[Effects of ppk1 deletion on the drug susceptibility of uropathogenic Escherichia coli producing ESBLs].

To investigate the effect and the mechanism of ppk1 gene deletion on the drug susceptibility of uropathogenic Escherichia coli producing extended-spectrum beta-lactamases (ESBLs-UPEC). The study was an experimental study. From March to April 2021, a strain of ESBLs-UPEC (genotype was TEM combined with CTX-M-14) named as UE210113, was isolated from urine sample of the patient with urinary tract infection in the Laboratory Department of Guangzhou Eighth People's Hospital, meanwhile its ppk1 gene knock-out strain Δpk1 and complemented strain Δpk1-C were constructed by suicide plasmid homologous recombination technique, which was used to study the effect of ppk1 gene on ESBLs-UPEC drug sensitivity and its mechanism. The drug susceptibility of UE210113, Δpk1, and Δpk1-C were measured by Vitek2 Compact System and broth microdilution method. The quantitative expression of ESBLs, outer membrane protein and multidrug efflux systems encoding genes of UE210113, Δpk1 and Δpk1-C were performed by using qRT-PCR analysis. By using two independent sample Mann-Whitney U test, the drug susceptibility results showed that, compared with UE210113 strain, the sensitivities of Δpk1 to ceftazidime, cefepime, tobramycin, minocycline and cotrimoxazole were enhanced (Z=-2.121,P<0.05;Z=-2.236,P<0.05;Z=-2.236,P<0.05;Z=-2.121,P<0.05), and the drug susceptibility of Δpk1-C restored to the same as which of UE210113 (Z=0,P>0.05). The expression levels of ESBLs-enconding genes blaTEM and blaCTX-M-14 in Δpk1 were significantly down-regulated compared with UE210113, but the expression was not restored in Δpk1-C. The expression of outer membrane protein gene omp F in Δpk1 was significantly up-regulated, while the expression of omp A and omp C were down-regulated. The results showed that the expression of multidrug efflux systems encoding genes tol C, mdt A and mdtG were down-regulated in Δpk1 compared with UE210113. The expression of all of the outer membrane protein genes and the multidrug efflux systems genes were restored in Δpk1-C. In conclusion,the lost of ppk1 gene can affect the expression of the outer membrane protein and multidrug efflux systems encoding genes of ESBLs-UPEC, which increase the sensitivity of ESBLs-UPEC to various drugs.

Molecular identification and biological characteristic analysis of an Apiotrichum mycotoxinivorans (formerly Trichosporon mycotoxinivorans) strain isolated from sputum specimens of a pediatric patient with pneumonia.

Apiotrichum mycotoxinivorans (formerly Trichosporon mycotoxinivorans) has long been used to degrade fungal toxins in livestock feed. However, clinic reports about this type of fungus are rare. In this study, we report the morphology, biochemistry, and molecular characteristics of an A. mycotoxinivorans strain isolated from a pediatric patient with congenital ventricular septal defect and pneumonia. A female patient, 26 months old, presented with congenital ventricular septal defect. Pulmonary infection symptoms were observed after the patient received cardiac repair surgery. Sputum bacterial and fungal cultures were positive for Elizabethkingia anophelis and a fungus, which was not readily identifiable using biochemical identification, or MALDI-TOF MS analysis. The strain was finally identified as A. mycotoxinivorans using amplification and sequencing of the D1/D2 region of 26S rDNA, ITS, and IGS1. Antifungal susceptibility test results suggested that fluconazole or voriconazole may be an appropriate choice for antifungal therapy. A biodegradability of ochratoxin A was considered as a characteristic of the fungal strain. Our results support the existing evidence that A. mycotoxinivorans is an opportunistic pathogen for human beings. Nucleic acid analysis allows for the accurate identification of the species in instances where conventional identification methods such as biochemical testing and MALDI-TOF MS may be unsuccessful.

Electro-optical control in a plasmonic metamaterial hybridised with a liquid-crystal cell.

We experimentally demonstrate efficient electro-optical control in an active nano-structured plasmonic metamaterial hybridised with a liquid-crystal cell. The hybridisation was achieved by simultaneously replacing the polarizer, transparent electrode and molecular alignment layer of the liquid-crystal cell with the metamaterial nano-structure. With the control signal of only 7 V we have achieved a fivefold hysteresis-free modulation of metamaterial transmission at the wavelength of 1.55 µm.

Electron-beam-driven collective-mode metamaterial light source.

We demonstrate experimentally that the energy from a highly localized free-electron-beam excitation can be converted via a planar plasmonic metamaterial to a low-divergence free-space light beam. This emission, which emanates from a collectively oscillating coupled metamolecule nanoantenna ensemble much larger in size than the initial excitation, is distinctly different from cathodoluminescence and bears some similarity with laser light. It offers a novel, flexible paradigm for the development of scalable, threshold-free light sources.

Low-loss plasmonic metamaterial based on epitaxial gold monocrystal film.

We demonstrate high-finesse plasmonic metamaterial with strong resonant response in the near-IR spectral range fabricated using a thin low-loss film of gold monocrystal. The monocrystal was grown using specially formulated simplified crystal growth procedure based on epitaxial deposition, which makes it readily accessible to both plasmonics and metamaterials communities.

"Digitally" addressable focusing of light into a subwavelength hot spot.

We show that a plasmonic metamaterial can act as a far-field to near-field transformer that focuses a free-space beam of light into a subwavelength energy hot spot at a prescribed location with a spot size only a small fraction of the wavelength. The hot spot position on the metamaterial can be prescribed and moved at will from one metamolecule of the array to another in a "digital" fashion simply by modulating the input phase profile, thus providing new opportunities for imaging and optical data processing.

Reconfigurable photonic metamaterials.

We introduce mechanically reconfigurable photonic metamaterials (RPMs) as a flexible platform for realizing metamaterial devices with reversible and large-range tunable characteristics in the optical part of the spectrum. Here we illustrate this concept for a temperature-driven RPM exhibiting reversible relative transmission changes of up to 50%.

Multifold enhancement of quantum dot luminescence in plasmonic metamaterials.

We report that hybridizing semiconductor quantum dots with plasmonic metamaterial leads to a multifold intensity increase and narrowing of their photoluminescence spectrum. The luminescence enhancement is a clear manifestation of the cavity quantum electrodynamics Purcell effect and can be controlled by the metamaterial's design. This observation is an essential step towards understanding loss compensation in plasmonic metamaterials with gain media and for developing metamaterial-enhanced gain media.