Colistin is a last-resort antimicrobial against multidrug-resistant gram-negative bacteria. The occurrence and spread of colistin resistance in humans and animals have been reported globally. This study was performed to investigate the prevalence and antimicrobial susceptibility of mcr-harboring colistinresistant Enterobacteriaceae from retail vegetables and food animals in South Korea in 2018. The mcr-1 gene was detected in Escherichia coli isolates from 0.076% (1/1324) of vegetables, 5.9% (2/34) of chickens, 6.8% (4/59) of pigs, and 0% (0/57) of cattle. Other mcr genes were not detected. All seven of the mcr-1positive isolates showed multidrug resistance and co-produced β-lactamases. Multilocus sequence typing analysis revealed five known E. coli sequence types (STs), including ST10 in the vegetable sample. The study findings demonstrated that the mcr-1 gene has emerged in vegetables and is increasingly detected in food animals in South Korea, highlighting the importance of continuous monitoring and control of colistin-resistant Enterobacteriaceae to prevent them from being transmitted to humans.

The deformation pathway of silicon induced by nanoindentation is investigated in detail at the atomic level using molecular dynamics. Due to the complex stresses associated with the directional loading along a specific crystallographic orientation, the initial Si I lattice is transformed into two different high-pressure phases, namely, Si II and BCT5-Si. The Si II phase, where atoms have the six nearest neighbors, is generated through the tetragonal deformation caused by the compressive loading along the [001] direction. In contrast, the BCT5-Si phase, where each silicon atom has the five nearest neighbors, is formed by flattening the initially stepped sixfold rings of the diamond lattice onto the (110) plane of the BCT lattice. These reconstructive transformations are accomplished only by adding additional bonds and do not involve any bond breaking.

We study problems related to smooth nondegenerate curves γ in R d . First we show the maximal operator M defined by the averaging operator At over the dilations tγ is bounded on L p for p > 2(d − 1) when d ≥ 4. The result is a consequence of the new sharp local smoothing estimate for At. Secondly, we prove the sharp L p Sobolev regularity estimates for At with a fixed t = 0 when d ≥ 5. This settles the problem of sharp L p regularity estimate except the endpoint cases.2010 Mathematics Subject Classification. 42B20 (42B25).

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Extended-spectrum β-lactam antimicrobials have been broadly used in food animals and humans to control infectious diseases. However, the emergence and rapid spread of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, mainly Escherichia coli, have seriously threatened global health in recent decades. In this study, we determined the prevalence, antimicrobial susceptibility, and genetic properties of ESBL-producing E. coli (ESBL-EC) strains isolated from food animals in South Korea. A total of 150 fecal samples from healthy chickens (n = 34), pigs (n = 59), and cattle (n = 57) were screened from January to July 2018. Among these, 77 non-duplicate cefotaxime-resistant ESBL-EC strains were isolated from 32 chicken, 41 pig, and 4 cattle samples, with the corresponding occurrence rates of 94.1, 69.5, and 7.0%, respectively. All the isolates showed multidrug resistance (MDR) and produced at least one type of β-lactamase, including CTX-M (98.7%) and TEM (40.3%). CTX-M-14 (53.1%), CTX-M-55 (53.7%), and CTX-M-65 (50.0%) were the predominant genotypes in the chicken, pig, and cattle samples, respectively. Multilocus sequence typing revealed 46 different sequence types (STs), including the human-associated extraintestinal pathogenic E. coli ST131 (n = 2), ST10 (n = 5), ST38 (n = 1), ST410 (n = 4), ST354 (n = 2), ST58 (n = 3), ST117 (n = 1), and ST457 (n = 1). To the best of our knowledge, this is the first report of pandemic E. coli ST131 in non-human isolates in South Korea. Our results demonstrate the high prevalence and diversity of MDR-ESBL-EC in food animals and highlight them as potential pathogenic ESBL-EC reservoirs that may pose a high risk to human health.