Actinomyces israelii has long been recognized as a causative agent of actinomycosis. During the past 3 decades, a large number of novel Actinomyces species have been described. Their detection and ...identification in clinical microbiology laboratories and recognition as pathogens in clinical settings can be challenging. With the introduction of advanced molecular methods, knowledge about their clinical relevance is gradually increasing, and the spectrum of diseases associated with Actinomyces and Actinomyces-like organisms is widening accordingly; for example, Actinomyces meyeri, Actinomyces neuii, and Actinomyces turicensis as well as Actinotignum (formerly Actinobaculum) schaalii are emerging as important causes of specific infections at various body sites. In the present review, we have gathered this information to provide a comprehensive and microbiologically consistent overview of the significance of Actinomyces and some closely related taxa in human infections.
Objective: This study was conducted to assess the susceptibility of human clinical isolates of Actinomyces species to 12 antimicrobial agents. Methods: Human clinical isolates of Actinomyces spp. ...were collected from stored collections held at the Microbiology Department, Edinburgh University, Anaerobe Reference Laboratory, Cardiff, Glasgow Dental Hospital and Glasgow Royal Infirmary. Each isolate was identified by restriction analysis of amplified 16S ribosomal DNA. MICs of 12 antibiotics comprising benzyl penicillin, amoxicillin, ceftriaxone, linezolid, tetracycline, deoxycycline, clindamycin, erythromycin, clarithromycin, ciprofloxacin, meropenem and piperacillin/tazobactam for 87 strains of Actinomyces species were obtained by Etest methodology. Results: The Actinomyces species identified for this study comprised: Actinomyces israelii, Actinomyces gerencseriae, Actinomyces turicensis, Actinomyces funkei, Actinomyces graevenitzii and Actinomyces europaeus. All isolates were susceptible to penicillin and amoxicillin. All but one strain of A. turicensis was susceptible to linezolid. A number of A. europaeus and A. graevenitzii isolates were resistant to ceftriaxone and piperacillin/tazobactam. A number of isolates of A. turicensis and A. europaeus also demonstrated resistance to erythromycin. All Actinomyces species tested appeared resistant to ciprofloxacin. Conclusions: Actinomyces species appear to be susceptible to a wide range of β-lactam agents and these, when combined with β-lactamase inhibitors, should be regarded as agents of first choice. Ciprofloxacin performed poorly. Tetracyclines also demonstrated poor performance. This is the first study of antimicrobial susceptibilities for a number of accurately identified clinical isolates of Actinomyces spp. There are a number of species differences in susceptibility profiles to the antimicrobials tested, suggesting that accurate identification and speciation may have an impact on clinical outcome.
Saccharibacteria (TM7) are obligate epibionts living on the surface of their host bacteria and are strongly correlated with dysbiotic microbiomes during periodontitis and other inflammatory diseases, ...suggesting they are putative pathogens. However, due to the recalcitrance of TM7 cultivation, causal research to investigate their role in inflammatory diseases is lacking. Here, we isolated multiple TM7 species on their host bacteria from periodontitis patients. These TM7 species reduce inflammation and consequential bone loss by modulating host bacterial pathogenicity in a mouse ligature-induced periodontitis model. Two host bacterial functions involved in collagen binding and utilization of eukaryotic sialic acid are required for inducing bone loss and are altered by TM7 association. This TM7-mediated downregulation of host bacterial pathogenicity is shown for multiple TM7/host bacteria pairs, suggesting that, in contrast to their suspected pathogenic role, TM7 could protect mammalian hosts from inflammatory damage induced by their host bacteria.
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•Saccharibacteria (TM7) is an epibiont that lives on the surface of Actinobacteria•Multiple TM7 isolates from periodontitis patients decrease inflammatory bone loss•TM7 reduce bone loss by modulating the pathogenicity of their host Actinobacteria•TM7 could serve a protective role for mammalian hosts in inflammatory diseases
If certain bacteria are increased in disease, does that mean they are bad? Chipashvili et al. show that this may not be the case for ultrasmall Saccharibacteria. By using a mouse model for periodontitis, they determined that Saccharibacteria offer protection by reducing the pathogenicity of other bacteria in inflammatory diseases.
Despite many examples of obligate epibiotic symbiosis (one organism living on the surface of another) in nature, such an interaction has rarely been observed between two bacteria. Here, we further ...characterize a newly reported interaction between a human oral obligate parasitic bacterium TM7x (cultivated member of Candidatus Saccharimonas formerly Candidate Phylum TM7), and its basibiont Actinomyces odontolyticus species (XH001), providing a model system to study epiparasitic symbiosis in the domain Bacteria. Detailed microscopic studies indicate that both partners display extensive morphological changes during symbiotic growth. XH001 cells manifested as short rods in monoculture, but displayed elongated and hyphal morphology when physically associated with TM7x. Interestingly, these dramatic morphological changes in XH001 were also induced in oxygen-depleted conditions, even in the absence of TM7x. Targeted quantitative real-time PCR (qRT-PCR) analyses revealed that both the physical association with TM7x as well as oxygen depletion triggered up-regulation of key stress response genes in XH001, and in combination, these conditions act in an additive manner. TM7x and XH001 co-exist with relatively uniform cell morphologies under nutrient-replete conditions. However, upon nutrient depletion, TM7x-associated XH001 displayed a variety of cell morphologies, including swollen cell body, clubbed-ends, and even cell lysis, and a large portion of TM7x cells transformed from ultrasmall cocci into elongated cells. Our study demonstrates a highly dynamic interaction between epibiont TM7x and its basibiont XH001 in response to physical association or environmental cues such as oxygen level and nutritional status, as reflected by their morphological and physiological changes during symbiotic growth.
Around one-quarter of bacterial diversity comprises a single radiation with reduced genomes, known collectively as the Candidate Phyla Radiation. Recently, we coisolated TM7x, an ultrasmall strain of ...the Candidate Phyla Radiation phylum Saccharibacteria, with its bacterial host Actinomyces odontolyticus strain XH001 from human oral cavity and stably maintained as a coculture. Our current work demonstrates that within the coculture, TM7x cells establish a longterm parasitic association with host cells by infecting only a subset of the population, which stay viable yet exhibit severely inhibited cell division. In contrast, exposure of a naïve A. odontolyticus isolate, XH001n, to TM7x cells leads to high numbers of TM7x cells binding to each host cell, massive host cell death, and a host population crash. However, further passaging reveals that XH001n becomes less susceptible to TM7x over time and enters a long-term stable relationship similar to that of XH001. We show that this reduced susceptibility is driven by rapid host evolution that, in contrast to many forms of phage resistance, offers only partial protection. The result is a stalemate where infected hosts cannot shed their parasites; nevertheless, parasite load is sufficiently low that the host population persists. Finally, we show that TM7x can infect and form stable longterm relationships with other species in a single clade of Actinomyces, displaying a narrow host range. This system serves as a model to understand how parasitic bacteria with reduced genomes such as those of the Candidate Phyla Radiation have persisted with their hosts and ultimately expanded in their diversity.
The human oral cavity is home to a large number of bacteria and bacteriophages (phages). However, the biology of oral phages as members of the human microbiome is not well understood. Recently, we ...isolated
subsp.
strain XH001 from the human oral cavity, and genomic analysis revealed the presence of an intact prophage named xhp1. Here, we demonstrated that xhp1 is a linear plasmid-like prophage, which is a newly identified phage of
The prophage xhp1 genome is a 35-kb linear double-stranded DNA with 10-bp single-stranded, 3' cohesive ends. xhp1 exists extrachromosomally, with an estimated copy number of 5. Annotation of xhp1 revealed 54 open reading frames, while phylogenetic analysis suggests that it has limited similarity with other phages. xhp1 phage particles can be induced by mitomycin C and belong to the
family, according to transmission electron microscopic examination. The released xhp1 particles can reinfect the xhp1-cured XH001 strain and result in tiny blurry plaques. Moreover, xhp1 promotes XH001 biofilm formation through spontaneous induction and the release of host extracellular DNA (eDNA). In conclusion, we identified a linear plasmid-like prophage of
, which enhances bacterial host biofilm assembly and could be beneficial to the host for its persistence in the oral cavity.
The biology of phages as members of the human oral microbiome is understudied. Here, we report the characterization of xhp1, a novel linear plasmid-like prophage identified from a human oral isolate,
subsp.
strain XH001. xhp1 can be induced and reinfect xhp1-cured XH001. The spontaneous induction of xhp1 leads to the lysis of a subpopulation of bacterial hosts and the release of eDNA that promotes biofilm assembly, thus potentially contributing to the persistence of
within the oral cavity.
Abstract This study investigated the prevalence of Actinomyces spp. in shallow, deep and very deep pockets of patients with chronic periodontitis compared to healthy controls and correlated the ...results with clinical status. Twenty patients with chronic periodontitis and 15 healthy subjects were enrolled in this study. Clinical indices were recorded in a six-point measurement per tooth. From each patient samples of supra and subgingival plaque were taken separately from teeth with shallow, deep and very deep pockets. Samples of supragingival plaque and sulcular microflora were collected from the healthy subjects. All the samples were cultivated on different media at 37 ̊C in an anaerobic atmosphere for 7 days. All the suspect colonies were identified using a rapid ID 32 A system (bioMèrieux) and MALDI-TOF-MS analysis using an Autoflex II Instrument (Bruker Daltonics) together with in house developed identification software and a reference spectra database. A total of 977 strains were identified as Actinomyces. Actinomyces naeslundii/oris/johnsonii (430 isolates) was the most prevalent species and was found in all patients and in almost all of the healthy subjects. Significant differences ( p = 0.003) between the groups were found for Actinomyces odontolyticus/meyeri and Actinomyces israelii which were associated with periodontitis patients. Actinomyces dentalis was found in higher percentage ( p = 0.015) in the periodontitis group. Actinomyces gerencseriae and Actinomyces massiliensis were significantly more often found supragingivally than subgingivally ( p = 0.004, p = 0.022, respectively) in the periodontitis group. Whether some Actinomyces species, definitely important plaque formers, are actively involved in the pathogenicity of chronic periodontitis needs further investigation.
Actinomyces são bactérias filamentosas gram-positivas anaeróbias mais comumente envolvidas em infecções granulomatosas cervicofaciais. Geralmente têm curso clínico indolente, porém, em alguns casos, ...podem ser localmente destrutivas. Estes organismos são raramente implicados em infecções do ouvido médio, ocasionalmente causando complicações como mastoidite crônica. Relatamos o caso de um homem, 48 anos, em situação de rua, com quadro de otalgia, otorreia purulenta e saída de cerca de trinta larvas de orelha esquerda há cinco dias. Também apresentava quadro de tosse subaguda, perda de peso e febre não aferida. Ao exame, constatou-se quadro de miíase em orelha esquerda com otite externa e pericondrite. Exame de tomografia computadorizada mostrou mastóide preenchida por material granulomatoso, com falhas ósseas da mastóide e osso temporal. Foram retiradas manualmente mais de quinze larvas e iniciado antibioticoterapia com ciprofloxacino. Cultura de secreção de orelha esquerda mostrou crescimento de Bacteroides ovatus e Streptococcus anginosus, sendo associado amoxicilina-clavulanato. Posteriormente, o paciente foi diagnosticado com tuberculose pulmonar e iniciou tratamento com esquema básico. Houve a suspeita de tuberculose do conduto auditivo, porém todas as pesquisas resultaram negativas. Realizada biópsia de conduto auditivo externo com crescimento de flora anaeróbia (Peptostreptococcus anaerobius, Bacteroides fragilis e Prevotella oris) e Actinomyces sp. Por manutenção da otorreia purulenta e otalgia, apesar de antibioticoterapia dirigida, paciente foi submetido a mastoidectomia radical à esquerda, com resolução daqueles sintomas. Paciente teve alta com prescrição de amoxicilina-clavulanato e terapia antituberculosa, porém perdeu seguimento ambulatorial posteriormente. A actinomicose da orelha média e mastóide é uma entidade rara. Clinicamente, apresenta-se como uma otite crônica supurativa refratária ao tratamento médico. Frequentemente a infecção é polimicrobiana, incluindo bactérias anaeróbias e espécies de Streptococcus. O diagnóstico geralmente é feito através da análise histopatológica devido dificuldade de crescimento em culturas e as penicilinas constituem-se como tratamento de primeira linha. Este caso reforça a importância do desbridamento cirúrgico e antibioticoterapia de longo prazo para controle da doença. Apesar de rara, esta infecção deve ser considerada no diagnóstico diferencial de otomastoidites crônicas resistentes à terapia padrão.
In dental plaque α-haemolytic streptococci, including Streptococcus gordonii, are considered beneficial for oral health. These organisms produce hydrogen peroxide (H₂O₂) at concentrations sufficient ...to kill many oral bacteria. Streptococci do not produce catalase yet tolerate H₂O₂. We recently demonstrated that coaggregation with Actinomyces naeslundii stabilizes arginine biosynthesis in S. gordonii. Protein arginine residues are sensitive to oxidation by H₂O₂. Here, the ability of A. naeslundii to protect S. gordonii against self-produced H₂O₂ was investigated. Coaggregation with A. naeslundii enabled S. gordonii to grow in the absence of arginine, and promoted survival of S. gordonii following growth with or without added arginine. Arginine-replete S. gordonii monocultures contained 20-30 μM H₂O₂ throughout exponential growth. Actinomyces naeslundii did not produce H₂O₂ but synthesized catalase, removed H₂O₂ from coaggregate cultures and decreased protein oxidation in S. gordonii. On solid medium, S. gordonii inhibited growth of A. naeslundii; exogenous catalase overcame this inhibition. In coaggregate cultures, A. naeslundii cell numbers were >90% lower than in monocultures after 24 h. These results indicate that coaggregation with A. naeslundii protects S. gordonii from oxidative damage. However, high cell densities of S. gordonii inhibit A. naeslundii. Therefore, H₂O₂ may drive these organisms towards an ecologically balanced community in natural dental plaque.
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