Publications (11)96.5 Total impact
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Article: Streptococcus tigurinus, a novel member of the Streptococcus mitis group, causes invasive infections.
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ABSTRACT: We recently described the novel species Streptococcus tigurinus sp. nov. belonging to the Streptococcus mitis group. The type strain AZ_3a(T) of S. tigurinus was originally isolated from a patient with infective endocarditis. According to its phenotypic and molecular characteristics, S. tigurinus is most closely related to Streptococcus mitis, Streptococcus pneumoniae, Streptococcus pseudopneumoniae, Streptococcus oralis, and Streptococcus infantis. Accurate identification of S. tigurinus is facilitated by 16S rRNA gene analysis. We retrospectively analyzed our 16S rRNA gene molecular database, which contains sequences of all clinical samples obtained in our institute since 2003. We detected 17 16S rRNA gene sequences which were assigned to S. tigurinus, including sequences from the 3 S. tigurinus strains described previously. S. tigurinus originated from normally sterile body sites, such as blood, cerebrospinal fluid, or heart valves, of 14 patients and was initially detected by culture or broad-range 16S rRNA gene PCR, followed by sequencing. The 14 patients had serious invasive infections, i.e., infective endocarditis (n = 6), spondylodiscitis (n = 3), bacteremia (n = 2), meningitis (n = 1), prosthetic joint infection (n = 1), and thoracic empyema (n = 1). To evaluate the presence of Streptococcus tigurinus in the endogenous oral microbial flora, we screened saliva specimens of 31 volunteers. After selective growth, alpha-hemolytic growing colonies were analyzed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and subsequent molecular methods. S. tigurinus was not identified among 608 strains analyzed. These data indicate that S. tigurinus is not widely distributed in the oral cavity. In conclusion, S. tigurinus is a novel agent of invasive infections, particularly infective endocarditis.Journal of clinical microbiology 07/2012; 50(9):2969-73. · 4.16 Impact Factor -
Article: Streptococcus tigurinus sp. nov., isolated from blood of patients with endocarditis, meningitis and spondylodiscitis.
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ABSTRACT: Four Gram-stain-positive, catalase-negative, coccus-shaped bacterial strains were isolated from multiple blood cultures of patients with endocarditis, meningitis and spondylodiscitis. The isolates were tentatively identified as viridans streptococcal species based on phenotypic characteristics. Comparative 16S rRNA gene sequencing studies showed that the organisms were members of the Streptococcus mitis group but did not correspond to any recognized species. The nearest phylogenetic relative was Streptococcus mitis ATCC 49456(T) with 98.6% sequence similarity. The representative strain AZ_3a(T) showed similarity values of less than 96.8%, 97.6%, 94.5% and 95.5% to the phylogenetically most closely related species by recA, rpoB, sodA and groEL gene sequence analysis, respectively. DNA-DNA hybridization analyses showed a low reassociation value of 32.2% between strain AZ_3a(T) and S. mitis DSM 12643(T). Reassociation values with other S. mitis group species ranged from 27.3% to 49.7%. The G+C content of the DNA is 40.0 mol%. Based on our biochemical and molecular analyses, the novel isolates represent a new species, for which the name Streptococcus tigurinus sp. nov. is proposed. The type strain is AZ_3a(T)( =CCOS 600(T) =DSM 24864(T)).INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 02/2012; · 2.11 Impact Factor -
Article: Broad-range 16S rRNA gene polymerase chain reaction for diagnosis of culture-negative bacterial infections.
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ABSTRACT: Broad-range 16S ribosomal RNA (rRNA) gene polymerase chain reaction (PCR) is used for detection and identification of bacterial pathogens in clinical specimens from patients with a high suspicion for infection. However, prospective studies addressing the impact and clinical value of broad-range bacterial 16S rRNA gene amplification for diagnosis of acute infectious diseases in nonselected patient populations are lacking. We first assessed the diagnostic performance of 16S rRNA gene PCR compared with routine bacterial culture. Second, we addressed prospectively the impact and clinical value of broad-range PCR for the diagnosis of acute infections using samples that tested negative by routine bacterial culture; the corresponding patients' data were evaluated by detailed medical record reviews. Results from 394 specimens showed a high concordance of >90% for 16S rRNA gene PCR and routine bacterial culture, indicating that the diagnostic performance of PCR for acute bacterial infections is comparable to that of bacterial culture, which is currently considered the gold standard. In thisprospective study, 231 specimens with a negative result on routine bacterial culture were analyzed with PCR, and patients' clinical data were reviewed. We found that broad-range 16S rRNA gene PCR showed a sensitivity, specificity, positive predictive value, and negative predictive value of 42.9%, 100%, 100%, and 80.2% for culture-negative bacterial infections. This study defines the role of 16S rRNA gene PCR for diagnosis of culture-negative bacterial infections. Our data show that 16S rRNA gene PCR is particularly useful for identification of bacterial pathogens in patients pretreated with antibiotics.Clinical Infectious Diseases 12/2011; 53(12):1245-51. · 9.15 Impact Factor -
Article: Mycobacterium algericum sp. nov., a novel rapidly growing species related to the Mycobacterium terrae complex and associated with goat lung lesions.
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ABSTRACT: A previously undescribed, rapid-growing, non-chromogenic Mycobacterium isolate from a goat lung lesion in Algeria is reported. Biochemical and molecular tools were used for its complete description and showed its affiliation to the Mycobacterium terrae complex. 16S rRNA, rpoB and hsp65 gene sequences were unique. Phylogenetic analyses showed a close relationship with M. terrae sensu stricto and Mycobacterium senuense. Culture and biochemical characteristics were generally similar to those of M. terrae and M. senuense. However, in contrast to M. terrae and M. senuense, the isolate was positive for urease production and had faster growth. The mycolic acid profile was distinct from those of M. terrae and M. senuense, thus further supporting the new taxonomic position of the isolate. We propose the name Mycobacterium algericum sp. nov. for this novel species. The type strain is TBE 500028/10(T) ( = Bejaia(T) = CIP 110121(T) = DSM 45454(T)).INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 08/2011; 61(Pt 8):1870-4. · 2.11 Impact Factor -
Article: Rapid molecular detection of tuberculosis.
New England Journal of Medicine 01/2011; 364(2):183; author reply 184-5. · 53.30 Impact Factor -
Article: Recognition of potentially novel human disease-associated pathogens by implementation of systematic 16S rRNA gene sequencing in the diagnostic laboratory.
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ABSTRACT: Clinical isolates that are difficult to identify by conventional means form a valuable source of novel human pathogens. We report on a 5-year study based on systematic 16S rRNA gene sequence analysis. We found 60 previously unknown 16S rRNA sequences corresponding to potentially novel bacterial taxa. For 30 of 60 isolates, clinical relevance was evaluated; 18 of the 30 isolates analyzed were considered to be associated with human disease.Journal of clinical microbiology 09/2010; 48(9):3397-402. · 4.16 Impact Factor -
Article: Septicemia caused by tick-borne bacterial pathogen Candidatus Neoehrlichia mikurensis.
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ABSTRACT: We have repeatedly detected Candidatus Neoehrlichia mikurensis, a bacterium first described in Rattus norvegicus rats and Ixodes ovatus ticks in Japan in 2004 in the blood of a 61-year-old man with signs of septicemia by 16S rRNA and groEL gene PCR. After 6 weeks of therapy with doxycycline and rifampin, the patient recovered.Emerging Infectious Diseases 07/2010; 16(7):1127-9. · 6.79 Impact Factor -
Article: Detection of a mixed infection in a culture-negative brain abscess by broad-spectrum bacterial 16S rRNA gene PCR.
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ABSTRACT: We describe the identification of two bacterial pathogens from a culture-negative brain abscess by the use of broad-spectrum 16S rRNA gene PCR. Simultaneous detection of Fusobacterium nucleatum and Porphyromonas endodontalis was possible due to a 24-bp length difference of their partially amplified 16S rRNA genes, which allowed separation by high-resolution polyacrylamide gel electrophoresis.Journal of clinical microbiology 06/2010; 48(6):2250-2. · 4.16 Impact Factor -
Article: Deletion of dop in Mycobacterium smegmatis abolishes pupylation of protein substrates in vivo.
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ABSTRACT: Proteasome-bearing bacteria make use of a ubiquitin-like modification pathway to target proteins for proteasomal turnover. In a process termed pupylation, proteasomal substrates are covalently modified with the small protein Pup that serves as a degradation signal. Pup is attached to substrate proteins by action of PafA. Prior to its attachment, Pup needs to undergo deamidation at its C-terminal residue, converting glutamine to glutamate. This step is catalysed in vitro by Dop. In order to characterize Dop activity in vivo, we generated a dop deletion mutant in Mycobacterium smegmatis. In the Deltadop strain, pupylation is severely impaired and the steady-state levels of two known proteasomal substrates are drastically increased. Pupylation can be re-established by complementing the mutant with either DopWt or a Pup variant carrying a glutamate at its ultimate C-terminal position (PupGGE). Our data show that Pup is deamidated by Dop in vivo and that likely Dop alone is responsible for this activity. Furthermore, we demonstrate that a putative N-terminal ATP-binding motif is crucial for catalysis, as a single point mutation (E10A) in this motif abolishes Dop activity both in vivo and in vitro.Molecular Microbiology 12/2009; 75(3):744-54. · 5.01 Impact Factor -
Article: Cloning, expression and characterization of Mycobacterium tuberculosis lipoprotein LprF.
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ABSTRACT: Lipoproteins are well known virulence factors of bacterial pathogens in general and of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, in particular. Lipoprotein lipidation between Gram-positive and Gram-negative bacteria differs significantly as these are di- and triacylated, respectively. Little is known about the lipid anchor of mycobacterial lipoproteins. We reported recently that mycobacterial LppX, a lipoprotein involved in synthesis of cell wall components is triacylated, although mycobacteria are classified as GC-rich Gram-positive bacteria. We here exploited the model organism Mycobacterium smegmatis for the expression of Mtb LprF and characterized N-terminal modifications at the molecular level. LprF is a putative lipoprotein of Mtb involved in signaling of potassium-dependent osmotic stress. LprF is extensively modified in a mycobacterium-specific manner by a thioether-linked diacylglyceryl residue with one ester-bound tuberculostearic- and one C16:0 fatty acid and additionally by a third N-linked C16:0 fatty acid, and a hexose.Biochemical and Biophysical Research Communications 11/2009; 391(1):679-84. · 2.48 Impact Factor -
Article: Tuberculosis vaccine strain Mycobacterium bovis BCG Russia is a natural recA mutant.
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ABSTRACT: The current tuberculosis vaccine is a live vaccine derived from Mycobacterium bovis and attenuated by serial in vitro passaging. All vaccine substrains in use stem from one source, strain Bacille Calmette-Guérin. However, they differ in regions of genomic deletions, antigen expression levels, immunogenicity, and protective efficacy. As a RecA phenotype increases genetic stability and may contribute restricting the ongoing evolution of the various BCG substrains while maintaining their protective efficacy, we aimed to inactivate recA by allelic replacement in BCG vaccine strains representing different phylogenetic lineages (Pasteur, Frappier, Denmark, Russia). Homologous gene replacement was achieved successfully in three out of four strains. However, only illegitimate recombination was observed in BCG substrain Russia. Sequence analyses of recA revealed that a single nucleotide insertion in the 5' part of recA led to a translational frameshift with an early stop codon making BCG Russia a natural recA mutant. At the protein level BCG Russia failed to express RecA. According to phylogenetic analyses BCG Russia is an ancient vaccine strain most closely related to the parental M. bovis. We hypothesize that recA inactivation in BCG Russia occurred early and is in part responsible for its high degree of genomic stability, resulting in a substrain that has less genetic alterations than other vaccine substrains with respect to M. bovis AF2122/97 wild-type.BMC Microbiology 01/2008; 8:120. · 3.04 Impact Factor
Top co-authors
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Institutions
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2008–2012
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University of Zurich
- Institut für Medizinische Mikrobiologie
Zürich, ZH, Switzerland
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2011
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Université Saad Dahlab Blida
Blida, Wilaya de Blida, Algeria
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