Effect of macrophage activation on killing of Listeria monocytogenes. Roles of reactive oxygen or nitrogen intermediates, rate of phagocytosis, and retention of bacteria in endosomes.

The role of macrophage activation in the killing of L. monocytogenes is unclear. Some studies suggest that activation for enhanced production of reactive oxygen and nitrogen intermediates may not be of central importance. Recent data have indicated an important role for interferon-gamma (IFN-gamma) induced retention of L. monocytogenes in endosomes. Data from the present study indicate that proteose peptone-elicited macrophages from DBA2/J, CD-1, and C3H/HeN mice are listericidal. Activation of these cells in vitro for 20 h by IFN-gamma (20 or 500 U/ml) increased H2O2 or nitrite production, but did not increase the number of L. monocytogenes killed during a subsequent 6-h or 7-h culture. Incubation of macrophages with IFN-gamma plus lipopolysaccharide (LPS) caused greater activation and increased the number of Listeria killed during a 6-h or 7-h culture. However, this seems primarily attributable to enhanced phagocytosis. Proteose peptone-elicited macrophages were significantly more effective than resident macrophages in preventing the escape of L. monocytogenes from endosomes into the cytoplasm. This capability was not significantly enhanced by IFN-gamma in vitro, but was enhanced by IFN-gamma plus LPS. This correlates well with the effects of these activation stimuli on killing of L. monocytogenes by proteose peptone-elicited macrophages. These results indicate that enhanced retention of L. monocytogenes in endosomes is induced by proteose peptone elicitation and that further macrophage activation in vitro by IFN-gamma does not improve listericidal activity.     

Changing pattern of human listeriosis, England and Wales, 2001-2004

Microbiologic and epidemiologic data on 1,933 cases of human listeriosis reported in England and Wales from 1990 to 2004 were reviewed. A substantial increase in incidence occurred from 2001 to 2004. Ten clusters (60 cases), likely to represent common-source outbreaks, were detected. However, these clusters did not account for the upsurge in incidence, which occurred sporadically, predominantly in patients > or =60 years of age with bacteremia and which was independent of sex; regional, seasonal, ethnic, or socioeconomic differences; underlying conditions; or Listeria monocytogenes subtype. The reasons for the increase are not known, but since multiple L. monocytogenes strains were responsible, this upsurge is unlikely to be due to a common-source outbreak. In the absence of risk factors for listeriosis in this emerging at-risk sector of the population, dietary advice on avoiding high-risk foods should be provided routinely to the elderly and immunocompromised, not just to pregnant women.     

Ongoing High Incidence and Case-Fatality Rates for Invasive Listeriosis,Germany, 2010–2019

We used 10 years of surveillance data to describe listeriosis frequency in Germany. Altogether, 5,576 cases were reported, 91% not pregnancy associated; case counts increased over time. Case-fatality rate was 13% in non–pregnancy-associated cases, most in adults ≥65 years of age. Detecting, investigating, and ending outbreaks might have the greatest effect on incidence     

Listerial meningitis in a patient with undiagnosed acquired immunodeficiency syndrome: ampicillin should be added to the empirical antibiotic coverage

Meningitis is an important differential diagnosis in patients with fever, headache, and/or altered consciousness in the emergency department (ED). With human immunodeficiency virus (HIV) infection becoming increasingly common, patients with acquired immunodeficiency syndrome (AIDS) need to be recognised promptly to facilitate the choice of appropriate antibiotic therapy for potential opportunistic infections. Physicians should be able to recognise a patient with undiagnosed AIDS who presents to the ED and perform further confirmational tests without violating the rights of the patient. Additional tests focusing on discovering potential opportunistic pathogens should be performed. Ampicillin should be added to the empirical regimen for the coverage of Listeria meningocerebritis, which should be considered in all potentially immunocompromised hosts with suggestive clinical presentations. Failure to recognise patients with AIDS and provide antibiotics active against L monocytogenes in such hosts may lead to a catastrophic outcome.     

Prolonged dysphagia due to Listeria-rhombencephalitis with brainstem abscess and acute polyradiculoneuritis

We report a case of previously healthy student with acute rhombencephalitis and brainstem abscess caused by Listeria monocytogenes. The disease begun with uncharacteristic prodromal symptoms of gastrointestinal infection followed by headache and vertigo. After hospital admission the patient rapidly deteriorated, presenting pronounced dysphagia and respiratory failure requiring mechanical ventilation. The diagnosis was established upon clinical symptoms of infection, brainstem involvement, typical MRI findings and positive for L. monocytogenes blood culture. Infection was complicated by acute, demyelinating neuropathy, diagnosed upon clinical symptoms of frail palsy confirmed by ENG. Initially introduced empirical doxycyclin/ceftriaxon treatment was subsequently changed to targeted ampicillin/gentamycin therapy, mechanical ventilation, intravenous human immunoglobulin treatment, tracheostomy and endoscopic gastrostomy. Prolonged dysphagia resolved after rehabilitation. After one year the patient remains well with only slight dysmetria.     

鉴定单增李斯特菌四个进化家系及两个亚系的多PCR方法的建立

目的利用多重PCR（multiplexPCR）技术,建立针对单增李斯特菌4个进化家系（LineageⅠ,LineageⅡ、LineageⅢ、LineageⅣ）及2个亚系（LineageⅢA、LineageⅢC）的鉴定方法。方法以InlA、Lmo0733、Lmo0038、Lmo0735和LmaA作为靶基因设计引物,建立同时鉴别LineageⅠ、LineageⅡ、LineageⅢA、LineageⅢC和LineageⅣ菌株的多重PCR反应体系,并对387株单增李斯特菌进行了所属进化家系及亚系的鉴定。结果387株单增李斯特菌可用本方法进行所属家系和亚系的分型,包括LineageⅠ246株、LineageⅡ123株、LineageⅢA4株、LineageⅢC13株和LineageⅣ1株。结论本方法能准确鉴定单增李斯特菌的4个进化家系及2个亚系的菌株,可用于食品、临床标本中单增李斯特菌的楠原学诊断和疫情暴发时的溯源调查。     

绵羊李斯特菌病病原诊断及其生物学特性研究

目的 单核细胞增生性李斯特菌(Lm)是引起人兽共患李斯特菌病的病原菌,该菌感染宿主中枢神经系统是导致高死亡率的主要原因.本研究对农场暴发的呈现神经症状的绵羊李斯特菌病病例进行病原诊断,进而对其病原学特性开展相关研究.方法 利用选择培养基和鉴别培养基进行细菌的分离和鉴定,借助多重PCR方法和Lm诊断血清对分离株的血清型进行研究,并测定了该菌株的溶血活性和药物敏感性,基于毒力基因actA的遗传谱系进行分型,最后对其LD50进行了测定.结果 从绵羊脑实质组织中成功地分离到一株血清型为4b的Lm菌株NTSN,其溶血效价为24,LD50为104.30CFU,是具脑侵袭性的强毒菌株,可用青霉素类药物治疗.遗传谱系分析表明Lm NTSN可能属于高侵袭性的流行克隆.结论 LmNTSN的分离鉴定及其生物学特性的研究,为深入探讨Lm的致病机理和预防控制奠定了基础.     

Treatment of bacterial meningitis: an update

Introduction: The introduction of protein conjugate vaccines for Haemophilus influenzae type b (Hib), Streptococcus pneumoniae (S. pneumoniae) and Neisseria meningitidis (N. menigitidis) has changed the epidemiology of bacterial meningitis. Bacterial meningitis continues to be an important cause of mortality and morbidity, and our incomplete knowledge of its pathogenesis and emergence of antimicrobial resistant bacteria contribute to such mortality and morbidity. An early empiric antibiotic treatment is critical for the management of patients with bacterial meningitis.

Areas covered: This article gives an overview on optimal treatment strategies of bacterial meningitis, along with considerations of new insights on epidemiology, clinical and laboratory findings supportive of bacterial meningitis, chemoprophylaxis, selection of initial antimicrobial agents for suspected bacterial meningitis, antimicrobial resistance and utility of new antibiotics, status on anti-inflammatory agents and adjunctive therapy, and pathogenesis of bacterial meningitis.

Expert opinion: Prompt treatment of bacterial meningitis with an appropriate antibiotic is essential. Optimal antimicrobial treatment of bacterial meningitis requires bactericidal agents able to penetrate the blood–brain barrier (BBB), with efficacy in cerebrospinal fluid (CSF). Several new antibiotics have been introduced for the treatment of meningitis caused by resistant bacteria, but their use in human studies has been limited. More complete understanding of the microbial and host interactions that are involved in the pathogenesis of bacterial meningitis and associated neurologic sequelae is likely to help in developing new strategies for the prevention and therapy of bacterial meningitis.     

Improving live attenuated bacterial carriers for vaccination and therapy

Live attenuated bacteria are well established as vaccines. Thus, their use as carriers for prophylactic and therapeutic macromolecules is a logical consequence. Here we describe several experimental applications of bacteria to carry heterologous macromolecules into the murine host. First, Listeria monocytogenes are described that are able to transfer eukaryotic expression plasmids into host cells for gene therapy. High multiplicities of infection are still required for efficient gene transfer and we point out some of the bottlenecks that counteract a more efficient transfer and application in vivo. Then, we describe Salmonella enterica serovar Typhimurium (S. typhimurium) as an expression plasmid transfer vehicle for oral DNA vaccination of mice. We demonstrate that the stabilization of the plasmid transformants results in an improved immune response. Stabilization was achieved by replacing the origin of replication of the original high-copy-number plasmid by a low-copy-number origin. Finally, we describe Salmonella carriers for the improved expression of heterologous proteins. We introduce a system in which the plasmid is carried as a single copy during cultivation but is amplified several fold upon infection of the host. Using the same in vivo inducible promoter for both protein expression and plasmid amplification, a substantial increase in antigen expression in vivo can be achieved. A modification of this approach is the introduction of inducible gene expression in vivo with a low-molecular-weight compound. Using P_BAD promoter and l-arabinose as inducer we were able to deliberately activate genes in the bacterial carrier. No background activity could be observed with P_BAD such that an inducible suicide gene could be introduced. This is adding an important safety feature to such live attenuated carrier bacteria.