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Introduction: Shewanella is an important opportunistic pathogen distributed in marine environments that has caused an increasing number of clinical infections. However, there are few reports on the distribution and characteristics of Shewanella in the diarrheal pathogen spectrum. In this study, we have systematically described the prevalence of Shewanella infections in diarrhea patients in Beijing, China 2017-2019, and genome characteristics and antimicrobial susceptibility of Shewanella isolates. Methods: Stool samples were collected from diarrhea patients in a surveillance project from 2017 to 2019. Shewanella strains were isolated, and identified using VITEKR 2 COMPACT and MALDI-TOF MS. Average nucleotide identity (ANI) analysis, multi-locus sequence typing (MLST), phylogenetic analysis, virulence-associated genes and antimicrobial resistance genes analysis were used for genome characteristics description. The antibiotic susceptibility test was performed with microbroth dilution method. Results: 1104 fecal samples were collected, and the Shewanella detection rate was 2.36% (26/1104). The main manifestations of infection caused by Shewanella spp. were diarrhea (100%, 26/26), abdominal pain (65.38%, 17/26), and vomiting (38.46%, 10/26). The 26 isolates were classified into 3 species (S. algae (n = 18), S. indica (n = 5), and S. chilikensis (n = 3)) and 22 sequence types. Core genome single nucleotide polymorphism-based evolutionary tree identified three clone groups corresponding to three infection events in the same months in 2017 and 2019. The putative virulence-associated gene pool consisted of 56 potential virulence genes, including 19 virulence gene factors. The resistance rates of the 26 isolates to 17 antibiotics from high to low were as follows: polymyxin E (76.92%), cefotaxime (57.69%), ampicillin (50%), ampicillin-sulbactam (34.62%), nalidixic acid (15.38%), ciprofloxacin (11.54%), selectrin (3.846%,1/26), and tetracycline (3.846%, 1/26). The rate of multidrug resistance was 38.46% (10/26). Discussion: Monitoring for Shewanella spp. should be added to the routine surveillance of infectious diarrhea during the epidemic season.
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The absorption coefficient of fused silica for a mid-infrared (IR) laser is higher than that for a near-IR laser, but smaller than that for a far-IR laser. Therefore, the energy coupling efficiency of the mid-IR laser is higher than that for the near-IR laser, while the penetration depth is higher than that for the far-IR laser. Thus, the mid-IR laser is highly efficient in mitigating damage growth. In this study, a deuterium fluoride (DF) laser with a center wavelength of 3.8 µm was used to interact with fused silica. The temperature variation, changes in the reflected and transmitted intensities of the probe light incident on the laser irradiation area, and the vaporization and melting sputtering process were analyzed. The results demonstrate that when the laser intensity was low (<1.2 kW/cm2), no significant melting was observed, and the reflection and transmission properties gradually recovered after the end of the laser irradiation process. With a further increase in the laser intensity, the sample gradually melted and vaporized. At a laser intensity above 5.1 kW/cm2, the temperature of the sample increased rapidly and vapors in huge quantity evaporated from the surface of the sample. Moreover, when the laser intensity was increased to 9.5 kW/cm2, the sample melted and an intense melting sputtering process was observed, and the sample was melted through.
