Isolation and taxonomy of filamentous fungi in endodontic infections

Microbial spectrum and resistance of odontogenic abscesses - microbiological analysis using next generation sequencing

OBJECTIVES

This study aimed to map the microbiome of odontogenic abscesses using next-generation sequencing (NGS) to identify bacterial and fungal species, as well as antibiotic resistances.

MATERIALS AND METHODS

Wound swabs were taken from patients treated for odontogenic abscesses at the Department of Oral and Maxillofacial Plastic Surgery, University Hospital Bonn. NGS was used to analyze the swabs, and bioinformatic analysis assigned the genetic material to microorganism profiles and identified antibiotic resistances.

RESULTS

Bacteria were detected in all samples from 51 patients. Anaerobes were found in 50 swabs, while aerobic bacteria were detected in 30. Four of the five most common bacterial genera were anaerobes (Fusobacterium, Prevotella, Parvimonas, Porphyromonas). A median of eight genera were identified per swab. Infections were mostly polymicrobial; only one case was a monoinfection with Streptococcus. Aerobic bacteria were less frequent in patients who had prior antibiotic therapy (p = 0.015). Fungi were present in 52.9% of cases, with Malassezia (33.3%), Aspergillus (9.8%), and Candida (3.9%) being the most common. Antibiotic resistance was detected in 66.7% of patients, mainly against lincosamides, macrolides and tetracyclines. Fusobacterium showed a 25.9% resistance rate to clindamycin.

CONCLUSIONS

The microbiome of odontogenic abscesses is polymicrobial, dominated by anaerobic bacteria, and more extensive than indicated by traditional cultural diagnostics. NGS provides detailed pathogen diagnostics, aiding in precise and individualized antibiotic therapy.

CLINICAL RELEVANCE

Improved understanding of the bacterial and fungal spectrum, along with current resistance patterns of odontogenic abscesses, is crucial for optimizing treatment outcomes. NGS offers rapid, accurate and detailed microbiome analysis, enhancing patient-specific therapeutic strategies.

The Effectiveness of Silver Nanoparticles Mixed with Calcium Hydroxide against Candida albicans: An Ex Vivo Analysis

INTRODUCTION

The purpose of this study was to assess the antifungal activity of silver nanoparticles (AgNPs) in combination with calcium hydroxide (Ca(OH)2) against Candida albicans (C. albicans).

METHODS

AgNPs was mixed with pure Ca(OH)2 powder in an aqueous base. A standard suspension (1 × 108 bacterial cells/mL) of C. albicans was prepared in a 96-well plate and incubated on shaker at 37 °C in 100% humidity to allow fungal biofilm formation in infected dentin slices (n = 98). The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of AgNPs alone or with Ca(OH)2 were determined. The samples were separately placed in 24-well tissue culture plates and divided into three experimental groups (0.03, 0.04, and 0.06) and three control groups; negative (saline) and positive chlorhexidine gel and Ca(OH)2. Quantitative measurements of fungal activity by XTT colorimetric assay and qualitative measurements using confocal laser microscopy and scanning electron microscopy were performed.

RESULTS

The cell viability of C. albicans in the experimental groups was significantly reduced compared to the negative control group. The combination of (AgNPs (0.04%) and Ca(OH)2) was the most potent against C. albicans.

CONCLUSIONS

The findings demonstrated that combining silver nanoparticles with Ca(OH)2 was more effective against C. albicans biofilm compared to Ca(OH)2 alone, suggesting a combing effect.

A novel experimental model to investigate fungal involvement shows expression of Dectin-1 in periapical lesion pathogenesis

BACKGROUND

Candida albicans is linked to persistent endodontic lesions. However, the recognition receptor that identifies it is not explored previously.

OBJECTIVES

The aim of this study was to (1) establish a zymosan-induced model of apical periodontitis in mouse, (2) observe the expression of Dectin-1 and its possible relationship with toll-like receptor (TLR) 2 and (3) observe relationship between Osteopontin (OPN) and inflammatory cytokines.

METHODS

A total of 138 Naval Medical Research Institute (NMRI) mice were randomly divided into; Experimental Group n = 69 and Zymosan Group n = 69. Periapical periodontitis was developed in right maxillary molar. The animals were sacrificed at 7, 21 and 42 days. Bone blocks containing the mesial root (n = 15 for qRT-PCR, n = 45 for enzyme-linked immune sorbent assay (ELISA)) were collected for mRNA expression and ELISA. While whole maxilla (n = 3 from each time interval) were used for histology and immunohistochemical analysis. One way analysis of variance (ANOVA) and Tuckey's posthoc was used for statistical analysis at p ≤ .05.

RESULTS

TLR-2, Dectin-1 and TLR4-positive cells was detected at all time intervals in both groups. A strong positive correlation was observed between TLR-2 and Dectin-1 in both lesions (regular r = .680, p = .015, zymosan (r = .861, p < .001)). A significant correlation was found between OPN and tumour necrosis factor-alpha (TNF-α) in zymosan lesion (r = .827, p = .001).

CONCLUSIONS

Immune cells of inflamed periapical tissue expressed Dectin-1 receptor in response to the microbial challenge from infected root canals and showed positive correlation with TLR-2 and OPN suggesting a possible receptor collaboration mediated by OPN. The expression of OPN and TNF-α showed positive correlation in response to fungal antigen, indicating a possible relationship.

Periodontitis is associated with the development of fungal sinusitis: A nationwide 12-year follow-up study

AIM

The incidence of fungal sinusitis is increasing; however, its pathophysiology has not been investigated previously. We investigate the effect of periodontitis on the incidence of fungal sinusitis over a 12-year follow-up period using nationwide population-based data.

MATERIALS AND METHODS

The periodontitis group was randomly selected from the National Health Insurance Service database. The non-periodontitis group was obtained by propensity score matching considering several variables. The primary end point was the diagnosis of sinonasal fungal balls (SFBs) and invasive fungal sinusitis (IFS).

RESULTS

The periodontitis and non-periodontitis groups included 12,442 and 12,442 individuals, respectively. The overall adjusted hazard ratio (aHR) for SFBs in the periodontitis group was 1.46 (p = .002). In subgroup analysis, the aHR for SFBs was 1.59 (p = 0.008) for those with underlying chronic kidney disease (CKD), 1.58 (p = .022) for those with underlying atopic dermatitis, 1.48 (p = .019) for those with chronic obstructive pulmonary disease (COPD), and 1.36 (p = .030) for those with diabetes mellitus (DM), but these values are applicable only when considering the relationship between periodontitis and SFB. The aHR for IFS in the periodontitis group was higher than in the non-periodontitis group (2.80; p = .004).

CONCLUSIONS

The risk of SFBs and IFS increased after diagnosis of periodontitis. This trend is often more severe in patients with DM, COPD, or CKD, but this association with underlying diseases is applicable only when considering the association between periodontitis and fungal sinusitis.

A Repertoire of Clinical Non-Dermatophytes Moulds

Humans are constantly exposed to micromycetes, especially filamentous fungi that are ubiquitous in the environment. In the presence of risk factors, mostly related to an alteration of immunity, the non-dermatophyte fungi can then become opportunistic pathogens, causing superficial, deep or disseminated infections. With new molecular tools applied to medical mycology and revisions in taxonomy, the number of fungi described in humans is rising. Some rare species are emerging, and others more frequent are increasing. The aim of this review is to (i) inventory the filamentous fungi found in humans and (ii) provide details on the anatomical sites where they have been identified and the semiology of infections. Among the 239,890 fungi taxa and corresponding synonyms, if any, retrieved from the Mycobank and NCBI Taxonomy databases, we were able to identify 565 moulds in humans. These filamentous fungi were identified in one or more anatomical sites. From a clinical point of view, this review allows us to realize that some uncommon fungi isolated in non-sterile sites may be involved in invasive infections. It may present a first step in the understanding of the pathogenicity of filamentous fungi and the interpretation of the results obtained with the new molecular diagnostic tools.

Oral microbiota associated with gingiva of healthy, gingivitis and periodontitis cases

Oral microbes coexist with each other in a symbiotic relationship or as commensals in healthy body. Teeth and oral cavity harbor diverse community of fungi and bacteria. This study focused on bacterial and fungal component of gingiva, where the last occupy little attention. In addition to study the antimicrobial activity of toothpastes, mouth washes and natural oils against microorganisms. Sixty swabs from outer surfaces of gingiva in healthy persons, as well as patients complaining of gingivitis and periodontitis were collected for fungal and bacterial analyses. Sensitivity of the isolated microorganisms to some pharmaceutical preparations and natural oils was also performed. Ten fungal and 9 bacterial species were identified. There is a highly significant variation in the frequency of Klebsiella pneumonia among healthy, gingivitis and periodontitis. Also, Candida tropicalis and cocci bacteria showed significant diversity among the three tested groups. Among pharmaceutical preparations (toothpastes and mouth washes) and natural oils, Paradontax, Hexitol and clove oil showed the best antimicrobial activity against tested fungal and bacterial strains. Although, minimum inhibition concentrations (MICs) of clove oil were high compared to Paradontax and Hexitol, nevertheless, it is highly recommended as both antifungal and antibacterial agent against oral pathogenic microorganisms, because it is a natural compound and nearly devoid of side effects.

Prevalence of Fungi in Primary Endodontic Infections of a Greek-living Population Through Real-time Polymerase Chain Reaction and Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry

INTRODUCTION

Fungi are considered to be opportunistic pathogens that may play a significant role in the pathogenesis of endodontic infections. The main purpose of this study was to assess the prevalence of 2 selected genera of fungi, Candida albicans and Aspergillus spp., using real-time polymerase chain reaction (RT-PCR) and to compare the findings with the respective ones obtained by a culture-dependent approach, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS). A secondary aim was to assess the presence of other bacteria growing under aerobic conditions.

METHODS

Microbial samples were obtained from the root canals of 60 teeth associated with pulp necrosis and apical periodontitis. DNA was extracted, and RT-PCR was applied for the detection of C. albicans and Aspergillus spp. pathogenic subtypes. In addition, MALDI-ToF MS was performed to identify microorganisms grown under aerobic conditions.

RESULTS

Based on RT-PCR, Aspergillus was detected in 8 cases, whereas C. albicans was detected in 4 cases. Using MALDI-ToF MS, no trace of Aspergillus was detected, whereas C. albicans was identified in 2 cases. Significant differences were revealed in the detection potential for Aspergillus spp. between MALDI-ToF MS and RT-PCR (P = .01); conversely, this was not the case for C. albicans (P = .50). After MALDI-ToF MS, 35 samples showed evidence of bacterial growth. The vast majority was colonized by Achromobacter xylosoxidans followed by Lactobacillus spp., Methylobacterium spp., and Enterococcus faecalis.

CONCLUSIONS

The findings confirm the presence of fungi in primarily infected canals with apical periodontitis as well as some rarely inspected aerobic bacterial species. A. xylosoxidans was prevalent; however, the clinical relevance of its presence needs to be investigated further.

Inhibition of adhesion-specific genes by Solidago virgaurea extract causes loss of Candida albicans biofilm integrity

AIMS

Candida albicans biofilms are commonly associated with severe oral infections. We previously discovered that a crude extract from the Solidago virgaurea plant (SV extract) was a potent inhibitor of C. albicans biofilm formation. Here, we further investigate the mechanisms underlying C. albicans biofilm inhibition by the SV extract.

METHODS AND RESULTS

The SV extract was shown to inhibit laboratory and clinical C. albicans isolates adherence and hyphal transition on inert support and epithelial human cells, without affecting viability and growth of planktonic yeasts. Interestingly, RT-PCR-based experiments demonstrated that some key genes involved in adhesion and hyphal morphological switch (e.g. Hwp1p, Ece1p, Als3p) were strongly down-regulated by the SV extract. Moreover, antimicrobial synergy testing (checkerboard assay) demonstrated that antifungal effects of miconazole, nystatin or a common antiseptic mouthwash were synergistically improved when used in combination with the SV extract.

CONCLUSIONS

The SV extract prevents C. albicans biofilm formation through direct inhibition of key adherence and hyphae-associated genes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Biofilm is considered as a key virulence factor of C. albicans infection. Our discovery of an inhibitor specifically acting on genes involved in biofilm formation paves the way for the future development of a new class of antifungal product.

Prevalence of Candida Species in Endodontic Infections: Systematic Review and Meta-analysis

INTRODUCTION

Candida in endodontic infections has been investigated in a large number of studies, but its role as an endodontic pathogen is still debatable. The aim of this study was to systematically review the literature on the prevalence of Candida species in root canal infections.

METHODS

Extensive literature research was performed in the most important electronic biomedical databases, and additional studies have been identified from references from relevant articles. Studies were critically appraised using a modified version of the Joanna Briggs Institute Critical Appraisal Checklist.

RESULTS

From 2225 unique records, 2118 were excluded on the basis of title and abstract. Of the remaining 107 studies, 50 were excluded after full-text review, and 57 were included for qualitative and quantitative analysis. The overall prevalence of Candida spp. in root canal infections was 8.20% (95% confidence interval, 5.56%-11.21%). Candida albicans was the most frequently isolated species. Significant heterogeneity among studies was observed (P < .001, I² = 86.07%). Subgroup analyses revealed a higher prevalence of Candida spp. from African samples. All studies considered, a high or unclear risk of bias was prevalent regarding 6 out of the 8 items considered in the critical appraisal.

CONCLUSIONS

Candida spp. occurred in a small proportion of root canal infections. Further and better designed research is needed to investigate the real contribution of Candida spp. to the microbial ecology in infected root canals.

Biodiversity of the human oral mycobiome in health and disease

The organisms that colonize the human body over a lifetime are diverse, extensive and gargantuan. A fair proportion of the microbiota that constitutes this human microbiome live within our oral cavities mostly as harmonious associates causing only sporadic disease. An important core constituent of the microbiome is the mycobiome, representing various fungal genera. Up until recently, only a few species of fungi, mainly Candida species, were thought to constitute the human oral mycobiome. The reasons for this are manifold, although the uncultivable nature of many fungi in conventional laboratory media, and their complex genetic composition seem to be the major factors which eluded their detection over the years. Nevertheless, recent advances in computing and high-throughput sequencing such as next-generation sequencing (NGS) platforms have provided us a panoramic view of a totally new world of fungi that are human oral cohabitués. Their diversity is perplexing, and functionality yet to be deciphered. Here, we provide a glimpse of what is currently known of the oral mycobiome, in health and disease, with some future perspectives.

Use of magnetic nanoparticles as a drug delivery system to improve chlorhexidine antimicrobial activity

Nanotechnology offers new tools for developing therapies to prevent and treat oral infections, particularly biofilm-dependent disorders, such as dental plaques and endodontic and periodontal diseases. Chlorhexidine (CHX) is a well-characterized antiseptic agent used in dentistry with broad spectrum activity. However, its application is limited due to inactivation in body fluid and cytotoxicity toward human cells, particularly at high concentrations. To overcome these limitations, we synthesized nanosystems composed of aminosilane-coated magnetic nanoparticles functionalized with chlorhexidine (MNP@CHX). In the presence of human saliva, MNPs@CHX displayed significantly greater bactericidal and fungicidal activity against planktonic and biofilm-forming microorganisms than free CHX. In addition, CHX attached to MNPs has an increased ability to restrict the growth of mixed-species biofilms compared to free CHX. The observed depolarization of mitochondria in fungal cells treated with MNP@CHX suggests that induction of oxidative stress and oxidation of fungal structures may be a part of the mechanism responsible for pathogen killing. Nanoparticles functionalized by CHX did not affect host cell proliferation or their ability to release the proinflammatory cytokine, IL-8. The use of MNPs as a carrier of CHX has great potential for the development of antiseptic nanosystems.

Investigations of the prevalence and virulence of Candida albicans in periodontal and endodontic lesions in diabetic and normoglycemic patients

Pulpal and periodontal tissues have similar microbiota that allows cross-contamination between the pulp and periodontal tissues.

Prevalence and nature of fungi in root canal infections: a systematic review and meta-analysis

The role of bacteria in causing apical periodontitis has been widely established, whilst the role of other microorganisms is studied less thoroughly. This systematic review and meta-analysis reviewed the literature for the prevalence and diversity of fungi in root canal infections. An extensive literature search was carried out in the Cochrane databases, EMBASE, MEDLINE, LILACS, SciELO and Web of Science. Additional studies were identified from six endodontic journals, four main endodontic textbooks and references of relevant papers. Selected clinical studies included sampling of necrotic pulps in permanent teeth and microbial analysis of these samples. Studies were critically appraised using the Joanna Briggs Institute Prevalence Critical Appraisal Checklist. Meta-analysis was performed using MetaXL. The screening of 1041 titles and abstracts and full-text reading yielded 54 studies. The overall prevalence of fungi in root canal infections was 7.5% (CI 95%: 3.6-11.8%) in the inverse variance fixed effect heterogeneity model. Candida albicans was the most frequently isolated species. Significant heterogeneity was observed (P < 0.001, I²  = 85.04%). Subgroup analyses based on geographical location, period of publication, type of infection, state of general health, communication with the oral cavity, type of sample and identification method revealed no factor influencing the prevalence. Better standardized techniques and a comprehensive analysis will reveal a more detailed and accurate representation of the prevalence and nature of fungi in root canal infections.

Mining the oral mycobiome: Methods, components, and meaning

Research on oral fungi has centered on Candida. However, recent internal transcribed spacer (ITS)-based studies revealed a vast number of fungal taxa as potential oral residents. We review DNA-based studies of the oral mycobiome and contrast them with cultivation-based surveys, showing that most genera encountered by cultivation have also been detected molecularly. Some taxa such as Malassezia, however, appear in high prevalence and abundance in molecular studies but have not been cultivated. Important technical and bioinformatic challenges to ITS-based oral mycobiome studies are discussed. These include optimization of sample lysis, variability in length of ITS amplicons, high intra-species ITS sequence variability, high inter-species variability in ITS copy number and challenges in nomenclature and maintenance of curated reference databases. Molecular surveys are powerful first steps to characterize the oral mycobiome but further research is needed to unravel which fungi detected by DNA are true oral residents and what role they play in oral homeostasis.

Interaction of Candida albicans with periodontal ligament fibroblasts limits biofilm formation over elastomer silicone disks

OBJECTIVE

Candida albicans is the most numerous commensal and potentially pathological yeast in the human oral cavity. The purpose herein is to investigate the ability of C. albicans to form a biofilm in the presence of periodontal ligament (PDL) fibroblasts.

MATERIAL AND METHODS

Silicone elastomer disks (SE) were transferred to wells containing PDL cells. C. albicans suspension was added to each well. The whole mixed culture was then allowed to form a biofilm for 48h. Biofilms were quantified by tetrazolium-salt-based (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenyl amino) carbonyl]- 2H-tetrazolium hydroxide (XTT). Furthermore, biofilm was visualized by confocal scanning laser and scanning electron microscopy. Migration of C. albicans and its ability to form biofilms in presence of PDL cells was determined by using a transwell system. Last, elutes obtained from co-culturing C. albicans and PDL cells were added to SE disks and covered with C. albicans. The culture plate was then incubated to allow biofilm formation. Biofilms formed over SE disks were quantified using XTT.

RESULTS

PDL cells significantly limited the biofilm formation at incubation interval of 48h. PDL cells induced less biofilm compared to mature and thick hyphae in the absence of PDL cells as seen in confocal scanning laser and scanning electron microscopy. The presence of PDL cells limited the migration and formation of biofilm by C. albicans. Elutes obtained from co-culturing PDL cells with C. albicans for one hour induced significantly less biofilm.

CONCLUSIONS

This is the first study to report that PDL cells exhibit antifungal activity. While the exact mechanism of how PDL cells limited biofilm formation is yet unknown, it was clear that competent PDL cells promote resistance to C. albicans biofilm formation.

Sterilization of rotary NiTi instruments within endodontic sponges

AIM

To determine whether the following can be sterilized by autoclaving - endodontic sponges, rotary nickel-titanium (NiTi) instruments within endodontic sponges, and rotary NiTi instruments with rubber stoppers.

METHODOLOGY

Sixty-four samples of eight different endodontic sponges (n = 512) were placed into brain heart infusion broth (BHI) for 72 h. An aliquot of this was then spread onto horse blood agar and cultured aerobically and anaerobically to test sterility at purchase. Bacterial suspensions of Enterococcus faecalis, Porphyromonas gingivalis and Geobacillus stearothermophilus in BHI were used to contaminate sterile sponges and rotary NiTi instruments (with and without rubber stoppers) inserted into sponges. The various samples were autoclaved and then cultured aerobically and anaerobically. Success of sterilization was measured qualitatively as no growth. The experiment was repeated with clinically used rotary NiTi instruments (n = 512). All experiments were conducted in quadruplicate.

RESULTS

No sponges on purchase had microbial growth when anaerobically cultured but some did when aerobically cultured. All autoclaved sponges and instruments (within or without sponges, and with or without rubber stoppers) were associated with no microbial growth. All nonautoclaved positive control samples showed microbial growth.

CONCLUSIONS

Autoclaving was effective in the sterilization of sponges and endodontic instruments. Endodontic sponges should be autoclaved before clinical use. For clinical efficiency and cost-effectiveness, rotary NiTi instruments can be sterilized in endodontic sponges without removal of rubber stoppers.

Aspergillus in endodontic infection near the maxillary sinus

Introduction

Diseases of the maxillary sinus have been associated with dental roots near the maxillary sinus that have undergone endodontic treatment.

Objective

To investigate the presence of filamentous fungi in patients with dental roots near the maxillary sinus who had apical periodontitis treated endodontically, and to alert practitioners that this could be a possible avenue of contamination of the sinus in patients who develop maxillary sinus infection.

Methods

Cross-sectional study in 60 palatal roots of the first maxillary molars near the maxillary sinus, that underwent endodontic treatment for apical periodontitis. After removal of the filling material, dentin shavings were collected and placed in test tubes containing Sabouraud dextrose agar and chloramphenicol. The phenotype was determined by macroscopic and microscopic examination of the colonies. For polymerase chain reaction, the primers ITS-5 and ITS-4 were used. The sequences obtained were compared with those deposited at GenBank using the Basic Local Alignment Search Tool program.

Results

Filamentous fungi were isolated from 6 of 60 canals (10%): Aspergillus niger (6.7%), Aspergillus versicolor (1.6%), and Aspergillus fumigatus (1.6%).

Conclusion

Root canals near the maxillary sinus with endodontic treatment and apical periodontitis may exhibit positive cultures for filamentous fungi. Interested professionals should be alert, because these microorganisms have pathogenic characteristics that can cause disease of odontogenic origin in the maxillary sinus.