Virulent infections due to alpha-haemolytic streptococci in cancer patients and their management

Streptococci of the viridans group have long been considered to be minor pathogens, except in bacterial endocarditis. For some years, however, these microorganisms have been the cause of serious bacteraemia in neutropenic patients receiving intensive chemotherapy. These infections can lead to severe complications such as endocarditis, respiratory distress syndromes or shock, and are associated with a mortality rate ranging from 6-30%. The principal risk factors for these infections are profound neutropenia, antibiotic prophylaxis with quinolones or cotrimoxazole, large doses of cytosine arabinoside, a recent history of chemotherapy, oropharyngeal mucositis and viridans streptococcal colonization. Protective factors are the early administration of parenteral antibiotics during periods of neutropenia, or the prophylactic administration of penicillin. Although the introduction of penicillin to prophylactic antibiotic regimens has led to a decrease in the incidence of these infections, the emergence of strains resistant to beta-lactams is a worrying problem which could compromise this type of treatment.

Respiratory effects of an exposure to wheat dust among grain workers and farmers: a longitudinal study

OBJECTIVES: Agriculture is considered one of the occupations most at risk of acute or chronic respiratory problems. The aim of our study was to determine from which level of exposure to organic dust the respiratory function is chronically affected in workers involved in wheat grain or straw manipulation and to test if some of these working populations can recover their respiratory function after an exposure decrease. METHOD: 87 workers exposed to wheat dust: farmers, harvesters, silo workers and livestock farmers and 62 non exposed workers, were included into a longitudinal study comprising two visits at a six months interval with lung function measurements and symptom questionnaires. Cumulative and mean exposure to wheat dust were generated from detailed work history of each worker and a task-exposure matrix based on task-specific exposure measurements. Immunoglobulins (IgG and IgE) specific of the most frequent microorganisms in wheat dust have been determined. RESULTS: FEV1 decreased significantly with the cumulative exposure and mean exposure levels. The estimated decrease was close to 200 mL per year of high exposure, which corresponds roughly to levels of wheat dust higher than 10 mg/m(3). Peak expiratory flow and several acute symptoms correlate with recent exposure level. Recovery of the respiratory function six months after exposure to wheat dust and evolution of exposure indicators in workers blood (IgG and IgE) will be discussed. CONCLUSIONS: These results show a chronic effect of exposure to wheat dust on bronchial obstruction. Short term effects and reversibility will be assessed using the full study results.

Molecular characterization and pathogenicity of isolates of Beauveria spp. to fall armyworm

The objective of this work was to evaluate the pathogenicity of 24 Beauveria isolates to Spodoptera frugiperda larvae, and characterize them molecularly through rDNA-ITS sequencing and RAPD markers. Sequencing of rDNA-ITS fragments of 570 bp allowed the identification of isolates as B. bassiana or B. brongniarti by sequence comparison to GenBank. Sixty seven polymorphic RAPD fragments were capable to differentiate 20 among 24 Beauveria isolates, grouping them according to the derived host insect and to pathogenicity against maize fall armyworm larvae. Three RAPD markers were highly associated to the pathogenicity against S. frugiperda, explaining up to 67% of the phenotypic variation. Besides identification and molecular characterization of Beauveria isolates, ITS sequence and RAPD markers proved to be very useful in selecting the isolates potentially effective against S. frugiperda larvae and in monitoring field release of these microorganisms in biocontrol programs.

Genomic islands: tools of bacterial horizontal gene transfer and evolution.

Abstract Bacterial genomes evolve through mutations, rearrangements or horizontal gene transfer. Besides the core genes encoding essential metabolic functions, bacterial genomes also harbour a number of accessory genes acquired by horizontal gene transfer that might be beneficial under certain environmental conditions. The horizontal gene transfer contributes to the diversification and adaptation of microorganisms, thus having an impact on the genome plasticity. A significant part of the horizontal gene transfer is or has been facilitated by genomic islands (GEIs). GEIs are discrete DNA segments, some of which are mobile and others which are not, or are no longer mobile, which differ among closely related strains. A number of GEIs are capable of integration into the chromosome of the host, excision, and transfer to a new host by transformation, conjugation or transduction. GEIs play a crucial role in the evolution of a broad spectrum of bacteria as they are involved in the dissemination of variable genes, including antibiotic resistance and virulence genes leading to generation of hospital 'superbugs', as well as catabolic genes leading to formation of new metabolic pathways. Depending on the composition of gene modules, the same type of GEIs can promote survival of pathogenic as well as environmental bacteria.

Rhizosphere bacterial communities of potato cultivars evaluated through PCR-DGGE profiles

The objective of this work was to determine the shifts on the PCR-DGGE profiles of bacterial communities associated to the rhizosphere of potato cultivars, in order to generate baseline information for further studies of environmental risk assessment of genetically modified potato plants. A greenhouse experiment was carried out with five potato cultivars (Achat, Bintje, Agata, Monalisa and Asterix), cultivated in pots containing soil from an integrated system for agroecological production. The experiment was conducted in a split plot randomized block design with five cultivars, three sampling periods and five replicates. Rhizosphere samples were collected in three sampling dates during plant development. DNA of rhizosphere microorganisms was extracted, amplified by PCR using bacterial universal primers, and analyzed through DGGE. Shifts on the rhizosphere bacterial communities associated to rhizosphere of different cultivars were related to both cultivar and plant age. Differences among rhizosphere bacterial communities were clearest at the earliest plant age, tending to decrease in later stages. This variation was detected among bacterial communities of the five tested cultivars. The characterization of soil microbial communities can be part of plant breeding programs to be used on studies of environmental risk assessment of genetically modified potatoes.

Detection of metabolite induction in fungal co-cultures on solid media by high-throughput differential ultra-high pressure liquid chromatography-time-of-flight mass spectrometry fingerprinting.

Access to new biological sources is a key element of natural product research. A particularly large number of biologically active molecules have been found to originate from microorganisms. Very recently, the use of fungal co-culture to activate the silent genes involved in metabolite biosynthesis was found to be a successful method for the induction of new compounds. However, the detection and identification of the induced metabolites in the confrontation zone where fungi interact remain very challenging. To tackle this issue, a high-throughput UHPLC-TOF-MS-based metabolomic approach has been developed for the screening of fungal co-cultures in solid media at the petri dish level. The metabolites that were overexpressed because of fungal interactions were highlighted by comparing the LC-MS data obtained from the co-cultures and their corresponding mono-cultures. This comparison was achieved by subjecting automatically generated peak lists to statistical treatments. This strategy has been applied to more than 600 co-culture experiments that mainly involved fungal strains from the Fusarium genera, although experiments were also completed with a selection of several other filamentous fungi. This strategy was found to provide satisfactory repeatability and was used to detect the biomarkers of fungal induction in a large panel of filamentous fungi. This study demonstrates that co-culture results in consistent induction of potentially new metabolites.

Mineralogical alteration of artificial meteorites during atmospheric entry. The STONE-5 experiment

The generic concept of the artificial meteorite experiment STONE is to fix rock samples bearing microorganisms on the heat shield of a recoverable space capsule and to study their modifications during atmospheric re-entry. The STONE-5 experiment was performed mainly to answer astrobiological questions. The rock samples mounted on the heat shield were used (i) as a carrier for microorganisms and (ii) as internal control to verify whether physical conditions during atmospheric re-entry were comparable to those experienced by "real" meteorites. Samples of dolerite (an igneous rock), sandstone (a sedimentary rock), and gneiss impactite from Haughton Crater carrying endolithic cyanobacteria were fixed to the heat shield of the unmanned recoverable capsule FOTON-M2. Holes drilled on the back side of each rock sample were loaded with bacterial and fungal spores and with dried vegetative cryptoendoliths. The front of the gneissic sample was also soaked with cryptoendoliths. <p>The mineralogical differences between pre- and post-flight samples are detailed. Despite intense ablation resulting in deeply eroded samples, all rocks in part survived atmospheric re-entry. Temperatures attained during re-entry were high enough to melt dolerite, silica, and the gneiss impactite sample. The formation of fusion crusts in STONE-5 was a real novelty and strengthens the link with real meteorites. The exposed part of the dolerite is covered by a fusion crust consisting of silicate glass formed from the rock sample with an admixture of holder material (silica). Compositionally, the fusion crust varies from silica-rich areas (undissolved silica fibres of the holder material) to areas whose composition is "basaltic". Likewise, the fusion crust on the exposed gneiss surface was formed from gneiss with an admixture of holder material. The corresponding composition of the fusion crust varies from silica-rich areas to areas with "gneiss" composition (main component potassium-rich feldspar). The sandstone sample was retrieved intact and did not develop a fusion crust. Thermal decomposition of the calcite matrix followed by disintegration and liberation of the silicate grains prevented the formation of a melt.</p> <p>Furthermore, the non-exposed surface of all samples experienced strong thermal alterations. Hot gases released during ablation pervaded the empty space between sample and sample holder leading to intense local heating. The intense heating below the protective sample holder led to surface melting of the dolerite rock and to the formation of calcium-silicate rims on quartz grains in the sandstone sample. (c) 2008 Elsevier Ltd. All rights reserved.</p>

Milk flow, teat morphology and subclinical mastitis prevalence in Gir cows

The aim of this work was to evaluate the association between milk flow, teat morphological measurements and subclinical mastitis prevalence in Gir cows. Eighty cows in the 2nd and 3rd lactations, with 90 to 200 days of lactation, were divided according to milk flow during milking into fast or slow groups. Teat morphometry was assessed by ultrasound scanning of the right anterior teat and external measurements. Milk samples were collected for somatic cells count (SCC) and microbiological culture. The effect of milk flow during milking was evaluated by analysis of variance of milk yield, SCC, morphometry and external measurements. The association of morphometry and external measurements of the teats with the SCC and microorganisms found in milk were analysed. Milk flow was significantly correlated to milk production. Gir cows with slower milk flow had longer teat canal and greater milk yield, in comparison to cows with fast milk flow. Teat-end to floor distance influenced SCC of Gir cows. Prevalence of subclinical mastitis and the type of mastitis-causing pathogens were not affected by milk flow during milking

Santé au travail : approche moléculaire pour évaluer le risque de l'exposition aux bioaérosols sur les lieux de travail

RESUME : Dans de nombreux environnements professionnels, des travailleurs sont exposés à des bioaérosols, que ce soit des bactéries, champignons, virus ou fragments de microorganismes. Ces bioaérosols peuvent être responsables de maladies infectieuses (p.ex. légionellose), ou de maladies non infectieuses (touchant principalement les voies respiratoires). Cependant, pour une majorité des bioaérosols, les relations entre une exposition à une certaine dose et les effets sur la santé humaine sont peu connues. Ce manque de connaissances étant dû principalement à une absence de méthodes adéquates permettant de quantifier cette exposition. La real-time quantitative PCR (Q-PCR) est un outil basé sur la quantification du DNA dont le potentiel de quantification des bioaérosols dans des environnements professionnels n'a pas été exploré. Le but de ce travail est de développer une méthode de Q-PCR permettant de quantifier des bioaérosols - en particulier des bactéries - et d'appliquer ces techniques pour des mesures préventives sur les lieux de travail. Dans ce travail, la Q-PCR a été appliquée à 1a quantification de pathogènes, de groupes taxonomiques spécifiques et de la charge bactérienne totale dans des environnements de travail, stations d'épuration et élevages industriels de volailles. Nous avons montré que la Q-PCR : 1) est capable de quantifier des pathogènes difficilement cultivables si ceux-ci sont présents en concentration importante, 2) a le potentiel pour être un outil performant dans l'étude des communautés bactériennes présentes dans l'air d'environnements professionnels, 3) est aussi performante que le comptage total des bactéries par DAPI pour quantifier 1a charge bactérienne totale et est donc une alternative prometteuse aux techniques culture-dépendantes. La Q-PCR pourrait être utilisée afin d'établir des relations doses-réponses pour la charge bactérienne ; soit dans des populations de travailleurs hautement exposés (p.ex. les éleveurs de volailles), soit en exposant des cellules à des concentrations de bioaérosols mesurées par Q-PCR. ABSTRACT : Many workers are exposed to bioaerosols such as bacteria, fungi, viruses or fragments of microorganisms. These bioaerosols can be responsible of infectious (e.g. legionellosis) or non infectious diseases (mainly respiratory symptoms). However, for a majority of them, the relationship between exposure and effects on human health is not clearly established. This is mainly due to the lack of valid quantitative assessment methods. Real-time quantitative PCR (Q-PCR) is a tool based on the quantification of DNA, of which the potential for the quantification of bioaerosols in work environments has not yet been explored. The aim of this work was to develop a Q-PCR method permitting to quantify bioaerosols -mainly bacteria and to apply those techniques in occupational environments. In this work, Q-PCR was applied to the quantification of pathogens, of specific taxonomic groups and of the total bacterial load in two different occupational settings, namely wastewater treatment plants and poultry houses. We showed that Q-PCR : 1) is capable of quantifying difficult to cultivate pathogens; when they are present at high concentrations, 2) has the potential to be a useful tool for studying bacterial communities in the air of work environments, 3) is as efficient as epifluorescence for the quantification of total bacterial load, and is a promising alternative to the culture-dependent methods. Q-PCR could be used to establish doses-responses relationships for bacterial load, either in populations of highly exposed workers such as poultry farmers, or by exposing cells to concentrations of bioaerosols quantified with Q-PCR.

Heterologously expressed Staphylococcus aureus fibronectin-binding proteins are sufficient for invasion of host cells.

Staphylococcus aureus invasion of mammalian cells, including epithelial, endothelial, and fibroblastic cells, critically depends on fibronectin bridging between S. aureus fibronectin-binding proteins (FnBPs) and the host fibronectin receptor integrin alpha(5)beta(1) (B. Sinha et al., Cell. Microbiol. 1:101-117, 1999). However, it is unknown whether this mechanism is sufficient for S. aureus invasion. To address this question, various S. aureus adhesins (FnBPA, FnBPB, and clumping factor [ClfA]) were expressed in Staphylococcus carnosus and Lactococcus lactis subsp. cremoris. Both noninvasive gram-positive microorganisms are genetically distinct from S. aureus, lack any known S. aureus surface protein, and do not bind fibronectin. Transformants of S. carnosus and L. lactis harboring plasmids coding for various S. aureus surface proteins (FnBPA, FnBPB, and ClfA) functionally expressed adhesins (as determined by bacterial clumping in plasma, specific latex agglutination, Western ligand blotting, and binding to immobilized and soluble fibronectin). FnBPA or FnBPB but not of ClfA conferred invasiveness to S. carnosus and L. lactis. Invasion of 293 cells by transformants was comparable to that of strongly invasive S. aureus strain Cowan 1. Binding of soluble and immobilized fibronectin paralleled invasiveness, demonstrating that the amount of accessible surface FnBPs is rate limiting. Thus, S. aureus FnBPs confer invasiveness to noninvasive, apathogenic gram-positive cocci. Furthermore, FnBP-coated polystyrene beads were internalized by 293 cells, demonstrating that FnBPs are sufficient for invasion of host cells without the need for (S. aureus-specific) coreceptors.

Les infections endo-artérielles, complications redoutables des infections à salmonelles non typhi [Endarterial infections, redoubtable complications of non-typhi salmonella infections].

Three cases are reported of salmonella aortitis observed in three men aged 55, 60 and 48 years, the last of whom had a prosthetic aortic valve and ascending aorta. The microorganisms were S. typhi murium, S. paratyphi B, and S. wien. Despite antibiotic treatment two patients died of perforating aortitis. The third patient developed S. wien gastroenteritis a few days after surgical replacement of the aortic valve and the ascending aorta. Five years later he presented with several bacteremic episodes due to S. wien, which recurred despite several courses of cotrimoxazole treatment. He has now been asymptomatic for over one year under prolonged cotrimoxazole treatment. Since vascular infection may occur following non typhi salmonellosis in 5% of patients over 50, or who have underlying endothelial lesions, the question arises as to whether non typhi S. gastroenteritis should be treated with antibiotics in these high risk patients, in contrast to present recommendations.

Microbial communities in Cerrado soils under native vegetation subjected to prescribed fire and under pasture

The objective of this work was to evaluate the effects of fire regimes and vegetation cover on the structure and dynamics of soil microbial communities, through phospholipid fatty acid (PLFA) analysis. Comparisons were made between native areas with different woody covers ("cerrado stricto sensu" and "campo sujo"), under different fire regimes, and a 20-year-old active palisadegrass pasture in the Central Plateau of Brazil. Microbial biomass was higher in the native plots than in the pasture, and the highest monthly values were observed during the rainy season in the native plots. No significant differences were observed between fire regimes or between communities from the two native vegetation types. However, the principal component (PC) analysis separated the microbial communities by vegetation cover (native x pasture) and season (wet x dry), accounting for 45.8% (PC1 and PC3) and 25.6% (PC2 and PC3), respectively, of the total PLFA variability. Changes in land cover and seasonal rainfall in Cerrado ecosystems have significant effects on the total density of soil microorganisms and on the abundance of microbial groups, especially Gram-negative and Gram-positive bacteria.

Role of neutrophils in the early shaping of the Leishmania major specific immune response in experimental murine cutaneous Leishmaniasis

The development of a protective immune response to microorganisms involves complex interactions between the host and the pathogen. The murine model of infection with Leishmania major (L. major) allows the study of the factors leading to the development of a protective immune response. Following infection with the protozoan parasite L. major, most strains of mice heal their lesions, while a few fail to control infection, both processes linked to the development of specific T helper subsets. The early events occurring during the first days following parasite inoculation are thought to be critical in the development of the Leishmania-specific immune response. Neutrophils are the first cells arriving massively to the site of infection, and recent evidence points to their role as organizers of the immune response, yet their specific role in this process remains elusive. Through interactions with cells present at the parasite inoculation site, and possibly within the draining lymph nodes, neutrophils could have an impact not only on the recruitment of inflammatory cells but also on the activation of local as well as newly migrated cells that will be crucial in shaping the Leishmania-specific immune response.

Functional diversity of bacterial genes associated with aromatic hydrocarbon degradation in anthropogenic dark earth of Amazonia

The objective of this work was to evaluate the catabolic gene diversity for the bacterial degradation of aromatic hydrocarbons in anthropogenic dark earth of Amazonia (ADE) and their biochar (BC). Functional diversity analyses in ADE soils can provide information on how adaptive microorganisms may influence the fertility of soils and what is their involvement in biogeochemical cycles. For this, clone libraries containing the gene encoding for the alpha subunit of aromatic ring-hydroxylating dioxygenases (α-ARHD bacterial gene) were constructed, totaling 800 clones. These libraries were prepared from samples of an ADE soil under two different land uses, located at the Caldeirão Experimental Station - secondary forest (SF) and agriculture (AG) -, and the biochar (SF_BC and AG_BC, respectively). Heterogeneity estimates indicated greater diversity in BC libraries; and Venn diagrams showed more unique operational protein clusters (OPC) in the SF_BC library than the ADE soil, which indicates that specific metabolic processes may occur in biochar. Phylogenetic analysis showed unidentified dioxygenases in ADE soils. Libraries containing functional gene encoding for the alpha subunit of the aromatic ring-hydroxylating dioxygenases (ARHD) gene from biochar show higher diversity indices than those of ADE under secondary forest and agriculture.

Accurate and early diagnosis of orthopedic device-related infection by microbial heat production and sonication.

Proper and rapid diagnosis of orthopedic device-related infection is important for successful treatment. Sonication has been shown to improve the diagnostic performance. We hypothesized that the combination of sonication with a novel method called microcalorimetry will further improve and accelerate the diagnosis of implant infection. We prospectively included 39 consecutive patients (mean age 59 years, 62% males) at our institution from whom 29 orthopedic prostheses and 10 osteosynthesis material were explanted. The explanted device was sonicated. The resulting sonication fluid was analyzed using microcalorimetry. Using standardized criteria to define orthopedic device-related infection, 12 cases (31%) were defined as infected. In all, positive periprosthetic tissue cultures were found. The sensitivity and specificity of microcalorimetry of sonication fluid were 100% and 97%, respectively. Mean time to detection, defined as time to reach a rising heat flow signal of 20 µW measured after equilibiration needed to get accurate measurement, was 10.9 h. In summary, microcalorimetry of sonication fluid is a reliable and a fast method in detecting the presence of microorganisms in orthopedic device-related infection. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1700-1703, 2013.