Bacterial community dynamics of a whole drinking water supply system (DWSS) were studied from source to tap. Raw water for this DWSS is provided by two reservoirs with different water characteristics in the Harz mountains of Northern Germany. Samples were taken after different steps of treatment of raw water (i.e., flocculation, sand filtration, and chlorination) and at different points along the supply system to the tap. RNA and DNA were extracted from the sampled water. The 16S rRNA or its genes were partially amplified by reverse transcription-PCR or PCR and analyzed by single-strand conformation polymorphism community fingerprints. The bacterial community structures of the raw water samples from the two reservoirs were very different, but no major changes of these structures occurred after flocculation and sand filtration. Chlorination of the processed raw water strongly affected bacterial community structure, as reflected by the RNA-based fingerprints. This effect was less pronounced for the DNA-based fingerprints. After chlorination, the bacterial community remained rather constant from the storage containers to the tap. Furthermore, the community structure of the tap water did not change substantially for several months. Community composition was assessed by sequencing of abundant bands and phylogenetic analysis of the sequences obtained. The taxonomic compositions of the bacterial communities from both reservoirs were very different at the species level due to their different limnologies. On the other hand, major taxonomic groups, well known to occur in freshwater, such as Alphaproteobacteria, Betaproteobacteria, and Bacteroidetes, were found in both reservoirs. Significant differences in the detection of the major groups were observed between DNA-based and RNA-based fingerprints irrespective of the reservoir. Chlorination of the drinking water seemed to promote growth of nitrifying bacteria. Detailed analysis of the community dynamics of the whole DWSS revealed a significant influence of both source waters on the overall composition of the drinking water microflora and demonstrated the relevance of the raw water microflora for the drinking water microflora provided to the end user.

In this study, we investigated the interactions of Staphylococcus aureus with mast cells, which are multifunctional sentinels lining the surfaces of the body. We found that bone marrow-derived murine mast cells (BMMC) exerted a powerful phagocytosis-independent antimicrobial activity against S. aureus. Both the release of extracellular traps as well as discharge of antimicrobial compounds were the mechanisms used by the BMMC to kill extracellular S. aureus. This was accompanied by the secretion of mediators such as TNF-α involved in the recruitment of effector cells. Interestingly, S. aureus subverted the extracellular antimicrobial activity of the BMMC by internalizing within these cells. S. aureus was also capable to internalize within human mast cells (HMC-1) and within murine skin mast cells during in vivo infection. Bacteria internalization was, at least in part, mediated by the α5β1 integrins expressed on the surface of the mast cell. In the intracellular milieu, the bacterium survived and persisted by increasing the cell wall thickness and by gaining access into the mast cell cytosol. The expression of α-hemolysin was essential for staphylococci intracellular persistence. By hiding within the long-life mast cells, staphylococci not only avoid clearance but also establish an infection reservoir that could contribute to chronic carriage.

The complex response of murine macrophages to infection with Streptococcus pyogenes was investigated at the level of gene expression with a high-density oligomer microarray. More than 400 genes were identified as being differentially regulated. Many of the up-regulated genes encode molecules involved in the immune response and in inflammation, transcription, signaling, apoptosis, the cell cycle, electron transport, and cell adhesion.

TREM-1 (triggering receptor expressed on myeloid cells) is a surface molecule expressed on neutrophils and macrophages which has been implicated in the amplification of inflammatory responses triggered during infection. In the present study, we have investigated the clinical significance of TREM-1 in Streptococcus pyogenes-induced severe sepsis in both experimentally infected mice as well as in patients with streptococcal toxic shock. We found that S. pyogenes induced a dose-dependent upregulation of TREM-1 in in vitro cultured phagocytic cells and in the organs of S. pyogenes-infected mice. Furthermore, we reported a positive correlation between serum levels of soluble TREM-1 (sTREM-1) and disease severity in infected patients as well as in experimentally infected mice. Hence, sTREM-1 may represent a useful surrogate marker for streptococcal sepsis. We found that modulation of TREM-1 by administration of the TREM-1 decoy receptor rTREM-1/Fc substantially attenuated the synthesis of inflammatory cytokines. More importantly, treatment of S. pyogenes-infected septic mice with rTREM-1/Fc or the synthetically produced conserved extracellular domain LP17 significantly improved disease outcome. In summary, our data suggest that TREM-1 may not only represent a valuable marker for S. pyogenes infection severity but it may also be an attractive target for the treatment of streptococcal sepsis.