Matrix metalloproteinases (MMPs) are a host cell-derived proteolytic enzyme family which plays a major role in tissue-destructive inflammatory diseases such as periodontitis. The aim of the present study was to evaluate the inhibitory effect of chlorhexidine (CHX) on MMP-2 (gelatinase A), MMP-9 (gelatinase B), and MMP-8 (collagenase 2) activity. Heat-denatured type I collagen (gelatin) was incubated with pure human MMP-2 or -9 activated with p-aminophenylmercuric acetate (APMA), and the proteolytic degradation of gelatin was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Coomassie blue staining. The effect of CHX on MMP-8 activity was also studied with a cellular model addressing the ability of phorbol myristate acetate (PMA)-triggered human peripheral blood neutrophils (polymorphonuclear leukocytes [PMNs]) to degrade native type I collagen. CHX inhibited the activities of both gelatinases (A and B), but MMP-2 appeared to be more sensitive than MMP-9. Adding calcium chloride to the assay mixtures almost completely prevented the inhibition of MMP-9 activity by CHX, while the inhibition of MMP-2 activity could be reversed only when CHX was used at a low concentration. This observation suggests that CHX may act via a cation-chelating mechanism. CHX dose-dependently inhibited collagenolytic activity of MMP-8 released by PMA-triggered PMNs. MMP-8 without APMA activation was inhibited clearly more efficiently than APMA-activated MMP-8. Our study suggests that the direct inhibition of the MMPs’ activities by CHX may represent a new valuable effect of this antimicrobial agent and explains, at least in part, the beneficial effects of CHX in the treatment of periodontitis.

t(alis, and Bacteroiles gingih'alis. (Note: Whenever possible, and appropriate, we will use the most accepted taxonomic designation for the members of the genus Bacteroides. When first discussed, we will use the original designation by the authors followed by our interpretation of that species, using presently accepted taxonomic criteria.) In this review we have attempted to provide a useful synthesis of the literature relevant to the taxonomy, ultrastructure, physiology, serology, ecology, and pathogenicity of the asaccharolytic BPBs and to provide a perspective for their possible role in pathogenesis. OVERVIEW OF THE TAXONOMY In 1921, Oliver and Wherry (130) isolated a small anaerobic gram-negative rod from a variety of sites, including the oral cavity, urine, human feces, and respiratory tract, as well as from postsurgical infections. This rod, when grown on blood agar plates, produced colonies which were black in pigmentation. The pigment was considered to be melanin, and they named the culture Bacteriumn inelaninogenicumn. This bacterium was first described in the third edition of Bergev 's Manula(il of Determinative Bacteriology (7) as Hue-mo10p/uilus 1el(anlilogenicius because better growth was obtained on solid medium containing X and V growth factors characteristic of the members of the genus Haie,niophiluis.

Extracellular vesicles of Bacteroides gingivalis (type strain 33277) were isolated, and some of their biological activities were characterized. The vesicles were obtained from a 2-day culture after ammonium sulfate precipitation, differential centrifugation, and dialysis. When viewed by electron microscopy, vesicles of approximately 50 nm predominated. The results indicated that the enriched vesicle fraction had a high proteolytic activity against collagen, Azocoll, and N-a-benzoyl-DL-arginine p-nitroanilide. The polypeptide pattern of the vesicles was similar but not identical to that of the outer membrane. The membrane vesicles could also promote bacterial adherence between homologous cells as well as mediate attachment between two noncoaggregating bacterial species. These vesicles could thus play an important role in periodontal diseases by serving as a vehicle for toxins and various proteolytic enzymes, as well as being involved in adherence.

Bacteroides endodontalis, a newly described asaccharolytic black-pigmented Bacteroides, along with the other two recognized species of this group (B. gingivalis and B. asaccharolyticus) were studied for their susceptibility to various dyes and inhibitory agents and for some of their enzymatic activities to facilitate differentiating between them. Bacteroides endodontalis resembles B. asaccharolyticus physiologically except for the fact that the former cannot grow on media containing methylene blue, neutral red, or 3% sodium chloride, whereas B. asaccharolyticus can. On the other hand, B. endodontalis and B. gingivalis can grow on a medium containing Congo red while B. asaccharolyticus cannot.

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