Antibiotic Susceptibility Patterns of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis Strains from Different Decades

Toxin-triggered liposomes for the controlled release of antibiotics to treat infections associated with the gram-negative bacterium, Aggregatibacter actinomycetemcomitans

Antibiotic resistance has become an urgent threat to health care in recent years. The use of drug delivery systems provides advantages over conventional administration of antibiotics and can slow the development of antibiotic resistance. In the current study, we developed a toxin-triggered liposomal antibiotic delivery system, in which the drug release is enabled by the leukotoxin (LtxA) produced by the Gram-negative pathogen, Aggregatibacter actinomycetemcomitans. LtxA has previously been shown to mediate membrane disruption by promoting a lipid phase change in nonlamellar lipids, such as 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-methyl (N-methyl-DOPE). In addition, LtxA has been observed to bind strongly and nearly irreversibly to membranes containing large amounts of cholesterol. Here, we designed a liposomal delivery system composed of N-methyl-DOPE and cholesterol to take advantage of these interactions. Specifically, we hypothesized that liposomes composed of N-methyl-DOPE and cholesterol, encapsulating antibiotics, would be sensitive to LtxA, enabling controlled antibiotic release. We observed that liposomes composed of N-methyl-DOPE were sensitive to the presence of low concentrations of LtxA, and cholesterol increased the extent and kinetics of content release. The liposomes were stable under various storage conditions for at least 7 days. Finally, we showed that antibiotic release occurs selectively in the presence of an LtxA-producing strain of A. actinomycetemcomitans but not in the presence of a non-LtxA-expressing strain. Together, these results demonstrate that the designed liposomal vehicle enables toxin-triggered delivery of antibiotics to LtxA-producing strains of A. actinomycetemcomitans.

Antibiotic resistance in periodontitis patients: A systematic scoping review of randomized clinical trials

OBJECTIVES

The objective of the study was to evaluate the prevalence and proportions of antibiotic-resistant species in periodontitis patients.

METHODS

A systematic scoping review of randomized clinical trials (RCTs) was conducted using the PRISMA extension for scoping reviews involving different databases. MeSH terms and keywords were provided to examine only RCTs with antibiotic-resistant results that included at least 3 months of follow-up of systematically healthy patients diagnosed with periodontitis and treated with systemic or local antibiotics adjunctive to subgingival debridement. RCTs that managed participants surgically, duplicate publications, and investigations implemented on animals were discarded.

RESULTS

Six RCTs were chosen. These studies included 465 patients. Most investigations observed that while Aggregatibacter actinomycetemcomitans, Tannerella forsythia, and Porphyromonas gingivalis had low resistance to amoxicillin, microorganisms in many sites showed resistance to tetracycline, metronidazole, and azithromycin pretreatment. A. actinomycetemcomitans showed high resistance to tetracycline pre- and post-therapy. The proportion of antibiotic-resistant samples augmented rapidly after the prescription of antibiotics in all test groups. The percentage of antibiotic-resistant microorganisms decreased over time; at the end of the follow-up period, resistance levels were close to baseline levels.

CONCLUSIONS

Adjunctive local and systemic antibiotic treatment temporarily increased the antibiotic resistance of subgingival microorganisms; nonetheless, many bacteria remained susceptible to antibiotics during their administration.

Toxin-Triggered Liposomes for the Controlled Release of Antibiotics to Treat Infections Associated with Gram-Negative Bacteria

Antibiotic resistance has become an urgent threat to health care in recent years. The use of drug delivery systems provides advantages over conventional administration of antibiotics and can slow the development of antibiotic resistance. In the current study, we developed a toxin-triggered liposomal antibiotic delivery system, in which the drug release is enabled by the leukotoxin (LtxA) produced by the Gram-negative pathogen, Aggregatibacter actinomycetemcomitans. LtxA has previously been shown to mediate membrane disruption by promoting a lipid phase change in nonlamellar lipids, such as 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-methyl (N-methyl-DOPE). In addition, LtxA has been observed to bind strongly and nearly irreversibly to membranes containing large amounts of cholesterol. Here, we designed a liposomal delivery system composed of N-methyl-DOPE and cholesterol to take advantage of these interactions. Specifically, we hypothesized that liposomes composed of N-methyl-DOPE and cholesterol, encapsulating antibiotics, would be sensitive to LtxA, enabling controlled antibiotic release. We observed that liposomes composed of N-methyl-DOPE were sensitive to the presence of low concentrations of LtxA, and cholesterol increased the extent and kinetics of content release. The liposomes were stable under various storage conditions for at least 7 days. Finally, we showed that antibiotic release occurs selectively in the presence of an LtxA-producing strain of A. actinomycetemcomitans but not in the presence of a non-LtxA-expressing strain. Together, these results demonstrate that the designed liposomal vehicle enables toxin-triggered delivery of antibiotics to LtxA-producing strains of A. actinomycetemcomitans.

Comparing the clinical effects of local administration of minocycline ointment and doxycycline solution in the treatment of acute periodontal abscesses: a retrospective clinical study

PURPOSE

The objective of this retrospective clinical study was to provide evidence supporting the adjunctive local application of doxycycline solution or minocycline ointment, in conjunction with drainage, for the treatment of acute periodontal abscesses.

METHODS

The study included 63 patients who had received treatment for acute periodontal abscesses through drainage supplemented with 1 of 3 types of adjunctive medications during their initial visit (visit 1; baseline): 1) saline irrigation (the control group), 2) 2% minocycline ointment (the TM group), or 3) 300 mg/mL doxycycline irrigation (the TD group). The same adjunctive medication was administered at visit 2, which took place 1 week after visit 1. Probing depth (PD), bleeding on probing (BOP), plaque index, gingival recession, clinical attachment level, and tooth mobility were clinically evaluated at visits 1, 2, and a third visit (visit 3; 4 weeks after visit 1). Statistical significance was considered to be indicated by P values <0.05.

RESULTS

By visit 3, all clinical indices and tooth mobility had significantly decreased in each group. At this visit, PD and BOP on the abscess side were significantly lower in the TM and TD groups compared to the control group. The TD group showed a significantly greater improvement than the TM group, with mean PD reductions of 1.09 mm in the control group, 1.88 mm in the TM group, and 2.88 mm in the TD group. Similarly, mean BOP reductions were 45% in the control group, 73.02% in the TM group, and 95.45% in the TD group.

CONCLUSIONS

Local and adjunctive administration of doxycycline and minocycline in combination with drainage exhibited clinical advantages over drainage alone in improving PD and BOP. Notably, a doxycycline solution of 300 mg/mL was more effective than a 2% minocycline ointment.

Synthesis, Characterization, Cytotoxicity Analysis and Evaluation of Novel Heterocyclic Derivatives of Benzamidine against Periodontal Disease Triggering Bacteria

Periodontal disease (PD) is multifactorial oral disease that damages tooth-supporting tissue. PD treatment includes proper oral hygiene, deep cleaning, antibiotics therapy, and surgery. Despite the availability of basic treatments, some of these are rendered undesirable in PD treatment due to side effects and expense. Therefore, the aim of the present study is to develop novel molecules to combat the PD triggering pathogens. The study involved the synthesis of 4-((5-(substituted-phenyl)-1,3,4-oxadiazol-2-yl)methoxy)benzamidine (5a-e), by condensation of 2-(4-carbamimidoylphenoxy)acetohydrazide (3) with different aromatic acids; and synthesis of 4-((4-(substituted benzylideneamino)-4H-1,2,4-triazol-3-yl)methoxy)benzamidine (6a-b) by treatment of compound 3 with CS₂ followed by hydrazination and a Schiff reaction with different aromatic aldehydes. Synthesized compounds were characterized based on the NMR, FTIR, and mass spectrometric data. To assess the effectiveness of the newly synthesized compound in PD, new compounds were subjected to antimicrobial evaluation against P. gingivalis and E. coli using the micro-broth dilution method. Synthesized compounds were also subjected to cytotoxicity evaluation against HEK-293 cells using an MTT assay. The present study revealed the successful synthesis of heterocyclic derivatives of benzamidine with significant inhibitory potential against P. gingivalis and E. coli. Synthesized compounds exhibited minimal to the absence of cytotoxicity. Significant antimicrobial potential and least/no cytotoxicity of new heterocyclic analogs of benzamidine against PD-triggering bacteria supports their potential application in PD treatment.

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.

Electrospun Azithromycin-Laden Gelatin Methacryloyl Fibers for Endodontic Infection Control

This study was aimed at engineering photocrosslinkable azithromycin (AZ)-laden gelatin methacryloyl fibers via electrospinning to serve as a localized and biodegradable drug delivery system for endodontic infection control. AZ at three distinct amounts was mixed with solubilized gelatin methacryloyl and the photoinitiator to obtain the following fibers: GelMA+5%AZ, GelMA+10%AZ, and GelMA+15%AZ. Fiber morphology, diameter, AZ incorporation, mechanical properties, degradation profile, and antimicrobial action against Aggregatibacter actinomycetemcomitans and Actinomyces naeslundii were also studied. In vitro compatibility with human-derived dental pulp stem cells and inflammatory response in vivo using a subcutaneous rat model were also determined. A bead-free fibrous microstructure with interconnected pores was observed for all groups. GelMA and GelMA+10%AZ had the highest fiber diameter means. The tensile strength of the GelMA-based fibers was reduced upon AZ addition. A similar pattern was observed for the degradation profile in vitro. GelMA+15%AZ fibers led to the highest bacterial inhibition. The presence of AZ, regardless of the concentration, did not pose significant toxicity. In vivo findings indicated higher blood vessel formation, mild inflammation, and mature and thick well-oriented collagen fibers interweaving with the engineered fibers. Altogether, AZ-laden photocrosslinkable GelMA fibers had adequate mechanical and degradation properties, with 15%AZ displaying significant antimicrobial activity without compromising biocompatibility.

Antimicrobial resistance of microorganisms present in periodontal diseases: A systematic review and meta-analysis

Objective

The aim of this study was to estimate the antimicrobial resistance in microorganisms present in periodontal diseases.

Methods

A systematic review was conducted according to the PRISMA statement. The MEDLINE (PubMed/Ovid), EMBASE, BVS, CINAHL, and Web of Science databases were searched from January 2011 to December 2021 for observational studies which evaluated the antimicrobial resistance in periodontal diseases in permanent dentition. Studies that allowed the antimicrobial consumption until the time of sample collection, studies that used laboratory acquired strains, studies that only characterized the microbial strain present, assessment of cellular morphological changes, sequencing system validation, and time series were excluded. Six reviewers, working in pairs and independently, selected titles, abstracts, and full texts extracting data from all studies that met the eligibility criteria: characteristics of patients, diagnosis of infection, microbial species assessed, antimicrobial assessed, identification of resistance genes, and virulence factors. “The Joanna Briggs Institute” critical appraisal for case series was adapted to assess the risk of bias in the included studies.

Results

Twenty-four studies (N = 2.039 patients) were included. Prevotella and Porphyromonas species were the most cited microorganisms in the included studies, and the virulence factors were related to Staphylococcus aureus. The antimicrobial reported with the highest frequency of resistance in the included studies was ampicillin (39.5%) and ciprofloxacin showed the lowest frequency of resistance (3.4%). The most cited genes were related to macrolides. The quality of the included studies was considered critically low.

Conclusion

No evidence was found regarding the profile of antimicrobial resistance in periodontal diseases, requiring further research that should focus on regional population studies to address this issue in the era of increasing antimicrobial resistance.

Clinical relevance

The knowledge about the present microorganism in periodontal diseases and their respective antimicrobial resistance profiles should guide dentists in prescribing complementary therapy for these infections.

Systematic review registration

[http://dx.doi.org/10.1097/MD.0000000000013158], identifier [CRD42018077810].

Pan-Genome Analysis of Oral Bacterial Pathogens to Predict a Potential Novel Multi-Epitopes Vaccine Candidate

Porphyromonas gingivalis is a Gram-negative anaerobic bacterium, mainly present in the oral cavity and causes periodontal infections. Currently, no licensed vaccine is available against P. gingivalis and other oral bacterial pathogens. To develop a vaccine against P. gingivalis, herein, we applied a bacterial pan-genome analysis (BPGA) on the bacterial genomes that retrieved a total number of 4908 core proteins, which were further utilized for the identification of good vaccine candidates. After several vaccine candidacy analyses, three proteins, namely lytic transglycosylase domain-containing protein, FKBP-type peptidyl-propyl cis-trans isomerase and superoxide dismutase, were shortlisted for epitopes prediction. In the epitopes prediction phase, different types of B and T-cell epitopes were predicted and only those with an antigenic, immunogenic, non-allergenic, and non-toxic profile were selected. Moreover, all the predicted epitopes were joined with each other to make a multi-epitopes vaccine construct, which was linked further to the cholera toxin B-subunit to enhance the antigenicity of the vaccine. For downward analysis, a three dimensional structure of the designed vaccine was modeled. The modeled structure was checked for binding potency with major histocompatibility complex I (MHC-I), major histocompatibility complex II (MHC-II), and Toll-like receptor 4 (TLR-4) immune cell receptors which revealed that the designed vaccine performed proper binding with respect to immune cell receptors. Additionally, the binding efficacy of the vaccine was validated through a molecular dynamic simulation that interpreted strong intermolecular vaccine-receptor binding and confirmed the exposed situation of vaccine epitopes to the host immune system. In conclusion, the study suggested that the model vaccine construct has the potency to generate protective host immune responses and that it might be a good vaccine candidate for experimental in vivo and in vitro studies.

Reverse Vaccinology and Immunoinformatic Assisted Designing of a Multi-Epitopes Based Vaccine Against Nosocomial Burkholderia cepacia

Burkholderia cepacia is a Gram-negative nosocomial pathogen and is considered as a troublesome bacterium due to its resistance to many common antibiotics. There is no licensed vaccine available to prevent the pathogen infections, thus making the condition more alarming and warrant the search for novel therapeutic and prophylactic approaches. In order to identify protective antigens from pathogen proteome, substantial efforts are put forth to prioritized potential vaccine targets and antigens that can be easily evaluated experimentally. In this vaccine design investigation, it was found that B. cepacia completely sequenced proteomes available in NCBI genome database has a total of 28,966 core proteins. Out of total, 25,282 proteins were found redundant while 3,684 were non-redundant. Subcellular localization revealed that 18 proteins were extracellular, 31 were part of the outer membrane, 75 proteins were localized in the periplasm, and 23 were virulent proteins. Five proteins namely flagellar hook protein (FlgE), fimbria biogenesis outer membrane usher protein, Type IV pilus secretin (PilQ), cytochrome c4, flagellar hook basal body complex protein (FliE) were tested for positive for antigenic, non-toxic, and soluble epitopes during predication of B-cell derived T-cell epitopes. A vaccine peptide of 14 epitopes (joined together via GPGPG linkers) and cholera toxin B subunit (CTBS) adjuvant (joined to epitopes peptide via EAAAK linker) was constructed. Binding interaction of the modeled vaccine with MHC-I, MHC-II, and Toll-like receptor 4 (TLR-4) immune receptors was studied using molecular docking studies and further analyzed in molecular dynamics simulations that affirms strong intermolecular binding and stable dynamics. The maximum root mean square deviation (RMSD) score of complexes in the simulation time touches to 2 Å. Additionally, complexes binding free energies were determined that concluded robust interaction energies dominated by van der Waals. The total energy of each complex is < -190 kcal/mol. In summary, the designed vaccine showed promising protective immunity against B. cepacia and needs to be examined in experiments.

Clinical and Microbiological Efficacy of Adjunctive Systemic Quinolones to Mechanical Therapy in Periodontitis: A Systematic Review of the Literature

Objectives

To assess the clinical and microbiological efficacy of systemic quinolones adjunctive to mechanical therapy in periodontitis patients. Materials and Methods. A systematic review of the scientific literature was carried out. The search scheme comprised the Scopus, PubMed/MEDLINE, SCIELO (Scientific Electronic Library Online), and LILACS (Literatura Latinoamericana y del Caribe en Ciencias de la Salud) databases, together with the gray literature. MeSH terms and keywords were utilized to explore publications in all idioms. Only randomized clinical trials (RCTs) that met the selection criteria were included.

Results

A total of 4 RCTs were selected. These RCTs found superior clinical and microbiological efficacy of adjunctive systemic moxifloxacin (MOX) and levofloxacin (LV) compared to subgingival debridement plus placebo. Improvements in PD and CAL were 2.4 ± 0.8 mm and 2.7 ± 0.9 mm for LV, and 1.5 ± 0.5 mm and 1.8 ± 0.5 mm for MOX, respectively. After six months of follow-up, adjunctive MOX reduced the presence of Aggregatibacter actinomycetemcomitans to imperceptible levels, while LV markedly reduced this microorganism. Some adverse events were reported in the LV group and none in the MOX group.

Conclusions

Adjunctive MOX and LV improve probing depth and clinical attachment level compared with subgingival debridement alone in patients with periodontitis. The efficacy of these quinolones against A. actinomycetemcomitans was also superior.

Vaccinomics to Design a Multi-Epitopes Vaccine for Acinetobacter baumannii

Antibiotic resistance (AR) is the result of microbes’ natural evolution to withstand the action of antibiotics used against them. AR is rising to a high level across the globe, and novel resistant strains are emerging and spreading very fast. Acinetobacter baumannii is a multidrug resistant Gram-negative bacteria, responsible for causing severe nosocomial infections that are treated with several broad spectrum antibiotics: carbapenems, β-lactam, aminoglycosides, tetracycline, gentamicin, impanel, piperacillin, and amikacin. The A. baumannii genome is superplastic to acquire new resistant mechanisms and, as there is no vaccine in the development process for this pathogen, the situation is more worrisome. This study was conducted to identify protective antigens from the core genome of the pathogen. Genomic data of fully sequenced strains of A. baumannii were retrieved from the national center for biotechnological information (NCBI) database and subjected to various genomics, immunoinformatics, proteomics, and biophysical analyses to identify potential vaccine antigens against A. baumannii. By doing so, four outer membrane proteins were prioritized: TonB-dependent siderphore receptor, OmpA family protein, type IV pilus biogenesis stability protein, and OprD family outer membrane porin. Immuoinformatics predicted B-cell and T-cell epitopes from all four proteins. The antigenic epitopes were linked to design a multi-epitopes vaccine construct using GPGPG linkers and adjuvant cholera toxin B subunit to boost the immune responses. A 3D model of the vaccine construct was built, loop refined, and considered for extensive error examination. Disulfide engineering was performed for the stability of the vaccine construct. Blind docking of the vaccine was conducted with host MHC-I, MHC-II, and toll-like receptors 4 (TLR-4) molecules. Molecular dynamic simulation was carried out to understand the vaccine-receptors dynamics and binding stability, as well as to evaluate the presentation of epitopes to the host immune system. Binding energies estimation was achieved to understand intermolecular interaction energies and validate docking and simulation studies. The results suggested that the designed vaccine construct has high potential to induce protective host immune responses and can be a good vaccine candidate for experimental in vivo and in vitro studies.

Antiplanktonic and Antibiofilm Activity of Rheum palmatum against Streptococcus oralis and Porphyromonas gingivalis

Periodontitis and peri-implantitis are inflammatory conditions with a high global prevalence. Oral pathogens such as Porphyromonas gingivalis play a crucial role in the development of dysbiotic biofilms associated with both diseases. The aim of our study was to identify plant-derived substances which mainly inhibit the growth of “disease promoting bacteria”, by comparing the effect of Rheum palmatum root extract against P. gingivalis and the commensal species Streptococcus oralis. Antiplanktonic activity was determined by measuring optical density and metabolic activity. Antibiofilm activity was quantified using metabolic activity assays and live/dead fluorescence staining combined with confocal laser scanning microscopy. At concentrations of 3.9 mg/L, R. palmatum root extract selectively inhibited planktonic growth of the oral pathogen P. gingivalis, while not inhibiting growth of S. oralis. Selective effects also occurred in mature biofilms, as P. gingivalis was significantly more stressed and inhibited than S. oralis. Our studies show that low concentrations of R. palmatum root extract specifically inhibit P. gingivalis growth, and offer a promising approach for the development of a potential topical agent to prevent alterations in the microbiome due to overgrowth of pathogenic P. gingivalis.

Antimicrobial Activity of Eucalyptus globulus, Azadirachta indica, Glycyrrhiza glabra, Rheum palmatum Extracts and Rhein against Porphyromonas gingivalis

Novel plant-derived antimicrobials are of interest in dentistry, especially in the treatment of periodontitis, since the use of established substances is associated with side effects and concerns of antimicrobial resistance have been raised. Thus, the present study was performed to quantify the antimicrobial efficacy of crude plant extracts against Porphyromonas gingivalis, a pathogen associated with periodontitis. The minimal inhibitory concentrations (MICs) of Eucalyptus globulus leaf, Azadirachta indica leaf, Glycyrrhiza glabra root and Rheum palmatum root extracts were determined by broth microdilution for P. gingivalis ATCC 33277 according to CLSI (Clinical and Laboratory Standards Institute). The MICs for the E. globulus, A. indica and G. glabra extracts ranged from 64 mg/L to 1024 mg/L. The lowest MIC was determined for an ethanolic R. palmatum extract with 4 mg/L. The MIC for the anthraquinone rhein was also measured, as the antimicrobial activity of P. palmatum root extracts can be partially traced back to rhein. Rhein showed a remarkably low MIC of 0.125 mg/L. However, the major compounds of the R. palmatum root extract were not further separated and purified. In conclusion, R. palmatum root extracts should be further studied for the treatment of periodontitis.

Antibacterial Effect of Functionalized Polymeric Nanoparticles on Titanium Surfaces Using an In Vitro Subgingival Biofilm Model

This investigation aimed to evaluate the antibacterial effect of polymeric nanoparticles (NPs), functionalized with calcium, zinc, or doxycycline, using a subgingival biofilm model of six bacterial species (Streptococcus oralis,Actinomyces naeslundii, Veillonela parvula, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans) on sandblasted, large grit, acid-etched titanium discs (TiDs). Undoped NPs (Un-NPs) or doped NPs with calcium (Ca-NPs), zinc (Zn-NPs), or doxycycline (Dox-NPs) were applied onto the TiD surfaces. Uncovered TiDs were used as negative controls. Discs were incubated under anaerobic conditions for 12, 24, 48, and 72 h. The obtained biofilm structure was studied by scanning electron microscopy (SEM) and its vitality and thickness by confocal laser scanning microscopy (CLSM). Quantitative polymerase chain reaction of samples was used to evaluate the bacterial load. Data were evaluated by analysis of variance (p < 0.05) and post hoc comparisons with Bonferroni adjustments (p < 0.01). As compared with uncovered TiDs, Dox-NPs induced higher biofilm mortality (47.21% and 85.87%, respectively) and reduced the bacterial load of the tested species, after 72 h. With SEM, scarce biofilm formation was observed in Dox-NPs TiDs. In summary, Dox-NPs on TiD reduced biofilm vitality, bacterial load, and altered biofilm formation dynamics.

The Antimicrobial Susceptibility of Porphyromonas gingivalis: Genetic Repertoire, Global Phenotype, and Review of the Literature

The in vitro antimicrobial susceptibility of 29 strains of the major periodontal pathogen Porphyromonas gingivalis and three P. gulae (as an ancestor) to nine antibiotics (amoxicillin, amoxicillin/clavulanate, clindamycin, metronidazole, moxifloxacin, doxycycline, azithromycin, imipenem, and cefoxitin) was evaluated by E-testing of minimal inhibitory concentration (MIC) according to international standards. The results were compared with 16 international studies reporting MICs from 1993 until recently. In addition, 77 currently available P. gingivalis genomes were screened for antimicrobial resistance genes. E-testing revealed a 100% sensitivity of P. gingivalis and P. gulae to all antibiotics. This was independent of the isolation year (1970 until 2021) or region, including rural areas in Indonesia and Africa. Regarding studies worldwide (675 strains), several method varieties regarding medium, McFarland inoculation standards (0.5-2) and incubation time (48-168 h) were used for MIC-testing. Overall, no resistances have been reported for amoxicillin + clavulanate, cefoxitin, and imipenem. Few strains showed intermediate susceptibility or resistance to amoxicillin and metronidazole, with the latter needing both confirmation and attention. The only antibiotics which might fail in the treatment of P. gingivalis-associated mixed anaerobic infections are clindamycin, macrolides, and tetracyclines, corresponding to the resistance genes erm(B), erm(F), and tet(Q) detected in our study here, as well as fluoroquinolones. Periodical antibiotic susceptibility testing is necessary to determine the efficacy of antimicrobial agents and to optimize antibiotic stewardship.

Haemophilus parasuis (Glaesserella parasuis) as a Potential Driver of Molecular Mimicry and Inflammation in Rheumatoid Arthritis

Background:Haemophilus parasuis (Hps; now Glaesserella parasuis) is an infectious agent that causes severe arthritis in swines and shares sequence similarity with residues 261–273 of collagen type 2 (Coll_261−273), a possible autoantigen in rheumatoid arthritis (RA).

Objectives/methods: We tested the presence of Hps sequencing 16S ribosomal RNA in crevicular fluid, synovial fluids, and tissues in patients with arthritis (RA and other peripheral arthritides) and in healthy controls. Moreover, we examined the cross-recognition of Hps by Coll_261−273-specific T cells in HLA-DRB1^*04^pos RA patients, by T-cell receptor (TCR) beta chain spectratyping and T-cell phenotyping.

Results:Hps DNA was present in 57.4% of the tooth crevicular fluids of RA patients and in 31.6% of controls. Anti-Hps IgM and IgG titers were detectable and correlated with disease duration and the age of the patients. Peripheral blood mononuclear cells (PBMCs) were stimulated with Hps virulence-associated trimeric autotransporter peptide (VtaA10_755−766), homologous to human Coll_261−273 or co-cultured with live Hps. In both conditions, the expanded TCR repertoire overlapped with Coll_261−273 and led to the production of IL-17.

Discussion: We show that the DNA of an infectious agent (Hps), not previously described as pathogen in humans, is present in most patients with RA and that an Hps peptide is able to activate T cells specific for Coll_261−273, likely inducing or maintaining a molecular mimicry mechanism.

Conclusion: The cross-reactivity between VtaA10_755−766 of a non-human infectious agent and human Coll_261−273 suggests an involvement in the pathogenesis of RA. This mechanism appears emphasized in predisposed individuals, such as patients with shared epitope.

Prevalence and antibiotic susceptibility trends of periodontal pathogens in the subgingival microbiota of German periodontitis patients: A retrospective surveillance study

OBJECTIVE

This retrospective surveillance study aimed to follow periodontitis-associated bacterial profiles and to identify time-dependent changes in antibiotic susceptibility patterns.

MATERIALS AND METHODS

From 2008 to 2015, bacterial specimen from deep periodontal pockets were collected from a total of 7804 German adults diagnosed with periodontitis. Presence of selected bacteria was confirmed by anaerobic culture and nucleic acid amplification. Antimicrobial susceptibility of clinical isolates was tested by disc diffusion with antibiotics used for the treatment of periodontitis and oral infections. The prevalences of periodontal pathogens were calculated and temporal evolution of antimicrobial susceptibility towards amoxicillin, amoxicillin/clavulanic acid, metronidazole, doxycycline, clindamycin, azithromycin, ciprofloxacin and ampicillin was analysed with logistic regression.

RESULTS

The prevalence of patients harbouring bacteria was 95.9% Fusobacterium nucleatum, 88.0% Tannerella forsythia, 76.4% Treponema denticola, 76.5%, Campylobacter rectus, 76.0% Eikenella corrodens, 75.0% Capnocytophaga spp., 68.2% Porphyromonas gingivalis, 57.7% Peptostreptococcus micros, 43.1% Prevotella intermedia, 30.4% Eubacterium nodatum and 21.5% Aggregatibacter actinomycetemcomitans. In 63.5% of patients, one or more isolates were not susceptible to at least one of the antibiotics tested. The data further revealed a trend towards decreasing susceptibility profiles (p < 0.05) with antibiotic non-susceptibilities in 37% of patients in 2008 and in 70% in 2015.

CONCLUSIONS

The present study confirmed a high prevalence of periodontal pathogens in the subgingival microbiota of German periodontitis patients. The data revealed an incremental increase in isolates displaying resistance to some antibiotics but no relevant change in susceptibility to amoxicillin and metronidazole.

Non-Surgical Periodontal Therapy with Adjunctive Amoxicillin/Metronidazole or Metronidazole When No Aggregatibacter actinomycetemcomitans Is Detected—A Randomized Clinical Trial

Background: The aim was to compare two different systemic antibiotics regimens adjunctive to non-surgical periodontal therapy when Aggregatibacter actinomycetemcomitans was not detected in the subgingival biofilm. Methods: A total of 58 patients with periodontitis and with no A. actinomycetemcomitans in the subgingival biofilm were treated with full-mouth subgingival instrumentation and either metronidazole (MET; n = 29) or amoxicillin/metronidazole (AMX/MET; n = 29). Probing depth (PD), clinical attachment level (CAL) and bleeding on probing (BOP) were recorded at baseline, as well as after three and six months. Subgingival biofilm and gingival crevicular fluid were collected and analyzed for major periodontopathogens and biomarkers. Results: PD, CAL and BOP improved at 3 and 6 months (each p < 0.001 vs. baseline) with no difference between the groups. Sites with initial PD ≥ 6 mm also improved in both groups after 3 and 6 months (p < 0.001) with a higher reduction of PD in the AMX/MET group (p < 0.05). T. forsythia was lower in the AMX/MET group after 3 months (p < 0.05). MMP-8 and IL-1β were without significant changes and differences between the groups. Conclusion: When A. actinomycetemcomitans was not detected in the subgingival biofilm, the adjunctive systemic use of amoxicillin/metronidazole results in better clinical and microbiological outcomes of non-surgical periodontal therapy when the application of systemic antibiotics is scheduled.