Biomedical subjects

Andreas Podbielski

Publications and source records attributed to Andreas Podbielski.

24 records · Page 2Linked to original sources

PubMed2003

Additive antimicrobial activity of calcium hydroxide and chlorhexidine on common endodontic bacterial pathogens.

It is an established procedure to use calcium hydroxide [Ca(OH)2] as a therapeutic component to achieve sterilization of infected root canals. Unfortunately, some bacterial species are relatively resistant to Ca(OH)2 and are therefore associated with treatment failures. The objective of this study was to identify combinations of substances that improve antimicrobial activity. Ca(OH)2 was used as a suspension or as a component of gutta-percha points. Efficacy of killing was compared for (a) Ca(OH)2 suspension alone; (b) zinc oxide (ZnO) points alone; (c) Ca(OH)2 suspension combined with ZnO points; (d) Ca(OH)2 suspension combined with ZnO/chlorhexidine points; and (e) Ca(OH)2 points combined with ZnO/chlorhexidine points. Common endodontopathogenic bacterial species (Enterococcus faecalis, Fusobacterium nucleatum, Peptostreptococcus micros, Porphyromonas gingivalis, Streptococcus intermedius) in pure cultures served as target organisms. In the in vitro assay, the antibacterial substances and approximately 10(7) colony forming units of test bacteria were co-incubated in diluted human serum under growth conditions appropriate for the single bacterial species. Samples were taken on days 0, 1, 2, 4, 7, and 14 of incubation and viable counts determined. Gram-negative bacteria were sufficiently killed by Ca(OH)2 alone. Combinations with other agents did not improve the killing kinetics. For the inactivation of the Gram-positive bacteria P. micros and S. intermedius, a combination of Ca(OH)2 and ZnO/chlorhexidine, killed the bacteria faster than Ca(OH)2 alone. For E. faecalis, combining Ca(OH)2 suspension with ZnO/chlorhexidine points lead to a faster decrease in the overall number of viable bacteria, but no test conditions lead to the complete loss of culture viability. The results of this study support the use of a combination of Ca(OH)2 and chlorhexidine for faster eradication of P. micros and S. intermedius from infected root canals.

Anti-Infective Agents, Local↗

PubMed2002

Effect of the enamel matrix derivative Emdogain on the growth of periodontal pathogens in vitro.

OBJECTIVES: The aim of this study was to evaluate the effect of Emdogain (EMD), used for periodontal regeneration, on the growth of periodontal pathogens like Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia. For comparison, we studied the effect of EMD on several microbes associated with other oral diseases as well as its effect on non-pathogenic oral inhabitants. METHODS: Freshly prepared EMD or its vehicle propylene glycol alginate (PGA) alone were added to calibrated suspensions of microbes. As a control, imitating the post-surgical subgingival situation after flap closure, a serum/NaCl-solution mixture was used. Aliquots for growth assays were taken at scheduled times for calculation of colony-forming units and cell densities over an observation period of 24 h. Additionally, EMD was spotted onto selected, newly seeded microbes growing on agar plates to see if growth inhibition zones could be produced. RESULTS: The study revealed a marked inhibitory effect of EMD on the growth of the gram-negative periodontal pathogens. A. actinomycetemcomitans showed a significant decrease (p=0.012) in viable counts after 24 h when EMD was added at baseline. P. gingivalis and P. intermedia also showed a marked growth reduction in the presence of EMD and in these cultures no viable microbes could be detected anymore after 24 h. In contrast, no significant growth inhibition was observed in gram-positive bacteria. CONCLUSIONS: The results suggest that EMD has a positive effect on the composition of bacterial species in the post-surgical periodontal wound, by selectively restricting growth of periopathogens that could hamper the wound healing and reduce the outcome of regenerative procedures.

Aggregatibacter actinomycetemcomitans↗

PubMed2002

The role of the map protein in Staphylococcus aureus matrix protein and eukaryotic cell adherence.

The Staphylococcus aureus Map protein was proposed to act as a multifunctional adhesin. Using a map- mutant, a complemented strain and recombinant Map, we demonstrated that Map was not a conventional adhesin and was not involved in binding soluble extracellular matrix (ECM) proteins and in staphylococcal adherence to immobilized ECM proteins. However, Map provided a substrate for efficient and species-specific adherence of staphylococcal cells. This interaction was dose-dependent and was inhibited by specific anti-Map antibodies. According to ligand blots, two staphylococcal surface proteins of 82 and 50 kDa appeared to function as Map receptors. Adherence of the mutant to epithelial cells was reduced by 80% as compared to wild-type and complemented strains. However, adherence was not followed by a similar high rate of internalization. In conclusion, Map can function as an endogenous adhesion substrate in the attachment to plastic surfaces and eukaryotic cells via interaction with staphylococcal surface adhesins.

Bacterial Adhesion↗

PubMed2002

Group A streptococcal RofA-type global regulators exhibit a strain-specific genomic presence and regulation pattern.

RofA-like protein (RALP) type regulators have been shown to exist in different forms in group A streptococci (GAS) and to regulate the expression of important bacterial adhesins. This study shows that the vast majority of strains from different GAS M serotypes carried a rofA virulence regulator gene in their genome and that this gene could be detected in combination with other RALP genes and RALP-dependent adhesin genes in a strain-specific manner. The gene encoding the Nra regulator was predominantly found in opacity factor (OF)-negative serotypes. When analysing a rofA mutant in a serotype M2 strain, the strain specificity was also found in the positive and negative regulatory functions of RALP genes as well as in the type and number of virulence genes and functions controlled by the RALP genes. Of 17 virulence-associated genes tested, only one, the putative streptolysin S gene, was observed to be derepressed in RALP mutants of three different GAS serotype strains. This strain-specific variability of RALP regulon sizes is associated with different patterns of host cell attachment and internalization. In addition, RofA2 was shown to control expression of the ribosomal protein gene rpsL. As a consequence, it was demonstrated for the first time in streptococci that aminoglycoside resistance mediated by rpsL expression is apparently controlled by a virulence gene regulator.

Bacterial Adhesion↗

PubMed2002

Involvement of Lsp, a member of the LraI-lipoprotein family in Streptococcus pyogenes, in eukaryotic cell adhesion and internalization.

Three open reading frames (ORFs) were identified by a genome walking strategy in the genomes of serotype M49 group A streptococcal (GAS) strains CS101 and 591. These ORFs were located between the mga core regulon and the dipeptide permease operon. The deduced amino acid (aa) sequences contained signature sequences indicative of a lipoprotein (306 aa), an intracellular protein (823 aa), and a secreted peptide (66 aa), respectively. ORF1 (named Lsp for lipoprotein of Streptococcus pyogenes) and ORF2 exhibited a high degree of homology to the lmb/ORF2 genes of S. agalactiae (B. Spellerberg et al., Infect. Immun. 67:871-878, 1999). The three ORFs were found to be present in each of the 27 GAS serotype strains tested. Transcription analysis revealed a polycistronic lsp/ORF2 and a monocistronic ORF3 message that were detected primarily at the transition from exponential to stationary growth phase. lsp and ORF2 mutants, ORF2- and ORF3-luciferase reporter fusions, and antiserum against recombinant Lsp were produced to examine the biological role of these genes. Although high Zn(2+) and Cu(2+) ion concentrations decreased lsp operon expression, Lsp did not transport divalent cations as described for other LraI-type operons. The lsp mutant had reduced fibronectin binding. Although no direct binding of Lsp to fibronectin could be demonstrated, the lsp mutant showed decreased transcription of prtF2 encoding the fibronectin-binding protein F2. Both the lsp and ORF2 mutants showed decreased laminin binding. Adherence to and internalization into A549 epithelial cells of both mutants was reduced without a detectable effect on eukaryotic cell viability. The transcription of a number of virulence factors was altered in the lsp mutants and ORF2 mutants. The changes in laminin binding and eukaryotic cell internalization could be explained by changes in transcription of speB (cysteine protease) and/or the global regulators mga, csrRS, and nra.

Bacterial Proteins↗

PubMedDate not supplied

Antibacterial activity of restorative dental biomaterials in vitro.

This study investigated the antibacterial effects against Streptococcus mutans of a fine-hybrid resin composite (FH-RC; Tetric ceram), an ion-releasing resin composite (Ariston pHc), a self-curing glass ionomer cement (SC-GIC; Ketac-Molar), a resin-modified GIC (RM-GIC; Photac-Fil), and a zinc oxide eugenol cement (ZOE; IRM). In a novel assay, bacterial suspensions were placed into narrow 20-microl conical cavities within the materials. After 0, 4, 8, 24, 48 h and 1 week of incubation, the suspensions were removed from the restoratives and the numbers of viable bacteria were determined. After incubation periods of 8 h or more, all restorative materials except the FH-RC showed significant growth inhibition when compared with controls. The strongest antibacterial activity was observed with ZOE. The inhibitory effect of Ariston pHc was similar to that of the SC-GIC and the RM-GIC. In the second assay, growth inhibition was evaluated in liquid cultures by incubating eluates of the materials with suspensions of S. mutans. Bacterial growth was determined up to 6 h by measuring absorption at 600 nm. The most marked inhibitory effect was again observed with ZOE. The SC-GIC caused a significant inhibition at all time intervals but the FH-RC, the RM-GIC and Ariston pHc exhibited no significant antibacterial effects. It is recommended to employ more than one method for assessing the antibacterial potential of restorative materials. Long-term clinical trials are necessary to determine whether the antimicrobial effects of dental materials are able to reduce the risk of secondary caries formation.

Colony Count, Microbial↗