Jan Turna

On the physiology and pathophysiology of antimicrobial peptides.

Antimicrobial peptides (AMP) are a heterogeneous group of molecules involved in the nonspecific immune responses of a variety of organisms ranging from prokaryotes to mammals, including humans. AMP have various physical and biological properties, yet the most common feature is their antimicrobial effect. The majority of AMP disrupt the integrity of microbial cells by 1 of 3 known mechanisms—the barrel-stave pore model, the thoroidal pore model, or the carpet model. Results of growing numbers of descriptive and experimental studies show that altered expression of AMP in various tissues is important in the pathogenesis of several gastrointestinal, respiratory, and other diseases. We discuss novel approaches and strategies to further improve the promising future of therapeutic applications of AMP. The spread of antibiotic resistance increases the importance of developing a clinical role for AMP.

Evaluation of different PCR-based approaches for the identification and typing of environmental enterococci

The aim of the work was the evaluation of different PCR-based methods to found an appropriate identification and typing strategy for environmental enterococci. Environmental enterococci were isolated mainly from surface- and waste-waters. Species identification was provided by combination of phenotypic (Micronaut System, Merlin) and molecular detection methods (fluorescent ITS-PCR, ddl-PCR, REP-PCR, AFLP). Very similar results were observed among molecular methods, however several discrepancies were recognized during comparison of molecular and biochemical identification. Seven enterococcal species (E. faecium, E. hirae, E. casseliflavus, E. mundtii, E. faecalis, E. durans and E. gallinarum) were identified within 166 environmental isolates. The results obtained in this work attest the importance of PCR-based methods for identification and typing of environmental enterococci. The fluorescent ITS-PCR (fITS-PCR) showed the best results in order to identify the enterococci strains, the method used the automated capillary electrophoresis to separate the PCR products in a very rapid and precise way. The AFLP method was suitable to identify and characterize the isolates, while the REP-PCR can be used for species identification.

In vivo andin vitro cloning and phenotype characterization of tellurite resistance determinant conferred by plasmid pTE53 of a clinical isolate ofEscherichia coli

A determinant encoding resistance against potassium tellurite (Ter) was discovered in a clinical isolate ofEscherichia coli strain KL53. The strain formed typical black colonies on solid LB medium with tellurite. The determinant was located on a large conjugative plasmid designated pTE53. Electron-dense particles were observed in cells harboring pTE53 by electron microscopy. X-Ray identification analysis identified these deposits as elemental tellurium and X-ray diffraction analysis showed patterns typical of crystalline structures. Comparison with JCPDS 4-0554 (Joint Committee on Powder Diffraction Standards) reference data confirmed that these crystals were pure tellurium crystals. In common with other characterized Ter determinants, accumulation studies with radioactively labeled tellurite showed that reduced uptake of tellurite did not contribute to the resistance mechanism. Tellurite accumulation rates forE. coli strain AB1157 harboring pTE53 were twice higher than for the plasmid-free host strain. In addition, no efflux mechanism was detected. The potassium tellurite resistance determinant of plasmid pTE53 was cloned using bothin vitro andin vivo techniques in low-copy-number vectors pACYC184 and mini-Mu derivative pPR46. Cloning of the functional Ter determinant into high-copy cloning vectors pTZ19R and mini-Mu derivatives pBEf and pJT2 was not successful. Duringin vivo cloning experiments, clones with unusual “white colony” phenotypes were found on solid LB with tellurite. All these clones were Mucts62 lysogens. Their tellurite resistance levels were in the same order as the wild type strains. Clones with the “white” phenotype had a 3.6 times lower content of tellurium than the tellurite-reducing strain. Transformation of a “white” mutant with a recombinant pACYC184 based Ter plasmid did not change the phenotype. However, when one clone was cured from Mucts62 the “white” phenotype reverted to the wild-type “black” phenotype. It was suggested that the “white” phenotype was the result of an insertional inactivation of an unknown chromosomal gene by Mucts62, which reduced the tellurite uptake.

Salmonella-mediated gene therapy in experimental colitis in mice.

Bacterial gene therapy – bactofection is a simple and effective method to deliver plasmid DNA into target tissue. We hypothesize that oral in vivo bactofection can be an interesting approach to influence the course of inflammatory bowel diseases. The aim of this study was to prove the effects of antioxidative and anti-inflammatory bactofection in dextran sulfate sodium (DSS)-treated mice. Attenuated bacteria Salmonella Typhimurium SL7207 carrying plasmids with genes encoding Cu-Zn superoxide dismutase and an N-terminal deletion mutant of monocyte chemoattractant protein-1 were prepared. Male Balb/c mice had ad libitum access to 1% DSS solution in drinking water during 10 days (mild model of colitis). The animals were daily fed with 200 Mio bacteria via gastric gavage during the experiment. Fecal consistency, clinical status, food and water intake were monitored. After 10 days samples were taken and markers of oxidative stress and inflammatory cytokine levels were measured. Colonic tissue was scored histologically by a blinded investigator. DSS treatment significantly increased the levels of inflammatory cytokines and malondialdehyde as a marker of lipoperoxidation in the colon. Anti-inflammatory gene therapy improved the total antioxidative capacity. In comparison with the untreated group, bacterial gene therapy lowered the histological colitis score. Salmonella-mediated antioxidative and anti-inflammatory gene therapy alleviated colitis in mice. The effect seems to be mediated by increased antioxidative status. Further studies will show whether recombinant probiotics expressing therapeutic gene might be used for the therapy of inflammatory bowel diseases.

PCR-based methods for identification of Enterococcus species.

Two DNA-based techniques were used for species identification of enterococci.PvuII digestion of the genus-specific PCR product yielded four different restriction profiles among 20 enterococcal species; one of them was species-specific forE. faecium. In the second case, 32 reference strains belonging to 20 enterococcal species were divided to 12 groups by amplification of internal transcribed spacer of rRNA operon. Interspecies and some intraspecies profile variability was determined. Both methods gave similar results.

Phage therapy of Cronobacter-induced urinary tract infection in mice

BACKGROUND Cronobacter spp. is an opportunistic pathogen causing rare but dangerous cases of meningitis, sepsis and urinary tract infection. Phage therapy overcomes antibiotic resistance and represents an alternative approach to standard antimicrobial treatment. There are no published studies on the use of phages against Cronobacter spp. in vivo. The aim of our study was to prove the effects of isolated Cronobacter-specific phages on renal colonization in a model of urinary tract infection in mice. MATERIAL/METHODS Urinary tract infection was induced by transurethral application of Cronobacter turicensis (1011 CFU/ml). Simultaneously, isolated Cronobacter-specific phages were administered intraperitoneally (1011 PFU/ml). After 24 hours, kidneys and bladder were collected and used for cultivation and analysis of gene expression and oxidative stress markers. RESULTS Phage therapy reduced the number of Cronobacter colonies in the kidney by 70%. Higher levels of malondialdehyde were reduced by phage therapy without affecting the antioxidant status. The expression of pro-inflammatory cytokines tumor necrosis factor-alpha and monocyte chemoattractant protein-1 increased by the infection and was attenuated by phage therapy. CONCLUSIONS Phage therapy proved effective in the prevention of ascending renal infection in a murine model of urinary tract infection. Long-term effects and safety of the treatment are currently unknown. Further studies should test phage therapy in other Cronobacter infection models.

Analysis of the tellurite resistance determinant on the pNT3B derivative of the pTE53 plasmid from uropathogenic Escherichia coli.

We have found and sequenced a significant part of the previously described tellurite resistance determinant on mini-Mu derivative pPR46, named pNT3B, originally cloned from a large conjugative plasmid pTE53, found in Escherichia coli. This plasmid contains genes essential for tellurite resistance, together with the protective region bearing genes terX, Y, W, and the conserved spacing region bearing several ORFs of unknown function. Computer analysis of obtained sequence revealed a close similarity to the formerly described ter operons found on the Serratia marcescens plasmid R478 and the chromosome of Escherichia coli O157:H7. This finding confirms the presence of a whole region on the large conjugative plasmid that pTE53 originated from a uropathogenic E. coli strain, and suggests its possible role in horizontal gene transfer, resulting in the development of new pathogenic E. coli strains.

Complex phenotypes blur conventional borders between Say-Barber-Biesecker-Young-Simpson syndrome and genitopatellar syndrome.

Say–Barber–Biesecker–Young–Simpson syndrome (SBBYSS) and genitopatellar syndrome (GTPTS) are clinically similar disorders with some overlapping features. Although they are currently considered to be distinct clinical entities, both were found to be caused by de novo truncating sequence variants in the KAT6B (lysine acetyltransferase 6B) gene, strongly suggesting that they are allelic disorders. Herein, we report the clinical and genetic findings in a girl presenting with a serious multiple congenital anomaly syndrome with phenotypic features overlapping both SBBYSS and GTPTS; pointing out that the clinical distinction between these disorders is not exact and there do exist patients, in whom conventional clinical classification is problematic. Genetic analyses revealed a truncating c.4592delA (p.Asn1531Thrfs*18) variant in the last KAT6B exon. Our findings support that phenotypes associated with typical KAT6B disease‐causing variants should be referred to as ‘KAT6B spectrum disorders’ or ‘KAT6B related disorders’, rather than their current SBBYSS and GTPTS classification.

On the origin of reactive oxygen species and antioxidative mechanisms in Enterococcus faecalis.

Abstract Enterococci cause serious infections due to a number of virulence factors and wide-spread antibiotic resistance. A molecular mechanism involved in the pathogenesis of enterococcal infections is oxidative stress. Enterococcus faecalis produces a variety of antioxidative enzymes involved in the oxidative stress response, a process that is regulated by several transcriptional regulators. In addition, direct production of free radicals derived from oxygen has been proved and hypothesized, respectively, to contribute to the pathogenesis of colorectal cancer and periodontitis. The understanding of molecular mechanisms behind the production of free radicals and the antioxidative status in E. faecalis might suggest new alternatives for the treatment of enterococcal infections and related diseases.

Proteomic analysis of the TerC interactome: Novel links to tellurite resistance and pathogenicity

The tellurite resistance gene operon (ter) is widely spread among bacterial species, particularly pathogenic species. The ter operon has been implicated in tellurite resistance, phage inhibition, colicine resistance, and pathogenicity. The TerC protein represents one of the key proteins in tellurite resistance and shows no significant homology to any protein of known function. So far, there is no experimental evidence for TerC interaction partners. In this study, proteomic-based methods, including blue native electrophoresis and co-immunoprecipitation combined with LC-MS/MS, have been used to identify TerC interaction partners and thus providing indirect evidence for tentative functions of TerC in Escherichia coli. An interactome has been constructed and robust physical interaction of integral membrane protein TerC with TerB, DctA, PspA, HslU, and RplK has been shown. The TerC-TerB complex appears to act as a central unit that may link different functional modules with biochemical activities of C4-dicarboxylate transport, inner membrane stress response (phage shock protein regulatory complex), ATPase/chaperone activity, and proteosynthesis. In previous reports, it was hypothesized that a transmembrane unit formed by TerC protein may interact with the TerD family, but herein neither TerD nor TerE proteins were identified as TerC complex components. We propose that TerD/TerE participates in tellurite resistance through TerC-independent action.