. Up-regulation of the receptors for IL-12 and IL-18 provides a mechanism for the ability of memory CD8+ T cells to respond in this antigen nonspecific manner. Thus, CD8+ T cells play an important role in the innate immune response against intracellular pathogens by rapidly secreting IFN-gamma in response to IL-12 and IL-18.     

Activity of daptomycin against Listeria monocytogenes isolates from cerebrospinal fluid

We tested the activity of daptomycin against 76 Listeria monocytogenes isolates from cerebrospinal fluid by broth dilution and Etest methods. For the broth dilution method, the MIC range was 1.0 to 8.0 and the MIC at which 90% of the isolates tested were inhibited (MIC(90)) was 4.0 mg/liter. For the Etest method, the MIC range was 1.0 to 4.0 and the MIC(90) was 4.0 mg/liter. Presently, daptomycin cannot be recommended for the treatment of L. monocytogenes meningitis.     

Type I interferon production enhances susceptibility to Listeria monocytogenes infection

Numerous bacterial products such as lipopolysaccharide potently induce type I interferons (IFNs); however, the contribution of this innate response to host defense against bacterial infection remains unclear. Although mice deficient in either IFN regulatory factor (IRF)3 or the type I IFN receptor (IFNAR)1 are highly susceptible to viral infection, we show that these mice exhibit a profound resistance to infection caused by the Gram-positive intracellular bacterium Listeria monocytogenes compared with wild-type controls. Furthermore, this enhanced bacterial clearance is accompanied by a block in L. monocytogenes-induced splenic apoptosis in IRF3- and IFNAR1-deficient mice. Thus, our results highlight the disparate roles of type I IFNs during bacterial versus viral infections and stress the importance of proper IFN modulation in host defense.     

Delayed presentation of prosthetic joint infection due to Listeria monocytogenes

Infection with Listeria monocytogenes is rare and has been described in prosthetic valves, stent grafts and prosthetic joints. The route of infection appears to be haematogenous. The choice between conservative treatment with antibiotics or surgical treatment with debridement and revision of the components remains controversial. The best antibiotic treatment is not known with ampicillin being the first choice in most cases. Prosthetic infections with Listeria monocytogenes usually occur in patients with malignancy, diabetes mellitus, chronic renal disease, liver disease, elderly patients and patients receiving immunosuppressive therapy. The hip is the commonest prosthetic joint affected followed by the knee. We report the seventh case of Listeria monocytogenes infection in a non-immunocompromised patient involving a prosthetic joint.     

Enhancement of resistance to Listeria monocytogenes infection in mice by pyrimidine analogs

The modulation of murine host resistance to infection with Listeria monocytogenes by the substituted pyrimidine anti-viral compounds, 2-amino-5-bromo-6-methyl-4-pyrimidinol (ABMP), 2-amino-5-bromo-6-phenyl-4-pyrimidinol (ABPP) and 2-amino-5-iodo-6-phenyl-4-pyrimidinol (AIPP) was investigated. BAF1 mice given three daily injections of ABMP, ABPP (as well as of the interferon-inducer poly I:C) demonstrated enhanced anti-listerial resistance, as measured by a 100-fold increase in the median lethal dose of Listeria compared to vehicle-treated control mice. This enhancement was also detectable as a decrease (up to 100-fold) in the number of viable Listeria recoverable from the livers and spleens of mice during the non-immune phase of natural resistance (24-72 h following infection) to this pathogen. In contrast, AIPP did not enhance anti-listerial resistance. Since each of the effective agents have been shown to induce the production of interferon, the role of interferon in the mechanism of natural resistance to Listeria was evaluated. The serum of untreated B10.A mice infected with Listeria was shown to contain high levels of interferon. Treatment of these mice with a potent anti-mouse interferon antibody preparation completely neutralized circulating interferon activity; however, such treatment had no apparent effect on the growth of Listeria. In addition, mice which received injections of both ABMP and anti-interferon demonstrated a level of resistance identical to that seen in mice given ABMP and normal serum. Based on these results, we propose that although interferon is produced in response to listerial infection, interferon is not a critically important mediator in the mechanism of natural resistance to this pathogen. Furthermore, it appears that the immunomodulating activity of these experimental compounds does not involve interferon.     

MyD88-mediated signals induce the bactericidal lectin RegIII gamma and protect mice against intestinal Listeria monocytogenes infection

Listeria monocytogenes is a food-borne bacterial pathogen that causes systemic infection by traversing the intestinal mucosa. Although MyD88-mediated signals are essential for defense against systemic L. monocytogenes infection, the role of Toll-like receptor and MyD88 signaling in intestinal immunity against this pathogen has not been defined. We show that clearance of L. monocytogenes from the lumen of the distal small intestine is impaired in MyD88(-/-) mice. The distal ileum of wild-type (wt) mice expresses high levels of RegIII gamma, which is a bactericidal lectin that is secreted into the bowel lumen, whereas RegIII gamma expression in MyD88(-/-) mice is nearly undetectable. In vivo depletion of RegIII gamma from the small intestine of wt mice diminishes killing of luminal L. monocytogenes, whereas reconstitution of MyD88-deficient mice with recombinant RegIII gamma enhances intestinal bacterial clearance. Experiments with bone marrow chimeric mice reveal that MyD88-mediated signals in nonhematopoietic cells induce RegIII gamma expression in the small intestine, thereby enhancing bacterial killing. Our findings support a model of MyD88-mediated epithelial conditioning that protects the intestinal mucosa against bacterial invasion by inducing RegIII gamma.     

Listeriolysin O is a target of the immune response to Listeria monocytogenes

The immunologic mechanism of protective immunity to the intracellular parasite Listeria monocytogenes (Lm) is not well understood, however, antilisterial immunity can be adoptively transferred with T lymphocytes from Lm-immune donors. The Lm-immune cells are believed to produce macrophage-activating lymphokines, which leads to the eventual macrophage-dependent eradication of the bacterium. Increasing evidence suggests that immunity to Lm resides exclusively within the CD8+ T cell subset. It is possible that the Lm-immune CD8+ T cells function to release sequestered Lm from nonprofessional phagocytes to awaiting activated macrophage populations. This study was conducted to determine if listeriolysin O (LLO), which is an essential determinant of Lm pathogenicity, is also a target of the antilisterial immune response. We have found that target cells infected with a LLO+ Lm strain are lysed by Lm-immune cytotoxic cells, whereas target cells infected with a LLO- Lm mutant, or pulsed with a heat-killed Lm preparation, are not lysed by the Lm-immune effector cells. We have used a Bacillus subtilis (Bs) construct that expresses the LLO gene product and found that target cells infected with the LLO+ Bs construct are lysed by antilisterial cytotoxic cells. The antilisterial cytotoxic response is targeted against LLO, in that we have also used a Bs construct that expresses the perfringolysin (PLO) gene product and found that target cells infected with the PLO+ Bs are not lysed by antilisterial cytotoxic effector cells. These data strongly suggest that LLO is a target antigen of antilisterial immunity and may represent the dominant target during the expression of the immune response to Lm.     

Listeria monocytogenes infection with brain abscess formation--the first case in Miyagi Prefecture

A rare type of brain abscess formation caused by infection with Listeria monocytogenes was observed in a 2-year-old boy. The patient did not respond to treatment with various antibiotics. The isolated organisms were found to be sero-type 4b. This is the first report of Listeria monocytogenes infection in Miyagi Prefecture.