Reassessment of minimal media reveals differences in growth among Porphyromonas gingivalis standard strains

Identification of nanaomycin A and its analogs by a newly established screening method for functional inhibitors of the type IX secretion system in Porphyromonas gingivalis

Porphyromonas gingivalis, a Gram-negative anaerobic bacterium, is a key pathogen in chronic periodontitis. P. gingivalis has a type IX secretion system (T9SS) that secretes highly hydrolytic proteinases called gingipains for obtaining peptides as an energy source. Although most T9SS-related proteins have been identified, no specific inhibitor of T9SS has been reported. To screen T9SS inhibitors, we focused on and characterized a minimal liquid medium called mC medium that contains milk casein as the sole protein source. We found that P. gingivalis wild-type strain ATCC 33277 caused cloudiness of mC medium without growth. In mC medium, an alkylating agent, iodoacetamide (IAM) that is an inhibitor of gingipains, and a protonophore, carbonyl cyanide 3-chlorophenylhydrazone (CCCP) that dissipates the proton motive force required for T9SS-mediated secretion, clearly inhibited the increase in turbidity. Moreover, neither the gingipain-null mutant nor the T9SS-deficient mutant caused mC medium cloudiness, suggesting that mC medium cloudiness is dependent on gingipain activity and T9SS. These results indicated that mC medium can be used to assess P. gingivalis gingipain activity and its functional T9SS. Using an assay system with mC medium, we discovered that OM-173αA and OM-173βA in the Ōmura Natural Compound Library and nanaomycin A were probable T9SS inhibitors. The compounds need to be further investigated as tools for analyzing T9SS and as potential therapeutic agents for periodontal disease.

Phylloquinone is preferable over menadione as a growth factor for Porphyromonas gingivalis

OBJECTIVES

Porphyromonas gingivalis is the etiological agent of chronic periodontitis. Menadione (vitamin K3) and phylloquinone (vitamin K1) are well-known growth factors for P. gingivalis, while menadione is widely used in growth experiments. Here we attempted to determine the differences in phylloquinone and menadione in P. gingivalis growth experiments, which have not been well studied to date.

METHODS

We investigated the effects of menadione and phylloquinone on the growth of two W83 strains and seven ATCC 33277 strains of P. gingivalis.

RESULTS

The ATCC 33277 strains grew well with phylloquinone at 2.9 μM in a complex medium (nutrient medium) and at 29 μM in two minimal media. In contrast, the W83 strains grew well without menadione or phylloquinone in three different culture media. Menadione at 2.9 μM, the conventionally used concentration for culturing P. gingivalis, supported the growth of most ATCC 33277 strains but inhibited the growth of some W83 and ATCC 33277 strains. Furthermore, menadione at 14.5 μM frequently inhibited cell growth, while phylloquinone at 145 μM promoted cell growth.

CONCLUSIONS

These results indicate that menadione and phylloquinone act as growth factors for ATCC 33277 but that menadione also can inhibit P. gingivalis growth. Thus, we propose that phylloquinone be used instead of menadione in P. gingivalis growth experiments requiring vitamin K.

The Efficacy of Minocycline Hydrochloride Combined with Multiple Antibiotic Paste in Elderly Patients with Chronic Periodontitis and Concomitant Pulp Lesions

Objective

To explore the efficacy of Minocycline hydrochloride combined with multiple antibiotic pastes in the treatment of chronic periodontitis with concomitant pulp lesions in elderly patients, as well as to analyze the changes in the levels of inflammatory markers.

Methods

100 patients suffering from chronic periodontitis with concomitant pulp lesions treated in our hospital from July 2018 to January 2020 were selected as the study subjects, and were randomly assigned to either an experimental group (n = 50) or a control group (n = 50). Patients in the experimental group were treated with Minocycline hydrochloride combined with multiple antibiotic pastes, while those in the control group were treated with Minocycline hydrochloride alone. The treatment efficacy in the two groups was then assessed using such factors as periodontal probing depth, dental plaque index, gingival index, periodontal attachment level, and the presence or absence of adverse effects. We also measured and compared the levels of inflammatory markers such as CRP, TNF-α, IL-1β, IL-5, IL-6, and others in both groups, before treatment, as well as after a week of treatment.

Results

There was a statistically significant difference in the treatment efficacy between the two groups (P < 0.05), with a higher treatment efficacy seen in the experimental group as compared to the control group. When compared to the control group, the experimental group had lower depths of periodontal probing, lower dental plaque indices, lower gingival indices, lower periodontal attachment levels, as well a significantly lower incidence of adverse reactions (P < 0.05). Before treatment, the levels of inflammatory markers such as CRP, TNF-α, IL-1β, IL-5, and IL-6 were elevated in both groups. After a week of treatment, there were reductions in the levels of inflammatory markers in both groups, but a more significant reduction was seen in the experimental than in the control group (P < 0.05).

Conclusion

Minocycline hydrochloride combined with various antibiotic pastes is more effective in the treatment of chronic periodontitis with concomitant pulp lesions in elderly patients than monotherapy with Minocycline hydrochloride alone.