Johannes Elias

A dual role of extracellular DNA during biofilm formation of Neisseria meningitidis

Major pathogenic clonal complexes (cc) of Neisseria meningitidis differ substantially in their point prevalence among healthy carriers. We show that frequently carried pathogenic cc (e.g. sequence type ST‐41/44 cc and ST‐32 cc) depend on extracellular DNA (eDNA) to initiate in vitro biofilm formation, whereas biofilm formation of cc with low point prevalence (ST‐8 cc and ST‐11 cc) was eDNA‐independent. For initial biofilm formation, a ST‐32 cc type strain, but not a ST‐11 type strain, utilized eDNA. The release of eDNA was mediated by lytic transglycosylase and cytoplasmic N‐acetylmuramyl‐l‐alanine amidase genes. In late biofilms, outer membrane phospholipase A‐dependent autolysis, which was observed in most cc, but not in ST‐8 and ST‐11 strains, was required for shear force resistance of microcolonies. Taken together, N. meningitidis evolved two different biofilm formation strategies, an eDNA‐dependent one yielding shear force resistant microcolonies, and an eDNA‐independent one. Based on the experimental findings and previous epidemiological observations, we hypothesize that most meningococcal cc display a settler phenotype, which is eDNA‐dependent and results in a stable interaction with the host. On the contrary, spreaders (ST‐11 and ST‐8 cc) are unable to use eDNA for biofilm formation and might compensate for poor colonization properties by high transmission rates.

Spatiotemporal Analysis of Invasive Meningococcal Disease, Germany

Meningococcal disease clustering was found by DNA sequence–based finetyping and cluster detection software.

Bacteremia in an Immunocompromised Patient Caused by a Commensal Neisseria meningitidis Strain Harboring the Capsule Null Locus (cnl)

ABSTRACT We recently described the capsule null locus (cnl) of constitutively unencapsulated Neisseria meningitidis clonal lineages. cnl meningococci were recovered from healthy carriers at high frequency. We here report on the first case of invasive disease caused by cnl meningococci in a severely immunosuppressed patient with chronic graft-versus-host disease after allogeneic peripheral blood stem cell transplantation. The sequence type 845 strain was extensively typed and, furthermore, shown to be sensitive to serum bactericidal activity.

Metabolism and virulence in Neisseria meningitidis

A longstanding question in infection biology addresses the genetic basis for invasive behavior in commensal pathogens. A prime example for such a pathogen is Neisseria meningitidis. On the one hand it is a harmless commensal bacterium exquisitely adapted to humans, and on the other hand it sometimes behaves like a ferocious pathogen causing potentially lethal disease such as sepsis and acute bacterial meningitis. Despite the lack of a classical repertoire of virulence genes in N. meningitidis separating commensal from invasive strains, molecular epidemiology suggests that carriage and invasive strains belong to genetically distinct populations. In recent years, it has become increasingly clear that metabolic adaptation enables meningococci to exploit host resources, supporting the concept of nutritional virulence as a crucial determinant of invasive capability. Here, we discuss the contribution of core metabolic pathways in the context of colonization and invasion with special emphasis on results from genome-wide surveys. The metabolism of lactate, the oxidative stress response, and, in particular, glutathione metabolism as well as the denitrification pathway provide examples of how meningococcal metabolism is intimately linked to pathogenesis. We further discuss evidence from genome-wide approaches regarding potential metabolic differences between strains from hyperinvasive and carriage lineages and present new data assessing in vitro growth differences of strains from these two populations. We hypothesize that strains from carriage and hyperinvasive lineages differ in the expression of regulatory genes involved particularly in stress responses and amino acid metabolism under infection conditions.

Bat-Associated Histoplasmosis Can Be Transmitted at Entrances of Bat Caves and Not Only Inside the Caves

Our observation of histoplasmosis cases augments the current knowledge on transmission by bats. In the presented cases, the only contact happened in the proximity of a bat cave but not inside the cave. We wish to communicate and stress that even outside of caves, bats may disperse the organism.

A Space–Time Conditional Intensity Model for Invasive Meningococcal Disease Occurrence

A novel point process model continuous in space-time is proposed for quantifying the transmission dynamics of the two most common meningococcal antigenic sequence types observed in Germany 2002-2008. Modeling is based on the conditional intensity function (CIF), which is described by a superposition of additive and multiplicative components. As an epidemiological interesting finding, spread behavior was shown to depend on type in addition to age: basic reproduction numbers were 0.25 (95% CI 0.19-0.34) and 0.11 (95% CI 0.07-0.17) for types B:P1.7-2,4:F1-5 and C:P1.5,2:F3-3, respectively. Altogether, the proposed methodology represents a comprehensive and universal regression framework for the modeling, simulation, and inference of self-exciting spatiotemporal point processes based on the CIF. Usability of the modeling in biometric practice is promoted by an implementation in the R package surveillance.

IS1301 Fingerprint Analysis of Neisseria meningitidis Strains Belonging to the ET-15 Clone

ABSTRACT Meningococci of the ET-15 clone frequently cause clusters of invasive meningococcal disease (IMD) and are associated with a high case-fatality ratio. Timely typing of strains from outbreaks of IMD caused by this clone is hampered by the low variability of its surface antigens. We present a new Southern blot-based typing method for ET-15 meningococci based on the insertion element IS1301, which was present in all 70 ET-15 strains tested. Fingerprints were stable in vitro over a period of 100 days of cultivation on agar plates. The discriminatory power of IS1301 fingerprinting exceeded that of typing by serogrouping and antigen sequencing of the outer membrane proteins PorA and FetA, as determined by the analysis of 52 epidemiologically unrelated strains. In addition, the method provided conclusive results with regard to the comparison of strains from clusters of IMD. The investigation of insertion sites of IS1301 revealed several new intragenic insertions, among others, into open reading frames homologous to mafB and tspB. A previously described insertion in nadA was present in more than two-thirds of the strains analyzed, suggesting that NadA is probably an unreliable vaccine candidate for the prevention of ET-15 disease.

First Survey of Metallo-β-Lactamases in Clinical Isolates of Pseudomonas aeruginosa in a German University Hospital

ABSTRACT A total of 489 clinical isolates of Pseudomonas aeruginosa was investigated for metallo-β-lactamase (MBL) production. Molecular analysis detected a blaVIM-1 gene in the chromosome of one isolate and a blaVIM-2 gene carried on the plasmid in seven isolates. Moreover, we showed that an initial screening by combined susceptibility testing of imipenem and ceftazidime followed by a confirmatory EDTA combination disk test represents a valid alternative to the molecular investigation of MBL genes, making MBL detection possible in routine diagnostic laboratories.

Capture-recapture analysis to estimate the incidence of invasive meningococcal disease in Germany, 2003

The incidence of invasive meningococcal disease (IMD) in Germany in 2003 was estimated by the two-source capture-recapture method. As a unique personal identifier was unavailable, cases with IMD tested at the National Reference Centre for Meningococci (NRZM) were matched with cases reported to the Robert Koch Institute (RKI) through the statutory surveillance system by using demographic and disease-specific variables common to both datasets. The estimated overall incidence was 1.1 IMD cases/100,000 inhabitants, with a sensitivity of ascertainment of 64.8% for NRZM and 89.4% for RKI. Case-fatality rate was estimated at 8.8%. Adjustment for heterogeneity of capture according to age, region and serogroup observed in the NRZM (but not RKI) source had minimal effect on the estimated incidence. The IMD incidence estimated by capture-recapture analysis is thus only slightly higher than through statutory surveillance data. As a degree of positive dependence between the systems cannot be ruled out, this estimate may still be an underestimate. However, under ascertainment appears insufficient to explain the low incidence of IMD in Germany compared to other European countries.

Epidemiology of invasive meningococcal disease in Germany, 2002–2010, and impact of vaccination with meningococcal C conjugate vaccine

OBJECTIVES To analyse serogroup (Sg)- and finetype-specific invasive meningococcal disease burden (IMD) in Germany, 2002-2010, with emphasis on effects of vaccination with conjugate SgC vaccines targeting one-year old children since 2006, including individual-based catch-up to 17 years of age. METHODS Serogroup- and age-specific IMD incidence and trends were calculated using statutory surveillance data. The national reference laboratory performed genetic finetyping. Vaccination uptake data were obtained from school entry surveys and prescription monitoring. RESULTS In persons <25 years, SgB and SgC IMD incidence decreased significantly from 0.63 to 0.32/100,000 and 0.26 to 0.10/100,000, respectively. The decline was significantly steeper for SgC than SgB in 1-5 year-olds, the primary vaccination target group, but not other ages. The slope of the SgC incidence curves was similar before and after vaccination implementation in all age groups; however, the decrease in incidence was steeper in states with higher vaccination uptake. Declining SgC incidence was associated with decreased SgC finetype diversity. An increase in SgY incidence was limited to adults. CONCLUSIONS Results suggest effects of the German SgC vaccination strategy are limited, although interpretation is complicated by already low and decreasing incidence before vaccination. More effective use of vaccination resources might be achieved by rigorously targeting adolescents in addition to 1-year-olds.