Biomedical subjects

L Vitkov

Publications and source records attributed to L Vitkov.

6 recordsLinked to original sources

PubMed2005

Chlorhexidine-induced ultrastructural alterations in oral biofilm.

Chlorhexidine, the most used biocide in periodontology, alters the permeability of the bacterial cell membrane. However, the chlorhexidine-induced morphological alterations in the oral biofilm have not been studied. To examine the effects of chlorhexidine on oral biofilm on an electron microscopic level, gingival epithelial cells with attached biofilm were collected from 10 volunteers, subjected to 0.1% chlorhexidine for 1 or 5 min, stained with ruthenium red-tetroxide, and analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM visualized the bacterial glycocalyces and the biofilm matrix on the biofilm surface; however, no chlorhexidine-induced alterations were observed. TEM revealed loss of bacterial membrane integrity and fimbrial disintegration in a few bacteria. In the proximity of these alterations, a restricted matrix disintegration was also observed. However, the chlorhexidine-induced alterations only effected a minor part of the oral biofilm and did not cause its disintegration. These findings suggest the insufficient efficiency of chlorhexidine against oral biofilm.

Adolescent↗

PubMed2005

Bacterial internalization in periodontitis.

BACKGROUND: Bacterial invasion of host epithelial cells plays an important role in the pathogenesis of periodontitis; however, the exact mechanism of the invasion has not been investigated. METHODS: Pocket epithelium biopsies in periodontitis were analysed via scanning and transmission electron microscopy using ultra-histochemical staining with ruthenium red for glycocalyx visualization. RESULTS: We demonstrated that oral bacteria adhered via fimbriae-mediated adhesion only. The bacterial internalization in periodontitis was marked by the hallmark of the fimbriae-induced zipper mechanism--the phagocytic cup formation--but we found no sign of the trigger mechanism of internalization. In addition, we frequently observed apoptosis in the phagocytizing epithelial cells. CONCLUSION: Fimbriae-mediated adhesion is a prerequisite for bacterial invasion in periodontitis. This occurs by the fimbriae-induced zipper mechanism of internalization. As internalization induces apoptosis, the subsequent exfoliation might play a significant role in the clearance of periodontal pathogens.

Apoptosis↗

PubMed2005

Ex vivo gingival-biofilm consortia.

AIMS: To develop a protocol for harvesting ex vivo samples of gingival-biofilm consortia and to investigate their basic characteristics. METHODS AND RESULTS: Gingival epithelial cells with attached biofilm were collected from healthy subjects by taking a smear. The bacterial viability was estimated via the alteration of the membrane permeability and metabolic activity via the double/single-stranded nucleic acid ratio using a confocal laser-scanning microscope. Morphological analysis was performed by scanning and transmission electron microscopy. Additionally, microbiological estimations were made. The electron microscopy revealed fimbriae-mediated adhesion and the formation of a biofilm matrix. Most bacteria were viable and had a high metabolic activity. CONCLUSIONS: The presented study offers an easy to follow approach for harvesting samples of gingival-biofilm consortia. The latter differs considerably from the supragingival plaque in viability and zonal distribution. Related to free-living and in vitro-grown biofilms, the gingiva-associated biofilm revealed an atypically high metabolic activity. SIGNIFICANCE AND IMPACT OF THE STUDY: Biofilm fragments should possess the basic features of the entire gingiva-associated biofilm; which as yet cannot be simulated in vitro. Thus, samples of ex vivo gingival-biofilm consortia can be used to investigate the resistance of oral biofilms against antibiotics and biocides.

Bacteria↗

PubMed2002

Candida attachment to oral epithelium.

Inflamed oral mucosa biopsies from patients with thrush and high candidal density were observed in a transmission electron microscope (TEM) using ultra-histochemical staining with ruthenium red for glycocalyx visualization. Fimbriae comprising the glycocalyx and enabling yeast adhesion to epithelial cells were clearly visualized by ruthenium red. All internalized portions of the yeast walls were devoid of glycocalyx, indicating that the growing tips of the hyphae mechanically penetrated the host cells. The attachment of Candida occurred in two ways: by fimbria-mediated adhesion enabling colonization of the epithelial surface, and by invasion of the superficial epithelial cells via hyphae. As the interaction between adhesin receptors and adhesins stimulates the production of proinflammatory cytokines, Candida adhesion itself is assumed to induce mucosal inflammation.

Adult↗

PubMed2001

Fimbria-mediated bacterial adhesion to human oral epithelium.

Oral mucosa biopsies and saliva samples from 12 individuals were processed for transmission (TEM) and scanning (SEM) electron microscopy with and without ruthenium red staining. Additionally performed microbiological estimations indicated in all bacteriological samples a facultative pathogenic flora. SEM and TEM investigation showed a diverse bacterial flora attached to the mucosal surface. Fimbriae comprising the glycocalyx and enabling bacterial attachment to the epithelial cells could be clearly visualised by ruthenium red. The only mode of bacterial attachment to the oral mucosa detected in the present investigation was fimbria-mediated adhesion and co-adhesion. The fimbria-mediated adhesion enables the bacterial persistence in the oral cavity and is the first step in the bacterial colonisation process.

Adult↗

PubMed1999

Glycaemic disorders in denture stomatitis.

The prevalence of glycaemic disorders was investigated in native Upper-Austrians with Candida-associated denture stomatitis. All patients with previously unknown diabetes mellitus were subjected to an oral glucose tolerance test (OGTT) and as a result diabetes was diagnosed in 13% of the patients over 50 years of age. Thirty-five percent of all inspected patients over 50 years of age with denture stomatitis had type 2 diabetes mellitus and 36% had impaired glucose tolerance (IGT). The correlation between Candida-associated denture stomatitis and diabetes mellitus indicates a means for the early diagnosis of diabetes. Hyperglycaemia could not be a predisposition to denture stomatitis, since all patients with denture stomatitis in the age-bracket 26-50 years were without diabetes and only very few of the older patients with diabetes were obese. The correlation between Candica-associated denture stomatitis and type 2 diabetes mellitus could be traced back to a reduced resistance to Candida that preceded the diabetes.

Adult↗