Putative Microorganisms Research Articles

Chemolithotrophic Biological Nitrogen Fixation Fueled by Antimonite Oxidation May Be Widespread in Sb-Contaminated Habitats.

Nitrogen (N) deficiency in mining-contaminated habitats usually hinders plant growth and thus hampers tailing revegetation. Biological N fixation (BNF) is an essential biogeochemical process that contributes to the initial accumulation of N in oligotrophic mining-contaminated regions. Previous studies reported that chemolithotrophic rather than heterotrophic diazotrophs frequently dominated in the mining-contaminated regions. Chemolithotrophic diazotrophs may utilize elements abundant in such habitats (e.g., sulfur (S), arsenic (As), and antimony (Sb)) as electron donors to fix N2. BNF fueled by the oxidation of S and As has been detected in previous studies. However, BNF fueled by Sb(III) oxidation (Sb-dependent BNF) has never been reported. The current study observed the presence of Sb-dependent BNF in slurries inoculated from Sb-contaminated habitats across the South China Sb belt, suggesting that Sb-dependent BNF may be widespread in this region. DNA-stable isotope probing identified bacteria associated with Rhodocyclaceae and Rhizobiaceae as putative microorganisms responsible for Sb-dependent BNF. Furthermore, metagenomic-binning demonstrated that Rhodocyclaceae and Rhizobiaceae contained essential genes involved in Sb(III) oxidation, N2 fixation, and carbon fixation, suggesting their genetic potential for Sb-dependent BNF. In addition, meta-analysis indicated that these bacteria are widespread among Sb-contaminated habitats with different niche preferences: Rhodocyclaceae was enriched in river sediments and tailings, while Rhizobiaceae was enriched only in soils. This study may broaden our fundamental understanding of N fixation in Sb-mining regions.

Microbially influenced corrosion: Towards an interdisciplinary perspective on mechanisms

A perspective is provided on mechanisms for microbially influenced corrosion by sulfate-reducing bacteria and metal-oxidizing bacteria. The authors discuss the confusion introduced by cross-disciplinary discussions of MIC mechanisms and the divergent terminologies used by microbiologists and electrochemists, e.g. “anaerobic” and “direct electron transfer.” Examination of the cathodic depolarization theory for corrosion of carbon steel by sulfate-reducing bacteria suggests that the theory cannot explain the observations. Stainless steels containing <20% chromium are vulnerable to pitting in the presence of iron and manganese oxides produced by iron- and manganese-oxidizing bacteria, respectively. However, mechanisms for pitting differ between the two oxides. In all cases, understanding mechanisms for microbially influenced corrosion must consider the environment, i.e., the composition of the electrolyte, in addition to the vulnerability of the material in the presence of putative microorganisms. Significant opportunity exists for more integrated approaches to interdisciplinary research and open discourse.

Biodegradation of Pesticides at the Limit: Kinetics and Microbial Substrate Use at Low Concentrations.

The objective of our study was to test whether limited microbial degradation at low pesticide concentrations could explain the discrepancy between overall degradability demonstrated in laboratory tests and their actual persistence in the environment. Studies on pesticide degradation are often performed using unrealistically high application rates seldom found in natural environments. Nevertheless, biodegradation rates determined for higher pesticide doses cannot necessarily be extrapolated to lower concentrations. In this context, we wanted to (i) compare the kinetics of pesticide degradation at different concentrations in arable land and (ii) clarify whether there is a concentration threshold below which the expression of the functional genes involved in the degradation pathway is inhibited without further pesticide degradation taking place. We set up an incubation experiment for four weeks using 14C-ring labeled 2-methyl-4-chlorophenoxyacetic acid (MCPA) as a model compound in concentrations from 30 to 20,000 μg kg–1 soil. To quantify the abundance of putative microorganisms involved in MCPA degradation and their degradation activity, tfdA gene copy numbers (DNA) and transcripts (mRNA) were determined by quantitative real-time PCR. Mineralization dynamics of MCPA derived-C were analyzed by monitoring 14CO2 production and 14C assimilation by soil microorganisms. We identified two different concentration thresholds for growth and activity with respect to MCPA degradation using tfdA gene and mRNA transcript abundance as growth and activity indices, respectively. The tfdA gene expression started to increase between 1,000 and 5,000 μg MCPA kg–1 dry soil, but an actual increase in tfdA sequences could only be determined at a concentration of 20,000 μg. Accordingly, we observed a clear shift from catabolic to anabolic utilization of MCPA-derived C in the concentration range of 1,000 to 5,000 μg kg–1. Concentrations ≥1,000 μg kg–1 were mainly associated with delayed mineralization, while concentrations ≤1,000 μg kg–1 showed rapid absolute dissipation. The persistence of pesticides at low concentrations cannot, therefore, be explained by the absence of functional gene expression. Nevertheless, significant differences in the degradation kinetics of MCPA between low and high pesticide concentrations illustrate the need for studies investigating pesticide degradation at environmentally relevant concentrations.

Comparative Evaluation of Antimicrobial Efficacy of Commercially Available Herbal Dentifrices against Selected Putative Oral Microorganisms: An In Vitro Study

Comparative Evaluation of Antimicrobial Efficacy of Commercially Available Herbal Dentifrices against Selected Putative Oral Microorganisms: An In Vitro Study

Revisiting the cosmic-ray induced Venusian radiation dose in the context of habitability

Context. Cosmic rays (CRs), which constantly bombard planetary magnetic fields and atmospheres, are the primary driver of atmospheric spallation processes. The higher the energy of these particles, the deeper they penetrate the planetary atmosphere, and the more likely interactions become with the ambient atmospheric material and the evolution of secondary particle showers. Aims. As recently discussed in the literature, CRs are the dominant driver of the Venusian atmospheric ionization and the induced radiation dose below ~100 km. In this study, we model the atmospherically absorbed dose and the dose equivalent to the effect of cosmic rays in the context of Venusian habitability. Methods. The Atmospheric Radiation Interaction Simulator was used to model the altitude-dependent Venusian absorbed dose and the Venusian dose equivalent. For the first time, we modeled the dose rates for different shape-, size-, and composition-mimicking detectors (phantoms): a CO2-based phantom, a water-based microbial cell, and a phantom mimicking human tissue. Results. Based on our new model approach, we give a reliable estimate of the altitude-dependent Venusian radiation dose in water-based microorganisms here for the first time. These microorganisms are representative of known terrestrial life. We also present a detailed analysis of the influence of the strongest ground-level enhancements measured at the Earth’s surface, and of the impact of two historic extreme solar events on the Venusian radiation dose. Our study shows that because a phantom based on Venusian air was used, and because furthermore, the quality factors of different radiation types were not taken into account, previous model efforts have underestimated the radiation hazard for any putative Venusian cloud-based life by up to a factor of five. However, because we furthermore show that even the strongest events would not have had a hazardous effect on putative microorganisms within the potentially habitable zone (51–62 km), these differences may play only a minor role.

Arbuscular Mycorrhizal Fungi and Plant Growth Promoting Rhizobacteria Avoid Processing Tomato Leaf Damage during Chilling Stress

Chilling stress limits processing tomato growth and yield, leading to high losses. An approach to increase the sustainability of crop production could involve the use of beneficial microorganisms. The objectives of this research were to investigate: (i) the efficacy of Funneliformis mosseae and Paraburkholderia graminis C4D1M in avoiding processing tomato damage during severe chilling stress; (ii) the synergic effect of the two microorganisms inoculated as a consortium; (iii) if the putative microorganism effects depended on the processing tomato genotype. To achieve these objectives, two experiments were carried out. In the first experiment, a modern genotype was assessed, while three genotypes were evaluated in the second experiment. At sowing, F. mosseae was mixed with peat. Nine days after sowing, P. graminis was inoculated close to the plant’s root collar. After 40 days of seed sowing, chilling treatment was performed at 1 °C for 24 h. F. mosseae mainly reduced the cell membrane injuries in term of electrolytic leakage and efficiency of photosystem II, after the chilling stress in both experiments. Conversely, in the second experiment, the consortium improved the seedling regrowth, increasing the efficiency of photosystem II. In addition, modern genotypes inoculated with microorganisms showed a better seedling regrowth.

Viability of the soddy–podzolic soil microbial community after 148–1250 kGy gamma irradiation

Ionizing radiation is considered the main factor limiting preservation of putative microorganisms and biomarkers in cryogenic space bodies, restricting interplanetary transportation of living cells. Defining the radioresistance limits of Earth-bound life is challenging but necessary to assessing the likelihood of the existence of life outside of Earth for the purpose of planning space missions and developing methods for detecting life. The viability of native soil microbial communities under effects of ionizing radiation has not been sufficiently investigated. According to previous studies, soil should be sterilized with 15–100 kGy doses of gamma radiation, depending on the irradiation conditions. However, the limits of radioresistance of the cells in situ have not been reliably elucidated. We performed gamma irradiation of soddy–podzolic soil (Moscow region, Russia) at doses ranging from 148 kGy to 1.25 MGy to assess the radioresistance of the soil microbial community by means of culturing, epifluorescence microscopy (EFM), multisubstrate testing, and gas chromatography–mass spectrometry of lipid biomarkers. The soil microbial community exhibited high resistance to the effects of gamma radiation. Culturable bacteria were isolated after exposure to 148 kGy. After exposure to 320 kGy, there were no cells capable of proliferation on nutrient media, although many prokaryotic cells (∼3 × 106 cells/g), without visible signs of DNA damage, were observed in situ using EFM. These data suggest a transition into a viable but nonculturable state. Thus, the results obtained indicate that microbial communities radioresistance (and microorganisms in general) in natural habitats is significantly underestimated.

A Mechanistic Approach to Understanding Microbiologically Influenced Corrosion by Metal-Depositing Bacteria

Iron (Fe)- and manganese (Mn)-oxidizing bacteria are often cited individually and collectively as putative microorganisms for microbiologically influenced corrosion (MIC). The two groups of microorganisms have in common the ability to attach to surfaces and produce macroscopic accumulations (deposits) of metal oxides/hydroxides/oxyhydroxides that can influence corrosion of some metals and alloys in some environments. In all cases, once initiated, the corrosion is independent of the activities of the colonizing species. Despite the phylogenetic diversity of Fe-oxidizing bacteria (FeOB), the following sections will deal with corrosion mechanisms attributed to neutrophilic, lithotrophic, microaerophilic FeOB. The mineralogy of biologically oxidized Fe is consistent over a wide range of environments. All FeOB produce dense deposits that can cause corrosion of low alloy stainless steels (SS) directly, i.e., under-deposit corrosion. Association of Mn-oxidizing bacteria (MnOB) and other microorganisms may stabil...

Ancient Microbial Activity in Deep Hydraulically Conductive Fracture Zones within the Forsmark Target Area for Geological Nuclear Waste Disposal, Sweden

Recent studies reveal that organisms from all three domains of life—Archaea, Bacteria, and even Eukarya—can thrive under energy-poor, dark, and anoxic conditions at large depths in the fractured crystalline continental crust. There is a need for an increased understanding of the processes and lifeforms in this vast realm, for example, regarding the spatiotemporal extent and variability of the different processes in the crust. Here, we present a study that set out to detect signs of ancient microbial life in the Forsmark area—the target area for deep geological nuclear waste disposal in Sweden. Stable isotope compositions were determined with high spatial resolution analyses within mineral coatings, and mineralized remains of putative microorganisms were studied in several deep water-conducting fracture zones (down to 663 m depth), from which hydrochemical and gas data exist. Large isotopic variabilities of δ13Ccalcite (−36.2 to +20.2‰ V-PDB) and δ34Spyrite (−11.7 to +37.8‰ V-CDT) disclose discrete periods of methanogenesis, and potentially, anaerobic oxidation of methane and related microbial sulfate reduction at several depth intervals. Dominant calcite–water disequilibrium of δ18O and 87Sr/86Sr precludes abundant recent precipitation. Instead, the mineral coatings largely reflect an ancient archive of episodic microbial processes in the fracture system, which, according to our microscale Rb–Sr dating of co-genetic adularia and calcite, date back to the mid-Paleozoic. Potential Quaternary precipitation exists mainly at ~400 m depth in one of the boreholes, where mineral–water compositions corresponded.

Filamentous microbial fossil from low-grade metamorphosed basalt in northern Chichibu belt, central Shikoku, Japan

The past two decades have seen the reporting of microbial fossils within ancient oceanic basalts that could be identical to microbes within modern basalts. Here, we present new petrographic, mineralogical, and stable isotopic data for metabasalts containing filamentous structures in a Jurassic accretionary complex within the northern Chichibu Belt of the Yanadani area of central Shikoku, Japan. Mineralized filaments within these rocks are present in interstitial domains filled with calcite, pumpellyite, or quartz, and consist of iron oxide, phengite, and pumpellyite. δ13CPDB values for filament-bearing calcite within these metabasalts vary from −2.49‰ to 0.67‰. A biogenic origin for these filamentous structures is indicated by (1) the geological context of the Yanadani metabasalt, (2) the morphology of the filaments, (3) the carbon isotope composition of carbonates that host the filaments, and (4) the timing of formation of these filaments relative to the timing of low-grade metamorphism in a subduction zone. The putative microorganisms that formed these filaments thrived between eruption (Late Paleozoic) and accretion (Early Jurassic) of the basalt. The data presented here indicate that cryptoendolithic life was present within water-filled vesicles in pre-Jurassic intraplate basalts. The mineralogy of the filaments reflects the low-grade metamorphic recrystallization of authigenic microbial clays similar to those formed by the encrustation of prokaryotes in modern iron-rich environments. These findings suggest that a previously unusual niche for life is present within intraplate volcanic rocks in accretionary complexes.

Recording and surveillance systems for periodontal diseases.

This paper describes tools used to measure periodontal diseases and the integration of these tools into surveillance systems. Tools to measure periodontal diseases at the surveillance level have focussed on current manifestations of disease (e.g. gingival inflammation) or disease sequelae (e.g. periodontal pocket depth or loss of attachment). All tools reviewed in this paper were developed based on the state of the science of the pathophysiology of periodontal disease at the time of their design and the need to provide valid and reliable measurements of the presence and severity of periodontal diseases. Therefore, some of these tools are no longer valid. Others, such as loss of periodontal attachment, are the current de-facto tools but demand many resources to undertake periodical assessment of the periodontal health of populations. Less complex tools such as the Community Periodontal Index, have been used extensively to report periodontal status. Laboratory tests for detecting putative microorganisms or inflammatory agents present in periodontal diseases have been used at the clinical level, and at least one has been tested at the population level. Other approaches, such as self-report measures, are currently under validation. In this paper, we do not review indices designed to measure plaque or residual accumulation around the tooth, indices focussed only on gingival inflammation or radiographic approaches with limited applicability in surveillance systems. Finally, we review current case-definitions proposed for surveillance of periodontal disease severity.

16s rDNA based microbial diversity analysis of eleven acid mine drainages obtained from three Chinese copper mines

Eleven acid mine drainage (AMD) samples were obtained from southeast of China for the analysis of the microbial communities diversity, and the relationship with geochemical variables and spatial distance by using a culture-independent 16S rDNA gene phylogenetic analysis approach and multivariate analysis respectively. The principle component analysis (PCA) of geochemical variables shows that eleven AMDs can be clustered into two groups, relative high and low metal rich (RHMR and RLMR) AMDs. Total 1 691 clone sequences are obtained and the detrended correspondence analysis (DCA) of operational taxonomic units (OTUs) shows that, γ-Proteobacteria, Acidobacteria, Actinobacteria, Cyanobacteria, Firmicutes and Nitrospirae are dominant species in RHMR AMDs. In contrast, α-Proteobacteria, β-Proteobacteria, Planctomycetes and Bacteriodetes are dominant species in RLMR AMD. Results also show that high-abundance putative iron-oxidizing and only putative sulfur-oxidizing microorganisms are found in RHMR AMD. Multivariate analysis shows that both geochemical variables (r=0.429 3, P=0.037 7) and spatial distance (r=0.321 3, P=0.018 1) are significantly positively correlated with microbial community and pH, Mg, Fe, S, Cu and Ca are key geochemistry factors in shaping microbial community. Variance partitioning analysis shows that geochemical variables and spatial distance can explain most (92%) of the variation.

Formation of gypsum and bassanite by cation exchange reactions in the absence of free‐liquid H2O: Implications for Mars

Smectites and hydrated Mg sulfate minerals have been identified in close association at various locations on the Martian surface. The hydration states of sulfates and smectites are dependent on temperature and relative humidity (RH), and therefore these minerals have the potential to affect cycling and bioavailability of H2O on Mars. We have conducted X‐ray powder diffraction experiments to investigate cycling of H2O within mixtures of Ca‐bearing smectites and hydrated Mg sulfate minerals under conditions of varying RH similar to those that exist at or just beneath the Martian surface. Our experiments show that under conditions of varying RH, cation‐exchange reactions occur between these two potential components of the Martian regolith, producing gypsum [CaSO4·2H2O] and bassanite [CaSO4·∼0.5H2O] in the absence of free‐liquid H2O. Cation‐exchange reactions were accompanied by significant loss of porosity, warping of the sample surface and, in some cases, volume expansion. The formation of Ca sulfate minerals in these experiments provides evidence for the development of thin films of H2O at mineral surfaces and suggests that similar processes may operate at the arid surface of Mars. Humidity‐driven cation‐exchange reactions between smectites and hydrated Mg sulfate minerals may therefore play a role in shaping the present‐day Martian surface and could have provided a transient source of H2O and nutrients (e.g., major and trace elements and possibly organic micro/macronutrients) for putative microorganisms.

On the possibility of microbiota transfer from Venus to Earth

The possibility of the clouds of Venus provid- ing habitats for extremophilic microorganisms has been dis- cussed for several decades. We show here that the action of the solar wind leads to erosion of parts of the atmosphere laden with aerosols and putative microorganisms, forming a comet-like tail in the antisolar direction. During inferior conjunctions that coincide with transits of the planet Venus this comet-like tail intersects the Earth's magnetopause and injects aerosol particles. Data from ESA's Venus Express spacecraft and from SOHO are used to discuss the ingress of bacteria from Venus into the Earth's atmosphere, which we estimate as ∼10 11 -10 13 cells for each transit event.

Gut content identification of larvae of the Anopheles gambiae complex in western Kenya using a barcoding approach

Although larvae feeding and food source are vital to the development, survival and population regulation of African malaria vectors, the prey organisms of Anopheles gambiae larvae in the natural environment have not been well studied. This study used a molecular barcoding approach to investigate the natural diets of Anopheles gambiae s.l. larvae in western Kenya. Gut contents from third- and fourth-instar larvae from natural habitats were dissected and DNA was extracted. The 18S ribosomal DNA gene was amplified, the resulting clones were screened using a restriction fragment length polymorphism method and nonmosquito clones were sequenced. Homology search and phylogenetic analyses were then conducted using the sequences of non-mosquito clones to identify the putative microorganisms ingested. The phylogenetic analyses clustered ingested microorganisms in four clades, including two clades of green algae (Chlorophyta, Chlorophyceae Class, Chlamydomonadales and Chlorococcales families), one fungal clade, and one unknown eukaryote clade. In parallel, using the same approach, an analysis of the biodiversity present in the larval habitats was carried out. This present study demonstrated the feasibility of the barcoding approach to infer the natural diets of Anopheles gambiae larvae. Our analysis suggests that despite the wide range of microorganisms available in natural habitats, mosquito larvae fed on specific groups of algae. The novel tools developed from this study can be used to improve our understanding of the larval ecology of African malaria vectors and to facilitate the development of new mosquito control tools.

Antimicrobial susceptibility variation of 50 anaerobic periopathogens in aggressive periodontitis: an interindividual variability study

The frequent use of antibiotics in developed countries has led to the emergence of widespread bacterial resistance. In this study, the interindividual variability of the antibiotic susceptibility of 50 putative microorganisms in aggressive periodontitis patients has been evaluated by means of VC (variation coefficient). A total of 60 microbial samples were collected from 20 adult patients diagnosed with aggressive periodontitis (2-4 samples by patient). Bacterial strains of Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, Fusobacterium nucleatum, and Peptostreptococcus micros were isolated according to Slots' rapid identification method. The susceptibilities to 10 antibiotics were studied: penicillin G (PEN), ampicillin (AMP), amoxicillin (AMX), amoxicillin/clavulanate (AMC), tetracycline (TET), doxycycline (DOX), ciprofloxacin (CIP), erythromycin (ERY), spiramycin (SPI) and clindamycin (CLIN), using the Disk Diffusion Susceptibility test (DDS test: Kirby-Bauer's modified method for anaerobic bacteria). The broth microdilution Minimum Inhibitory Concentration test was carried out as a control test. Among the 50 identified bacteria, 15 were P. gingivalis, 12 P. intermedia, 8 T. forsythia, 9 F. nucleatum, and 6 P. micros. The results of the DDS test show that penicillins (especially AMC, AMP, and AMX), cyclines (especially DOX) and CLIN are highly effective against the 50 anaerobic studied bacteria. CIP and ERY have the lowest efficacy against those bacteria. CIP shows a very variable activity according to anaerobic bacteria species, being particularly inactive against P. gingivalis and very efficient against T. forsythia and P. micros. SPI is also highly efficient but not against P. micros. The interindividual susceptibility of principal periodontal pathogens to antibiotics is not homogeneous and seems to vary according to bacterial species and antimicrobial molecules. This variability seems to be greater with older molecules (PEN, TET, ERY) than with more recent ones, which indicates more stable results (AMC, AMX, AMP, and DOX). P. intermedia appeared to be the bacteria most resistant to penicillins and showed the highest coefficient variation. Together with scaling and root planing, the combination of two antibiotics would therefore seem to be recommended in the treatment of aggressive periodontitis, particularly in the presence of P. intermedia.

Radiation therapy for localized low-grade non-Hodgkin's lymphomas

The most common low grade B-cell non-Hodgkin's lymphomas are follicular lymphomas, and extranodal marginal zone lymphomas, also known as mucosa-associated lymphoid tissue (MALT) lymphomas. Localized presentations of follicular lymphoma occur in 20-30% of cases, while for MALT lymphomas, stage I-II disease presentations occur in 70-90%. These are radiation-sensitive lymphomas. Following moderate dose local radiation treatment (30-35 Gy) for these stage I and II low grade lymphomas, the clinical results indicate long-term local control and possible cure. While local control is achieved with minimal morbidity with involved-field radiation therapy, a significant proportion of patients relapse with systemic disease outside of radiation fields. For follicular lymphoma, this occurs in approximately 50% of patients after 15 years, and for non-gastric MALT lymphoma, 30-40% after 10 years. Although patients with relapsed systemic disease are not curable with chemotherapy, the disease often behaves in an indolent fashion and prolonged survival is observed. For gastric MALT lymphomas, radiation therapy is indicated in patients whose lymphoma did not respond to Helicobacter pylori eradication therapy, or in gastric lymphoma not related to this microorganism. The subject of causative agents responsible for non-gastric MALT lymphomas is under active study and the identification of putative microorganisms will lead to improved treatment strategies for these unusual lymphomas, similar to the success in gastric lymphomas over the last decade.

IgG antibody levels to Porphyromonas gingivalis and clinical measures in children.

Periodontopathic clinical markers are poorly understood in the pediatric population. Several studies have proposed Porphyromonas gingivalis (P. gingivalis) and an antibody response to the microorganism as factors in periodontal tissue destruction in children. The objective of this study was to examine the prevalence of P. gingivalis in dental plaque and of serum immunoglobulin G (IgG) antibody levels to P. gingivalis, and their relationship to periodontal clinical measures in children. Thirty-one subjects, aged 20 to 163 months, participated in this study. Clinical measures examined included gingivitis, plaque, alveolar bone height, age, gender, ethnicity, medical status, caries, and IgG antibody levels to P. gingivalis. Five ml of blood was collected for serum analysis, and IgG antibody levels to P. gingivalis were determined by using enzyme-linked immunosorbent assay. Plaque samples were examined for the presence of P. gingivalis by DNA-DNA checkerboard. Data were analyzed on a person-level basis for relationships to serum IgG antibody levels to P. gingivalis and on a site-specific level for relationships to the presence of P. gingivalis in plaque. A majority (77%) of the subjects were systemically healthy, non-white (74%), and did not have detectable P. gingivalis in their plaque. Fifty-two percent of the subjects had positive serum IgG antibody levels to P. gingivalis. Based on univariate linear regression, factors related to IgG antibody levels to P. gingivalis (P<0.05) included age, average gingival index (GI), average probing depth, and number of teeth with alveolar bone crest to cemento-enamel junction (ABC-CEJ) distances >2 mm. When all clinical measures were considered together, only age remained statistically significantly related to serum IgG antibody levels to P. gingivalis. Age is one of the most important factors in the development of the immune response to putative microorganisms such as P. gingivalis in children. The role of IgG as a time-sensitive measure of periodontal health in children needs to be investigated further.

Detection rate of Actinobacillus actinomycetemcomitans on the permanent 1st molars of primary school children in Taiwan by polymerase chain reaction.

Actinobacillus actinomycetemcomitans (Aa) has been implicated as the putative micro-organism for localized juvenile periodontitis (LJP). The most distinct clinical features of LJP include severe angular bony defects of the mesial sides of permanent first molars and the onset of disease during puberty. Currently, no large-scale studies have been performed which address the change in detection rates of Aa on the mesial sides of permanent 1st molars following eruption and up to puberty. In this study, subgingival plaque samples were taken from the mesial pockets of 2 randomly selected permanent 1st molars from 328 primary school children and 50 adult staff, and analyzed by polymerase chain reaction (PCR) to detect Aa. The results showed a 5.5% prevalence rate of Aa which increased after the eruption of 1st molars and peaked near puberty. There were no significant differences in the detection rates of Aa among different groups in terms of gender, plaque index (PII), and gingival index (GI); however, the higher detection rates of Aa were significantly associated with increased probing depths at p<0.05. PCR analysis of the subgingival plaques demonstrated a prevalence of Aa which peaked near puberty, suggesting that Aa may be important for LJP in Taiwan.

Septic and aseptic arthritis: a continuum?

This chapter considers the likelihood that a wide spectrum of infection-provoked arthritis exists, ranging from overt sepsis to apparently aseptic chronic arthritis in which very small numbers of causal bacteria can be detected only by using highly sensitive techniques. It asks whether joints are, as conventionally held, normally devoid of micro-organisms and how to judge the significance of bacteria detected within apparently sterile joints. Through a consideration of known septic, probably infective and apparently aseptic forms of arthritis, a set of criteria for attributing causality to putative arthritogenic micro-organisms is proposed.