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Environ Microbiol. 2016 Sep 15. doi: 10.1111/1462-2920.13531. [Epub ahead of print]

Geochemical and microbial community determinants of reductive dechlorination at a site biostimulated with glycerol.

Atashgahi S1,2,3, Lu Y4, Zheng Y4, Saccenti E5, Suarez-Diez M5, Ramiro-Garcia J4,5, Eisenmann H6, Elsner M7, Stams AJ4,8, Springael D9, Dejonghe W10, Smidt H4.

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Abstract

Biostimulation is widely used to enhance reductive dechlorination of chlorinated ethenes in contaminated aquifers. However, the knowledge on corresponding biogeochemical responses is limited. In this study glycerol was injected in an aquifer contaminated with cis-dichloroethene (cDCE), and geochemical and microbial shifts were followed for 265 days. Consistent with anoxic conditions and sulfate reduction after biostimulation, MiSeq 16S rRNA gene sequencing revealed temporarily increased relative abundance of Firmicutes, Bacteriodetes and sulfate reducing Deltaproteobacteria. In line with 13 C cDCE enrichment and increased Dehalococcoides mccartyi (Dcm) numbers, dechlorination was observed towards the end of the field experiment, albeit being incomplete with accumulation of vinyl chloride. This was concurrent with i) decreased concentrations of dissolved organic carbon (DOC), reduced relative abundances of fermenting and sulfate reducing bacteria that have been suggested to promote Dcm growth by providing electron donor (H2 ) and essential corrinoid cofactors, ii) increased sulfate concentration and increased relative abundance of Epsilonproteobacteria and Deferribacteres as putative oxidizers of reduced sulfur compounds. Strong correlations of DOC, relative abundance of fermenters and sulfate reducers, and dechlorination imply the importance of syntrophic interactions to sustain robust dechlorination. Tracking microbial and environmental parameters that promote/preclude enhanced reductive dechlorination should aid development of sustainable bioremediation strategies. This article is protected by copyright. All rights reserved.

© 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

PMID: 27631786 DOI: 10.1111/1462-2920.13531

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42.

Intern Med. 2016;55(18):2731-5. doi: 10.2169/internalmedicine.55.6593. Epub 2016 Sep 15.

Capnocytophaga ochracea-related Bacterium Bacteremia in a Hypertrophic Cardiomyopathy Patient without Neutropenia.

Ito S1, Hagiya H, Kimura K, Nishi I, Yoshida H, Kioka H, Ohtani T, Yamaguchi O, Tanabe K, Tomono K, Sakata Y.

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Abstract

Gram-negative fusiform rods were detected in a blood culture obtained from a 63-year-old man who had been hospitalized for a long duration for severe heart failure. Although the organism could not be identified using a conventional method, it was finally identified as a bacterium of the Capnocytophaga ochracea group based on the results of biochemical testing, 16S rRNA sequencing and a matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis. Although neutropenic patients with poor oral hygiene are exclusively vulnerable to Capnocytophaga bacteremia, this case was unique because such predisposing conditions were not noted. A multi-centered investigation is warranted for a better understanding of this clinically rare, but potentially pathogenic organism.

PMID: 27629977 DOI: 10.2169/internalmedicine.55.6593

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43.

J Clin Microbiol. 2016 Sep 14. pii: JCM.01240-16. [Epub ahead of print]

Comparison of PCR/Electrospray Ionization Mass Spectrometry with 16S rRNA PCR and Amplicon Sequencing for Detection of Bacteria in Excised Heart Valves.

Peeters B1, Herijgers P2, Beuselinck K1, Peetermans WE3, Herregods MC4, Desmet S1, Lagrou K5.

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Identification of the causative pathogen of infective endocarditis is crucial for adequate management and therapy. A broad range PCR/electrospray ionization mass spectrometry (PCR/ESI-MS) technique was compared with broad-spectrum 16S rRNA PCR and amplicon sequencing (16S rRNA PCR) for detecting bacterial pathogens in 40 heart valves obtained from 34 definite infective endocarditis patients according to the modified Duke Criteria and six non-endocarditis patients. Concordance between both molecular techniques was 98% for being positive or negative, 97% for concordant identification up to genus level and 77% for concordant identification up to species level. Sensitivity for detecting the causative pathogen (up to genus level) in excised heart valves was 88% for 16S rRNA PCR and 85% for PCR/ESI-MS, specificity was 83% for both methods. Both molecular techniques were significantly more sensitive than valve culture (18%) and accurately identified bacteria in excised heart valves. In eight patients with culture negative IE following results were obtained: concordant detection of Coxiella burnetii (n=2), Streptococcus gallolyticus (n=1), Propionobacterium acnes (n=1) and viridans group streptococci (n=1) by both molecular tests, detection of P. acnes by PCR/ESI-MS whereas 16S rRNA PCR was negative (n=1) and a false negative result by both molecular techniques (n=2). In one case of IE caused by viridans streptococci, PCR/ESI-MS was positive for Enterococcus spp.. Advantages of PCR/ESI-MS compared to 16S rRNA PCR are its automated workflow and shorter turn-around-times.

Copyright © 2016, American Society for Microbiology. All Rights Reserved.

PMID: 27629895 DOI: 10.1128/JCM.01240-16

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BMC Microbiol. 2016 Sep 15;16:214. doi: 10.1186/s12866-016-0833-1.

Dental plaque bacteria with reduced susceptibility to chlorhexidine are multidrug resistant.

Saleem HG1,2, Seers CA2, Sabri AN1, Reynolds EC3.

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BACKGROUND:

Chlorhexidine (CHX) is used in oral care products to help control dental plaque. In this study dental plaque bacteria were grown on media containing 2 μg/ml chlorhexidine gluconate to screen for bacteria with reduced CHX susceptibility. The isolates were characterized by 16S rRNA gene sequencing and antibiotic resistance profiles were determined using the disc diffusion method.

RESULTS:

The isolates were variably resistant to multiple drugs including ampicillin, kanamycin, gentamicin and tetracycline. Two species, Chryseobacterium culicis and Chryseobacterium indologenes were able to grow planktonically and form biofilms in the presence of 32 μg/ml CHX. In the CHX and multidrug resistant C. indologenes we demonstrated a 19-fold up-regulation of expression of the HlyD-like periplasmic adaptor protein of a tripartite efflux pump upon exposure to 16 μg/ml CHX suggesting that multidrug resistance may be mediated by this system. Exposure of biofilms of these resistant species to undiluted commercial CHX mouthwash for intervals from 5 to 60 s indicated that the mouthwash was unlikely to eliminate them from dental plaque in vivo.

CONCLUSIONS:

The study highlights the requirement for increased vigilance of the presence of multidrug resistant bacteria in dental plaque and raises a potential risk of long-term use of oral care products containing antimicrobial agents for the control of dental plaque.

KEYWORDS:

Antimicrobial resistance; Chlorhexidine; Chryseobacterium culicis; Chyseobacterium indologenes

PMID: 27629863 PMCID: PMC5024456 DOI: 10.1186/s12866-016-0833-1

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