Dental biofilms produce acids from carbohydrates that result in caries. According to the extended caries ecological hypothesis, the caries process consists of 3 reversible stages. The microflora on ...clinically sound enamel surfaces contains mainly non-mutans streptococci and Actinomyces, in which acidification is mild and infrequent. This is compatible with equilibrium of the demineralization/remineralization balance or shifts the mineral balance toward net mineral gain (dynamic stability stage). When sugar is supplied frequently, acidification becomes moderate and frequent. This may enhance the acidogenicity and acidurance of the non-mutans bacteria adaptively. In addition, more aciduric strains, such as ‘low-pH’ non-mutans streptococci, may increase selectively. These microbial acid-induced adaptation and selection processes may, over time, shift the demineralization/remineralization balance toward net mineral loss, leading to initiation/progression of dental caries (acidogenic stage). Under severe and prolonged acidic conditions, more aciduric bacteria become dominant through acid-induced selection by temporary acid-impairment and acid-inhibition of growth (aciduric stage). At this stage, mutans streptococci and lactobacilli as well as aciduric strains of non-mutans streptococci, Actinomyces, bifidobacteria, and yeasts may become dominant. Many acidogenic and aciduric bacteria are involved in caries. Environmental acidification is the main determinant of the phenotypic and genotypic changes that occur in the microflora during caries.
We present the case of a 60-year-old woman with ESRD diagnosed with polymicrobial (PD) catheter-associated peritonitis including Actinomyces neuii treated with catheter retention and intraperitoneal ...antibiotics and a review of eight previously-described cases of PD-catheter-associated Actinomyces peritonitis. While data are limited, catheter retention in such cases may succeed if responding rapidly to therapy.
•We report a case of polymicrobial peritoneal dialysis catheter-associated peritonitis.•Actinomyces neuii is an uncommon cause of peritoneal-dialysis catheter associated peritonitis.•Catheter removal may not be necessary in cases where patients progress well.•A prolonged course of a penicillin or ceftriaxone is likely necessary though data are limited.
Pulmonary mass lesions are very commonly encountered in our practice. Sometimes they present as homogenous opacity on a Chest Xray or CT scan and sometimes as a collapsed lung. Most of them are ...malignant and some are benign also. Lung infections rarely present as endobronchial mass. Only histopathology can aid us in diagnosing. One rare disease that can present as an invasive mass lesion is Pulmonary actinomycosis. We present a case of Lung actinomycosis coinfected with Mycobacterium tuberculosis that presented to us with the complaint of right lung collapse and effusion due to endobronchial growth mimicking lung malignancy.
Coeliac disease is characterized by intestinal inflammation caused by gluten, proteins which are widely contained in the Western diet. Mammalian digestive enzymes are only partly capable of cleaving ...gluten, and fragments remain that induce toxic responses in patients with coeliac disease. We found that the oral microbiome is a novel and rich source of gluten-degrading organisms. Here we report on the isolation and characterization of the cultivable resident oral microbes that are capable of cleaving gluten, with special emphasis on the immunogenic domains. Bacteria were obtained by a selective culturing approach and enzyme activities were characterized by: (i) hydrolysis of paranitroanilide-derivatized gliadin-derived tripeptide substrates; (ii) gliadin degradation in-gel (gliadin zymography); (iii) gliadin degradation in solution; (iv) proteolysis of the highly immunogenic α-gliadin-derived 33-mer peptide. For selected strains pH activity profiles were determined. The culturing strategy yielded 87 aerobic and 63 anaerobic strains. Species with activity in at least two of the four assays were typed as: Rothia mucilaginosa HOT-681, Rothia aeria HOT-188, Actinomyces odontolyticus HOT-701, Streptococcus mitis HOT-677, Streptococcus sp. HOT-071, Neisseria mucosa HOT-682 and Capnocytophaga sputigena HOT-775, with Rothia species being active in all four assays. Cleavage specificities and substrate preferences differed among the strains identified. The approximate molecular weights of the enzymes were ~75 kD (Rothia spp.), ~60 kD (A. odontolyticus) and ~150 kD (Streptococcus spp.). In conclusion, this study identified new gluten-degrading microorganisms in the upper gastrointestinal tract. A cocktail of the most active oral bacteria, or their isolated enzymes, may offer promising new treatment modalities for coeliac disease.
The diversity of bacterial species in the human oral cavity is well recognized, but a high proportion of them are presently uncultivable. Candidate division TM7 bacteria are almost always detected in ...metagenomic studies but have not yet been cultivated. In this paper, we identified candidate division TM7 bacterial phylotypes in mature plaque samples from around orthodontic bonds in subjects undergoing orthodontic treatment. Successive rounds of enrichment in laboratory media led to the isolation of a pure culture of one of these candidate division TM7 phylotypes. The bacteria formed filaments of 20 to 200 μm in length within agar plate colonies and in monospecies biofilms on salivary pellicle and exhibited some unusual morphological characteristics by transmission electron microscopy, including a trilaminated cell surface layer and dense cytoplasmic deposits. Proteomic analyses of cell wall protein extracts identified abundant polypeptides predicted from the TM7 partial genomic sequence. Pleiomorphic phenotypes were observed when the candidate division TM7 bacterium was grown in dual-species biofilms with representatives of six different oral bacterial genera. The TM7 bacterium formed long filaments in dual-species biofilm communities with Actinomyces oris or Fusobacterium nucleatum. However, the TM7 isolate grew as short rods or cocci in dual-species biofilms with Porphyromonas gingivalis, Prevotella intermedia, Parvimonas micra, or Streptococcus gordonii, forming notably robust biofilms with the latter two species. The ability to cultivate TM7 axenically should majorly advance understanding of the physiology, genetics, and virulence properties of this novel candidate division oral bacterium.
Host range is a fundamental component of symbiotic interactions, yet it remains poorly characterized for the prevalent yet enigmatic subcategory of bacteria/bacteria symbioses. The recently ...characterized obligate bacterial epibiont Candidatus Nanosynbacter lyticus TM7x with its bacterial host Actinomyces odontolyticus XH001 offers an ideal system to study such a novel relationship. In this study, the host range of TM7x was investigated by coculturing TM7x with various related Actinomyces strains and characterizing their growth dynamics from initial infection through subsequent co-passages. Of the twenty-seven tested Actinomyces, thirteen strains, including XH001, could host TM7x, and further classified into "permissive" and "nonpermissive" based on their varying initial responses to TM7x. Ten permissive strains exhibited growth/crash/recovery phases following TM7x infection, with crash timing and extent dependent on initial TM7x dosage. Meanwhile, three nonpermissive strains hosted TM7x without a growth-crash phase despite high TM7x dosage. The physical association of TM7x with all hosts, including nonpermissive strains, was confirmed by microscopy. Comparative genomic analyses revealed distinguishing genomic features between permissive and nonpermissive hosts. Our results expand the concept of host range beyond a binary to a wider spectrum, and the varying susceptibility of Actinomyces strains to TM7x underscores how small genetic differences between hosts can underly divergent selective trajectories.
Two previously undescribed, Gram-stain-positive, rod-shaped strains, 410
and 553, were isolated from faeces of the Tibetan antelope (
) from the Tibet-Qinghai Plateau, PR China. The optimum growth ...conditions of the two novel strains were 1 % (w/v) NaCl, 37 °C and pH 7. The end products from glucose fermentation included ethanol and lactic acid. Based on results of 16S rRNA gene sequence comparison and phylogenetic and phylogenomic analyses, strains 410
and 553 were classified into the genus
, and were closely related to
(97.6 %),
(93.5 %) and
(90.8 %). The genomic G+C content of strain 410
was 67.4 mol%. Digital DNA-DNA hybridization values between strain 410
and each of the closely related species were under 70 %. The respiratory quinones were MK-10 (68 %) and MK-9 (32 %). The main cellular fatty acids of the isolates were C
, followed by C
9
. The major polar lipids were diphosphatidylglycerol and phosphatidylinositol-mannoside. The whole-cell sugars contained rhamnose, ribose and glucose. The diagnostic amino acids of cell-wall peptidoglycan included alanine, glutamic acid, lysine and ornithine. The results of biochemical, chemotaxonomic and genotypic analyses revealed that the two novel strains represent a novel species of genus
, for which the name
s
sp. nov. is proposed. The type strain is 410
(=CGMCC 1.16361
= DSM 106201
).
Atmospheric and room temperature plasma (ARTP) was first employed to generate mutants of
Actinomyces
JN537 for improving acarbose production. To obtain higher acarbose producing strains, the method ...of screening the strains for susceptibility to penicillin was used after treatment with ARTP. The rationale for the strategy was that mutants showing penicillin susceptibility were likely to be high acarbose producers, as their ability to synthesize cell walls was weak which might enhance metabolic flux to the pathway of acarbose biosynthesis. Acarbose yield of the mutant strain M37 increased by 62.5 % than that of the original strain. The contents of monosaccharides and amino acids of the cell wall of M37 were lower than that of the original strain. The acarbose production ability in mutant strain remained relatively stable after 10 generations. This work provides a promising strategy for obtaining high acarbose-yield strains by combination of ARTP mutation method and efficient screening technique.
The aim of this study was to investigate and clarify the ambiguous taxonomy of
and its closely related species using state-of-the-art high-throughput sequencing techniques, and, furthermore, to ...determine whether sub-clusters identified within
and
in a previous study by multi locus sequence typing (MLST) using concatenation of seven housekeeping genes should either be classified as subspecies or distinct species. The strains in this study were broadly classified under
group as
genospecies I and genospecies II. Based on MLST data analysis, these were further classified as
and
. The whole genome sequencing of selected strains of
(
= 17) and
(
= 19) was carried out using Illumina Genome Analyzer IIxe and Roche 454 allowing paired-end and single-reads sequencing, respectively. The sequences obtained were aligned using CLC Genomic workbench version 5.1 and annotated using RAST (Rapid Annotation using Subsystem Technology) release version 59 accessible online. Additionally, genomes of seven publicly available strains of
(k20, MG1, c505, OT175, OT171, OT170, and
) were also included. Comparative genomic analysis (CGA) using Mauve, Progressive Mauve, gene-by-gene, Core, and Pan Genome, and finally Digital DNA-DNA homology (DDH) analysis was carried out. DDH values were obtained using in silico genome-genome comparison. Evolutionary analysis using ClonalFrame was also undertaken. The mutation and recombination events were compared using chi-square test among
and
isolates (analysis methods are not included in the study). CGA results were consistent with previous traditional classification using MLST. It was found that strains of
k20, MG1, c505, and OT175 clustered in
group of isolates, while OT171, OT170, and
appeared as separate branches. Similar clustering to MLST was observed for other isolates. The mutation and recombination events were significantly higher in
than
, highlighting the diversity of
strains in the oral cavity. These findings suggest that
forms six distinct groups, whereas
forms three. The correct designation of isolates will help in the identification of clinical
isolates found in dental plaque. Easily accessible online genomic sequence data will also accelerate the investigation of the biochemical characterisation and pathogenesis of this important group of micro-organisms.
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