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Letters in Applied Microbiology

Cover image for Vol. 56 Issue 2

February 2013

Volume 56, Issue 2

Pages 83–160

  1. Original Articles

    1. Top of page
    2. Original Articles
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      Mycobactericidal activity of hydrogen peroxide activated by a novel heterogeneous Fentons-like catalyst system (pages 83–87)

      S.L. Price, K.D. Huddersman, J. Shen and S.E. Walsh

      Article first published online: 3 DEC 2012 | DOI: 10.1111/lam.12010

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      Significance and Impact of the Study: This study expands on previous published work by demonstrating the enhanced mycobactericidal activity gained by using the novel heterogeneous polyacrylonitrile catalyst, developed at De Montfort University, to potentiate the activity of hydrogen peroxide as a biocide. The increased activation of hydrogen peroxide by this system enables lower concentrations, and shorter contact times, to be used. This system could be used as an alternative within the healthcare sector, such as endoscope disinfection.

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      Detection of Salmonella spp. from large volumes of water by modified Moore swabs and tangential flow filtration (pages 88–94)

      R. McEgan, C.A.P. Rodrigues, A. Sbodio, T.V. Suslow, L.D. Goodridge and M.D. Danyluk

      Article first published online: 3 DEC 2012 | DOI: 10.1111/lam.12016

      Significance and Impact of the Study: Large-volume water samples may be screened for the presence of Salmonella both preseason and preharvest. This will provide better data from which to make risk management decisions to improve fresh produce safety. The time required to complete screening (2 days) will make it more practical to screen surface waters for Salmonella prior to use during produce production, to facilitate source tracking in root-cause determination or to determine risk associated with water nearby produce fields. The method enables the direct screening for pathogens in a timely manner, which avoids the need to rely on indicator or index organisms to evaluate food safety risks. Use of this method has the potential to decrease the risk of in-field fresh produce contamination.

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      Antimicrobial efficacy of cryotreatment against Enterococcus faecalis in root canals (pages 95–98)

      N. Mandras, V. Allizond, A. Bianco, G. Banche, J. Roana, L. Piazza, P. Viale and A.M. Cuffini

      Article first published online: 27 DEC 2012 | DOI: 10.1111/lam.12017

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      Significance and Impact of the Study The cryotreatment seems to have a greater effect on the reduction in bacteria compared to a standard NaOCl irrigation. The effect of root canal treatment by the statistically bacterial load reduction on the clinical outcome after cryotreatment remains unknown. The interesting potential of cryotreatment should be further investigated through clinical studies aimed to establish a correct irrigation protocol.

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      Lead-resistant Providencia alcalifaciens strain 2EA bioprecipitates Pb+2 as lead phosphate (pages 99–104)

      M.M. Naik, D. Khanolkar and S.K. Dubey

      Article first published online: 7 JAN 2013 | DOI: 10.1111/lam.12026

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      Significance and Impact of the Study: Providencia alcalifaciens strain 2EA resist lead nitrate up to 0·0014 mol l−1 by precipitating soluble lead (Pb+2) as insoluble light brown solid. Scanning electron microscopy coupled with energy-dispersive X-ray spectrometric analysis (SEM-EDX) and X-ray diffraction spectroscopy (XRD) revealed extracellular light brown precipitate as lead orthophosphate mineral, that is, Pb9 (PO4)6 catalysed by phosphatase enzyme. Providencia alcalifaciens strain 2EA could be used for bioremediation of lead-contaminated environmental sites, as it can efficiently precipitate lead as insoluble lead phosphate.

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      A simple method of DNA isolation from jute (Corchorus olitorius) seed suitable for PCR-based detection of the pathogen Macrophomina phaseolina (Tassi) Goid (pages 105–110)

      C. Biswas, P. Dey, S. Satpathy, S.K. Sarkar, A. Bera and B.S. Mahapatra

      Article first published online: 28 NOV 2012 | DOI: 10.1111/lam.12020

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      Significance and Impact of the Study: Stem rot caused by Macrophomina phaseolina is the most important disease of jute, a bast fibre crop. Seedborne infection of the pathogen is generally detected by conventional methods such as blotter method and agar-plate method followed by microscopy. But, these techniques are time-consuming and not sensitive. In the present investigation, M. phaseolina was detected from jute seeds by PCR, which is a rapid and reliable technique. However, high contents of mucilage and secondary metabolites in jute seed hinder DNA isolation and PCR amplification. To address these problems, we developed a Miniprep which yielded a sufficient amount of good quality DNA as compared to other methods and standardized a PCR protocol, which could amplify the fungal DNA present in seed. It would enable efficient PCR-based detection of M. phaseolina from large number of jute seed lots.

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      Analysis of microbial diversity on deli slicers using polymerase chain reaction and denaturing gradient gel electrophoresis technologies (pages 111–119)

      O.K. Koo, A.W. Mertz, E.L. Akins, S.A. Sirsat, J.A. Neal, R. Morawicki, P.G. Crandall and S.C. Ricke

      Article first published online: 21 NOV 2012 | DOI: 10.1111/lam.12021

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      Significance and impact of the Study: This study is the first to demonstrate the application of DGGE methodology to investigate the microbial diversity of food-contact surfaces such as deli slicer. These results can further enhance current understanding of the microbial ecology of food-contact surfaces and aid in developing effective cleaning and sanitization methods.

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      Shiga toxin–producing Escherichia coli from raw milk cheese in Egypt: prevalence, molecular characterization and survival to stress conditions (pages 120–127)

      M. Elhadidy and M.A. Mohammed

      Article first published online: 28 NOV 2012 | DOI: 10.1111/lam.12023

      Significance and Impact of the Study: The results obtained from this work highlighted the potential occurrence of STEC in Kareish and Damietta cheese. Kareish and Damietta cheese samples are considered one of the traditional Egyptian dairy products and are made from raw unpasteurized milk, and their manufacture and handling techniques are still rudimentary and unsanitary. Our survival studies highlighted the importance of better understanding of how non-O157:H7 STEC behave under stress conditions for better control of the occurrence, growth or survival of this organism in food.

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      Identification and typing of Francisella tularensis with a highly automated genotyping assay (pages 128–134)

      D.D. Duncan, A.J. Vogler, M.J. Wolcott, F. Li, D.S. Sarovich, D.N. Birdsell, L.M. Watson, T.A. Hall, R. Sampath, R. Housley, L.B. Blyn, S.A. Hofstadler, D.J. Ecker, P. Keim, D.M. Wagner and M.W. Eshoo

      Article first published online: 28 NOV 2012 | DOI: 10.1111/lam.12022

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      Significance and Impact of the Study: Molecular characterization of pathogenic subspecies of Francisella tularensis can be obscured by their near neighbours, which can be prevalent in environmental samples. This study describes a multilocus PCR assay for characterizing key species and subspecies of Francisella at multiple levels of resolution, using stable markers defining phylogenetic groups, together with more variable strain-defining markers. Target loci were selected to form an integrated and semi-redundant panel enabling robust identification of samples, including unique samples showing novel assay signatures. Analyses of environmental isolates and a diverse panel of curated samples exemplified the applications of this approach in surveillance and outbreak studies.

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      Validation of IRS PCR, a molecular typing method, for the study of the diversity and population dynamics of Legionella in industrial cooling circuits (pages 135–141)

      D. Jakubek, M. Le Brun, G. Leblon, M. DuBow and M. Binet

      Article first published online: 3 DEC 2012 | DOI: 10.1111/lam.12025

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      Significance and Impact of the Study: IRS PCR, unlike PFGE and SBT, is a suitable tool for the ecological study of Legionella pneumophila in a large scale. It will be helpful to investigate diversity and dynamics of Leg. populations in water systems where these bacteria are strongly represented, as in cooling circuits.

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      Multiple-pass high-pressure homogenization of milk for the development of pasteurization-like processing conditions (pages 142–148)

      H. Ruiz-Espinosa, G.G. Amador-Espejo, M.E. Barcenas-Pozos, J.O. Angulo-Guerrero, H.S. Garcia and J. Welti-Chanes

      Article first published online: 20 DEC 2012 | DOI: 10.1111/lam.12027

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      Significance and Impact of the Study: Milk is usually heat-preserved, but certain thermal-related modifications in nutritional, sensory and functional properties may arise. Consequently, nonthermal technologies such as ultrahigh pressure homogenization (UHPH) are currently explored. As part of the scientific criteria needed to assess UHPH equivalency to thermal pasteurization, microbial reduction of both the most baroresistant pathogen and native milk microflora must be determined and processing conditions could be defined through multiple response optimization. Results from the present study show that optimized multiple-pass UHPH treatments are capable of a 5-D reduction of both spoilage and pathogenic flora in whole milk.

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      Sub-lethal concentrations of antibiotics increase mutation frequency in the cystic fibrosis pathogen Pseudomonas aeruginosa (pages 149–154)

      C.G. Nair, C. Chao, B. Ryall and H.D. Williams

      Article first published online: 7 JAN 2013 | DOI: 10.1111/lam.12032

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      Significance and Impact of the Study: A wide spectrum of antibiotics is used against infections of the lungs of cystic fibrosis (CF) sufferers, who are subjected to antibiotic therapy at regular intervals throughout their lives. However, high antibiotic concentrations are difficult to achieve in vivo, and bacteria that are repeatedly exposed to sublethal levels develop resistance. We demonstrate that sublethal levels of clinically important bactericidal antibiotics lead to an increase in mutation frequency in the major CF pathogen Pseudomonas aeruginosa. These findings could be clinically significant because sublethal concentrations of antibiotics present during chronic infection may act as mutagens and facilitate adaptation of bacteria to the CF lung.

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      Combined effect of sodium nitrite with high-pressure treatments on the inactivation of Escherichia coli BW25113 and Listeria monocytogenes NCTC 11994 (pages 155–160)

      M. De Alba, D. Bravo, M. Medina, S.F. Park and B.M. Mackey

      Article first published online: 7 JAN 2013 | DOI: 10.1111/lam.12031

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      Significance and Impact of the Study: High hydrostatic pressure (HHP) is an effective nonthermal food preservation technology that can be used to increase food safety and shelf life with minimal changes in food quality. Various antimicrobial agents including bacteriocins, lysozyme, chitosan, lactoperoxidase and essential oils have been tested in combination with HHP to enhance the effect of mild-pressure treatments. This is the first report of a synergistic bactericidal effect of high pressure and acidified nitrite. A better understanding of combined preservation processes and synergistic effects will help ensure the safety of processed foods.

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