Current Issue : October - December Volume : 2020 Issue Number : 4 Articles : 5 Articles
Loquat fruit is one of the most perishable fruits in China, and has a very limited shelf\nlife because of mechanical injury and microbial decay. Due to an increasing concern about human\nhealth and environmental security, antagonistic microorganisms have been a potential alternative\nfor fungicides to control postharvest diseases. In this work, the antifungal effect of volatile organic\ncompounds (VOCs) produced by Bacillus methylotrophicus BCN2 and Bacillus thuringiensis BCN10\nagainst five postharvest pathogens isolated from loquat fruit, Fusarium oxysporum, Botryosphaeria\nsp., Trichoderma atroviride, Colletotrichum gloeosporioides, and Penicillium expansum were evaluated\nby in vitro and in vivo experiments. As a result, the VOCs released by BCN2 and BCN10 were\nable to suppress the mycelial growth of all targeted pathogens according to inhibition ratio in the\ndouble petri-dish assay as well as disease incidence and disease diameter on loquat fruits. The main\nvolatile compounds were identified by solid-phase microextraction (SPME)-gas chromatography.\nThese VOCs produced by the two strains played complementary roles in controlling these five molds\nand enabled loquat fruits to keep fresh for ten days, significantly. This research will provide a theoretic\nfoundation and technical support for exploring the functional components of VOCs applicable in\nloquat fruit preservation....
We have attempted to define the prevalence and risk factors of extended-spectrum\nbeta-lactamase-producing Enterobacteriaceae (ESBL-Enterobacteriaceae) carriage, and to characterize\nantimicrobial susceptibility, beta-lactamase genes, and major types of isolated strains in volunteers,\nwith a specific focus on humans in contact with animals. Samples were collected from 207 volunteers\n(veterinarians, pig farmers, dog owners, etc.) and cultured on selective agar. Clonal relationships\nof the isolated ESBL-Enterobacteriaceae were determined by whole genome sequencing and\nmulti-locus sequence typing. Beta-lactamases were detected using a homology search. Subjects filled\nin questionnaires analyzed by univariate and multiple logistic regression. Colonization with\nESBL-Enterobacteriaceae was found in fecal samples of 14 individuals (6.8%; 95%CI: 3.75â??11.09%).\nIn multiple regression analysis, working as a pig farmer was a significant risk factor for\nESBL-Enterobacteriaceae carriage (OR 4.8; 95%CI 1.2â??19.1). The only species isolated was Escherichia coli\nthat distributed into 11 sequence types. All ESBL-Enterobacteriaceae isolates were of CTX-M genotype,\nwith the blaCTX-M-1 being the most prevalent and more common in pig farmers than in other groups.\nDespite the generally low prevalence of ESBL-Enterobacteriaceae in Estonia, the pig farmers may still\npose a threat to transfer resistant microorganisms. The clinical relevance of predominant blaCTX-M-1\ncarrying E. coli is still unclear and needs further studies....
The mechanisms of linezolid resistance among 13 E. faecalis and 6 E. faecium isolates,\nrecovered from six Spanish hospitals during 2017â??2018, were investigated. The presence of acquired\nlinezolid resistance genes and mutations in 23S rDNA and in genes encoding for ribosomal proteins\nwas analyzed by PCR and amplicon sequencing. Moreover, the susceptibility to 18 antimicrobial\nagents was investigated, and the respective molecular background was elucidated by PCR-amplicon\nsequencing and whole genome sequencing. The transferability of the linezolid resistance genes was\nevaluated by filter-mating experiments. The optrA gene was detected in all 13 E. faecalis isolates;\nand one optrA-positive isolate also carried the recently described cfr(D) gene. Moreover, one E. faecalis\nisolate displayed the nucleotide mutation G2576T in the 23S rDNA. This mutation was also present in\nall six E. faecium isolates. All linezolid-resistant enterococci showed a multiresistance phenotype and\nharbored several antimicrobial resistance genes, as well as many virulence determinants. The fexA\ngene was located upstream of the optrA gene in 12 of the E. faecalis isolates. Moreover, an erm(A)-like\ngene was located downstream of optrA in two isolates recovered from the same hospital. The optrA\ngene was transferable in all but one E. faecalis isolates, in all cases along with the fexA gene. The cfr(D)\ngene was not transferable. The presence of optrA and mutations in the 23S rDNA are the main\nmechanisms of linezolid resistance among E. faecalis and E. faecium, respectively. We report the first\ndescription of the cfr(D) gene in E. faecalis. The presence of the optrA and cfr(D) genes in Spanish\nhospitals is a public health concern....
New streptothiazolidine A (1), streptodiketopiperazines A (2) and B (3), and (S)-1-(3-\nethylphenyl)-1,2-ethanediol (4), together with eight known compounds (5â??12), were isolated from\nthe Mariana Trench sediment-associated actinomycete Streptomyces sp. SY1965. The racemic\nmixtures of ()-streptodiketopiperazine (2 and 3) and ()-1-(3-ethylphenyl)-1,2-ethanediol (4 and 5)\nwere separated on a chiral high-performance liquid chromatography (HPLC) column. Structures\nof the new compounds were elucidated by their high-resolution electrospray ionization mass\nspectroscopy (HRESIMS) data and extensive nuclear magnetic resonance (NMR) spectroscopic\nanalyses. Streptothiazolidine A is a novel salicylamide analogue with a unique thiazolidine-contained\nside chain and its absolute configuration was established by a combination of nuclear Overhauser eect\nspectroscopy (NOESY) experiment, electronic circular dichroism (ECD) and 13C NMR calculations.\nNew streptothiazolidine A (1) and streptodiketopiperazines A (2) and B (3) showed antifungal activity\nagainst Candida albicans with MIC values of 47, 42, and 42 g/mL, respectively....
Post-antibiotic effect (PAE) is the continued suppression of bacterial growth following a\nlimited exposure to an antimicrobial agent. The presence of PAE needs consequential consideration\nin designing antibiotic dosage regimens. To understand the behavior of bacteria, PAE provides\ninformation on how long antibiotics are applied to the bacteria. Conventional methods of measuring\nPAE depend on population detection and have limitations for understanding the individual behavior\nof bacteria. To observe the PAE, we utilized an imaging technique with the use of microscopy. Here,\nwe discuss the microscopic image analysis system we used to study the PAE at a single-colony level.\nThe size and number of colonies of bacteria were measured prior to and following antibiotic removal.\nWe could count a single colony, see the development of the settlement prior to and following exposure\nof antibiotics and track the colony by microscopy according to the incubation time and the image\nprocessed by our own image processing program. The PAE of antibiotics was quantified by comparing\nbacteria size and number based on their exposure time. In our study, we discovered that the longer\nexposure of antibiotics causes the bacteria to be suppressedâ??even after washing the antibiotics from\nthe solution. This finding suggests that microscopic imaging detection provides a new method for\nunderstanding PAE. In addition, the behavior of the cell in response to drugs and chemicals and their\nremoval can be examined with the use of single colony analysis....
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