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Concept: Gram positive bacteria

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BACKGROUND: Tea has been suggested to promote oral health by inhibiting bacterial attachment to the oral cavity. Most studies have focused on prevention of bacterial attachment to hard surfaces such as enamel. FINDINGS: This study investigated the effect of five commercial tea (green, oolong, black, pu-erh and chrysanthemum) extracts and tea components (epigallocatechin gallate and gallic acid) on the attachment of five oral pathogens (Streptococcus mutans ATCC 25175, Streptococcus mutans ATCC 35668, Streptococcus mitis ATCC 49456, Streptococcus salivarius ATCC 13419 and Actinomyces naeslundii ATCC 51655) to the HGF-1 gingival cell line. Extracts of two of the teas (pu-erh and chrysanthemum) significantly (p < 0.05) reduced attachment of all the Streptococcus strains by up to 4 log CFU/well but effects of other teas and components were small. CONCLUSIONS: Pu-erh and chrysanthemum tea may have the potential to reduce attachment of oral pathogens to gingival tissue and improve the health of oral soft tissues.

Concepts: Bacteria, Streptococcus, Tea, Camellia sinensis, Gram positive bacteria, Streptococcaceae, Pu-erh tea, Oolong

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The in vitro antimicrobial screening of Gymnema sylvestre leaves against 13 test pathogens established its broad spectrum activity with average inhibition zone ranging from 14 to 23 mm. The antimicrobial activity of the classically- optimized aqueous extract was enhanced up to 1.45 folds, when subjected to statistical optimization using Response Surface Methodology (RSM) and was thermostable. Ethyl acetate was found to be the best organic extractant with Klebsiella pneumoniae 1 (31.5 mm) and Staphylococcus epidermidis (25.5 mm) being the most sensitive among Gram negative and Gram positive bacteria, respectively. Among the major group of phytoconstituents detected, tannins were the most abundant followed by flavonoids and phytosterols, while triterpenes were absent. Flavonoids and cardiac glycosides exhibited a broad range of antimicrobial potential, with inhibition zone ranging from 13 to 35 mm, where Candida albicans was the most sensitive organism. Ethyl acetate extract showed better potency with lowest Minimum inhibitory concentration (0.1-1 mg ml(-1)) than the aqueous extract (1-3 mg ml(-1)) and all partially purified phytoconstituents (0.1-10 mg ml(-1)). The ethyl acetate extract and flavonoids were highly potent, as they exhibited a total activity potency ranging from 41.4 to 1045 ml g(-1). Time kill studies revealed their microbicidal action, where ethyl acetate extract had a kill time from 0 to 12 h. However, among phytoconstituents, flavonoids were the most effective (0-8 h). The MIC and time kill study was also compared to that of standard antibiotics. These findings indicate that Gymnema sylvestre can be a potential source for development of leading metabolites against pathogens of clinical importance like Pseudomonas aeruginosa, Candida albicans, Escherichia coli, Staphylococcus aureus etc. They were neither mutagenic nor cytotoxic, as revealed by Ames and MTT assay.

Concepts: Bacteria, Microbiology, Antibiotic resistance, Escherichia coli, Gram positive bacteria, Gram staining, Gram-positive bacteria, Gymnema sylvestre

45

We have isolated Clostridium perfringens type B, an epsilon toxin-secreting bacillus, from a young woman at clinical presentation of Multiple Sclerosis (MS) with actively enhancing lesions on brain MRI. This finding represents the first time that C. perfringens type B has been detected in a human. Epsilon toxin’s tropism for the blood-brain barrier (BBB) and binding to oligodendrocytes/myelin makes it a provocative candidate for nascent lesion formation in MS. We examined a well-characterized population of MS patients and healthy controls for carriage of C. perfringens toxinotypes in the gastrointestinal tract. The human commensal Clostridium perfringens type A was present in approximately 50% of healthy human controls compared to only 23% in MS patients. We examined sera and CSF obtained from two tissue banks and found that immunoreactivity to ETX is 10 times more prevalent in people with MS than in healthy controls, indicating prior exposure to ETX in the MS population. C. perfringens epsilon toxin fits mechanistically with nascent MS lesion formation since these lesions are characterized by BBB permeability and oligodendrocyte cell death in the absence of an adaptive immune infiltrate.

Concepts: Magnetic resonance imaging, Multiple sclerosis, Cerebrospinal fluid, Gram positive bacteria, Clostridium, Clostridium perfringens, Gas gangrene, Clostridia

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As well as the search for new antibiotics, a new resource or strains for the known antibiotics is also important. Microbial symbionts in the gut of termites could be regarded as one of the feasible resource for such purpose. In this study, antibiotic-producing actinomycetes were screened from symbionts of the termite gut. 16SrRNA sequence analysis for the 10 isolates revealed that they belong to actinomycetes such as Streptomyces sp., Kitasatospora sp., and Mycobacterium sp. A culture broth from one of the isolate, namely strain CA1, belonging to the genera Streptomyces exhibited antagonistic activity against actinomycetes (Micrococcus spp.), gram-positive bacteria (Bacillus spp.), and yeast (Candida spp.). The structures of 2 compounds isolated from the culture broth of the strain CA1 were identified as those of actinomycin X2 and its analog, D. This study is the first to report that some symbionts of the termite gut are antibiotic-producing actinomycetes, and suggest that the termite gut is a feasible resource for bioprospecting. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

Concepts: Bacteria, Gut flora, Microbiology, Antibiotic, Gram positive bacteria, Streptomyces, Actinobacteria, Termite

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Recent research has suggested that Staphylococcus epidermidis is a reservoir of genes that, after horizontal transfer, facilitate the potential of Staphylococcus aureus to colonize, survive during infection, or resist antibiotic treatment, traits that are notably manifest in methicillin-resistant S. aureus (MRSA). S. aureus is a dangerous human pathogen and notorious for acquiring antibiotic resistance. MRSA in particular is one of the most frequent causes of morbidity and death in hospitalized patients. S. aureus is an extremely versatile pathogen with a multitude of mechanisms to cause disease and circumvent immune defenses. In contrast, most other staphylococci, such as S. epidermidis, are commonly benign commensals and only occasionally cause disease. Recent findings highlight the key importance of efforts to better understand how genes of staphylococci other than S. aureus contribute to survival in the human host, how they are transferred to S. aureus, and why this exchange appears to be uni-directional.

Concepts: Bacteria, Staphylococcus aureus, Antibiotic resistance, Staphylococcus, Gram positive bacteria, Coagulase, Staphylococcus epidermidis, Staphylococcaceae

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Genomic, taxonomic and biochemical studies were performed on two strains of alpha-haemolytic streptococci that showed to be clustered with major members of the Streptococcus mitis group. These Gram-positive strains were isolated from tooth surfaces of caries-free humans and show the classical spherical-shape of streptococcal species growing in chains. Sequence analysis from concatenated 16S and 23S rDNA, and sodA genes showed that these strains belonged to the Mitis group, but both of them cluster into a new phylogenetic branch. The genomes of these two isolates were sequenced, and whole-genome Average Nucleotide Identity (ANI) demonstrated that these strains significantly differ from any streptococcal species, showing ANI values under 91% even when compared to their phylogenetically closest species such as Streptococcus oralis and Streptococcus mitis. Biochemically, the two isolates also showed distinct metabolic features relative to close species, like an α-galactosidase activity. From the results of the present study, the name Streptococcus dentisani sp. nov. is proposed for these new couple of strains deposited in open collection at the Spanish Type Culture Collection (CECT) and Leibniz Institute DSMZ-German Collection of Microorganism and Cell Cultures (DSMZ); being respectively identified as Streptococcus dentisani Str. 7746 (CECT 8313, DSM 27089) and Streptococcus dentisani Str. 7747 (CECT 8312T, DSM 27088T).

Concepts: Gene, Bacteria, Organism, Streptococcus, Gram positive bacteria, Streptococcaceae, Streptococcus oralis, Streptococcus mitis

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To examine several poorly understood or contentious aspects of the antibacterial activity of silver (Ag(+)), including its cidality, mode of action, the prevalence of resistance amongst clinical staphylococcal isolates and the propensity for Staphylococcus aureus to develop Ag(+) resistance.

Concepts: Bacteria, Staphylococcus aureus, Staphylococcus, Gram positive bacteria, Coagulase, Staphylococcaceae, Resistance movement

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The mechanisms of linezolid resistance among 86 staphylococcal isolates from two intensive care units were investigated. The most frequent was the G2576T mutation in the 23S rRNA (82%). The cfr gene was found in 17% of the isolates, seven S. aureus and eight S. epidermidis. Four of the S. epidermidis had the G2576T mutation and the cfr gene. In four S. haemolyticus isolates the mechanism could not be identified.

Concepts: DNA, Staphylococcus aureus, Antibiotic resistance, Staphylococcus, Gram positive bacteria, Staphylococcus epidermidis, Staphylococcaceae, Staphylococcus haemolyticus

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Staphylococcus xylosus is a coagulase-negative staphylococcus. It is a commensal bacterium associated with skin and mucous membranes and occasionally it can cause human infections. We report the first case of erythema nodosum developed in a young woman with S. xylosus septicemia and specific serum antibody response.

Concepts: Antibody, Bacteria, Staphylococcus aureus, Staphylococcus, Gram positive bacteria, Staphylococcaceae, Erythema nodosum, Staphylococcus xylosus

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Staphylococcus aureus, a Gram-positive bacterium, can cause a range of illnesses from minor skin infections to life-threatening diseases, such as bacteraemia, endocarditis, meningitis, osteomyelitis, pneumonia, toxic shock syndrome and sepsis. Due to the emergence of antibiotic resistance strains, there is a need to develop of new class of antibiotics or drug for this pathogen. The phosphotransacetylase enzyme plays an important role in the acetate metabolism and found to be essential for the survival of the S. aureus. This enzyme was evaluated as a putative drug target for S. aureus by in silico analysis. The 3D structure of the phosphotransacetylase from S. aureus was modelled, using the 1TD9 chain ‘A’ from Bacillus subtilis as a template at the resolution of 2.75 Å. The generated model has been validated by PROCHECK, WHAT IF and SuperPose. The docking was performed by the Molegro virtual docker using the ZINC database generated ligand library. The ligand library was generated within the limitation of the Lipinski rule of five. Based on the dock-score, five molecules have been subjected to ADME/TOX analysis and subjected for pharmacophore model generation. The zinc IDs of the potential inhibitors are ZINC08442078, ZINC8442200, ZINC 8442087 and ZINC 8442184 and found to be pharmacologically active antagonist of phosphotransacetylase. The molecules were evaluated as no-carcinogenic and persistent molecule by START programme.

Concepts: Bacteria, Microbiology, Pneumonia, Staphylococcus aureus, Antibiotic resistance, Clindamycin, Toxic shock syndrome, Gram positive bacteria