Minimal inhibitory concentrations of various antimicrobial agents for human oral anaerobic bacteria

Acetyleugenol from Acacia nilotica (L.) Exhibits a Strong Antibacterial Activity and Its Phenyl and Indole Analogues Show a Promising Anti-TB Potential Targeting PknE/B Protein Kinases

Acetyleugenol is a phytochemical compound with broad effects against infectious diseases and tumors. Here, we extracted, characterized, and elucidated the structure of acetyeugenol, for the first time, from the leaves of Acacia nilotica (L.)—a well-known medicinal plant. The broad antibacterial potential of acetyleugenol was first confirmed against seven bacterial clinical isolates, which reveal a strong activity against Proteus sp., Salmonella typhi, Staphylococcus aureus, and Streptococcus pneumonia with similar or better zone of inhibition comparing to that of the control amoxicillin. To further investigate its effect against Mycobacterium tuberculosis, acetyleugenol and its indole and phenyl analogues were subjected to molecular docking experiments against two potential tuberculosis drug targets—MtPknE and MtPknB Ser/Thr protein kinases. The results reveal that all of the analogs have improved docking scores compared to the acetyleugenol. The indole analogues EUG-1 and EUG-3 were more effective with better docking scores for MtPknE with −11.08 and −10.05 kcal/mol, respectively. Similar results were obtained for the MtPknB. In contrast, only the EUG-2 phenyl analogue has given rise to similar docking scores for both targets. This opens the door for further comprehensive studies on these acetyleugenol analogues with in vitro and in vivo experiments to validate and get more insights into their mechanisms of action.

Sustained Release of Minocycline From Minocycline-Calcium-Dextran Sulfate Complex Microparticles for Periodontitis Treatment

It is important to address the periodontitis-associated bacteria in the residual subgingival plaque after scaling and root planing to successfully treat periodontitis. In this study, we explored the possibility of exploiting the ion pairing/complexation of minocycline, Ca²⁺, and sulfate/sulfonate-bearing biopolymers to develop an intrapocket delivery system of minocycline as an adjunct to scaling and root planing. Minocycline-calcium-dextran sulfate complex microparticles were synthesized from minocycline, CaCl₂, and dextran sulfate. They were characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. An in vitro release study was conducted to evaluate the release kinetics of minocycline from these microparticles. Agar disk diffusion assays and biofilm-grown bacteria assays were used to assess antibacterial capability. High loading efficiency (96.98% ± 0.12%) and high loading content (44.69% ± 0.03%) for minocycline were observed for these complex microparticles. Mino-Ca-DS microparticles achieved sustained release of minocycline for at least 9 days at pH 7.4 and 18 days at pH 6.4 in phosphate-buffered saline, respectively. They also demonstrated potent antimicrobial effects against Streptococcus mutans and Aggregatibacter actinomycetemcomitans in agar disk diffusion and biofilm assays. These results suggested that the ion pairing/complexation of minocycline, Ca²⁺, and sulfonate/sulfate-bearing biopolymers can be exploited to develop complex microparticles as local delivery systems for periodontitis treatment.

Effect of azithromycin on a red complex polymicrobial biofilm

Azithromycin has recently gained popularity for the treatment of periodontal disease, despite sparse literature supporting efficiency in treating periodontal bacterial biofilms. The aim of this study was to evaluate the effect of azithromycin on biofilms comprised of Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia in comparison to an amoxicillin and metronidazole combination. P. gingivalis W50, T. denticola ATCC35405, and T. forsythia ATCC43037 grown under anaerobic conditions at 37°C were aliquoted into 96-well flat-bottom plates in different combinations with addition of azithromycin or amoxicillin + metronidazole at various concentrations. For the biofilm assay, the plates were incubated at 37°C anaerobically for 48 h, after which the biofilms were stained with crystal violet and measured for absorbance at AU₆₂₀. In this model, polymicrobial biofilms of P. gingivalis + T. denticola, P. gingivalis + T. forsythia, and T. denticola + T. forsythia were cultured. Combination of all three bacteria enhanced biofilm biomass. Azithromycin demonstrated a minimal biofilm inhibitory concentration (MBIC) of 10.6 mg/L, while the amoxicillin + metronidazole combination was more effective in inhibiting biofilm formation with a MBIC of 1.63 mg/L. Polymicrobial biofilm formation was demonstrated by combination of all three red complex bacteria. Azithromycin was ineffective in preventing biofilm formation within a clinically achievable concentration, whereas the combination of amoxicillin and metronidazole was more effective for this purpose.

Concentrations of amoxicillin and clindamycin in teeth following a single dose of oral medication

OBJECTIVES

The main purpose of this study is the detection of amoxicillin and clindamycin concentrations in teeth.

MATERIALS AND METHODS

Eleven patients received 2 g of amoxicillin, and 11 patients received 600 mg of clindamycin in a single dose of oral medication at least 60 min prior to tooth extraction due to systemic diseases. The concentrations were determined in crowns and roots separately using liquid chromatography-tandem mass spectrometry (LC-MS-MS).

RESULTS

Amoxicillin (13 samples) and clindamycin (12 samples) were detected in the samples of the root and crown preparations of the extracted teeth. The mean concentration of amoxicillin was 0.502 μg/g in the roots and 0.171 μg/g in the crowns. The mean concentration of clindamycin was 0.270 μg/g in the roots and 0.064 μg/g in the crowns.

CONCLUSIONS

A single dose of oral amoxicillin and clindamycin leads to concentrations of both antibiotics in teeth which exceed the minimal inhibition concentration of some oral bacteria.

CLINICAL RELEVANCE

The proof of antibacterial activity in dental hard tissue after oral single-dose application is new. The antimicrobial effect of amoxicillin and clindamycin concentrations in roots of teeth may be of clinical relevance to bacterial reinfection from dentinal tubules.

Effect of repeated local minocycline administration on periodontal healing following guided tissue regeneration

BACKGROUND

Infection after a periodontal surgical site has been prepared for guided tissue regeneration (GTR) is one of the common complications that can compromise healing. The purpose of this study was to assess the effect of repeated local antimicrobial therapy following GTR for improving clinical attachment gains, and to histologically evaluate the various cell populations and bacterial contamination of the retrieved expanded polytetrafluoroethylene membrane (ePTFE).

METHODS

Forty periodontal intrabony defects in 40 patients were treated by a flap procedure that included the use of ePTFE membranes to allow GTR. Patients were randomly assigned to 2 treatment groups: 20 patients were treated with the ePTFE alone (control group), and the other 20 were treated with the ePTFE combined with the administration of a weekly repeated local application of minocycline ointment for 8 weeks after membrane placement (test group). The membranes were retrieved 6 weeks after the initial surgery and sectioned serially in a coronal-apical plane. The sections were then divided into 9 fields and examined by light microscopy for the presence of inflammatory cells and oral bacteria. Clinical measurements were taken at the time of baseline examination and at a 6-month follow-up examination after removal of the ePTFE.

RESULTS

At the 6-month follow-up examination, control and test groups showed significant improvement; i.e., reduction in the probing depth and increased clinical attachment gain compared with the values at the baseline examination. However, the mean clinical attachment gain of the test group (3.0+/-0.3 mm) was significantly (P = 0.03) greater than that of the control group (2.0+/-0.5 mm). Histologically, the total number of the cells of both groups was similar. In both groups, mononuclear cells were dominant and fibroblasts, neutrophils, and plasma cells were rarely encountered. There was a tendency for the number of macrophages to be somewhat higher in the control group. The total number of bacteria in the test group was significantly less than that in the control group. The number of bacteria in both control and test groups decreased toward the apical portion.

CONCLUSIONS

In the present study, clinical attachment gain of intrabony defects following GTR was favorable with repeated local administration of minocycline ointment. However, a complete microbial eradication was not achieved.

Human periodontal ligament fibroblast behavior on chemically conditioned dentine: an in vitro study

BACKGROUND

Chemical root conditioning is widely used in an attempt to improve the outcome of regenerative periodontal surgery, but its effect on connective tissue cell proliferation and biosynthetic activity has been poorly studied. The goal of the present study was to test in vitro the consequences of conditioning human dentine by citric acid or minocycline on the behavior of attached human periodontal ligament (HPDL) cells in terms of proliferation, protein synthesis and morphological appearance.

METHODS

HPDL cells were seeded on powdered human dentine, either untreated or conditioned for 3 minutes with 3% citric acid or 2.5% minocycline HCI. Scanning (SEM) and transmission (TEM) electron microscopic observations were performed, and 3H-thymidine and 3H-proline incorporation tests were used to evaluate the proliferative and the biosynthetic activities.

RESULTS

Cell spreading was already evident and the penetration of cytoplasmic processes into dentinal tubules were frequently observed on all dentine types after 2 hours of attachment. After 24 hours of incubation, citric acid conditioning promoted an intense spreading of the cells, while minocycline HCI conditioning induced the formation of a dense feltwork of cellular processes. HPDL fibrolasts adherent to both types of surface-conditioned dentine exhibited a significantly higher rate of proliferation (P<0.01) as well as a significantly higher level of total protein and of collagen synthesis (P<0.01) than on untreated dentine.

CONCLUSIONS

These data suggest that during periodontal surgery a conditioning of the root surface by citric acid or by minocycline HCI could promote the attachment, the proliferation, and the biosynthetic activity of HDPL, prerequisites to periodontal regeneration.

In vitro stimulation of human gingival epithelial cell attachment to dentin by surface conditioning

BACKGROUND

Chemical root conditioning is widely used to improve the outcome of regenerative periodontal therapies by favoring the attachment of the regenerated periodontal structures. Although the effect of root conditioning on periodontal mesenchymal cells is well documented, very little is known about its potential effect on the re-formation of the junctional epithelium, a crucial event for the protection of the wound. The goal of the present study was to test in vitro the consequences of dentin conditioning with citric acid or minocycline on the attachment kinetics and morphology of human gingival keratinocytes (HGK).

METHODS

The attachment kinetics of HGK to samples of powdered human dentin (particle size 44 to 76 microm) were examined by use of 3H-labeled cells. The morphology of attached epithelial cells was then determined by scanning electron microscopy (SEM).

RESULTS

When the initial adhesion kinetics of cells on untreated dentin were tested, the percentage of attached HGK proved to be dependent on the number of plated cells and the time of incubation (from 0 to 12 hours). Conditioning the dentin by 3% citric acid or by minocycline-HCl (at 0.01, 0.1, or 2.5%) significantly increased (P <0.005) keratinocyte attachment beyond 6 hours, without notable differences between the 2 substances at any concentration. The attachment kinetics of HGK preincubated for 24 hours by 10 microg/ml minocyline-HCl on untreated dentin was found to be similar to that observed for non-preincubated cells. These results are in agreement with the SEM observations: indeed, the surface conditioning of dentin significantly modified the morphology of attached HGK, whereas the preincubation of these cells with minocyline-HCl did not.

CONCLUSIONS

These results suggest that minocycline-HCl does not exert a direct effect on human gingival epithelial cells. In contrast, conditioning the dentin by citric acid or by minocycline stimulates the attachment of HGK, which could lead to a rapid periodontal healing by favoring the re-formation of a junctional epithelium.

A 15-month evaluation of the effects of repeated subgingival minocycline in chronic adult periodontitis

BACKGROUND

A double-blind, randomized, parallel, comparative study was designed to evaluate the long-term safety and efficacy of subgingivally administered minocycline ointment versus a vehicle control.

METHODS

One hundred four patients (104) with moderate to severe adult periodontitis (34 to 64 years of age; mean 46 years) were enrolled in the study. Following scaling and root planing, patients were randomized to receive either 2% minocycline ointment or a matched vehicle control. Study medication was administered directly into the periodontal pocket with a specially designed, graduated, disposable applicator at baseline; week 2; and at months 1, 3, 6, 9, and 12. Scaling and root planing was repeated at months 6 and 12. Standard clinical variables (including probing depth and attachment level) were evaluated at baseline and at months 1, 3, 6, 9, 12, and 15. Microbiological sampling using DNA probes was done at baseline; at week 2; and at months 1, 3, 6, 9, 12, and 15.

RESULTS

Both treatment groups showed significant and clinically relevant reductions in the numbers of each of the 7 microorganisms measured during the entire 15-month study period. When differences were detected, sites treated with minocycline ointment always produced statistically significantly greater reductions than sites which received the vehicle control. For initial pockets > or =5 mm, a mean reduction in probing depth of 1.9 mm was seen in the test sites, versus 1.2 mm in the control sites. Sites with a baseline probing depth > or =7 mm and bleeding index >2 showed an average of 2.5 mm reduction with minocycline versus 1.5 mm with the vehicle. Gains in attachment (0.9 mm and 1.1 mm) were observed in minocycline-treated sites, with baseline probing depth > or =5 mm and > or =7 mm, respectively, compared with 0.5 mm and 0.7 mm gain at control sites. Subgingival administration of minocycline ointment was well tolerated.

CONCLUSIONS

Overall, the results demonstrate that repeated subgingival administration of minocycline ointment in the treatment of adult periodontitis is safe and leads to significant adjunctive improvement after subgingival instrumentation in both clinical and microbiologic variables over a 15-month period.

In vitro modulation of human gingival epithelial cell attachment and migration by minocycline-HCL

Although the influence of tetracyclines on periodontal connective tissue cells has been the topic of many in vitro and in vivo studies, data regarding their effects on gingival epithelial cells are scarce. The present in vitro study was designed to examine the influence of minocycline, a semi-synthetic analog of tetracycline, on human gingival keratinocyte (HGK) attachment and migration. Attachment tests were performed with HGK prelabeled by tritiated amino-acids. Increasing concentrations of minocycline (10, 50, 100 micrograms/ml) in the medium produced no significant modification of cell adhesion kinetics compared to control conditions, except for 100 micrograms/ml which statistically significantly (p < 0.05) reduced the number of attached cells beyond 6 h. A 24-h cell preincubation in 10 micrograms/ml of minocycline did not alter the kinetics of HGK attachment. Scanning electron microscopic observations of attached HGK showed that the presence of 10 micrograms/ml of minocycline in the "attachment medium" induced the production of multiple filopodial extensions. Migration tests in Boyden chambers for 40 h demonstrated that HGK preincubation for 24 h in a 10 micrograms/ml minocycline-HCl solution increased significantly (p < 0.005) cell migration towards a gradient of fetal calf serum. The presence of 10 micrograms/ml of minocycline in contact with the keratinocytes in the upper compartment of the migration chambers also produced a significant (p < 0.005) result. In contrast, the presence of minocycline in the lower compartments did not produce any chemoattractive effect. Within the limits of their significance, these results suggest that, at concentrations not beyond 50 micrograms/ml, minocycline could fasten the periodontal wound coverage by epithelial cells and allow the normal reformation of a junctional epithelium.

Evaluation of the long-term efficacy and safety of locally-applied minocycline in adult periodontitis patients

The objectives of the present study were to establish in a long-term investigation the safety as well as the clinical and microbiological efficacy of scaling and rootplaning combined with local application of 2% minocycline hydrochloride-gel versus placebo-gel in patients with moderate to severe chronic adult periodontitis. This was an 18 months, randomized, double-blind, parallel, comparative study, in which 20 healthy patients with moderate to severe chronic periodontitis participated. At baseline, all patients received professional oral hygiene-instruction and supra- and subgingival scaling and root planing. The minocycline-gel was applied subgingivally baseline, 2 weeks, 1, 3, 6, 9 and 12 months. Microbiological evaluation was carried out using DMDx to identify the following bacteria: Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans, Campylobacter rectus, Fusobacterium nucleatum and Treponema denticola. In addition standard microbiological techniques were used for the detection of P. gingivalis, P. intermedia, P. micros, A. actinomycetemcomitans, C. rectus, F. nucleatum, C. albicans and Enterobacteriaceae. Results showed a statistically significant improvement for all clinical parameters irrespective of the treatment modality. No differences were observed between test and control with regard to probing depth and attachment level. The DMDx data showed a significant reduction in both the numbers and the prevalence over the 15 months period, but no significant difference between groups. Culture data showed that at baseline two-third were positive for P. gingivalis and P. intermedia. Analysis over the 18 month period showed no significant difference between the two treatment modalities. C. albicans and Enterobacteriaceae were detected only in small proportions at each time interval in a limited number of patients. No adverse reactions were observed during the trial period. The present patient group responded favourably to scaling and rootplaning, but did not benefit from an effect of local of minocycline. Subgingival debridement in combination with oral hygiene instruction by itself has been shown to be effective. It remains to be studied whether local application of minocycline can be effective as an adjunct to mechanical therapy in sites that respond poorly to conventional treatment.

Antimicrobial susceptibility of periodontopathic bacteria associated with failing implants

The aim of this study was to examine the subgingival microflora associated with failing implants, and to determine their susceptibility to commonly used antibiotics in periodontal therapy and dental practice. Thirteen partially edentulous patients with 19 failing implants were selected. Clinical examination included probing depth, attachment level, gingival index, plaque index, and radiographic analyses. Two subgingival plaque samples were taken from each failing implant and analyzed for microbial composition. Fusobacterium nucleatum, Porphyromonas gingivalis, and Prevotella intermedia were the prevalent cultivable microflora. Antimicrobial susceptibility of isolates was determined by the agar dilution technique. Antibacterial activity of penicillin G, amoxicillin, amoxicillin-clavulanate, and the combination amoxicillin-metronidazole was significantly higher than with other antibiotics tested. These data indicated that the commonly-used antibiotics were highly effective against bacteria isolated around failing implants, which would suggest the use of these antibiotics to control peri-implant infections.

Evaluation of the E test for antimicrobial susceptibility testing of Porphyromonas gingivalis

The antimicrobial susceptibilities of 81 recent clinical Porphyromonas gingivalis isolates and two reference strains were determined by the E test, a new method, and were compared with the minimal inhibitory concentrations for these strains obtained by the reference agar dilution method on supplemented Brucella blood agar. The following agreements were obtained: benzylpenicillin 100%, ampicillin 96%, cefaclor 82%, cefuroxime 91%, erythromycin 93%, clindamycin 99%, tetracycline 66%, doxycycline 89%, metronidazole 77% and ciprofloxacin 77%. Very major discrepancies were observed with ciprofloxacin. This study indicates that the E test is an acceptable method to determine the susceptibility of P. gingivalis for most antimicrobials.

Subgingival minocycline hydrochloride ointment in moderate to severe chronic adult periodontitis: a randomized, double-blind, vehicle-controlled, multicenter study

The safety and efficacy of subgingivally-applied 2% minocycline ointment was evaluated in a randomized, double-blind study of 103 adults with moderate to severe periodontitis. Two groups were compared; one received the test minocycline ointment and the other a vehicle control. Both groups had scaling and root planing at baseline, after which the test or control ointments were applied with an applicator into the periodontal pockets at baseline, and at 2, 4, and 6 weeks. Assessment of clinical response was made by measuring probing depth and probing attachment level and gingival bleeding. These measurements were made at baseline prior to scaling and root planing, and at weeks 4 and 12. Microbiological assessment of the subgingival flora was carried out with DNA probes at baseline, and at weeks 2, 4, 6, and 12 to identify and quantify Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans. Subgingival minocycline ointment resulted in statistically significantly greater reduction of P. gingivalis at weeks 2, 4, 6, and 12; P. intermedia at weeks 2, 4, 6, and 12; and A. actinomycetemcomitans at weeks 6 and 12. Probing depth reductions were seen for both groups at weeks 4 and 12; however, this reduction was statistically significantly greater in subjects treated with minocycline ointment. Reduction in gingival index and probing attachment gain were seen in both groups, however, the differences between the groups were not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Microbial composition and pattern of antibiotic resistance in subgingival microbial samples from patients with refractory periodontitis

A series of 993 subgingival microbial samples sent to a diagnostic microbiology laboratory included 196 samples that could be identified as compatible with a clinical diagnosis of refractory or recurrent periodontitis. In descending order of prevalence the associated microbiota included Bacteroides forsythus (84%), spirochetes (83%), motile rods (76%), Fusobacterium species (68%), Porphyromonas gingivalis (63%), Campylobacter rectus (47%), Capnocytophaga species (38%), Prevotella intermedia (23%), Peptostreptococcus micros (18%), Actinobacillus actinomycetemcomitans (16%), Candida (14%), enteric rods (9%), Staphylococcus species, not including aureus (5.6%). Eikenella corrodens (3%), Staphylococcus aureus (1.5%), and Enterococcus species (< 1%). Antibiotic resistance to tetracycline, penicillin G, or metronidazole was particularly noticeable for enteric rods, Fusobacterium species, Capnocytophaga species, Staphylococcus, and Actinobacillus actinomycetemcomitans. It was largely absent for Campylobacter rectus. No antibiotic sensitivity data were obtained for Porphyromonas gingivalis or Bacteroides forsythus, as these species were detected by immunofluorescence. The results indicate that a substantial number of microorganisms associated with refractory periodontitis are variably resistant to commonly-used antibiotics. Diagnostic microbiology must be considered an essential adjunct to the therapist faced with periodontal lesions refractory to conventional treatment.

Antibiotic resistance of the subgingival microbiota following local tetracycline therapy

The antibiotic resistance of the subgingival microbiota was studied by 3 approaches. First, we assessed the ability of subgingival isolates taken following therapy to grow on media containing tetracycline (TC). Higher percentages of TC-resistant organisms appeared at TC fiber-treated periodontal sites and within the saliva 1 week after treatment as compared with pre-treatment levels. By 1 month, the percentage of TC-resistant organisms had returned to levels comparable to those seen before treatment. In the second approach, subgingival isolates taken following therapy were grown on media without antibiotics, and isolates were selected for Gram-stain and cell morphology determination. This study indicated that subgingival sites became colonized with gram-positive cocci in the same time period that an increase of TC-resistant isolates was observed in the first study. This may account for the transient increase in TC resistance, because many gram-positive cocci are intrinsically resistant to TC. In the third approach, the antibiotic resistance of subgingival gram-negative species was determined. The predominant cultivable microbiota of 9 sites from 3 subjects were isolated immediately before and 6 months after TC fiber treatment. Gram-negative rods were characterized and tested for sensitivity to TC (minimum inhibitory concentration [MIC] 1-128 micrograms/ml), penicillin at 80 micrograms/ml, and erythromycin at 8 micrograms/ml. None of the gram-negative rods were resistant to TC (MIC greater than or equal to 16 micrograms/ml), either before or after treatment. Before treatment 98% of the gram-negative rods were susceptible to TC at 1-2 micrograms/ml and after therapy 88% were susceptible.(ABSTRACT TRUNCATED AT 250 WORDS)

Root surface characteristics associated with subgingival placement of monolithic tetracycline-impregnated fibers

The purpose of this investigation was to inspect and characterize the subgingival root surface after a 10-day exposure in vivo to 25% tetracycline hydrochloride by weight in an ethylene vinyl acetate copolymer fiber matrix with and without root planing therapy. The root surfaces were examined by fluorescent-light microscopy (FLM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Thirty-two teeth were selected for study, 4 from each of 8 patients. The teeth of each patient were randomly assigned to one of four treatment groups: non-treated control (C), scaling and root planing only (RP), tetracycline-impregnated fiber only (F), and scaling and root planing with tetracycline-impregnated fiber application (RP/F). SEM revealed a visible reduction in the subgingival microbial flora in both the F and RP/F treatment groups in comparison with the C group specimens. Many of the residual bacteria observed in F and RP/F specimens appeared non-viable, exhibiting obvious loss of membrane integrity. In contrast, the RP specimens exhibited randomly distributed areas of residual subgingival plaque and calculus with newly developing plaque fronts; the plaque fronts undoubtedly having formed during the 10 days post-therapy. All RP/F specimens exhibited an incomplete removal of adsorbed root surface pellicle and demineralization of the subsequently exposed root surface. EDS analysis of large crystals adhering to root surfaces of F and RP/F specimens revealed high chloride peaks, suggesting the presence of residual tetracycline. FLM examination of F and RP/F treated specimens showed a superficial penetration of tetracycline into the root surface of about 10 microns. Areas of demineralized root showed slight tetracycline penetration into exposed dentinal tubules.

Minocycline slow-release formulation effect on subgingival bacteria

The purpose of this study was to determine the microbiological efficacy of an adjunctive minocycline periodontal formulation delivered subgingivally. Subjects were systemically healthy but exhibited severe periodontitis; i.e., probing depths greater than 6 mm. The two study groups included individuals who received minocycline or a placebo periodontal formulation after root planing. Subgingival plaque samples were obtained at baseline; prior to treatment; and at 1, 3, and 6 months. Plaque was evaluated by darkfield microscopy and further analyzed for total dark-pigmented Bacteroides species, P. intermedia, P. gingivalis and Streptococcus, Actinomyces, Eikenella, Actinobacillus, Capnocytophaga, and Fusobacterium species using cultivable flora techniques. In addition, plaque was evaluated for yeast on a selective agar medium. When compared to the placebo, the minocycline group had significantly lower proportions of spirochetes at 1 and 3 months and lower proportions of motile rods at 3 months. Furthermore, when compared to the placebo group, the minocycline patients had lower mean proportions of dark-pigmented Bacteroides spp. and P. intermedia at 1 and 3 months as well as lower proportions of E. corrodens at 1 month. The minocycline group had significant decreases in proportions of spirochetes at 1 and 3 months, motile rods at 1 and 3 months, and increases in cocci at 1, 3, and 6 months when compared to baseline. In the placebo group, root planing was also effective at decreasing spirochetes at 1, 3, and 6 months, but with significant differences seen only at 3 and 6 months. However, the degree of reduction in spirochete proportions was greater in the minocycline group when compared with the placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)

A morphological comparison of radicular dentin following root planing and treatment with citric acid or tetracycline HCl

The conditioning of root surfaces with saturated solutions of citric acid or tetracycline is unpredictable in facilitating new attachment, perhaps due to the low pH of these solutions which may be denaturing the organic matrix of the root as well as demineralizing the surface. The purpose of the present study was to compare the effects of a saturated solution of citric acid (pH = 1) with that of a 0.5% solution of tetracycline HCl (pH = 3.2) on radicular dentin with regard to the removal of the smear layer, exposure of dentinal tubule openings, and demineralization of the peritubular dentin. 10 bovine incisors were used in this study. The crowns and apical 1/3 of the root were resected and the resulting root segments were then frozen in icy freon. The cementum was fractured off of the root to produce a fracture-exposed, non-instrumented dentin surface. This fracture-exposed dentin surface was divided into 4 specimens, the 1st being a fracture-exposed, non-instrumented dentin control specimen (FE). After removal of the (FE) specimen from the root segment, the remainder of the fracture-exposed dentin surface was thoroughly root planed and then subdivided into the 3 remaining specimens. One of these specimens served as the root planed dentin surface (RP); another specimen (CA) was immersed in saturated citric acid (pH = 1) for 5 min and then washed in water for 5 min; the final specimen (T) was immersed in a 0.5 mg/ml solution of tetracycline HCl for 5 min and rinsed in water for 5 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Using antimicrobial agents to manage periodontal diseases

Periodontal diseases are bacterial infections and anti-microbials have been shown to be useful in their treatment and prevention. State-of-the-art treatment of refractory forms of destructive periodontal disease presently includes adjunctive use of systemic antibiotics directed to eliminating or suppressing pathogenic subgingival bacteria. Also, local application of antimicrobials by subgingival deposition or their use as irrigants during periodontal therapy are soon likely to be major components of anti-infective management of periodontal diseases. A new approach to anti-infective periodontal therapy combines ultrasonic surgical debridement with antimicrobial irrigation.

Topical application of doxycycline on periodontally involved root surfaces in vitro: comparative analysis of substantivity on cementum and dentin

In this study, substantivity of topically applied doxycycline hydrochloride on root surfaces obtained from patients with periodontal disease was studied in vitro. Cementum and dentin specimens were impregnated with aqueous solutions of doxycycline for 3 minutes, and incubated in serum for 10 minutes, 7 days, and 14 days. Substantivity was determined by agar diffusion inhibition assay. Comparative analyses of cementum versus dentin groups were conducted with 2-way analysis of variance. Results indicated that there was no statistically significant differences between the binding potential of doxycycline to cementum and dentin specimens. Antibacterial effect of specimens treated with the concentration of 100 mg/ml persisted for 14 days, indicating the presence of doxycycline in biologically active form. Our findings demonstrate the long lasting substantivity of doxycycline hydrochloride on periodontally diseased root surfaces and supports the concept of using root surfaces as a substrate for the deposition and slow release for local tetracycline delivery.

Antimicrobial activities of thiolactomycin against gram-negative anaerobes associated with periodontal disease. f1

Thiolactomycin (TLM), (4R)-(2E,5E)-2,4,6-trimethyl-3-hydroxy-2,5, 7-octatriene-4-thiolide, purified from a culture filtrate of a strain of the Nocardia species, was examined for antimicrobial activities against more than 100 strains of oral and periodontally associated bacteria. Nine other commonly used antibiotics were also included for the test. We found that TLM exhibited strong and selective antimicrobial activities against Bacteroides gingivalis and other oral black-pigmented Bacteroides species that may be etiologically associated with adult periodontitis. TLM also inhibited the growth of Actinobacillus actinomycetemcomitans, but did not affect the growth of oral streptococcal species and Eubacterium species. Strains of Eikenella corrodens were moderately susceptible to TLM, while Actinomyces viscosus strains were only slightly susceptible to it. Other antibiotics used for comparison showed a broad spectrum of antimicrobial activities in general. In conclusion, TLM exhibited highly selective antimicrobial activities to black-pigmented Bacteroides species and A. actinomycetemcomitans, both of which are implicated in the pathogenesis of human periodontal disease.

Evaluation of the activity of four antimicrobial agents using an in vitro rapid micromethod against oral streptococci and various bacterial strains implicated in periodontitis

The activity of various antibacterial agents (amoxicillin, josamycin, doxycycline and metronidazole) was established in vitro using a rapid micromethod. The activity of these agents, which are widely used in oral medicine, was evaluated against microorganisms responsible for periodontitis and bucco-dental infections. Their action against alpha-hemolytic streptococci (including pneumococci) which make up the majority of the indigenous oral flora was also tested. Amoxicillin was found to be effective against all the strains tested. Doxycycline was active against periodontal bacteria, but not against 50% of the streptococcal flora. Josamycin was found to be effective against streptococci, but appeared without effect on Eikenella corrodens and Actinobacillus actinomycetemcomitans. Metronidazole, inactive against streptococci, displayed greater activity towards the strict anaerobes. The use of these antibiotics for the treatment of bucco-dental infections, especially periodontitis, is discussed. For periodontitis and periodontal suppurations, antimicrobial agents present a valuable adjunct to local treatments such as scaling or rootplaning. This may prevent more serious infections such as endocarditis that can develop after tooth extraction.

The effect of subminimal inhibitory concentrations of antimicrobial agents on three bacterial mixtures

A test tube technique was developed to screen bacterial mixtures to detect interbacterial interactions that play a role in determining sensitivity to antimicrobial agents. We found 3 mixtures where these bacterial interactions change the sensitivity to antimicrobials or change the proportions of each bacterial species in the mixture. The mixtures were: Fusobacterium nucleatum 102.3 and Bacteroides endodontalis ATCC 35406; F. nucleatum 102.3 and B. endodontalis BN11 a-f; and Capnocytophaga ochracea 1956c and Eubacterium saburreum 162.4. The antimicrobials used were metronidazole for the first 2 mixtures and tetracycline for the last. F. nucleatum seems to protect B. endodontalis from the action of metronidazole. Conversely, the growth inhibition of C. ochracea by E. saburreum was lifted when tetracycline was present. We also found that the growth of C. ochracea can then permit the subsequent growth of E. saburreum. The test tube method permits the evaluation both of interbacterial interactions and the detection of any protective mechanism against antimicrobial agents in a bacterial mixture. We found that F. nucleatum 102.3 can decrease the metronidazole level in the culture medium, and by the use of 14C-metronidazole we demonstrated that acetamide is produced from metronidazole.

Tissue interactions with dentin specimens after demineralization using tetracycline

Greater cell attachment to demineralized dentin has been associated with subsequent development of a fiber attachment system. The purpose of this study was to evaluate tissue interactions to dentin demineralized with different concentrations of tetracycline solution. Dentin specimens were obtained from beneath root surfaces covered by periodontal ligament. Each rectangular specimen had a face of root surface dentin and an opposite surface of pulpal dentin. Experimental specimens were treated with a tetracycline solution of either 200 mg/cc or 100 mg/cc for five minutes. The remaining group of specimens served as untreated controls. Specimens were implanted transcutaneously into incisional wounds on the dorsal surface of rats with one end protruding through the skin. Four specimens in each group were available for examination one and ten days after implantation. Histologic and histometric analysis of both root and pulpal surface of implants included counts of adhering cells, assessment of implant length within the connective tissue, and evaluation of connective tissue fiber relationships. In each group, specimens became severely extruded between days one and ten, the number of attached cells decreased, and a fiber attachment system did not develop. Tetracycline-treated surfaces had greater numbers of attached cells at both time points compared to untreated controls. No differences were discernible relating to different tetracycline concentrations. It was concluded that tetracycline-demineralized dentin provided a substrate that increased cell attachment; however, this enhanced response did not result in a connective tissue attachment.

Biology of asaccharolytic black-pigmented Bacteroides species

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Structural determinants of activity of chlorhexidine and alkyl bisbiguanides against the human oral flora

We assayed chlorhexidine and a series of its analogues, in which the chlorophenyl terminal substituents were replaced with alkyl chains, for their in vitro antimicrobial activity against the Gram-negative and Gram-positive oral bacteria. Changes in antimicrobial activity were correlated with changes in agent structure for identification of structural criteria which may be important in the optimization of agent activity. Chlorhexidine showed substantial antimicrobial activity against the Gram-negative as well as the Gram-positive oral bacteria. The alkyl agents were comparable with chlorhexidine in their activity against Bacteroides gingivalis and Bacteroides intermedius, black-pigmented Gram-negative obligate anaerobes associated with periodontal disease in adults. Alkyl agents alexidine, heptihexidine (1,6-bis-n-heptylbiguanidohexane), hexoctidine (1,8-bis-n-hexylbiguanidoctane), and hexhexidine (1,6-bis-n-hexylbiguanidohexane), as well as chlorhexidine, were active against Actinobacillus actinomycetemcomitans, a Gram-negative organism associated with localized juvenile periodontitis. Hexidecidine (1,10-bis-n-hexylbiguanidodecane) and heptoctidine (1,8-bis-n-heptylbiguanidooctane) were more active, and hexhexidine was as active as chlorhexidine against Fusobacterium nucleatum, also associated with periodontal disease. Seven of the agents were more active than chlorhexidine against Actinomyces species. All test agents were active against Streptococcus mutans, a Gram-positive coccus associated with dental caries. Hexidecidine had activity equal to that of chlorhexidine when evaluated against the entire battery of organisms. Analysis of structure-activity relationships revealed that alkyl chains could replace chlorophenyl groups with retention or improvement of antimicrobial activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Penicillin resistance in the subgingival microbiota associated with adult periodontitis

In this investigation, the penicillin-resistant and beta-lactamase-producing subgingival microbiota associated with adult periodontitis was identified, and the impact of a recent exposure to penicillin on the recovery of resistant organisms from this microbiota was assessed. Subjects with adult periodontitis were examined clinically and microbiologically. Twenty-one subjects had a documented history of penicillin therapy within the previous 6 months whereas an additional 21 subjects had no history of antibiotic use within 1 year. Subgingival plaque samples were cultured anaerobically on nonselective and penicillin-containing elective media. MICs and beta-lactamase production were determined for the isolates from the elective medium. The penicillin-resistant microbiota consisted primarily of gram-negative organisms, including Bacteroides, Veillonella, Haemophilus, Eikenella, and Capnocytophaga species. The prevalence (P less than 0.05) and proportions (P less than 0.005) of both penicillin-resistant pigmented Bacteroides and Veillonella species were significantly greater in subjects with recent penicillin exposure. Of the penicillin-resistant genera identified, beta-lactamase production was detected in species of pigmented Bacteroides, Capnocytophaga, and Streptococcus. The prevalence of beta-lactamase-producing Bacteroides species was significantly greater in subjects with recent penicillin exposure (P less than 0.05). Of the antibiotics examined, no single agent was uniformly effective against all of the penicillin-resistant strains, but metronidazole and clindamycin were active against all of the penicillin-resistant pigmented Bacteroides strains.

Antibiotic susceptibility of anaerobic bacteria from the human oral cavity

Anaerobic, agar-dilution, minimal inhibitory concentrations (MICs) of 18 antibiotics are given for the numerically important bacterial groups from the human oral cavity. Strains are divided into susceptibility categories using the guidelines for interpretation of MICs suggested by the National Committee for Clinical Laboratory Standards. These guidelines are based on data on antibiotic concentrations attainable in serum following various dosage regimens. MICs are also compared with attainable gingival fluid levels where these are known. The highest percentages of strains were susceptible to tetracycline, with 89% of the 139 strains tested susceptible to serum levels and 97% conditionally susceptible to attainable gingival fluid levels. Ninety-eight percent of strains were conditionally susceptible to attainable gingival fluid levels of minocycline, but many strains, including Actinobacillus actinomycetemcomitans, were only moderately susceptible to attainable serum levels of this tetracycline analogue. Carbenicillin was effective against most groups of organisms, with the important exception of A. actinomycetemcomitans, at serum levels attainable with oral formulations of carbenicillin. Only 2% of the total strains tested were resistant to penicillin, while 33% of strains were categorized as moderately susceptible. Clindamycin was active against many strains of Gram-negative bacteria but was not active against A. actinomycetemcomitans, some Bacteroides, Eikenella corrodens, or the anaerobic vibrios. Metronidazole was active against A. actinomycetemcomitans, all five groups of oral Bacteroides tested, and against Capnocytophaga species. Chloramphenicol was active against A. actinomycetemcomitans, but not against most of the other groups of oral organisms. Nearly all groups contained strains non-susceptible to serum levels attainable with the usual doses of erythromycin, spiramycin, vancomycin, kanamycin, neomycin, streptomycin, doxycycline, oxytetracycline, or chlortetracycline; several strains were resistant to maximum attainable serum levels of each of these antibiotics except doxycycline.