Prevalence and spread of enterohepatic Helicobacter species in mice reared in a specific-pathogen-free animal facility

Infections with enterohepatic Helicobacter species (EHS) can change the results of animal experiments. However, there is little information about the prevalence of EHS in noncommercial animal facilities. The aim of this study was to investigate the prevalence and the spread of EHS in specific-pathogen-free (SPF) mice. Fecal samples of 40 mouse lines were analyzed for members of the family Helicobacteraceae using a group-specific PCR targeting the 16S rRNA gene. Additional experiments were carried out to evaluate the spread of EHS among mice harbored in different caging systems. Helicobacter species were detected in 87.5% of the mouse lines tested. Five different Helicobacter species were identified: H. ganmani, H. hepaticus, H. typhlonicus, and the putative Helicobacter species represented by the isolates hamster B and MIT 98-5357. Helicobacter infection did not spread between animals in neighboring cages when individually ventilated cages were used; in contrast, when the mice were reared in open-air cages, EHS were found to spread from cage to cage. However, the spread was prevented by adding polycarbonate filter tops to the cages. When Helicobacter-negative and infected mice shared the same cage, transmission of the infection occurred in 100% within 2 weeks. Furthermore, we found that mice from commercial breeding facilities may carry undetected Helicobacter infections. Taken together, we show that infection with EHS may frequently occur and spread easily in mice reared under SPF conditions despite extensive safety precautions. Moreover, there is a high prevalence of rather uncommon Helicobacter species that may be a consequence of the current routine procedures used for health screening of SPF mice.

Heterogeneity of methicillin-susceptible Staphylococcus aureus strains at a German University Hospital implicates the circulating-strain pool as a potential source of emerging methicillin-resistant S. aureus clones

Recently, we demonstrated rapid dissemination of different methicillin-resistant Staphylococcus aureus (MRSA) clones at the Institute for Microbiology at the University of Magdeburg (B. Ghebremedhin, W. König, and B. König, Eur. J. Clin. Microbiol. Infect. Dis. 24:388-398, 2005). The majority of them harbored the readily transmissible mec cassette type IV. Thus, theoretically, methicillin-susceptible Staphylococcus aureus (MSSA) might capture the mecA gene from circulating MRSA, or MRSA strains might catch mobile toxin genes from MSSA. Therefore, we characterized MSSA strains circulating at the University Hospital in Magdeburg. Among a total of 84 MSSA strains under study, about 40% possessed the tst (toxic shock syndrome toxin) gene and up to four additional enterotoxin genes. tst-positive MSSA strains belonged to all known agr groups (I to IV) and to 14 different spa types (t008, t012, t015, t019, t024, t056, t065, t127, t133, t162, t271, t287, t399, and t400), and they were classified by multilocus sequence typing (MLST) as ST1, ST8, ST30, ST39, ST45, ST101, ST121, ST395, and ST426. In contrast, simultaneously circulating MRSA strains (n = 24) harbored in general two or three genes of the enterotoxin gene cluster, and the tst-positive MRSA isolates belonged to the well-known epidemic types ST22, ST45, and ST228 and were classified as spa types t001, t028, and t032. From our results, one may conclude that the pool of circulating MSSA strains is an important parameter with regard to the epidemiology of hospital- and community-acquired MRSA clones and their potential virulence.

Gene expression and protein profiling of AGS gastric epithelial cells upon infection with Helicobacter pylori

Helicobacter pylori, one of the most common bacterial pathogens, colonizes the human stomach and causes a variety of gastric diseases. This pathogen elicits a range of phenotypic responses in infected cultured AGS gastric epithelial cells, including expression of proinflammatory genes and changes in the actin cytoskeleton. Some of these responses are mediated by the type IV secretion system (T4SS) encoded by the cag pathogenicity island. We have used two global approaches, namely 2-DE combined with PMF and cDNA expression array analyses, to study in both a comprehensive and quantitative manner the protein profile and the temporal patterns of mRNA accumulation in AGS cells upon infection with H. pylori and isogenic T4SS mutants. We identified 140 transcripts and detected 190 protein species that were differentially regulated upon infection. Infection with wild-type H. pylori induced expression of a variety of host genes and changes in protein pattern involved in transcriptional responses, cell shape regulation and signal transduction. Among them, some were differentially regulated in a cag PAI-dependent manner, as shown by both the proteomic and cDNA expression array approaches. While 2-DE and PMF allowed us to examine the protein profiles in the infected host, array analysis enabled us to demonstrate dynamic temporal changes in host gene expression profile. In conclusion, our combined application of the two global approaches provides further molecular details on how the host cell responds to infection by H. pylori and its isogenic T4SS mutants on both transcriptional and protein levels. The findings pinpoint host proteins such as serine/threonine and tyrosine kinases, transcription factors, cell cycle related components and actin cytoskeletal signaling molecules as potential targets of individual H. pylori virulence determinants. This study serves as a basis for future work on transcription and proteome analyses of the H. pylori infection model.

Differential effects of PDGF-BB on matrix metalloproteases and cytokine release in fibroblasts of Type 2 diabetic patients and normal controls in vitro

AIMS/HYPOTHESIS

The complex process of wound healing is regulated by various growth factors. The systemic character of diabetes mellitus favors the chronification of diabetic wounds. In this study, the in vitro effects of platelet-derived growth factor (PDGF)-BB on the expression of cytokines and matrix metalloproteases (MMPs) in fibroblasts of Type 2 diabetic patients and healthy controls were investigated.

METHODS

We studied six Type 2 diabetic patients (mean Hba1(c)=7.5%) and six healthy controls. For proliferation studies, cultivated fibroblasts, prepared from biopsies taken from the thigh, were stimulated with different concentrations of PDGF. After 48 h, the expression of MMPs and cytokines was measured. We analysed the mRNA expression by RT-PCR (TaqMan), tissue protein levels by zymography, and cell supernatant levels by ELISA.

RESULTS

Levels of MMP-mRNA were elevated in diabetic fibroblasts compared with healthy controls. At baseline, MMP-2 protein levels were significantly increased in the fibroblast of diabetic patients (P=.019). For MMP-9, a trend towards higher levels (P=.3) was found. After incubation with PDGF, a significant reduction of MMP-9 (P=.01) and MMP-13 (P=.04) was found. Analysis of cytokine release in cell culture supernatant showed elevated levels of interleukin (IL)-8 at baseline conditions. MMP-1 and MMP-2 levels in the supernatant were concentration-dependently reduced.

CONCLUSIONS

This study, for the first time, demonstrates elevated MMPs in cultivated fibroblasts (derived from intact skin and not from an open wound) of diabetic patients compared with healthy controls under in vitro conditions. Therefore, our data support the hypothesis of alterations of wound healing in diabetic patients on the cellular level, reflecting the systemic character of the disease.

Conjugative plasmid DNA transfer in Helicobacter pylori mediated by chromosomally encoded relaxase and TraG-like proteins

One of the striking characteristics of Helicobacter pylori is the extensive genetic diversity among clinical isolates. This diversity has been attributed to an elevated mutation rate, impaired DNA repair, DNA transfer and frequent recombination events. Plasmids have also been identified in H. pylori but it remained unknown whether conjugation can contribute to DNA transfer between clinical isolates. To examine whether H. pylori possesses intrinsic capability for conjugative plasmid transfer, shuttle vectors were introduced into H. pylori containing an oriT sequence of the conjugative IncPalpha plasmid RP4 but no mobilization (mob) genes. It was shown that these vectors could stably replicate and be mobilized among clinical H. pylori strains. It was also demonstrated that traG and relaxase (rlx) homologues carried on the H. pylori chromosome were important for plasmid transfer. Primer extension studies and mutagenesis further confirmed that the relaxase homologue rlx1 in H. pylori encodes a functional enzyme capable of acting on the RP4 oriT. Furthermore, the findings of this study indicate that traG and rlx1 act independently of the previously described type IV secretion systems, including that encoded by the cag pathogenicity island and the comB transformation apparatus, in mediating conjugative plasmid DNA transfer between H. pylori strains.

Peroxisome-proliferator-activated receptor-gamma agonists inhibit the release of proinflammatory cytokines from RSV-infected epithelial cells

The epithelial cells of the airways are the target cells for respiratory syncytial virus (RSV) infection and the site of the majority of the inflammation associated with the disease. Recently, peroxisome-proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor superfamily, has been shown to possess anti-inflammatory properties. Therefore, we investigated the role of PPARgamma agonists (15d-PGJ(2), ciglitazone and troglitazone) on the synthesis of RSV-induced cytokine release from RSV-infected human lung epithelial cells (A549). We observed that all PPARgamma ligands inhibited dose-dependently the release of TNF-alpha, GM-CSF, IL-1alpha, IL-6 and the chemokines CXCL8 (IL-8) and CCL5 (RANTES) from RSV-infected A549 cells. Concomitantly, the PPARgamma ligands diminished the cellular amount of mRNA encoding for IL-6, CXCL8 and CCL5 and the RSV-induced binding activity of the transcription factors NF-kappaB (p65/p50) and AP-1 (c-fos), respectively. Our data presented herein suggest a potential application of PPARgamma ligands in the anti-inflammatory treatment of RSV infection.

Intra- and interpatient variability of the hsp65 and 16S-23S intergenic gene region in Mycobacterium abscessus strains from patients with cystic fibrosis

To establish the exact pathogenic role of Mycobacterium abscessus in cystic fibrosis (CF), molecular tests are required for accurate identification. Forty-eight M. abscessus isolates from seven patients with CF were analyzed by sequence analysis for sequence variants within the hsp65 gene and the 16S-23S intergenic sequence (ITS). We detected two different hsp65 genes and correspondingly two ITS sequevars belonging to M. abscessus type I and type II.

Interplay of bacterial toxins with host defence: molecular mechanisms of immunomodulatory signalling

Mucosal surfaces are protected by a first line of defence termed the innate immune system, which controls the resident microflora to effectively prevent microbial diseases. Inflammatory processes are activated as a consequence of a complex interplay between microbes and host target cells. Many bacterial pathogens have developed mechanisms to avoid host recognition. Some are even able to exploit the immune response through sophisticated interactions with the host signalling cascades in order to increase their replication and propagation. While in the past major emphasis on bacterial protein toxins was directed towards their cytotoxic role, it is increasingly evident that toxins can also modulate various cellular functions at non-cytolytic concentrations. Here, we review important aspects on the molecular mechanisms of immunomodulatory interference by bacterial toxins, with emphasis on the signalling induced in the intestinal epithelium.

Respiratory syncytial virus infection of human lung endothelial cells enhances selectively intercellular adhesion molecule-1 expression

Respiratory syncytial virus (RSV) is worldwide the most frequent cause of bronchiolitis and pneumonia in infants requiring hospitalization. In the present study, we supply evidence that human lung microvascular endothelial cells, human pulmonary lung aorta endothelial cells, and HUVEC are target cells for productive RSV infection. All three RSV-infected endothelial cell types showed an enhanced cell surface expression of ICAM-1 (CD54), which increased in a time- and RSV-dose-dependent manner. By using noninfectious RSV particles we verified that replication of RSV is a prerequisite for the increase of ICAM-1 cell surface expression. The up-regulated ICAM-1 expression pattern correlated with an increased cellular ICAM-1 mRNA amount. In contrast to ICAM-1, a de novo expression of VCAM-1 (CD106) was only observed on RSV-infected HUVEC. Neither P-selectin (CD62P) nor E-selectin (CD62E) was up-regulated by RSV on human endothelial cells. Additional experiments performed with neutralizing Abs specific for IL-1alpha, IL-1beta, IL-6, and TNF-alpha, respectively, excluded an autocrine mechanism responsible for the observed ICAM-1 up-regulation. The virus-induced ICAM-1 up-regulation was dependent on protein kinase C and A, PI3K, and p38 MAPK activity. Adhesion experiments using polymorphonuclear neutrophil granulocytes (PMN) verified an increased ICAM-1-dependent adhesion rate of PMN cocultured with RSV-infected endothelial cells. Furthermore, the increased adhesiveness resulted in an enhanced transmigration rate of PMN. Our in vitro data suggest that human lung endothelial cells are target cells for RSV infection and that ICAM-1 up-regulated on RSV-infected endothelial cells might contribute to the enhanced accumulation of PMN into the bronchoalveolar space.

Gene transfer of tissue inhibitor of metalloproteinases-3 reverses the inhibitory effects of TNF-alpha on Fas-induced apoptosis in rheumatoid arthritis synovial fibroblasts

Apart from counteracting matrix metalloproteinases, tissue inhibitor of metalloproteinases-3 (TIMP-3) has proapoptotic properties. These features have been attributed to the inhibition of metalloproteinases involved in the shedding of cell surface receptors such as the TNFR. However, little is known about effects of TIMP-3 in cells that are not susceptible to apoptosis by TNF-alpha. In this study, we report that gene transfer of TIMP-3 into human rheumatoid arthritis synovial fibroblasts and MRC-5 human fetal lung fibroblasts facilitates apoptosis and completely reverses the apoptosis-inhibiting effects of TNF-alpha. Although TNF-alpha inhibits Fas/CD95-induced apoptosis in untransfected and mock-transfected cells, fibroblasts ectopically expressing TIMP-3 are sensitized most strongly to Fas/CD95-mediated cell death by TNF-alpha. Neither synthetic MMP inhibitors nor glycosylated bioactive TIMP-3 are able to achieve these effects. Gene transfer of TIMP-3 inhibits the TNF-alpha-induced activation of NF-kappaB in rheumatoid arthritis synovial fibroblasts and reduces the up-regulation of soluble Fas/CD95 by TNF-alpha, but has no effects on the cell surface expression of Fas. Collectively, our data demonstrate that intracellularly produced TIMP-3 not only induces apoptosis, but also modulates the apoptosis-inhibiting effects of TNF-alpha in human rheumatoid arthritis synovial fibroblast-like cells. Thus, our findings may stimulate further studies on the therapeutic potential of gene transfer strategies with TIMP-3.