Neutrophil chemotaxis induced by anaerobic bacteria isolated from necrotic dental pulps

Microorganisms in periradicular tissues: Do they exist? A perennial controversy

There is no greater association between the basic science and the practice of endodontics than that of microbiology. One of the strongest factors contributing to the controversies often encountered in the endodontic field is the lack of understanding that the disease processes of the pulp and periradicular tissues generally have a microbiological etiology. The vast majority of diseases of dental pulp and periradicular tissues are associated with microorganisms. After the microbial invasion of these tissues, the host responds with both nonspecific inflammatory responses and with specific immunologic responses to encounter such infections. The aim of this study is to fill the gaps in our knowledge regarding the role of microorganisms in endodontics and to discuss in depth whether their presence in periradicular lesions is a myth or a reality. An electronic search was carried out on PubMed database (custom range of almost 50 years) and Google using specific keywords and phrases. Inclusion and exclusion criteria were specified and around 50 articles were found suitable for inclusion. Full text of all the articles was retrieved and studied. Appropriate data were extracted and pooled and finally synthesized. It is important to understand the close relationship between the presence of microorganisms and endodontic disease process to develop an effective rationale for treatment.

Pathogenic synergy: mixed intra-abdominal infections

In this article we review our researches into the pathogenesis of mixed infections. These may conveniently be divided into in vitro and in vivo studies. In vitro we confirmed that interference with the killing of aerobes by polymorphonuclear leucocytes (PMN's) is a property of the Bacteroides strains tested and appears to depend on competition for opsonins i.e. complement factors. Further studies are in progress to define which complement factors and which bacterial structures are involved. The influence of B. fragilis on chemotaxis has also been studied. Our preliminary data suggest that B. fragilis is itself poorly chemotactic and reduces the chemoattractivity of Proteus mirabilis. This observation is surprising when we consider that abscess formation is the hall-mark of B. fragilis infections and needs clarification. In vivo we have developed a skin infection model in mice which is economical and gives reproducible and quantitative results. In this model we have demonstrated pathogenic synergy between Escherichia coli and B. fragilis. Further studies are planned to assess the role of complement and bacterial factors in this in vivo synergy.

Isolation of a major cell envelope protein from Fusobacterium nucleatum

A major, heat-modifiable cell envelope protein was identified in Fusobacterium nucleatum FDC 364 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This protein, designated HM-1, had apparent molecular weights of 38,500 and 50,000 when heated in sodium dodecyl sulfate at 50 and 100 degrees C, respectively. Whole cells were labeled with 125I, and the results suggested that the HM-1 protein may be exposed on the bacterial surface. The HM-1 protein was isolated in association with the peptidoglycan by extraction of whole cells or cell envelopes with 2% sodium dodecyl sulfate at 55 degrees C. Heating the peptidoglycan-HM-1 protein complex in the detergent at 100 degrees C resulted in the quantitative release of the protein. Isoelectric focusing experiments and amino acid analysis revealed that the HM-1 protein had a basic character and was moderately hydrophilic. Various strains of F. nucleatum as well as three oral fusiform isolates contained a serologically related protein. The abundance and location of the HM-1 protein in F. nucleatum suggest that it has the potential to participate in cell surface-related interactions of this bacterium.