1,721,144 research outputs found
Production, Secretion and Biological Activity of Bacillus cereus Enterotoxins
Full text linkBacillus cereus behaves as an opportunistic pathogen frequently causing gastrointestinal diseases, and it is increasingly recognized to be responsible for severe local or systemic infections. Pathogenicity of B. cereus mainly relies on the secretion of a wide array of toxins and enzymes and also on the ability to undergo swarming differentiation in response to surface-sensing. In this report, the pathogenicity exerted by B. cereus toxins is described with particular attention to the regulatory mechanisms of production and secretion of HBL, Nhe and CytK enterotoxins
Characterization of seawater bacterial communities within environments colonized by the tropical green seaweed Caulerpa taxifolia
No full textAFLP genotyping of Candida metapsilosis clinical isolates: evidence for recombination
Full text linkIn a collection of 395 independent clinical isolates classified as Candida parapsilosis on a biochemical profile basis, 20 Candida metapsilosis strains were identified by molecular tests with an isolation frequency of 5%. Isolates were screened for their susceptibility to conventionally used antifungals and for virulence determinants, such as biofilm formation and protease production. Molecular characterization of C. metapsilosis independent isolates by amplified fragment length polymorphism (AFLP) revealed a high percentage of polymorphic bands. Statistical analysis of the pairwise genetic distances and bootstrapping revealed that recombination occurs and significantly contributes to C. metapsilosis genetic population variability. No association between specific AFLP markers and drug resistance or other phenotypes was observed
Identification of non-flagellar genes involved in swarm cell differentiation using a Bacillus thuringiensis mini-Tn10 mutant library
No full textSwarming is a social phenomenon that enables motile bacteria to move co-ordinately over solid surfaces. The molecular basis regulating this process is not completely known and may vary among species. Insertional mutagenesis of a swarming-proficient Bacillus thuringiensis strain was performed, by use of the transposon mini-Tn10, to identify novel genetic determinants of swarming that are dispensable for flagellation, swimming motility, chemotaxis and active growth. Among the 67 non-swarming mutants obtained, six were selected that showed no defect in flagellar assembly and function, chemotaxis or growth rate. Sequence analysis of DNA flanking the transposon insertion led to the identification of previously uncharacterized genes that are involved in the development of swarming colonies by B. thuringiensis and that are highly conserved in all members of the Bacillus cereus sensu lato group. These genes encode non-flagellar proteins with putative activity as sarcosine oxidase, catalase-2, amino acid permease, ATP-binding cassette transporter, dGTP triphosphohydrolase and acetyltransferase. Functional analysis of two of the isolated mutants demonstrated that swarming differentiation depends on the intracellular levels of the osmoprotectant glycine betaine and on the quantity of synthesized phenazine secondary metabolites. The finding that proteins involved in diverse physiological processes have a role in swarming motility underlines the complexity of the molecular mechanisms governing this behaviour in B. thuringiensis
Bacillus thuringiensis membrane-damaging toxins acting on mammalian cells
No full textBacillus thuringiensis is widely used as a biopesticide in forestry and agriculture, being able to produce potent species-specific insecticidal toxins and considered nonpathogenic to other animals. More recently, however, repeated observations are documenting the association of this microorganism with various infectious diseases in humans, such as food-poisoning-associated diarrheas, periodontitis, bacteremia, as well as ocular, burn, and wound infections. Similar to B. cereus, B. thuringiensis produces an array of virulence factors acting against mammalian cells, such as phosphatidylcholine- and phosphatidylinositol-specific phospholipase C (PC-PLC and PI-PLC), hemolysins, in particular hemolysin BL (HBL), and various enterotoxins. The contribution of some of these toxins to B. thuringiensis pathogenicity has been studied in animal models of infection, following intravitreous, intranasal, or intratracheal inoculation. These studies lead to the speculation that the activities of PC-PLC, PI-PLC, and HBL are responsible for most of the pathogenic properties of B. thuringiensis in nongastrointestinal infections in mammals. This review summarizes data regarding the biological activity, the genetic basis, and the structural features of these membrane-damaging toxins
Flagella, swarming motility, and virulence in Bacillus cereus and Bacillus thuringiensis
No full textIn vitro evaluation of the potential of ciclopirox to induce resistance in Trichophyton rubrum, in comparison to terbinafine, amorolfine, and itraconazole
No full textThe main causative agent of dermatophytosis is Trichophyton rubrum, a widespread filamentous fungus that can infect keratinized tissue such as skin, nails and hair. T rubrum is known to account for almost 70% of all dermatophyte infections. Several antifungal drugs have become available for the treatment of dermatophytosis and among these, terbinafine (TRB), amorolfine (AMF), itraconazole (ITC), and ciclopirox (CPX) are the most frequently used to treat T rubrum infections. Although, therapeutic strategies based on the use of TRB, AMF, ITC or CPX are generally considered effective, the onset of resistant strains against some of these antifungal agents has been reported
Rapid determination of vitamin B2 secretion by bacteria growing on solid media
No full textAims: Development of an agar‐diffusion assay to measure vitamin B2 in biological samples and application of the method to determine the amount of vitamin B2 secreted by bacteria.
Methods and Results: A riboflavin‐auxotrophic mutant of Bacillus cereus was generated by mini‐Tn10 insertion in the ribD gene. ribD mutant sensitivity to exogenous vitamin B2 was investigated by turbidimetric and agar‐diffusion assays. In turbidimetric assays, the B. cereus mutant displayed a similar level of sensitivity to vitamin B2 to that of Lactobacillus casei ATCC 7469, the reference organism used for microbiological vitamin B2 quantification. However, only the ribD mutant could be used as an indicator organism in agar‐diffusion assays. A total of eight probiotic strains, from five different probiotic formulations, were analysed by the ribD mutant‐based assay on agar plates in order to determine their ability to secrete vitamin B2 during growth.
Conclusion: The agar diffusion method with the ribD mutant of B. cereus is highly reproducible, sensitive, rapid, inexpensive, and can be applied to measure the amount of vitamin B2 in different samples.
Significance and Impact of the Study: The method developed in this study appears to be a good candidate for the screening of vitamin B2 secretion by bacteria growing on solid media
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