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Journal of Microbiological Methods

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https://www.readbyqxmd.com/read/30240812/novel-sensor-platform-for-rapid-detection-and-quantification-of-coliforms-on-food-contact-surfaces
#1
Grigori Badalyan, Cecilia Díaz, Mark Bücking, André Lipski
In this paper, a novel sensor platform based on screen printed carbon electrode coated by graphene modified polyacrylamide gel (GR/PAAGC) was developed and implemented for sampling, detection and enumeration of coliform bacteria (coliforms) on food contact surfaces. The optimized formula of polyacrylamide (PAA) and agar-agar increased the adhesive properties of the gel, being crucial for the coliforms recovery, attached to food contact surfaces. The 6-Chloro-3-indoxyl-β-D-galactopyranoside (6-CIGP) was used as a new electrochemical reporter for β-D-galactosidase activity...
September 18, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30240811/method-for-isolation-of-both-lactose-fermenting-and-non-fermenting-escherichia-albertii-strains-from-stool-samples
#2
Andrée F Maheux, Stéphanie Brodeur, Ève Bérubé, Dominique K Boudreau, Jehane Y Abed, Maurice Boissinot, Luc Bissonnette, Michel G Bergeron
Initially, Escherichia albertii has been described as a non-lactose fermenting bacterium and methods used to isolate it were first based on this phenotypic property. However, a recent study showed a variable lactose fermentation phenotype for E. albertii suggesting that this microorganism could have been underestimated by previous studies using isolation methods based on lactose fermentation. In this study, we present a method for the isolation and identification of both lactose fermenting and non-fermenting-E...
September 18, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30240810/subtle-changes-in-host-cell-density-cause-a-serious-error-in-monitoring-of-the-intracellular-growth-of-chlamydia-trachomatis-in-a-low-oxygen-environment-proposal-for-a-standardized-culture-method
#3
Kouhei Sakai, Junji Matsuo, Takanori Watanabe, Torahiko Okubo, Shinji Nakamura, Hiroyuki Yamaguchi
We monitored Chlamydia trachomatis growth in HeLa cells cultured with either DMEM or RPMI medium containing 10% FCS under 2% or 21% O2 conditions for 2 days. Bacterial numbers, host cell numbers, and fibrosis-related gene expression in the host cells were estimated by an inclusion forming unit assay, a cell counting assay, and a PCR array, respectively. In contrast to RPMI, bacterial growth under low oxygen conditions in DMEM rapidly decreased with increasing host cell density. The addition of supplements (glucose, glutamine, vitamin B12, D-biotin, non-essential amino acids, glutathione) to the media had no effect...
September 18, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30201412/evaluation-of-dna-extraction-methods-to-detect-bacterial-targets-in-aerosol-samples
#4
John Dunbar, La Verne Gallegos-Graves, Jason Gans, Stephen A Morse, Segaran Pillai, Kevin Anderson, David R Hodge
DNA-based monitoring of pathogens in aerosol samples requires extraction methods that provide high recovery of DNA. To identify a suitable method, we evaluated six DNA extraction methods for recovery of target-specific DNA from samples with four bacterial agents at low abundance (<10,000 genome copies per detection assay). These methods differed in rigor of cell disruption, approach for DNA capture, and extent of DNA purification. The six methods varied 1000-fold in the recovery of DNA from spores or cells of surrogates of Bacillus anthracis, Yersinia pestis, Burkholderia pseudomallei, and Francisella tularensis, each at about 105  CFU per sample...
September 8, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30195830/automated-counting-of-bacterial-colonies-on-agar-plates-based-on-images-captured-at-near-infrared-light
#5
Guozhen Zhu, Bin Yan, Mengting Xing, Chunna Tian
Counting colonies is usually used in microbiological analysis to assess if samples meet microbiological criteria. Although manual counting remains gold standard, the process is subjective, tedious, and time-consuming. Some developed automatic counting methods could save labors and time, but their results are easily affected by uneven illumination and reflection of visible light. To offer a method which counts colonies automatically and is robust to light, we constructed a convenient and cost-effective system to obtain images of colonies at near-infrared light, and proposed an automatic method to detect and count colonies by processing images...
September 6, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30195829/concentration-of-listeria-monocytogenes-in-skim-milk-and-soft-cheese-through-microplate-immunocapture
#6
Steven A Rogers, Melissa Calicchia, Rosalee S Hellberg
Microplate immunocapture is an inexpensive method for the concentration of foodborne pathogens using an antibody-coated microplate. The objective of this study was to determine the efficacy of microplate immunocapture as an alternative to traditional enrichment for concentrating Listeria monocytogenes to levels detectable with selective plating or real-time PCR. L. monocytogenes isolates serologically characterized as Type 1 (1/2a) and Type 4 (untypeable) were grown overnight and diluted to 100 to 106 colony-forming units (CFU)/mL...
September 6, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30194948/separation-of-cells-in-density-gradients-with-temporary-solidification-of-the-gradient-application-to-escherichia-coli-forms-obtained-by-microwave-treatment-of-pure-cultures
#7
Tatiana Abashina, Mikhail Vainshtein, Saara Korpela, Timo Korpela
Gelatin added in certain concentration into the density gradient mixtures allows to solidify and melt the gradient reversibly. Such a method was applied to separation of partially disintegrated Escherichia coli VKM B-125 cells in discontinuous sucrose gradient which was optimized to obtain small round "nano-cells" free from other cell components. Gelatin added to the sucrose solutions had the advantages: i) accurate gradient layers were formed, ii) gelatin did not interfere with the cells and sub-particles during centrifugation, iii) solidified gelatin allowed to cut out the separated cell components, and iv) gelatin allowed to prepare ready-made solidified gradient centrifugation tubes into storage...
September 5, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30193924/rapid-antimicrobial-susceptibility-testing-by-matrix-assisted-laser-desorption-ionization-time-of-flight-mass-spectrometry-using-a-qualitative-method-in-acinetobacter-baumannii-complex
#8
Mengjiao Li, Minxue Liu, Qifei Song, Li Xiong, Zhixing Chen, Mei Kang, Yi Xie
The transmission and infections of multidrug-resistant bacteria can be prevented by rapid identification and antibiotic susceptibility testing (AST) for pathogenic bacteria in a clinical microbiology laboratory. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been routinely used as a tool for the identification of pathogens; however, a simple and accurate method for a rapid determination of the antimicrobial susceptibility profile is an urgent requisite. The present study established a method based on mass spectrometry to determine the drug resistance...
September 4, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30189222/detection-of-carbapenem-resistant-enterobacteriaceae-by-chromogenic-screening-media
#9
REVIEW
Naser Alizadeh, Mohammad Ahangarzadeh Rezaee, Hossein Samadi Kafil, Mohammad Hossein Soroush Barhaghi, Mohammad Yousef Memar, Morteza Milani, Alka Hasani, Reza Ghotaslou
Enterobacteriaceae are a part of the human intestinal flora easily spread by hand carriage, water and food. Treatment of infections due to Enterobacteriaceae is difficult mainly in countries with a low socioeconomic state. Carbapenems are considered as a last-resort antibiotic for the treatment of infections due to multidrug-resistant Enterobacteriaceae. Carbapenem-resistant Enterobacteriaceae (CRE) presents a major threat to public health and are rapidly disseminating globally. The most important resistance mechanism of Enterobacteriaceae to carbapenems is carbapenemase production...
September 4, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30170019/new-growth-media-for-oral-bacteria
#10
Bénédicte Martin, Kanchana Chathoth, Souad Ouali, Vincent Meuric, Martine Bonnaure-Mallet, Christine Baysse
New growth media have been designed for the iron-controlled co-cultures of three oral bacteria. These media share a common core composition enabling the switch from mono- to co-cultures, and efficiently promote both planktonic and biofilm cultures of Porphyromonas gingivalis, Treponema denticola and Streptococcus gordonii.
August 28, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30165087/in-vitro-approaches-for-generation-of-mycobacterium-tuberculosis-mutants-resistant-to-bedaquiline-clofazimine-or-linezolid-and-identification-of-associated-genetic-variants
#11
N Ismail, S V Omar, N A Ismail, R P H Peters
Bedaquiline, clofazimine and linezolid are pertinent drugs for drug-resistant tuberculosis. Drug-resistant mutants provide insight into important resistance acquisition mechanisms. Methods for in vitro Mycobacterium tuberculosis mutant generation are poorly described. Induction (serial passaging) and spontaneous (adapted Luria-Delbrück assay) approaches using M. tuberculosis ATCC reference strains (one fully-susceptible, four unique mono-resistant) were performed. Mutant MIC values were confirmed (MGIT960) and resultant RAVs compared between approaches and to a catalog of previously published RAVs...
August 28, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30165088/six-species-of-nontuberculous-mycobacteria-carry-non-identical-16s-rrna-gene-copies
#12
Keita Takeda, Kinuyo Chikamatsu, Yuriko Igarashi, Yuta Morishige, Yoshiro Murase, Akio Aono, Hiroyuki Yamada, Akiko Takaki, Satoshi Mitarai
Nontuberculous mycobacteria (NTM) can carry two or more 16S rRNA gene copies that are, in some instances, non-identical. In this study, we used a combined cloning and sequencing approach to analyze 16S rRNA gene sequences of six NTM species, Mycobacterium cosmeticum, M. pallens, M. hodleri, M. crocinum, M. flavescens, and M. xenopi. Our approach facilitated the identification of two distinct gene copies in each species. The two M. cosmeticum genes had a single nucleotide difference, whereas two nucleotide polymorphisms were identified in M...
August 27, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30144480/improved-ph-ratiometry-for-the-three-dimensional-mapping-of-ph-microenvironments-in-biofilms-under-flow-conditions
#13
Sebastian Schlafer, Vibeke Baelum, Irene Dige
Confocal microscopy-based monitoring of pH in biofilms is gaining increasing interest, as it allows for a quick assessment of horizontal pH gradients without mechanically perturbing the biofilm. Ratiometric monitoring of pH with the fluorescent dye C-SNARF-4 has been used to reliably map extracellular pH in the basal layers of biofilms, but only under static conditions. Here, we expand this methodology to measurements of vertical gradients in multispecies in vitro-grown and in situ-grown dental biofilms of different age, and to pH measurements in in vitro-grown biofilms under flow conditions...
August 23, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30144479/evaluation-of-rapid-polymyxin-np-test-to-detect-colistin-resistant-klebsiella-pneumoniae-isolated-in-a-tertiary-greek-hospital
#14
Ergina Malli, Zoi Florou, Katerina Tsilipounidaki, Ioanna Voulgaridi, Aggelos Stefos, Stelios Xitsas, Costas C Papagiannitsis, Efthimia Petinaki
The efficiency of Rapid Polymyxin NP test for detection of colistin-resistant isolates was tested against a collection of 131 non-repetitive Klebsiella pneumoniae, including 98 colistin-resistant and 33 colistin-susceptible isolates. In addition, the performance of this test was compared with those of the automated systems, BD Phoenix™ and VITEK®2, and the Etest. Determination of imipenem and meropenem MICs showed that 95 of colistin-resistant (Col-R) isolates were also resistant to at least one carbapenem...
August 23, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30142357/aerobic-cultivation-of-anaerobic-rumen-protozoa-entodinium-caudatum-and-epidinium-caudatum
#15
Tansol Park, Zhongtang Yu
Rumen protozoa, primarily ciliates, are one of the important groups of strictly anaerobic microbes living in the rumen. Despite their ubiquitous occurrence in the rumen and significant contribution to host animals, it is still poorly understood why they live only in the rumen and similar environment. Because rumen protozoa require strict anaerobic conditions to sustain their viability and grow, only a few laboratories equipped with protozoology expertise and anaerobic facilities can grow rumen protozoa in laboratory...
August 21, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30138644/development-of-a-molecular-serotyping-scheme-and-a-multiplexed-luminex-based-array-for-providencia
#16
Yuhui Du, Huiying Li, Zhiqiu Yin, Antoni Rozalski, Agnieszka Torzewska, Pan Yang, Chengqian Qian, Tingting Xu, Hengchun Cao, Pan Wu, Lingyan Jiang, Xi Guo, Di Huang, Bin Liu
Providencia is an opportunistic human pathogen that belongs to the Enterobacteriaceae family. The bacterial cell surface O-antigen is one of the most structurally variable cell constituents and serves as a basis for serotyping gram-negative bacteria. In this work, the genomes of 12 Providencia strains were sequenced, and genes driving O-antigen biosynthesis were analyzed. The O-antigen-synthesizing genes of Providencia are located in the O-antigen gene cluster (OGC) between the cpxA and yibK genes. The gene functions predicted in silico agreed with the known O-antigen structures...
August 20, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30138643/the-edta-based-disk-combination-tests-are-unreliable-for-the-detection-of-mcr-mediated-colistin-resistance-in-enterobacteriaceae
#17
Mathieu Clément, Thomas Büdel, Odette J Bernasconi, Luigi Principe, Vincent Perreten, Francesco Luzzaro, Andrea Endimiani
We evaluated several EDTA-based combined-disk tests to detect 25 mcr producers among 48 Enterobacteriaceae. Colistin disks plus EDTA (292/584 μg) on MH and CAMH agar were used. Results were positive if with chelator there was an inhibition zone increase ≥3 mm compared to colistin alone. All tests resulted unreliable (sensitivity ≤68%).
August 20, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30125587/directed-freeze-fracturing-of-bacillus-subtilis-biofilms-for-conventional-scanning-electron-microscopy
#18
Felix M Fuchs, Gudrun Holland, Ralf Moeller, Michael Laue
Biofilms have been intensively investigated over the past decades. Bacillus subtilis is able to form highly structured colony biofilms, and as one of the most studied Gram-positive model organisms, has helped to decipher the complex genetic regulation of biofilms. Several methods have been developed to analyze the architecture of biofilms. In this paper, we describe a method which allows the analysis of the internal structures of biofilms by scanning electron microscopy (SEM). The method uses a modified freeze-fracturing of chemically fixed biofilm to generate defined, well-preserved fractures at millimeter-scale which allows to analyze systematically the internal biofilm structure from macro- to nano-scale...
August 17, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30110601/quantification-of-bacteriuria-caused-by-hemolysin-positive-escherichia-coli-in-human-and-mouse-urine-using-quantitative-polymerase-chain-reaction-qpcr-targeting-hlyd
#19
Michelle N Chamoun, Matthew J Sullivan, Glen C Ulett
Uropathogenic Escherichia coli (UPEC) cause the majority of community-acquired urinary tract infections (UTIs). Quantitation of bacteriuria (the number of bacteria in urine) is important for diagnostic approaches and in diverse research applications. Most UPEC strains express hemolysin, the expression of which has been correlated with the severity of UTI in murine models of infection. In this study, we sought to develop and optimise a quantitative Polymerase Chain Reaction (qPCR) assay for enumeration of hemolysin-positive UPEC in urine...
August 12, 2018: Journal of Microbiological Methods
https://www.readbyqxmd.com/read/30099005/sensitive-and-rapid-detection-of-salmonella-enterica-serovar-indiana-by-cross-priming-amplification
#20
Yong-Xiang Wang, An-Yun Zhang, Yong-Qiang Yang, Chang-Wei Lei, Guang-Yang Cheng, Wen-Cheng Zou, Jin-Xin Zeng, Yan-Peng Chen, Hong-Ning Wang
Salmonella enterica serovar Indiana (S. Indiana) was the most frequently reported foodborne pathogen, which has a broad host range including poultry, swine, and humans. Traditional methods used for the detection of S. Indiana from contaminated food products are time-consuming and labor-intensive. Therefore, rapid detection methods with high sensitivity and specificity are vitally important to prevent the spread of S. Indiana. In this study, we developed a nearly instrument-free, simple molecular method which incorporates cross-priming amplification (CPA) combined with a nucleic acid detection strip (NADS) for sensitive detection of S...
August 9, 2018: Journal of Microbiological Methods
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