Microparticles released by Listeria monocytogenes-infected macrophages are required for dendritic cell-elicited protective immunity

Interplay between macrophages and dendritic cells in the processing and presentation of bacterial antigens for T-cell immune responses remains poorly understood. Using a Listeria monocytogenes (Lm) infection model, we demonstrate that dendritic cells (DCs) require the support of macrophages to elicit protective immunity against Lm infection. DCs themselves were inefficient at taking up Lm but capable of taking up microparticles (MPs) released by Lm-infected macrophages. These MPs transferred Lm antigens to DCs, allowing DCs to present Lm antigen to effector T cells. MP-mediated Lm antigen transfer required MHC class I participation, since MHC class I deficiency in macrophages resulted in a significant reduction of T-cell activation. Moreover, the vaccination of mice with MPs from Lm-infected macrophages produced strong protective immunity against Lm infection. We here identify an intrinsic antigen transfer program between macrophages and DCs during Lm infection, and emphasize that macrophages also play an essential role in DC-elicited Lm-specific T-cell responses.     

Characterization of an anti-listerial enterocin from wheat silage based Enterococcus faecium

Two Enterococcus faecium and one E. faecalis strains isolated and identified from wheat silage were characterized based on plasmid content, hemolytic activity, antibiotic resistance patterns, bacteriocin production potential, and presence of enterocin structural genes (entA, entB, entP, entL50B). Among the isolates, only the E. faecium U7 strain exhibited bacteriocin activity against Listeria monocytogenes ATCC 7644, and vancomycin resistant Enterococcus spp. (VRE). A combination of three structural genes (entA, entB, and entP) was detected in E. faecium U7. A relationship between the presence of enterocin structural genes, and bacteriocin activity was detected in E. faecium U7; therefore partially purified enterocin (PPE) was further investigated from the isolate. Several bands of different molecular weights were expressed from PPE extracts following tricine SDS‐PAGE analysis. However, the only band showing bacteriocin activity was in an approximate 4‐kDa region. PPE treatment with proteinase K, lysozyme, and α ‐amylase caused complete loss of bacteriocin activity. PPE heat treatment at various temperatures resulted in a notable reduction in bacteriocin expression. Enterocin U7 was relatively heat stable, and presumably exhibits a glucoprotein nature with distinct inhibitory properties. Specific bacterial inhibitory activity of enterocin U7, and the producer strain absence of β ‐hemolysis and vancomycin susceptibility features deserves further investigation to evaluate its potential application in silage inoculation and food preservation. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

2009—2010年山东省食品中单核细胞增生李斯特菌的耐药性和分子分型研究

目的 了解山东省单核细胞增生李斯特菌(单增李斯特菌)耐药及分子分型特点,并探讨耐药表型与PFGE基因组型之间的关系.方法 从2009-2010年山东省6个城市的生畜禽肉、熟肉制品、水产品等食品中采集80株单增李斯特菌,采用微量肉汤稀释法测定其抗生素敏感性,采用PFGE进行分子分型,并对耐药谱与PFGE型别关系进行分析.结果 16.25％(13/80)的菌株存在耐药,其中,业胺培南的耐药率最高(12.50％,10/80),其次是四环素和强力霉素(3.75％,3/80;2.50％,2/80).耐药分型可将80株菌分为9个型别.PFGE将80株菌分为34个带型,以17型和29型为主.A型耐药谱分布范围较广,出现在79.41％ (27/34)的PFGE型别中.结论 2009-2010年山东省单增李斯特菌存在较为严重的耐药现象,单增李斯特菌的PFGE分型与其药敏分型无对应关系.     

单核细胞增生性李斯特菌致病相关机制的研究进展

单核细胞增生性李斯特菌(Listeria monocytogens,LM)是一种重要的食源性疾病病原菌,能引起人和动物较为严重的感染症状.LM采用多种策略逃逸宿主天然防御屏障,进而侵入宿主细胞并复制生存.本文结合近年来LM致病机制方面的研究,介绍了致病相关毒力因子的分子特点及其在致病过程中的作用.     

Acquired resistance to Listeria monocytogenes during a secondary infection in a murine model fed dietary lipids

Objective

The ω-3 polyunsaturated fatty acids can suppress immune system functions. This property may cause adverse effects by impairing host resistance to infection. The present study focused on estimating the impact of different dietary lipids on the immune system of mice after a secondary infection with Listeria monocytogenes.

Methods

BALB/c mice were divided into five dietary groups of olive oil, fish oil, sunflower oil, high-oleic sunflower oil, or low fat that was administered for 8 wk. The mice were immunized with 10³ colony-forming units. Thirty-eight days later, each mouse was challenged with 10⁴ colony-forming units. Mice survival and bacterial clearance from livers and spleens were determined. In addition, cytokine, chemokine, and adhesion molecule productions were quantified from the sera.

Results

Survival percentage in mice fed a fish oil diet was 100% and bacterial numbers from spleen were decreased at 72 h. Interleukin-12, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 productions were decreased. Levels of tumor necrosis factor-α and interferon-γ were increased, whereas macrophage inflammatory protein-1α (MIP-1α) production was unaltered.

Conclusion

Immune defense in mice fed a fish oil diet was improved after secondary exposure, acquiring an adequate resistance. This result could be attributable to an increase of a T-helper type 1 response.     

Concurrent conditions and human listeriosis, England, 1999-2009

The epidemiology of listeriosis in England and Wales changed during 2001-2008; more patients ≥60 years of age had bacteremia than in previous years. To investigate these changes, we calculated risk for listeriosis by concurrent condition for non-pregnancy-associated listeriosis cases reported to the national surveillance system in England during 1999-2009. Conditions occurring with L. monocytogenes infection were coded according to the International Classification of Diseases, 10th Revision, and compared with appropriate hospital episode statistics inpatient denominator data to calculate incidence rates/million consultations. Malignancies (especially of the blood), kidney disease, liver disease, diabetes, alcoholism, and age ≥60 years were associated with an increased risk for listeriosis. Physicians should consider a diagnosis of listeriosis when treating patients who have concurrent conditions. Providing cancer patients, who accounted for one third of cases, with food safety information might help limit additional cases.     

Listeriosis, Taiwan, 1996-2008

During 1996-2008, a total of 48 patients with listeriosis were identified at a Taiwan hospital. Average annual incidence increased from 0.029 to 0.118 cases per 1,000 admissions before and after January 2005. Serotype 1/2b predominated; serotype 4b emerged since 2004. Food monitoring and disease surveillance systems could help control listeriosis in Taiwan.     

Worldwide distribution of major clones of Listeria monocytogenes

Listeria monocytogenes is worldwide a pathogen, but the geographic distribution of clones remains largely unknown. Genotyping of 300 isolates from the 5 continents and diverse sources showed the existence of few prevalent and globally distributed clones, some of which include previously described epidemic clones. Cosmopolitan distribution indicates the need for genotyping standardization.     

1例产后哺乳期腹泻患者分离单增李斯特菌的生物学特征分析

目的 分析1例单增李斯特菌所致产后哺乳期腹泻患者的临床特征、病原学、菌株的毒力基因携带及分子特征。方法 搜集病例的临床相关信息;采用选择性增菌和显色培养基分离单增李斯特菌,用VITEK- 2 COMPACT30 全自动细菌分析仪鉴定分离菌株,采用单增李斯特菌诊断血清对分离株进行血清分型,使用脉冲场凝胶电泳技术及多位点序列分型技术进行分子分型,应用PCR检测毒力基因,并用E-test方法检测分离菌株对5种抗生素的药物敏感性。结果 产后哺乳期患者食用甜瓜和冰箱冷藏的酸奶后引起不能自限的腹泻,检测结果证实病原为4b血清型、ST145序列型单增李斯特菌。分离菌株携带毒力基因plcB、act、hly、iap、prfA、inlA,对青霉素、氨苄西林、美罗培南、红霉素和复方磺胺均敏感。结论 单增李斯特菌引起的腹泻患者容易漏诊,加强孕妇等高危人群腹泻患者粪便标本中单增李斯特菌的检测,对于单增李斯特菌病病人的及时治疗,预防不良预后具有重要的公共卫生意义,尤其对这一特殊型别单增李斯特菌在我国引起的病例感染应引起重视,其可能的感染来源和致病风险值得进一步的研究。