Synergistic effects between amoxicillin, metronidazole, and the hydroxymetabolite of metronidazole against Actinobacillus actinomycetemcomitans

Europe's contribution to the evaluation of the use of systemic antimicrobials in the treatment of periodontitis

This narrative review celebrates Europe's contribution to the current knowledge on systemically administered antimicrobials in periodontal treatment. Periodontitis is the most frequent chronic noncommunicable human disease. It is caused by dysbiotic bacterial biofilms and is commonly treated with subgingival instrumentation. However, some sites/patients do not respond adequately, and its limitations and shortcomings have been recognized. This has led to the development of alternative or adjunctive therapies. One is the use of antimicrobials to target bacteria in subgingival biofilms in the periodontal pocket, which can be targeted directly through the pocket entrance with a locally delivered antibiotic or systemically by oral, intravenous, or intramuscular methods. Since the early 20th century, several studies on systemic antibiotics have been undertaken and published, especially between 1990 and 2010. Europe's latest contribution to this topic is the first European Federation of Periodontology, S3-level Clinical Practice Guideline, which incorporates recommendations related to the use of adjuncts to treat stage I-III periodontitis. Understanding the etiopathogenesis of periodontal diseases, specifically periodontitis, has influenced the use of systemic periodontal antibiotic therapy. Randomized clinical trials and systematic reviews with meta-analyses have demonstrated the clinical advantages of adjunctive systemic antimicrobials. However, current recommendations are restrictive due to concerns about antibiotic misuse and the increase in microbial antibiotic resistance. European researchers have contributed to the use of systemic antimicrobials in the treatment of periodontitis through clinical trials and by providing rational guidelines. Nowadays, European researchers are exploring alternatives and directing clinical practice by providing evidence-based guidelines to limit the use of systemic antimicrobials.

Hydrocinnamic Acid and Perillyl Alcohol Potentiate the Action of Antibiotics against Escherichia coli

The treatment of bacterial infections has been troubled by the increased resistance to antibiotics, instigating the search for new antimicrobial therapies. Phytochemicals have demonstrated broad-spectrum and effective antibacterial effects as well as antibiotic resistance-modifying activity. In this study, perillyl alcohol and hydrocinnamic acid were characterized for their antimicrobial action against Escherichia coli. Furthermore, dual and triple combinations of these molecules with the antibiotics chloramphenicol and amoxicillin were investigated for the first time. Perillyl alcohol had a minimum inhibitory concentration (MIC) of 256 µg/mL and a minimum bactericidal concentration (MBC) of 512 µg/mL. Hydrocinnamic acid had a MIC of 2048 µg/mL and an MBC > 2048 µg/mL. Checkerboard and time-kill assays demonstrated synergism or additive effects for the dual combinations chloramphenicol/perillyl alcohol, chloramphenicol/hydrocinnamic acid, and amoxicillin/hydrocinnamic acid at low concentrations of both molecules. Combenefit analysis showed synergism for various concentrations of amoxicillin with each phytochemical. Combinations of chloramphenicol with perillyl alcohol and hydrocinnamic acid revealed synergism mainly at low concentrations of antibiotics (up to 2 μg/mL of chloramphenicol with perillyl alcohol; 0.5 μg/mL of chloramphenicol with hydrocinnamic acid). The results highlight the potential of combinatorial therapies for microbial growth control, where phytochemicals can play an important role as potentiators or resistance-modifying agents.

Antimicrobial Chemotherapy for Recalcitrant Severe Human Periodontitis

This study evaluated a combined systemic and topical anti-infective periodontal treatment of 35 adults who had experienced ongoing periodontal breakdown following conventional surgical periodontics. The prescribed anti-infective therapy, based on microbiological testing, consisted of a single course of metronidazole plus ciprofloxacin (23 patients), metronidazole plus amoxicillin/clavulanic acid (10 patients), and metronidazole plus ciprofloxacin followed by metronidazole plus amoxicillin/clavulanic acid (2 patients). In addition, the study patients received 0.1% povidone-iodine subgingival disinfection during non-surgical root debridement and daily patient administered oral irrigation with 0.1% sodium hypochlorite. At 1 and 5 years post-treatment, all study patients showed gains in clinical periodontal attachment with no further attachment loss, and significant decreases in pocket probing depth, bleeding on probing, and subgingival temperature. The greatest disease resolution occurred in patients who at baseline harbored predominantly major periodontal pathogens which post-antibiotics became non-detectable and substituted by non-periodontopathic viridans streptococci. The personalized and minimally invasive anti-infective treatment regimen described here controlled periodontitis disease activity and markedly improved the clinical and microbiological status of the refractory periodontitis patients.

Periodontal microbiology and microbial etiology of periodontal diseases: Historical concepts and contemporary perspectives

This narrative review summarizes the collective knowledge on periodontal microbiology, through a historical timeline that highlights the European contribution in the global field. The etiological concepts on periodontal disease culminate to the ecological plaque hypothesis and its dysbiosis-centered interpretation. Reference is made to anerobic microbiology and to the discovery of select periodontal pathogens and their virulence factors, as well as to biofilms. The evolution of contemporary molecular methods and high-throughput platforms is highlighted in appreciating the breadth and depth of the periodontal microbiome. Finally clinical microbiology is brought into perspective with the contribution of different microbial species in periodontal diagnosis, the combination of microbial and host biomarkers for this purpose, and the use of antimicrobials in the treatment of the disease.

Efficacy of Systemic Amoxicillin–Metronidazole in Periodontitis Patients with Diabetes Mellitus: A Systematic Review of Randomized Clinical Trials

Systemic amoxicillin–metronidazole was proven to be effective in managing periodontitis in systemically healthy patients. It was demonstrated that systemic antibiotic therapy can effectively improve clinical periodontal parameters and reduce periodontopathogenic organisms in the subgingival biofilm. However, the evidence for prescribing this drug combination to patients with diabetes remains insufficient. This systematic review was designed to evaluate the effectiveness of a systemic amoxicillin–metronidazole combination as an adjunct to nonsurgical periodontal therapy in patients with diabetes presenting with chronic periodontitis. The PubMed, Scopus, and Web of Science databases were electronically searched for randomized clinical trials in January 2022. Randomized clinical trials evaluating systemic amoxicillin–metronidazole therapy as an adjunct to nonsurgical periodontal therapy in patients with type 2 diabetes presenting with periodontitis were selected for screening. The qualities of the studies were assessed using the Cochrane Collaboration’s Tool for Assessing Risk of Bias Version 2.0 (ROB-2), and a GRADE assessment was applied to estimate the overall certainty of the evidence. Using predefined eligibility criteria, four clinical trials examining 209 patients were selected from the 611 articles identified in the search. Two studies reported a better reduction in clinical parameters when SRP was combined with systemic amoxicillin–metronidazole. Systemic amoxicillin–metronidazole was found to be as effective as clindamycin. Surgical therapy with systemic amoxicillin–metronidazole was more effective than nonsurgical therapy with systemic amoxicillin–metronidazole, even though both resulted in reduced clinical parameters. Combined amoxicillin–metronidazole was observed to reduce periodontal probing depth (PPD), clinical attachment level (CAL), and bleeding on probing (BOP) compared to no treatment or NSPT alone. However, the effect was not greater when compared to NSPT with clindamycin or surgical therapy with amoxicillin–metronidazole. Further randomized trials are required before clinical guidelines can be established for the use of systemic amoxicillin–metronidazole. Future randomized controlled clinical trials with long-term follow-ups are required to assess the efficacy of systemic antibiotic therapy in managing periodontitis in patients with diabetes.

A systematic review on bacterial community changes after periodontal therapy with and without systemic antibiotics: An analysis with a wider lens

BACKGROUND

This systematic review aimed to provide a comprehensive view on microbial community shifts after periodontal therapy with and without systemic antibiotics, conducted in randomized controlled trials (RCTs).

METHODS

Search functions in PubMed, Scopus, the Web of Knowledge, and the Cochrane Oral Health Library databases were used to locate studies published up to December 2018 that reported at least two bacteria before and after periodontal therapy. Gray literature and manual searching were done. Information about reported bacteria in those studies were extracted, and a descriptive microbial community analysis was conducted to observe trends and influencing factors on microbial dynamics. Methodological aspects were examined, including the bacterial detection method, heterogeneity of procedures, and risk of bias (RoB) of the studies.

RESULTS

The 30 included studies reported 130 different bacterial genera. Four different detection methods were reported: cultivation, polymerase chain reaction, DNA-DNA-checkerboard hybridization, and 16S rDNA amplicon sequencing. No general compositional change between the antibiotic and placebo groups could be found after therapy on the community level. Fifty-five bacteria were reported in two or more studies. Of those, 24 genera decreased and 13 increased more frequently after antibiotic use. Great heterogeneity between procedures and variability in RoB were found among the studies.

CONCLUSIONS

Microbial shifts occurred regardless of the use of antibiotics. Antibiotic therapy seems to induce more changes in single bacteria. The heterogeneity in methods and reporting of the included studies preclude clinical recommendations on the use or not of adjunctive antibiotics. The present results may guide further research on the topic.

Drug-Drug Interaction Discovery: Kernel Learning from Heterogeneous Similarities

We develop a pipeline to mine complex drug interactions by combining different similarities and interaction types (molecular, structural, phenotypic, genomic etc). Our goal is to learn an optimal kernel from these heterogeneous similarities in a supervised manner. We formulate an extensible framework that can easily integrate new interaction types into a rich model. The core of our pipeline features a novel kernel-learning approach that tunes the weights of the heterogeneous similarities, and fuses them into a Similarity-based Kernel for Identifying Drug-Drug interactions and Discovery, or SKID3. Experimental evaluation on the DrugBank database shows that SKID3 effectively combines similarities generated from chemical reaction pathways (which generally improve precision) and molecular and structural fingerprints (which generally improve recall) into a single kernel that gets the best of both worlds, and consequently demonstrates the best performance.

Impact of PCL nanofiber mat structural properties on hydrophilic drug release and antibacterial activity on periodontal pathogens

Electrospinning enables to design and manufacture novel drug delivery systems capable of advancing the local antibacterial therapy. In this study, two hydrophilic drugs - metronidazole and ciprofloxacin hydrochloride - were loaded both individually and in combination into hydrophobic poly(ε-caprolactone) (PCL) matrix using electrospinning. We aimed to develop prolonged release drug delivery systems suitable for the treatment of periodontal diseases and understand how different rarely studied structural features, such as nanofiber mat thickness, surface area, wettability, together with intrinsic properties, like solid state and localization of incorporated drugs in nanofibers, affect the drug release. Furthermore, the safety of nanofiber mats was assessed in vitro on fibroblasts, and their antibacterial activity was tested on selected strains of periodontopathogenic bacteria. The results showed that the structural properties of nanofiber mat are crucial in particular drug-polymer combinations, affecting the drug release and consequently the antibacterial activity. The hydrophobicity of a PCL nanofiber mat and its thickness are the key characteristics in prolonged hydrophilic drug release, but only when wetting is the rate-limiting step for the drug release. Combination of drugs showed beneficial effects by inhibiting the growth of all tested pathogenic bacterial strains important in periodontal diseases.

Nonsurgical and surgical treatment of periodontitis: how many options for one disease?

Treatment of periodontitis aims at preventing further disease progression with the intentions to reduce the risk of tooth loss, minimize symptoms and perception of the disease, possibly restore lost periodontal tissue and provide information on maintaining a healthy periodontium. Therapeutic intervention includes introduction of techniques to change behavior, such as: individually tailored oral-hygiene instructions; a smoking-cessation program; dietary adjustment; subgingival instrumentation to remove plaque and calculus; local and systemic pharmacotherapy; and various types of surgery. No single treatment option has shown superiority, and virtually all types of mechanical periodontal treatment benefit from adjunctive antimicrobial chemotherapy. Periodontal treatment, because of the chronic nature of periodontitis, is a lifelong commitment to intricate oral-hygiene techniques, which, when properly implemented, will minimize the risk of disease initiation and progression.

Do we treat our patients or rather periodontal microbes with adjunctive antibiotics in periodontal therapy? A 16S rDNA microbial community analysis

Empiric antibiotics are often used in combination with mechanical debridement to treat patients suffering from periodontitis and to eliminate disease-associated pathogens. Until now, only a few next generation sequencing 16S rDNA amplicon based publications with rather small sample sizes studied the effect of those interventions on the subgingival microbiome. Therefore, we studied subgingival samples of 89 patients with chronic periodontitis (solely non-smokers) before and two months after therapy. Forty-seven patients received mechanical periodontal therapy only, whereas 42 patients additionally received oral administered amoxicillin plus metronidazole (500 and 400 mg, respectively; 3x/day for 7 days). Samples were sequenced with Illumina MiSeq 300 base pairs paired end technology (V3 and V4 hypervariable regions of the 16S rDNA). Inter-group differences before and after therapy of clinical variables (percentage of sites with pocket depth ≥ 5mm, percentage of sites with bleeding on probing) and microbiome variables (diversity, richness, evenness, and dissimilarity) were calculated, a principal coordinate analysis (PCoA) was conducted, and differential abundance of agglomerated ribosomal sequence variants (aRSVs) classified on genus level was calculated using a negative binomial regression model. We found statistically noticeable decreased richness, and increased dissimilarity in the antibiotic, but not in the placebo group after therapy. The PCoA revealed a clear compositional separation of microbiomes after therapy in the antibiotic group, which could not be seen in the group receiving mechanical therapy only. This difference was even more pronounced on aRSV level. Here, adjunctive antibiotics were able to induce a microbiome shift by statistically noticeably reducing aRSVs belonging to genera containing disease-associated species, e.g., Porphyromonas, Tannerella, Treponema, and Aggregatibacter, and by noticeably increasing genera containing health-associated species. Mechanical therapy alone did not statistically noticeably affect any disease-associated taxa. Despite the difference in microbiome modulation both therapies improved the tested clinical parameters after two months. These results cast doubt on the relevance of the elimination and/or reduction of disease-associated taxa as a main goal of periodontal therapy.

The effect of metronidazole plus amoxicillin or metronidazole plus penicillin V on periodontal pathogens in an in vitro biofilm model

A combination of metronidazole (MET) and amoxicillin (AMX) is commonly used as adjunct to mechanical therapy of periodontal disease. The use of broad spectrum antibiotics such as AMX may contribute to development of antibiotic resistance. The aim was to evaluate the in vitro effect of replacing AMX with penicillin V (PV) in combination with MET on a biofilm model. A biofilm model consisting of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Fusobacterium nucleatum was developed. The biofilms were exposed to AMX + MET and PV + MET in two different concentrations. Bacterial viability in biofilms following antibiotic exposure was assessed by viable counts and by confocal microscopy. No live colonies of P. gingivalis nor F. nucleatum were retrieved from biofilms exposed to AMX + MET or PV + MET. The amount of A. actinomycetemcomitans was 4-5 logs reduced following antibiotic treatment; no statistical significance was achieved between AMX + MET or PV + MET treated biofilms. Replacement of AMX with PV at the same concentration, in combination with MET, resulted in similar effect on bacterial viability in this in vitro model. The option of using PV + MET instead of AMX + MET deserves further investigation, as this may contribute to reduce the risk of antibiotic resistance development.

Effect of Exposure to Portland Cement Dust on the Periodontal Status and on the Outcome of Non-Surgical Periodontal Therapy

BACKGROUND

Cement dust contains heavy metals like nickel, cobalt, lead and chromium, pollutants hazardous to the biotic environment, with adverse impact for vegetation, human and animal health and ecosystems.

OBJECTIVE

To investigate if long term exposure to cement dust can affect the periodontal health and affect the outcome of non-surgical periodontal therapy.

METHODS

A total of sixty subjects were included in this study. Forty patients with chronic periodontitis were grouped into; Group I comprised of 20 patients with chronic periodontitis working in the Portland Cement Company and Group II comprised of 20 patients with chronic periodontitis who does not work in cement factories nor live near any of them. Twenty healthy subjects were included in this study as healthy control group (Group III). Clinical parameters including gingival index (GI), plaque index (PI), pocket depth (PD) and clinical attachment loss (CLA) were scored for all patients before and after periodontal therapy. All patients received non-surgical periodontal therapy together with strict oral hygiene program for one month. Gingival crevicular fluid (GCF) samples were collected from both groups at baseline and one month after periodontal therapy. Real time PCR (RT-PCR) was used to analyze the GCF samples for detection and assessment of the levels of IL-1β and TNFα.

RESULTS

The two studied groups responded well to non-surgical periodontal treatment and there was no significant difference between GI and GII (P>0.05). The levels of TNFα was higher in GI than in GII before and after periodontal therapy (P<0.05). The levels of IL-1β did not show any significant difference between the two groups at base line (P>0.05), but represented with a highly significant difference between G1 and GII after periodontal therapy (P<0.001). A significant positive correlation was found between the levels of both IL-1β and TNFα and all the clinical parameters in GI before and after periodontal therapy and in GII before periodontal therapy (P<0.05).

CONCLUSION

It seems that long term exposure to cement dust does not affect the clinical outcome of non-surgical periodontal treatment but it affects the levels of the pro-inflammatory mediators leading to more periodontal tissue destruction.

The concomitant administration of systemic amoxicillin and metronidazole compared to scaling and root planing alone in treating periodontitis: =a systematic review=

Background

The treatment of periodontitis begins with a non-surgical phase that includes scaling and root planing(SRP) and on occasion the use of systemic antibiotics. The goal was to systematically evaluate in systemic healthy adults the effect of the concomitant administration of amoxicillin (amx) and metronidazole (met) adjunctive to SRP compared to SRP alone.

Methods

The PubMed-MEDLINE, Cochrane-CENTRAL and EMBASE databases were searched up to November 2014 to identify appropriate studies. Probing Pocket Depth (PD), Clinical Attachment Level (CAL), Bleeding on Pocket Probing(BOP) and Plaque Indices(PI) were selected as outcome variables. Based on the extracted data a meta-analysis was conducted.

Results

A total of 526 unique articles were found, 20 studies met the eligibility criteria. A meta-analysis showed that SRP + amx + met provided significantly better effects overall and more pronounced PD reduction in periodontal pockets initially measuring ≥6 mm (DiffM:-0.86 mm, p < 0.00001) and gain in CAL(DiffM:+0.75 mm, p = 0.0001). The meta-analysis for the secondary inflammatory parameter BOP showed that SRP + amx + met provided full mouth significantly greater reduction in BOP than SRP alone (DiffM:-6.98 %, p = 0.0001).

Conclusion

Adjunctive systemic amoxicillin and metronidazole medication to SRP significantly improved the clinical outcomes with respect to mean PD, CAL and BOP compared to SRP alone. There is moderate to strong evidence in support of the recommendation that adjunctive amx + met therapy to SRP significantly improves the clinical outcomes, with respect to mean PD and CAL compared to SRP alone especially in initially deep (≥6 mm) pockets. No major side effects associated with the intake of amx + met were reported. This treatment regimen is an efficacious, minimally invasive, practical and inexpensive approach for periodontitis therapy. The key components are mechanical tooth and pocket debridement, supportive treatment of the disease with systemic antibiotics and attention to proper self-care.

Electronic supplementary material

The online version of this article (doi:10.1186/s12903-015-0123-6) contains supplementary material, which is available to authorized users.

Effects of azithromycin, metronidazole, amoxicillin, and metronidazole plus amoxicillin on an in vitro polymicrobial subgingival biofilm model

Chronic periodontitis is one of the most prevalent human diseases and is caused by dysbiosis of the subgingival microbiota. Treatment involves primarily mechanical disruption of subgingival biofilms and, in certain cases, adjunctive use of systemic antibiotic therapy. In vitro biofilm models have been developed to study antimicrobial agents targeting subgingival species. However, these models accommodate a limited number of taxa, lack reproducibility, and have low throughput. We aimed to develop an in vitro multispecies biofilm model that mimics subgingival plaque, to test antimicrobial agents. Biofilms were cultivated using the Calgary Biofilm Device and were exposed to amoxicillin (AMX), metronidazole (MTZ), azithromycin (AZM), and AMX-MTZ at four different concentrations for 12, 24, or 36 h. Chlorhexidine (CHX) (0.12%) was used as the positive control. The compositions of the biofilms were analyzed by checkerboard DNA-DNA hybridization, and the percent reduction in biofilm metabolic activity was determined using 2,3,5-triphenyltetrazolium chloride and spectrophotometry. Thirty-five of the 40 species used in the inoculum were consistently recovered from the resulting in vitro biofilms. After 36 h of exposure at the 1:27 dilution, AMX-MTZ reduced metabolic activity 11% less than CHX (q = 0.0207) but 54% more than AMX (q = 0.0031), 72% more than MTZ (q = 0.0031), and 67% more than AZM (q = 0.0008). Preliminary evidence of a synergistic interaction between AMX and MTZ was also observed. In summary, we developed reproducible biofilms with 35 subgingival bacterial species, and our results suggested that the combination of AMX and MTZ had greater antimicrobial effects on these in vitro multispecies biofilms than expected on the basis of the independent effects of the drugs.

Treatment of aggressive periodontitis

Despite etiological differences between aggressive and chronic periodontitis, the treatment concept for aggressive periodontitis is largely similar to that for chronic periodontitis. The goal of treatment is to create a clinical condition that is conducive to retaining as many teeth as possible for as long as possible. When a diagnosis has been made and risk factors have been identified, active treatment is commenced. The initial phase of active treatment consists of mechanical debridement, either alone or supplemented with antimicrobial drugs. Scaling and root planing has been shown to be effective in improving clinical indices, but does not always guarantee long-term stability. Antimicrobials can play a significant role in controlling aggressive periodontitis. Few studies have been published on this subject for localized aggressive periodontitis, but generalized aggressive periodontitis has been subject to more scrutiny. Studies have demonstrated that systemic antibiotics as an adjuvant to scaling and root planing are more effective in controlling disease compared with scaling and root planing alone or with supplemental application of local antibiotics or antiseptics. It has also become apparent that antibiotics ought to be administered with, or just after, mechanical debridement. Several studies have shown that regimens of amoxicillin combined with metronidazole or regimens of clindamycin are the most effective and are preferable to regimens containing doxycycline. Azithromycin has been shown to be a valid alternative to the regimen of amoxicillin plus metronidazole. A limited number of studies have been published on surgical treatment in patients with aggressive periodontitis, but the studies available show that the effect can be comparable with the effect on patients with chronic periodontitis, provided that proper oral hygiene is maintained, a strict maintenance program is followed and modifiable risk factors are controlled. Both access surgery and regenerative techniques have shown good results in patients with aggressive periodontitis. Once good periodontal health has been obtained, patients must be enrolled in a strict maintenance program that is directed toward controlling risk factors for disease recurrence and tooth loss. The most significant risk factors are noncompliance with regular maintenance care, smoking, high gingival bleeding index and poor plaque control. There is no evidence to suggest that daily use of antiseptic agents should be part of the supportive periodontal therapy for aggressive periodontitis.

Combinatorial effects of amoxicillin and metronidazole on selected periodontal bacteria and whole plaque samples

OBJECTIVE

The aim of the present study was to analyze in vitro the combinatorial effects of the antibiotic combination of amoxicillin plus metronidazole on subgingival bacterial isolates.

DESIGN

Aggregatibacter (Actinobacillus) actinomycetemcomitans, Prevotella intermedia/nigrescens, Fusobacterium nucleatum and Eikenella corrodens from our strain collection and subgingival bacteria isolated from patients with periodontitis were tested for their susceptibility to amoxicillin and metronidazole using the Etest. The fractional inhibitory concentration index (FICI), which is commonly used to describe drug interactions, was calculated.

RESULTS

Synergy, i.e. FICI values ≤ 0.5, between amoxicillin and metronidazole was shown for two A. actinomycetemcomitans (FICI: 0.3), two F. nucleatum (FICI: 0.3 and 0.5, respectively) and one E. corrodens (FICI: 0.4) isolates. Indifference, i.e. FIC indices of >0.5 but ≤4, occurred for other isolates and the 14 P. intermedia/nigrescens strains tested. Microorganisms resistant to either amoxicillin or metronidazole were detected in all samples by Etest.

CONCLUSION

Combinatorial effects occur between amoxicillin and metronidazole on some strains of A. actinomycetemcomitans, F. nucleatum and E. corrodens. Synergy was shown for a few strains only.

Low-cost periodontal therapy

Periodontitis is a complex infectious disease that affects low-income individuals disproportionately. Periodontitis is associated with specific bacterial species and herpesviruses, and successful prevention and treatment of the disease is contingent upon effective control of these pathogens. This article presents an efficacious, highly safe, minimally invasive, practical and low-cost periodontal therapy that involves professional and patient-administered mechanical therapy and antimicrobial agents. The major components are scaling for calculus removal, periodontal pocket irrigation with potent antiseptics, and treatment with systemic antibiotics for advanced disease. Povidone-iodine and sodium hypochlorite have all the characteristics for becoming the first-choice antiseptics in the management of periodontal diseases. Both agents show excellent antibacterial and antiviral properties, are readily available throughout the world, have been safely used in periodontal therapy for decades, offer significant benefits for individuals with very limited financial resources, and are well accepted by most dental professionals and patients. Four per cent chlorhexidine applied with a toothbrush to the most posterior part to the tongue dorsum can markedly reduce or eliminate halitosis in most individuals. Systemic antibiotics are used to treat periodontopathic bacteria that are not readily reached by topical therapy, such as pathogens within gingival tissue, within furcation defects, at the base of periodontal pockets, and on the tongue, tonsils and buccal mucosae. Valuable antibiotic therapies are amoxicillin-metronidazole (250 mg of amoxicillin and 250 mg of metronidazole, three times daily for 8 days) for young and middle-aged patients, and ciprofloxacin-metronidazole (500 mg of each, twice daily for 8 days) for elderly patients and for patients in developing countries who frequently harbor enteric rods subgingivally. Scaling to remove dental calculus and the prudent use of inexpensive antimicrobial agents can significantly retard or arrest progressive periodontitis in the great majority of patients.

Risks to aquatic organisms posed by human pharmaceutical use

In order to help prioritize future research efforts within the US, risks associated with exposure to human prescription pharmaceutical residues in wastewater were estimated from marketing and pharmacological data. Masses of 371 active pharmaceutical ingredients (APIs) dispensed in the US in 2004 were estimated from marketing data, and then divided by therapeutic dose rate to normalize for potency. Metabolic inactivation of the 50 most dispensed APIs was estimated from published data, and active metabolites were tabulated. Comparing maximum likely average wastewater concentrations of API-associated activity to exposure rates that produce therapeutic effects in humans suggests that the threat to healthy human adults from aquatic exposure is low, even when likely mixture effects are considered. Comparing predicted wastewater concentrations to human therapeutic plasma concentrations suggests that some APIs may be present at sufficient concentrations to affect organisms which eliminate them inefficiently. Comparing predicted antimicrobial concentrations to published minimum inhibitory concentrations suggests that antibacterial APIs in wastewater, but probably not antifungal APIs, may select for low-level antimicrobial resistance. The taxonomic distribution of molecular targets of the 50 most dispensed APIs suggests that potential effects of some APIs are likely restricted to vertebrates, while other APIs can probably affect many eukaryotic and prokaryotic clades.

Adjunctive benefits of systemic amoxicillin and metronidazole in non-surgical treatment of generalized aggressive periodontitis: a randomized placebo-controlled clinical trial

BACKGROUND

The objective of this study was to assess the adjunctive clinical effect of the administration of systemic amoxicillin and metronidazole in the non-surgical treatment of generalized aggressive periodontitis (GAP).

METHODS

Forty-one systemically healthy subjects with GAP were included in this 6-month double-blind, placebo-controlled, randomized clinical trial. Patients received a course of full-mouth non-surgical periodontal treatment delivered over a 24 h period using machine-driven and hand instruments. Test subjects received an adjunctive course of systemic antibiotic consisting of 500 mg amoxicillin and 500 mg metronidazole three times a day for 7 days. Clinical parameters were collected at baseline, and at 2 and 6 months post-treatment.

RESULTS

In both the test and the placebo groups, all clinical parameters improved at 2 and 6 months. In deep pockets (> or =7 mm), the test treatment resulted in an additional 1.4 mm (95% confidence interval 0.8, 2.0 mm) in full-mouth probing pocket depth (PPD) reduction and 1 mm (0.7, 1.3 mm) of life cumulative attachment loss (LCAL) gain at 6 months. In moderate pockets (4-6 mm), the adjunctive benefit was smaller in magnitude: PPD reduction was 0.4 mm (0.1, 0.7 mm) and LCAL gain was 0.5 mm (0.2, 0.8 mm). In addition, the 6-month data showed LCAL gains > or =2 mm at 25% of sites in test patients compared with 16% in placebo (p=0.028). Similarly, PPD reductions of 2 mm or more were observed in 30% of sites in test and 21% of sites in placebo patients. Seventy-four percent of pockets with PPD > or =5 mm at baseline were 4 mm or shallower at 6 months in the test group. This compared with 54% in the placebo group (p=0.008). Disease progression at 6 months was observed at 1.5% of test and 3.3% of sites in test and placebo, respectively (p=0.072).

CONCLUSIONS

These data indicate that a 7-day adjunctive course of systemic metronidazole and amoxicillin significantly improved the short-term clinical outcomes of full-mouth non-surgical periodontal debridement in subjects with GAP.

Antimicrobial profiles of periodontal pathogens isolated from periodontitis patients in the Netherlands and Spain

BACKGROUND AND AIM

Antimicrobial resistance of periodontal pathogens towards currently used antibiotics in periodontics has been investigated in a previous study. Microbial resistance in the periodontal microflora was more frequently observed in Spanish patients in comparison with Dutch patients. The aim of the present study was to compare antimicrobial susceptibility profiles of five periodontal bacteria isolated from periodontitis patients in Spain and in The Netherlands.

MATERIAL AND METHODS

Subgingival plaque samples from adult patients with periodontitis were collected and cultured on selective and non-selective plates. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum and Micromonas micros were isolated and used for minimal inhibitory concentration tests using the Epsilometer (E-test) technique. Eight different antibiotics were tested on all bacterial isolates. MIC50 and MIC90 values for each antibiotic and each species were determined and the percentage of resistant strains was calculated.

RESULTS

Significantly higher MIC values were noted in Spanish strains of F. nucleatum for penicillin, ciprofloxacin, of P. intermedia for penicillin, amoxicillin and tetracycline, of M. micros for tetracycline, amoxicillin and azithromycin, and of P. gingivalis for tetracycline and ciprofloxacin. Based on breakpoint concentrations, a higher number of resistant strains in Spain were found in F. nucleatum for penicillin, amoxicillin and metronidazole, in Prevotella intermedia for tetracycline and amoxicillin, and in A. actinomycetemcomitans for amoxicillin and azithromycin. Resistance of P. gingivalis strains was not observed for any of the antibiotics tested both in Spain and The Netherlands.

CONCLUSIONS

Differences exist in the susceptibility profiles of periodontal pathogens isolated from periodontitis patients in Spain and in The Netherlands. This implicates that antibiotic susceptibility testing is necessary to determine efficacy of antimicrobial agents. Also, clinical studies with antibiotics should take these differences into account. The information from the present study indicates that it may not be possible to develop uniform protocols for usage of antibiotics in the treatment of severe periodontitis in the European Union.

Topical and systemic antibiotics in the management of periodontal diseases

Both systemic and topical antibiotics are increasingly used in the management of periodontal infections. Whilst these drugs are used mostly on an empirical basis, some contend that rational use of antibiotics should be the norm due to their wide abuse and consequential global emergence of antibiotic resistance organisms. Here we review the rationale and principles of antimicrobial therapy, treatment goals, drug delivery routes and various antibiotics that are used in the management of periodontal diseases. The pros and cons of systemic and local antibiotic therapy are described together with practical guidelines for their delivery. The available data indicate, in general, that mechanical periodontal treatment alone is adequate to ameliorate or resolve the clinical condition in most cases, but adjunctive antimicrobial agents, delivered either locally or systemically, can enhance the effect of therapy in specific situations. This is particularly true for aggressive (early onset) periodontitis, in patients with generalised systemic disease that may affect host resistance and in case of poor response to conventional mechanical therapy. Locally delivered antibiotics together with mechanical debridement are indicated for non-responding sites of focal infection or in localised recurrent disease. After resolution of the periodontal infection, the patient should be placed on an individually tailored maintenance care programme. Optimal plaque control by the patient is of paramount importance for a favourable clinical and microbiological response to any form of periodontal therapy.

Specific Antibiotics in the Treatment of Periodontitis – A Proposed Strategy

BACKGROUND

The purpose of the present study was to propose a strategy for the selection of antibiotics that specifically target complexes of periodontal pathogens present in patients with periodontitis.

METHODS

Seven hundred seventy-four (774) patients with various forms of periodontitis were included in the study. Subgingival plaque samples were taken from the deepest periodontal pockets in each quadrant using a sterile curet, and pooled. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Eikenella corrodens, Tannerella forsythensis, Prevotella intermedia, and Prevotella nigrescens were identified by polymerase chain reaction, and the prevalence of combinations of these pathogens was determined. To each pathogen complex (PC), i.e., combination of pathogens, those antibiotics were assigned that were most specific according to the published minimum inhibitory concentration (MIC90) values and the gingival crevicular fluid (GCF) concentrations achievable in vivo. Antibiotic GCF concentrations had to be at least 10 times the MIC90 values, and the narrowest spectrum was selected with respect to the assessed periodontal pathogens.

RESULTS

Nine major PCs (each > or = 3% of all patients) were found in 73.4% of all patients, whereas 38 minor PCs (each < 3% of all patients) were distributed in 26.6% of all patients. Ten different antibiotic regimens were found to be specific for the total of 46 PCs; i.e., metronidazole and amoxicillin in 11 PCs (55.0% of all patients), metronidazole and amoxicillin/clavulanic acid or metronidazole and ciprofloxacin in 13 PCs (18.9%), amoxicillin in 4 PCs (8.3%), doxycycline in 2 PCs (6.1%), metronidazole in 8 PCs (4.1%), amoxicillin/clavulanic acid in 3 PCs (2.9%), clindamycin in 2 PCs (1.5%), ciprofloxacin in 2 PCs (0.4%), and tetracycline in 1 PC (0.3%).

CONCLUSION

The results of the study indicate that there are at least 46 different combinations of the assessed periodontal pathogens in subjects with periodontitis, and at least 10 different antibiotic regimens might be required to specifically target the various pathogen complexes.

Local antibiotic therapy guided by microbiological diagnosis

BACKGROUND

The aim of this study was to determine the distribution patterns of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans in periodontitis patients after standard mechanical periodontal therapy, and to evaluate the effect of additional local antibiotic therapy, given to all teeth with cultural evidence of these bacteria.

METHODS

17 patients were included. 852 separate subgingival microbial samples were taken from the mesial and distal aspect of every tooth in 17 subjects at baseline. 46 of these samples, from 10 positive subjects, showed cultural evidence for P. gingivalis. 82 samples, from 5 subjects, were A. actinomycetemcomitans-positive. Three subjects showed no evidence for persistence of A. actinomycetemcomitans or P. gingivalis. In the other 14 subjects, all A. actinomycetemcomitans- or P. gingivalis-positive teeth were treated with tetracycline fibers (ACTISITE(R)). Sub-gingival microbial samples were again taken from two sites of every tooth, 1 month after fiber removal. 89% of the initially P. gingivalis-positive sites were now negative, but 16 previously negative sites now tested positive. 77% of the initially A. actinomycetemcomitans-positive sites were now negative, but 5 previously negative sites now tested positive. The teeth with persisting P. gingivalis or A. actinomycetemcomitans were again treated with fibers. Two sites of every tooth were once more sampled after 1 month. At this time, 5 subjects still showed cultural evidence of P. gingivalis at a total of 19 sites, and 4 subjects were positive for A. actinomycetemcomitans in a total of 27 sites. These 9 patients were finally submitted to systemic antibiotic therapy (3 x 250 mg metronidazole plus 3 x 375 mg amoxicillin/d for 7 days). Despite of all efforts, P. gingivalis was again detected 3 months later in isolated sites in 3 subjects, and A. actinomycetemcomitans could be cultivated from one single site.

CONCLUSIONS

Therapy with tetracycline fibers guided by microbiological diagnosis effectively reduced P. gingivalis and A. actinomycetemcomitans locally, but was unable to completely eradicate the target organisms. Additional systemic antibiotic therapy further reduced P. gingivalis and A. actinomycetemcomitans. The observed persistence patterns suggest that reemergence of A. actinomycetemcomitans was due to recolonization, whereas the strikingly reproducible local reemergence of P. gingivalis in some sites indicated failed eradication.

Pharmacokinetics and pharmacodynamics of the nitroimidazole antimicrobials

Metronidazole, the prototype nitroimidazole antimicrobial, was originally introduced to treat Trichomonas vaginalis, but is now used for the treatment of anaerobic and protozoal infections. The nitroimidazoles are bactericidal through toxic metabolites which cause DNA strand breakage. Resistance, both clinical and microbiological, has been described only rarely. Metronidazole given orally is absorbed almost completely, with bioavailability > 90% for tablets; absorption is unaffected by infection. Rectal and intravaginal absorption are 67 to 82%, and 20 to 56%, of the dose, respectively. Metronidazole is distributed widely and has low protein binding (< 20%). The volume of distribution at steady state in adults is 0.51 to 1.1 L/kg. Metronidazole reaches 60 to 100% of plasma concentrations in most tissues studied, including the central nervous system, but does not reach high concentrations in placental tissue. Metronidazole is extensively metabolised by the liver to 5 metabolites. The hydroxy metabolite has biological activity of 30 to 65% and a longer elimination half-life than the parent compound. The majority of metronidazole and its metabolites are excreted in urine and faeces, with less than 12% excreted unchanged in urine. The pharmacokinetics of metronidazole are unaffected by acute or chronic renal failure, haemodialysis, continuous ambulatory peritoneal dialysis, age, pregnancy or enteric disease. Renal dysfunction reduces the elimination of metronidazole metabolites; however, no toxicity has been documented and dosage alterations are unnecessary. Liver disease leads to a decreased clearance of metronidazole and dosage reduction is recommended. Recent pharmacodynamic studies of metronidazole have demonstrated activity for 12 to 24 hours after administration of metronidazole 1 g. The post-antibiotic effect of metronidazole extends beyond 3 hours after the concentration falls below the minimum inhibitory concentration (MIC). The concentration-dependent bactericidal activity, prolonged half-life and sustained activity in plasma support the clinical evaluation of higher doses of metronidazole given less frequently. Metronidazole-containing regimens for Helicobacter pylori in combination with proton pump inhibitors demonstrate higher success rates than antimicrobial regimens alone. The pharmacokinetics of metronidazole in gastric fluid appear contradictory to these results, since omeprazole reduces peak drug concentration and area under the concentration-time curve for metronidazole and its hydroxy metabolite; however, concentrations remain above the MIC. Other members of this class include tinidazole, ornidazole and secnidazole. They are also well absorbed and distributed after oral administration. Their only distinguishing features are prolonged half-lives compared with metronidazole. The choice of nitroimidazole may be influenced by the longer administration intervals possible with other members of this class; however, metronidazole remains the predominant antimicrobial for anaerobic and protozoal infections.

Clinical and microbiological effects of adjunctive antibiotics in treatment of localized juvenile periodontitis. A controlled clinical trial

The aim of this study was to assess the clinical and microbiologic effects of the combination of amoxicillin and metronidazole therapy as an adjunct to mechanical treatment in the management of localized juvenile periodontitis. Twenty-five localized juvenile periodontitis (LJP) patients from a Brazilian population were randomly allocated into an experimental group receiving mechanical treatment and antibiotics, and a control group receiving mechanical treatment and placebo. Clinical and radiographic assessments, as well as microbiologic sampling for Actinobacillus actinomycetemcomitans, were performed at baseline and one year after the end of the treatment. At the termination of the study A. actinomycetemcomitans could be isolated from the oral cavity of all patients in the control group who harbored the bacterium at baseline and in 4 out of 8 patients in the experimental group. Both treatment modalities resulted in significant benefit on an individual basis. The experimental group, however, displayed better results than did the control group regarding gingival index (GI), probing depth (PD), clinical attachment level (CAL), and radiographic analysis of crestal alveolar bone mass, but not with respect to plaque index (PI). No serious adverse effects of the antibiotic treatment were observed in the present study.

The use of locally delivered metronidazole in the treatment of periodontitis. Clinical results

Local delivery of antimicrobials has been investigated as a possible method for controlling and treating periodontal disease. A number of antimicrobial agents have been studied both as adjunctive therapies with scaling and root planing and as stand-alone chemotherapies. More recent investigations have focussed on the delivery of antimicrobials in sustained-release formulations designed to maintain effective concentrations of drug within the periodontal pocket. This article provides an overview of the development of the use of locally-delivered metronidazole in periodontal therapy and the current state-of-the-art of the technique. It is concluded that treatment with local delivery of metronidazole seems to be as effective as scaling and root planing in untreated as well as in recall subjects. However, there are reasons to suggest that local delivery of metronidazole should not be used as a substitute for conventional treatment of periodontal disease, since side-effects of long-term use and repeated use are not known. The antibiotic regimen should preferably be used as an adjunct to surgical and non-surgical therapy.

Differential clinical treatment outcome after systemic metronidazole and amoxicillin in patients harboring Actinobacillus actinomycetemcomitans and/or Porphyromonas gingivalis

48 adult patients with untreated periodontitis harboring subgingival Actinobacillus actinomycetemcomitans and/or Porphyromonas gingivalis as assessed by PCR were randomly assigned to receive full-mouth scaling alone (control) or scaling with systemic metronidazole plus amoxicillin and supragingival irrigation with chlorhexidine digluconate (test). In patients harboring A. actinomycetemcomitans intraorally at baseline, the adjunctive antimicrobial therapy resulted in a significantly higher incidence of probing attachment level (PAL) gain of 2 mm or more compared to scaling alone over 12 months (p<0.05). In addition, suppression of A. actinomycetemcomitans in subgingival plaque below detectable levels was associated with an increased incidence of PAL gain. In contrast, patients initially harboring P. gingivalis but not A. actinomycetemcomitans in the oral cavity showed a significantly higher incidence of PAL loss following adjunctive antimicrobial therapy compared to scaling alone (p<0.05). When the presence of pathogens at baseline was disregarded in the analysis, adjunctive antimicrobial therapy did not significantly enhance clinical treatment outcome. The results indicated that adults with untreated periodontitis harboring A. actinomycetemcomitans may benefit from the adjunctive antimicrobial therapy for a minimum of 12 months, whereas, the regimen may adversely affect the clinical treatment outcome of patients harboring P. gingivalis but not A. actinomycetemcomitans.

Metronidazole. A therapeutic review and update

The nitroimidazole antibiotic metronidazole has a limited spectrum of activity that encompasses various protozoans and most Gram-negative and Gram-positive anaerobic bacteria. Metronidazole has activity against protozoans like Entamoeba histolytica, Giardia lamblia and Trichomonas vaginalis, for which the drug was first approved as an effective treatment. Anaerobic bacteria which are typically sensitive are primarily Gram-negative anaerobes belonging to the Bacteroides and Fusobacterium spp. Gram-positive anaerobes such as peptostreptococci and Clostridia spp. are likely to test sensitive to metronidazole, but resistant isolates are probably encountered with greater frequency than with the Gram-negative anaerobes. Gardnerella vaginalis is a pleomorphic Gram-variable bacterial bacillus that is also susceptible to metronidazole. Helicobacter pylori has been strongly associated with gastritis and duodenal ulcers. Classic regimens for eradicating this pathogen have included metronidazole, usually with acid suppression medication plus bismuth and amoxicillin. The activity of metronidazole against anaerobic bowel flora has been used for prophylaxis and treatment of patients with Crohn's disease who might develop an infectious complication. Treatment of Clostridium difficile-induced pseudomembraneous colitis has usually been with oral metronidazole or vancomycin, but the lower cost and similar efficacy of metronidazole, coupled with the increased concern about imprudent use of vancomycin leading to increased resistance in enterococci, have made metronidazole the preferred agent here. Metronidazole has played an important role in anaerobic-related infections. Advantages to using metronidazole are the percentage of sensitive Gram-negative anaerobes, its availability as oral and intravenous dosage forms, its rapid bacterial killing, its good tissue penetration, its considerably lower chance of inducing C. difficile colitis, and expense. Metronidazole has notable effectiveness in treating anaerobic brain abscesses. Metronidazole is a cost-effective agent due to its low acquisition cost, its pharmacokinetics and pharmacodynamics, an acceptable adverse effect profile, and its undiminished antimicrobial activity. While its role as part of a therapeutic regimen for treating mixed aerobic/anaerobic infections has been reduced by newer, more expensive combination therapies, these new combinations have not been shown to have any therapeutic advantage over metronidazole. Although the use of metronidazole on a global scale has been curtailed by newer agents for various infections, metronidazole still has a role for these and other therapeutic uses. Many clinicians still consider metronidazole to be the 'gold standard' antibiotic against which all other antibiotics with anaerobic activity should be compared.

Microbiological response to mechanical treatment in combination with adjunctive therapy. A review of the literature

The recognition of the microbial origin and the specificity of periodontal infections has resulted in the development of several adjunctive therapies (antibiotics and/or antiseptics) to scaling and root planing in the treatment of chronic adult periodontitis. This article aims to review the "additional" effect of a subgingival irrigation with chlorhexidine, or a local or systemic application of tetracycline or metronidazole, performed in combination with a single course of scaling and root planing in patients with chronic adult periodontitis. All treatment modalities are compared with scaling and root planing, based on their impact on: the probing depth (PD); total number of colony forming units per ml (CFU/ml); the proportions and/or the detection-frequency of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia; and/or on the percentages of cocci, spirochetes, motile, and other micro-organisms on dark field microscopy examination. All treatment modalities, including scaling and root planing without additional chemical therapy, resulted in significant reductions in the probing depth and the proportions of periodontopathogens, at least during the first 8 weeks post-therapy. However in comparison to a single course of scaling and root planing, the supplementary effect of adjunctive therapies seems to be limited. In general, only the irrigation with chlorhexidine 2%, the local application of minocycline, and the systemic use of metronidazole (in case of large proportions of spirochetes) or doxycycline (in case of large proportions of A. actinomycetemcomitans) seem to result in a prolonged supplementary effect when compared to scaling and root planing. Therefore, the use of antibiotics on a routine basis, especially in a systemic way, in the treatment of chronic adult periodontitis, can no longer be advocated, considering the increasing danger for the development of microbial resistance.

[The GTR technic within the framework of combined periodontal-orthodontic treatments. A case report]

Periodontal defects in adolescents or young adults are often an incidental finding within the framework of orthodontic treatment. Often these patients are suffering from a special form of periodontal disease, juvenile periodontitis. Guided tissue regeneration (GTR) offers a technique for long-term therapy in such cases. In the case presented here, the periodontal problems were aggravated by malpositioning of the affected teeth. Orthodontic and periodontal treatment enabled the malpositioning to be corrected and the osseous defects to be largely regenerated. Controls on regular bases up to now revealed a stable status over 2 years.

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.

The prevalence of A. actinomycetemcomitans, P. gingivalis and P. intermedia in selected subjects with periodontitis

The present study was carried out in a private periodontal practice. 8 clinical criteria were chosen to select patients for microbiological examination. These criteria characterize prominent features of disease which at the start, during, or in the maintenance phase of treatment suggest difficulties in the progress of the periodontal therapy. Based on these clinical characteristics, an inventory was made of the prevalence of the 3 putative periodontal pathogens: Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia. Out of 320 referred patients 91 patients did meet > or = 1 of the clinical criteria and consequently were selected for microbiological examination. Results showed that young patients (19-30 years) with periodontitis demonstrated the presence of A. actinomycetemcomitans more often (69%: p < 0.005) compared to older age cohorts. A. actinomycetemcomitans was found more often when localized breakdown (in particular in the 1st molar and incisor region) was observed and in patient who responded poorly to scaling and rootplaning. P. gingivalis and P. intermedia were most frequently recovered in patients showing primarily a bone loss pattern of angular defects of > or = 5 mm. Retrospectively, these patients were further categorized, based on full mouth radiographs, in (1) patients with primarily horizontal bone loss and (2) patients with primarily angular bony defects. Results showed that A. actinomycetemcomitans occurred less frequently in patients showing horizontal bone loss (p < 0.05).

Microbiological and clinical effects of metronidazole and amoxicillin in Actinobacillus actinomycetemcomitans-associated periodontitis. A 2-year evaluation

In this study, we evaluated the microbiological and clinical effects of mechanical debridement in combination with metronidazole and amoxicillin therapy in 48 patients with Actinobacillus actinomycetemcomitans-associated periodontitis, 3 months and at least 24 months after active treatment. The results of this study showed that 47 out of 48 patients were still negative for A. actinomycetemcomitans subgingivally, at the mucous membranes, the tonsillar area and in the saliva, 2 years after therapy. The clinical results showed that a reduction of probing pocket depth, probing attachment level, bleeding index and plaque index was not only seen in the time between baseline and 3 months after therapy, but further clinical improvement was observed between 3 and 24 months after active treatment. We conclude that combined mechanical debridement and metronidazole plus amoxicillin therapy is very effective in suppressing A. actinomycetemcomitans below cultivable levels over a long period of time, suggesting elimination of this organism, and that recolonization of A. actinomycetemcomitans seems to be a rare event. The elimination of A. actinomycetemcomitans is paralleled by a further improvement of the periodontal status of the patients, even up to 24 months after active treatment.

In vitro antimicrobial susceptibility of different serotypes of Actinobacillus actinomycetemcomitans

In vitro susceptibility of Actinobacillus actinomycetemcomitans (A.a.) serotypes to selected antimicrobial agents was investigated by the agar dilution method on supplemented Mueller-Hinton test medium. Eighty-three A.a. strains, 80 recent isolates from 40 periodontally healthy or diseased subjects, and three type strains were included in the study. Serotype a represented 20, serotype b 32, serotype c 17, and serotype e 7 and nontypable 4 of the tested strains. The most effective drugs against all A.a. serotypes in vitro were cefaclor, cefuroxime, tetracycline hydrochloride, doxycycline, trimethoprim-sulfamethoxazole (cotrimoxazole), and ciprofloxacin, which inhibited 100% of the strains at 4.0 micrograms/ml, 4.0 micrograms/ml, 1.0 microgram/ml, 2.0 micrograms/ml, 0.06 microgram/ml, and 0.015 microgram/ml, respectively. Serotypes a and e were more susceptible to cefaclor and cefuroxime than were serotypes b and c; 100% of the first two groups were inhibited at 2.0 micrograms/ml and 1.0 microgram/ml. Ampicillin inhibited 92% of the tested strains at 1.0 microgram/ml. Serotype b was always susceptible to ampicillin. Metronidazole exhibited the best activity against serotype a strains. The lowest minimal inhibitory concentration values for benzylpenicillin, ampicillin, erythromycin, doxycycline, and metronidazole were encountered among serotype b isolates. The results of the present study indicate minor differences in the in vitro antimicrobial susceptibility patterns of different A.a. serotypes, except to metronidazole. Also, the new oral cephalosporins and cotrimoxazole, rare antimicrobial agents in periodontology, showed promising efficacy against all A.a. strains.

Current status of systemic antibiotic usage in destructive periodontal disease

The recognition that periodontal diseases are primarily caused by specific microorganisms has led researchers to explore the possibility that antibiotics may enhance the effect of mechanical debridement procedures such as scaling and surgery. For some selected periodontal diseases, this has proven to be true. This paper will review systemically-administered antibiotics and the clinical studies and case reports supporting their use. In periodontal therapy, the tetracyclines are the most commonly-used antibiotics in the United States. Tetracycline hydrochloride, minocycline, and doxycycline have been shown to inhibit in vitro most putative periodontal pathogens. Several studies support the use of tetracyclines in the treatment of localized juvenile periodontitis. Penicillins such as amoxicillin are effective in vitro against most periodontal pathogens but have limited efficacy due to the presence of beta-lactamases in gingival fluid. Amoxicillin/clavulanate potassium (Au) has proven effective in treating adult refractory periodontitis characterized by a Gram-positive flora. Metronidazole is an effective adjunct in adult periodontitis associated with high numbers of "black-pigmented Bacteroides" ad spirochetes. A combination of metronidazole and amoxicillin produces a synergistic effect against A. actinomycetemcomitans and has been shown to be effective at eliminating this organism. Clindamycin is an effective adjunct in the treatment of adult refractory periodontitis associated with a predominantly Gram-negative flora. The use of macrolides, quinolones, and combinations of antibiotics is discussed. Clinical studies do not support the use of systemically-administered antibiotics in routine adult periodontitis. Clinical studies do, however, support the use of antibiotics in the treatment of specific periodontal diseases.

In vitro susceptibility of Helicobacter pylori to several antimicrobial combinations

Synergy between metronidazole and its hydroxymetabolite and between each compound and amoxicillin or tetracycline-HCl was determined against Helicobacter pylori. Metronidazole plus its hydroxymetabolite and either compound combined with amoxicillin showed synergism against all 10 strains of H. pylori tested. Metronidazole plus tetracycline-HCl or the hydroxymetabolite plus tetracycline-HCl acted synergistically against seven and six strains, respectively, acted additively against three strains, and had no additional effect against one strain. These results may help to explain the in vivo efficacies of metronidazole combinations in the treatment of H. pylori-associated gastritis.

The role of metronidazole in the treatment of periodontal diseases

This article discusses the ability of metronidazole to improve periodontal health. Review of the drug's pharmacology and potential side effects indicate that it poses little threat to humans of inducing acute toxicity, mutagenesis, or cancer if used according to recommended dosing regimens. Studies addressing metronidazole utilization in a variety of clinical conditions demonstrate that its routine use does not enhance root planing. However, adjunctive antibiotic therapy may be advantageous in the treatment of sites where effective root planing is precluded due to deep pockets or when anaerobic periodontal infections do not respond to conventional therapy.

In vitro susceptibilities of Actinobacillus actinomycetemcomitans to a number of antimicrobial combinations

The in vitro susceptibilities of Actinobacillus actinomycetemcomitans to 14 antimicrobial combinations were studied by using the checkerboard titration technique. The results, expressed as the range of the fractional inhibitory concentration indices, were as follows: for metronidazole or its hydroxymetabolite combined with cefixime, 0.2 to 0.6; for moxalactam, 0.2 to 0.6; for penicillin G, 0.3 to 0.6; for tobramycin, 0.8 to 2.0; for erythromycin, 0.8 to 1.7; for ciprofloxacin, 0.2 to 0.6; for tetracycline, 0.8 to 1.2. Our observations indicated that the beta-lactam antibiotics as well as ciprofloxacin act synergistically with both metronidazole and its hydroxymetabolite against A. actinomycetemcomitans. Synergistic interactions were independent of the individual MICs of the antibiotics tested. Erythromycin, tobramycin, and tetracycline combined with either metronidazole or its hydroxymetabolite showed additive to indifferent effects against the five strains of A. actinomycetemcomitans, with the fractional inhibitory concentration indices ranging from 0.8 to 2.0. A. actinomycetemcomitans was found to be highly susceptible to ciprofloxacin (MIC of ciprofloxacin for 90% of strains tested, 0.010 micrograms/ml) and cefixime (MIC of cefixime for 90% of strains tested, 0.8 micrograms/ml). The results indicate that in patients who are allergic to penicillin, cefixime and ciprofloxacin may be useful alternative antibiotics in combination with metronidazole for the treatment of A. actinomycetemcomitans-associated periodontitis.

In vitro activity of azithromycin compared with that of erythromycin against Actinobacillus actinomycetemcomitans

The in vitro susceptibility of Actinobacillus actinomycetemcomitans to azithromycin, a new macrolide antibiotic of a new class known as azalides, was compared with that of erythromycin by the agar dilution method on Mueller-Hinton Haemophilus test medium. Eighty-two A. actinomycetemcomitans strains, 79 recent clinical isolates obtained from 40 periodontally healthy or diseased subjects, and 3 type strains were included in the study. Erythromycin showed poor in vitro activity against A. actinomycetemcomitans. Azithromycin, however, was highly effective against A. actinomycetemcomitans: all strains were inhibited at 2.0 micrograms/ml. Azithromycin exhibited the best in vitro activity against the serotype a subpopulation of A. actinomycetemcomitans: 100% of the strains were inhibited at 1.0 micrograms/ml. The lowest MICs were, however, recorded by serotype b strains. Since azithromycin has favorable pharmacokinetic properties, including excellent distribution into tissues, it could be expected to pass into gingival crevicular fluid at levels sufficient to inhibit A. actinomycetemcomitans in vivo. Therefore, it is a good candidate for future clinical trials in A. actinomycetemcomitans-associated periodontitis.

Microbiological and clinical results of metronidazole plus amoxicillin therapy in Actinobacillus actinomycetemcomitans-associated periodontitis

We report on the microbiological and clinical effects of mechanical debridement in combination with metronidazole plus amoxicillin therapy in 118 patients with Actinobacillus actinomycetemcomitans-associated periodontitis. Patients were categorized into 3 groups: 28 had localized periodontitis; 50 had generalized periodontitis, and 40 had refractory periodontitis. After initial treatment and metronidazole plus amoxicillin therapy 114 of 118 (96.6%) patients had no detectable A. actinomycetemcomitans. Significant reduction in pocket probing depth and gain of clinical attachment were achieved in almost all patients. Four patients were still positive for A. actinomycetemcomitans after therapy. Metronidazole resistance (MIC greater than 25 micrograms/ml) was observed in 2 of 4 strains from these patients. Patients still positive for A. actinomycetemcomitans or Porphyromonas gingivalis showed a significant higher bleeding tendency after therapy. It was concluded that mechanical periodontal treatment in combination with the metronidazole plus amoxicillin therapy is effective for subgingival suppression of A. actinomycetemcomitans in patients with severe periodontitis.