Transcriptomic Analysis of after Exposure to a Sublethal Concentration of Hydrogen Peroxide Revealed a Coordinated Up-Regulation of the Cysteine Biosynthesis Pathway.

Hydrogen peroxide (HO) is a key defense component of host-microbe interaction. However, HO concentrations generated by immune cells or epithelia are usually insufficient for bacterial killing and rather modulate bacterial responses. Here, we investigated the impact of sublethal HO concentration on gene expression of BW25113 after 10 and 60 min of exposure.

Hydrogen Peroxide Affects Growth of Through Downregulation of Genes Involved in Pyrimidine Biosynthesis.

Reactive oxygen species (ROS) play a crucial role in the cellular defense against , as evidenced by the importance of this pathogen in patients lacking the ROS-generating phagocyte NADPH oxidase NOX2. ROS concentrations required to kill are much higher than those found in the phagosome. We therefore hypothesized that sublethal ROS concentrations may play a role in gene dysregulation and investigated the transcriptomic response of to sublethal concentrations of hydrogen peroxide (HO).

The structure of the antimicrobial human cathelicidin LL-37 shows oligomerization and channel formation in the presence of membrane mimics.

The human cathelicidin LL-37 serves a critical role in the innate immune system defending bacterial infections. LL-37 can interact with molecules of the cell wall and perforate cytoplasmic membranes resulting in bacterial cell death. To test the interactions of LL-37 and bacterial cell wall components we crystallized LL-37 in the presence of detergents and obtained the structure of a narrow tetrameric channel with a strongly charged core.

Genetic Adaptation of a Mevalonate Pathway Deficient Mutant in .

In this study we addressed the question how a mevalonate (MVA)-auxotrophic Δ mutant can revert to prototrophy. This mutant couldn't grow in the absence of MVA. However, after a long lag-phase of 4-6 days the mutant adapted from auxotrophic to prototrophic phenotype.

Structural remodeling and oligomerization of human cathelicidin on membranes suggest fibril-like structures as active species.

Antimicrobial peptides as part of the mammalian innate immune system target and remove major bacterial pathogens, often through irreversible damage of their cellular membranes. To explore the mechanism by which the important cathelicidin peptide LL-37 of the human innate immune system interacts with membranes, we performed biochemical, biophysical and structural studies. The crystal structure of LL-37 displays dimers of anti-parallel helices and the formation of amphipathic surfaces.

Rapid identification of ST131 Escherichia coli by a novel multiplex real-time allelic discrimination assay.

Escherichia coli sequence type 131 is increasingly described in severe hospital infections. We developed a rapid real-time allelic discrimination assay for the rapid identification of E. coli ST131 isolates.

Daptomycin Tolerance in the Staphylococcus aureus pitA6 Mutant Is Due to Upregulation of the dlt Operon.

Understanding the mechanisms of how bacteria become tolerant toward antibiotics during clinical therapy is a very important object. In a previous study, we showed that increased daptomycin (DAP) tolerance of Staphylococcus aureus was due to a point mutation in pitA (inorganic phosphate transporter) that led to intracellular accumulation of both inorganic phosphate (Pi) and polyphosphate (polyP). DAP tolerance in the pitA6 mutant differs from classical resistance mechanisms since there is no increase in the MIC.

Meropenem/colistin synergy testing for multidrug-resistant Acinetobacter baumannii strains by a two-dimensional gradient technique applicable in routine microbiology.

Objectives: Precise assessment of potential therapeutic synergy, antagonism or indifference between antimicrobial agents currently depends on time-consuming and hard-to-standardize in vitro chequerboard titration methods. We here present a method based on a novel two-dimensional antibiotic gradient technique named Xact™.

Methods: We used a test comprising a combination of perpendicular gradients of meropenem and colistin in a single quadrant.

Mupirocin-induced mutations in ileS in various genetic backgrounds of methicillin-resistant Staphylococcus aureus.

Topical mupirocin is widely used for the decolonization of methicillin-resistant Staphylococcus aureus (MRSA) carriers. We evaluated the capacity of various MRSA clonotypes to develop mutations in the ileS gene associated with low-level mupirocin resistance. Twenty-four mupirocin-sensitive MRSA isolates from a variety of genotypes (determined by a multilocus variable-number tandem-repeat assay) were selected.

Diagnosis of whooping cough in Switzerland: differentiating Bordetella pertussis from Bordetella holmesii by polymerase chain reaction.

Bordetella holmesii, an emerging pathogen, can be misidentified as Bordetella pertussis by routine polymerase chain reaction (PCR). In some reports, up to 29% of the patients diagnosed with pertussis have in fact B. holmesii infection and invasive, non-respiratory B.

Robustness of a loop-mediated isothermal amplification reaction for diagnostic applications.

We evaluated the robustness of loop-mediated isothermal amplification (LAMP) of DNA for bacterial diagnostic applications. Salmonella enterica serovar Typhi was used as the target organism and compared with a real-time quantitative PCR (qPCR) for testing assay performance and reproducibly, as well as the impact of pH and temperature stability. This isothermal amplification method appeared to be particularly robust across 2 pH units (7.

Rapid and high-throughput genotyping of Staphylococcus epidermidis isolates by automated multilocus variable-number of tandem repeats: a tool for real-time epidemiology.

Fast and reliable genotyping methods allowing real-time epidemiology would be instrumental to discriminate Staphylococcus epidermidis isolates, in order to evaluate potential cross-infections or to follow genome content of infecting strains of this important opportunistic pathogen. We describe an automated multilocus variable-number tandem repeat-based assay (MLVA) for the rapid genotyping of S. epidermidis.

Novel microarray design strategy to study complex bacterial communities.

Assessing bacterial flora composition appears to be of increasing importance to fields as diverse as physiology, development, medicine, epidemiology, the environment, and the food industry. We report here the development and validation of an original microarray strategy that allows analysis of the phylogenic composition of complex bacterial mixtures. The microarray contains approximately 9,500 feature elements targeting 16S rRNA gene-specific regions.