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H N Shah

Publications and source records attributed to H N Shah.

At least 37 records · Page 2Linked to original sources
PubMed1994

Species-specificity of monoclonal antibodies recognising Prevotella intermedia and Prevotella nigrescens.

Prevotella intermedia and Prevotella nigrescens are not easily distinguished, making it difficult to assess their roles in disease. This study examined the specificity of three monoclonal antibodies (mAbs) for these species. Differentiation between P. intermedia (13 isolates) and P. nigrescens (24 isolates) was by the electrophoretic mobility of their malate and glutamate dehydrogenase enzymes or by DNA homology grouping. All P. intermedia reacted strongly with mAb 40BI3.2.2 whereas P. nigrescens strains did not. Monoclonal antibodies 37BI6.1 and 39BI1.1.2 recognised all strains of both species but most P. nigrescens reacted weakly with mAb 39BI1.1.2. Monoclonal antibody 40BI3.2.2 therefore recognises an antigen specific for P. intermedia but not P. nigrescens and provides an easy and reliable means of distinguishing between these species. Three vaginal isolates identified biochemically as P. intermedia had enzymes with mobilities corresponding to neither P. intermedia nor P. nigrescens. These isolates were not recognised by mAbs 39BI1.1.2 or 40BI3.2.2 and may represent an undescribed taxon within this group of organisms.

Antibodies, Monoclonal↗
PubMed1994

Progress in the identification of nonmotile Bacteroidaceae from dental plaque.

Over the last decade, biochemical and chemical analyses have been used widely to study the intrageneric structure of Bacteroidaceae. New chromogenic substrates (e.g., naphthylamide-linked compounds) and fluorogenic substrates (e.g., 4-methylumbelliferyl or 7-amido-4-methyl-coumarin compounds) can be used to identify certain species within a few hours under aerobic conditions. Clarification of the taxonomy of many oral anaerobic species that are now considered important putative periodontal pathogens has permitted the development of panels of both polyclonal and monoclonal antibodies for their detection. Similarly, both DNA and RNA gene probes, derived through nucleic acid sequence analysis, have been constructed for several species; many such probes are now commercially available. In the long term, the application of these techniques will lead to a better understanding of the distribution, transmission, and ecological and clinical importance of many species that have hitherto remained poorly characterized.

Bacteroidaceae↗
PubMed1994

Characterization of Prevotella intermedia and Prevotella nigrescens isolates from periodontic and endodontic infections.

The occurrence and surface properties of prevotella intermedia and P. nigrescens in healthy sites and in periodontic and endodontic infections were studied among 73 strains, tentatively identified as P. intermedia. Fifteen strains were from necrotic root canal infections, 41 were from periodontal samples, and 17 isolates were obtained from healthy gingival sites. Identification of isolates as either P. intermedia or P. nigrescens was based on differences in malate and glutamate dehydrogenase electrophoretic mobilities which allowed unambiguous separation of P. intermedia and P. nigrescens. The majority of strains from periodontal samples were P. intermedia (29 of 41 strains). In endodontic samples only 4 out of 15 isolates were P. intermedia, while all except 1 of 17 strains from healthy gingival sites were identified as P. nigrescens. SDS-PAGE of whole cell proteins revealed 31 and 38 kDa proteins in P. nigrescens which were not detected in P. intermedia. Surface biotinylation of cells, followed by Western blotting and detection by alkaline phosphatase conjugated extravidin, showed strong staining of the 31 kDa protein in P. nigrescens indicating that this protein is located on the surface of the cell. Corresponding staining was not seen in P. intermedia. Fimbria-like projections were observed using electron microscopy of negatively-stained cells of P. nigrescens. The results show that P. intermedia and P. nigrescens may have different site specificities and surface properties and thus emphasize the need for accurate identification of these two species for the evaluation of their role in the pathogenesis of oral infections.

Bacterial Capsules↗
PubMed1993

Ecophysiology and taxonomy of Bacteroides and related taxa.

Recent taxonomic changes among Bacteroides and related species has led to a clearer insight into the site specificity of these taxa. Two recently described centers of variation within the genus Bacteroides sensu stricto and Prevotella intermedia are reported. However, considerable taxonomic problems still remain unresolved within this large and complex group of microorganisms. These bacteria are metabolically diverse, and this is reflected in their colonization sites. In the rumen, gastrointestinal tract, or the oral cavity, specific members of this group contribute significantly to the initial attack on both simple and complex carbohydrates, and by doing so, obtain carbon and energy for their survival. Depletion of carbohydrates from the milieu results in a gradual change in microbial activity to proteolysis. In some sites, such as the periodontal pocket, potent proteinases produced by species such as Porphyromonas gingivalis may facilitate degradation of available proteins to their constituent peptides and amino acids. These products are not only likely to affect the growth of these species, but must profoundly affect the nutrient network of this ecosystem.

Animals↗
PubMed1993

Measurement of electrical bioimpedance for studying utilization of amino acids and peptides by Porphyromonas gingivalis, Fusobacterium nucleatum, and Treponema denticola.

The growth response of Porphyromonas gingivalis, Fusobacterium nucleatum, and Treponema denticola to peptides (supplied as trypticase) and amino acids (supplied as casamino acids) was measured over 24 hours by monitoring changes in alternating-current conductivity at 37 degrees C. All species utilized peptides preferentially over amino acids. These results are consistent with those obtained previously with conventional growth-response experiments. The duration of the linear growth response to trypticase of P. gingivalis was 9.7 hours, whereas that of both F. nucleatum and T. denticola was > 24 hours. By contrast, there was more uniformity in the utilization of amino acids from the casamino acid mixture, which previously has been shown to be a poor growth substrate. Furthermore, subtle differences in growth patterns, such as the ability of F. nucleatum to metabolize its storage glycopolymers before utilizing amino acids, were clearly evident. The present method provides an excellent means of studying bacterial growth kinetics and delineating bacterial/substrate specificities of both synthetic and natural substrates.

Amino Acids↗
PubMed1992

Fusobacterium nucleatum subsp. fusiforme subsp. nov. and Fusobacterium nucleatum subsp. animalis subsp. nov. as additional subspecies within Fusobacterium nucleatum.

Using a variety of physiological, biochemical, and molecular systematic analyses, we have shown previously that there are four groups within the species Fusobacterium nucleatum. Two of these groups of strains correspond to the recently proposed taxa F. nucleatum subsp. nucleatum and F. nucleatum subsp. polymorphum. In this paper we show that the two remaining groups are distinct and formally propose that they should be recognized as F. nucleatum subsp. fusiforme (type strain, NCTC 11326) and F. nucleatum subsp. animalis (type strain, NCTC 12276). The tests which we used did not allow a full assessment of the status of F. nucleatum subsp. vincentii compared with F. nucleatum subsp. nucleatum.

Electrophoresis↗
PubMed1992

Biochemical and chemical studies on strains designated Prevotella intermedia and proposal of a new pigmented species, Prevotella nigrescens sp. nov.

A total of 31 strains of Prevotella intermedia were subjected to DNA-DNA hybridization and were characterized by performing physiological tests and by performing a multilocus enzyme analysis, using malate dehydrogenase and glutamate dehydrogenase. All of the strains assigned to P. intermedia fermented glucose and sucrose, hydrolyzed starch but not esculin, and produced indole, acetic, isobutyric, isovaleric, and succinic acids as metabolic end products. The results of DNA reassociation experiments performed with the reference probe permitted separation of the strains into two well-defined homology groups. In addition, strains with DNAs that hybridized with DNA from strain ATCC 25611T (T = type strain) had high levels of peptidase activity and cleaved lipid substrates (4-methylumbelliferyl laurate and 4-methylumbellifelyl elaidate). Multilocus enzyme electrophoresis revealed two electromorphic profiles, one characteristic of strain ATCC 25611T and the other characteristic of strain ATCC 33563T. We propose that a new species, Prevotella nigrescens, should be created for the genetically distinct group of strains that hybridized with strain ATCC 33563T. Strain ATCC 33563 is designated the type strain of P. nigrescens.

Bacterial Typing Techniques↗
PubMed1992

Evidence for independent molecular identity and functional interaction of the haemagglutinin and cysteine proteinase (gingivain) of Porphyromonas gingivalis.

The sequence of events involved in haemagglutination and lysis of erythrocytes by washed cells, vesicles and the culture supernate of Porphyromonas gingivalis strain W83 was monitored by 51Cr release and transmission electronmicroscopy. All preparations, except capsular material and lipopolysaccharide, caused haemagglutination and, by a slow process of attachment and specific attack on the surface structures of the red blood cells, produced minute pores and eventual leakage of cellular contents. N-acetylglucosamine, N-acetylgalactosamine and several other sugars such as glucose and sucrose had no effect on haemagglutination. Antiserum raised against a cloned haemagglutinin of P. gingivalis strain 381 inhibited the activity of strain W83 cells, vesicles and supernate. The antiserum-neutralised supernate lost 70-80% of its hydrolytic activity towards alpha-N-benzoyl-L-arginine-4-nitroanilide but the residual activity behaved in a manner similar to the native supernate in that it was completely inhibited by the addition of 2,2'-dipyridyl disulphide and was fully restored upon addition of a low-Mr mercaptan. Binding of the antiserum to the haemagglutinin epitope of P. gingivalis still permitted titration of the active centre cysteinyl thiol group of the proteinase. Purified gingivain caused lysis of erythrocytes and was not neutralised by antiserum to the haemagglutinin. These results suggest that, although the haemagglutinin and gingivain are probably separate molecules, they are closely associated on the outer membrane of P. gingivalis and may be functionally related.

2,2'-Dipyridyl↗
PubMed1992

Assessment of the relative cytotoxicity of Porphyromonas gingivalis cells, products, and components on human epithelial cell lines.

Established human cell lines derived from a transitional cell carcinoma (J82), a squamous carcinoma (SCaBER), and a normal urothelium (HCV-29) were used to assess the relative cytotoxicity and tissue specificity of putative virulence determinants of P. gingivalis W83. Intact cells of W83 had no effect on any of the cell lines, whereas disrupted cells caused extensive cytotoxicity particularly to monolayers of HCV-29 and J82. The purified cysteine proteinase, gingivain, caused marked disruption of the basement membrane of the SCaBER monolayers but had no cytotoxic effects. Use of the thiol-inhibitor, 2,2'-dipyridyl disulphide revealed that the effects observed with the vesicles and the culture supernatant were due to the presence of the cysteine proteinase. The attachment of vesicles to the SCaBER cells was evident in electron micrographs. Short-chain volatile fatty acids added in concentrations equivalent to those present in the culture supernatant had no effect on any of the cell lines tested. Culture supernatants obtained from high speed centrifugation (150,000 x g) showed no cytotoxic effects. This was in marked contrast to the supernatant obtained by lower sedimentation (18,000 x g), which damaged all monolayers tested. These results suggest that these cell lines are potentially useful for assessing putative virulence determinants of P. gingivalis and other periodontal pathogens.

2,2'-Dipyridyl↗