BlaPSZ-1, a novel AmpC gene identified from a Pantoea isolate

BackgroundPantoea species of the family Erwiniaceae are well-known plant pathogens and animal and human conditional pathogens. Due to the widespread and continuous use of antimicrobials, multidrug-resistant strains continue to emerge, making clinical treatment difficult; therefore, there is an increasing need to clarify the mechanisms of drug resistance.MethodsA rabbit anal fecal sample was collected by a swab and the streak plate method was used to isolate single colonies. The standard agar dilution method was used to determine the minimum inhibitory concentrations (MICs) against antimicrobials. The complete genome sequence of the bacterium was obtained using Next-Generation Sequencing platforms. The potential resistance gene was annotated based on the Comprehensive Antibiotic Resistance Database (CARD) and verified by molecular cloning. The β-lactamase PSZ-1 was expressed via the pCold I expression vector and its enzyme kinetic parameters were analyzed. The genetic environment and evolutionary process of the novel resistance gene-related sequences were analyzed by bioinformatic methods.ResultsThe isolate Pantoea endophytica X85 showed some degree of resistance to penicillins as well as cephalosporins. A novel AmpC resistance gene, designated blaPSZ-1 in this research, was identified to be encoded in the plasmid (pPEX85) of P. endophytica X85. BlaPSZ-1 showed resistance to penicillins and several first-, second-and third-generation cephalosporins as well as aztreonam, but it did not show resistance to the fourth-generation cephalosporins or carbapenems tested. Enzyme kinetic assays revealed that it could hydrolyze amoxicillin, penicillin G, cephalothin, and cefazolin, and its hydrolytic activity could be strongly inhibited by the inhibitor avibactam, which was generally consistent with antimicrobial susceptibility testing results. No hydrolytic activity was observed for third-generation cephalosporins or aztreonam.ConclusionIn this study, a novel AmpC β-lactamase gene, designated blaPSZ-1, was characterized and it was encoded in the plasmid of the bacterium P. endophytica X85. It shows resistance to penicillins and several cephalosporins. The discovery of novel drug resistance mechanisms can help guide the scientific use of drugs in animal husbandry and clinical practice, effectively avoiding the abuse of antimicrobials and thus preventing the further development and spread of bacterial resistance

Identification and characterization of a novel chromosomal aminoglycoside 3’-O-phosphotransferase, APH(3′)-Id, from Kluyvera intermedia DW18 isolated from the sewage of an animal farm

BackgroundAminoglycosides, as important clinical antimicrobials, are used as second-line drugs for treating multidrug-resistant tuberculosis or combined with β-lactam drugs for treating severe infections such as sepsis. Aminoglycoside-modifying enzyme (AME) is the most important mechanism of aminoglycoside resistance and deserves more attention.MethodsThe bacterium Kluyvera intermedia DW18 was isolated from the sewage of an animal farm using the conventional method. The agar dilution method was used to determine the minimum inhibitory concentrations (MICs) of antimicrobials. A novel resistance gene was cloned, and the enzyme was expressed. The kinetic parameters were measured by a SpectraMax M5 multifunctional microplate reader. Bioinformatic analysis was performed to reveal the genetic context of the aph(3′)-Id gene and its phylogenetic relationship with other AMEs.ResultsA novel aminoglycoside 3′-O-phosphotransferase gene designated aph(3′)-Id was identified in K. intermedia DW18 and shared the highest amino acid identity of 77.49% with the functionally characterized aminoglycoside 3′-O-phosphotransferase APH(3′)-Ia. The recombinant plasmid carrying the novel resistance gene (pMD19-aph(3′)-Id/E. coli DH5α) showed 1,024-, 512-, 128- and 16-fold increased MIC levels for kanamycin, ribostamycin, paromomycin and neomycin, respectively, compared with the reference strain DH5α. APH(3′)-Id showed the highest catalytic efficiency for ribostamycin [kcat/Km of (4.96 ± 1.63) × 105 M−1/s−1], followed by paromomycin [kcat/Km of (2.18 ± 0.21) × 105 M−1/s−1], neomycin [kcat/Km of (1.73 ± 0.20) × 105 M−1/s−1], and kanamycin [kcat/Km of (1.10 ± 0.18) × 105 M−1/s−1]. Three conserved functional domains of the aminoglycoside phosphotransferase family and ten amino acid residues responsible for the phosphorylation of kanamycin were found in the amino acid sequence of APH(3′)-Id. No mobile genetic element (MGE) was discovered surrounding the aph(3′)-Id gene.ConclusionIn this work, a novel aminoglycoside 3’-O-phosphotransferase gene designated aph(3′)-Id encoded in the chromosome of the environmental isolate Kluyvera intermedia DW18 was identified and characterized. These findings will help clinicians select effective antimicrobials to treat infections caused by pathogens with this kind of resistance gene

Study on ocean oil spill detection using different ERS SAR resolution data

International Geoscience and Remote Sensing Symposium (IGARSS)2806-808IGRS

Buckling Test of Composite Cylindrical Shells with Large Radius Thickness Ratio

A buckling test of composite cylindrical shells with a radius–thickness ratio (r/t) = 893 under axial compression was conducted to investigate the effects of the radius–thickness ratio (r/t). It is known that the buckling load of cylinders shows large differences and scatter between theory and experiment. The ratio of the experimental buckling load and theoretical buckling load is called the knockdown factor (KDF). Many investigations have been conducted to find the cause of the degradation and scatter in the KDF, but as yet, no cause has been found. In 1968, NASA’s buckling design criterion, NASA SP-8007, gave an empirical KDF curve that decreased with the increasing r/t (up to 2000) for metal cylinders. The same curve has been applied to composite cylinders. Recently, Takano derived a flat lower-bound KDF in terms of A- and B-basis values (99% and 90% probability with a 95% confidence level) through a statistical analysis of experimental buckling loads. The result, however, based on experimental results up to r/t = 500 and, thus, the dependency on a large range of r/t, is not clear. Thus, the authors focused on a larger range of r/t. Cylindrical shells made from carbon fiber-reinforced plastic (CFRP) were tested. The nominal radius, thickness, and length were r = 100.118 mm, t = 0.118 mm, and L = 200 mm and, thus, the r/t = 848 and length-to-radius ratio (L/r) = 2.0. Shape imperfections were also measured by using in-house laser displacement equipment. The buckling load was slightly affected by the r/t, but the reduction in the KDF was insignificant

Buckling Test of Composite Cylindrical Shells with Large Radius Thickness Ratio

A buckling test of composite cylindrical shells with a radius–thickness ratio (r/t) = 893 under axial compression was conducted to investigate the effects of the radius–thickness ratio (r/t). It is known that the buckling load of cylinders shows large differences and scatter between theory and experiment. The ratio of the experimental buckling load and theoretical buckling load is called the knockdown factor (KDF). Many investigations have been conducted to find the cause of the degradation and scatter in the KDF, but as yet, no cause has been found. In 1968, NASA’s buckling design criterion, NASA SP-8007, gave an empirical KDF curve that decreased with the increasing r/t (up to 2000) for metal cylinders. The same curve has been applied to composite cylinders. Recently, Takano derived a flat lower-bound KDF in terms of A- and B-basis values (99% and 90% probability with a 95% confidence level) through a statistical analysis of experimental buckling loads. The result, however, based on experimental results up to r/t = 500 and, thus, the dependency on a large range of r/t, is not clear. Thus, the authors focused on a larger range of r/t. Cylindrical shells made from carbon fiber-reinforced plastic (CFRP) were tested. The nominal radius, thickness, and length were r = 100.118 mm, t = 0.118 mm, and L = 200 mm and, thus, the r/t = 848 and length-to-radius ratio (L/r) = 2.0. Shape imperfections were also measured by using in-house laser displacement equipment. The buckling load was slightly affected by the r/t, but the reduction in the KDF was insignificant

Semi-HFL: semi-supervised federated learning for heterogeneous devices

Abstract In the vanilla federated learning (FL) framework, the central server distributes a globally unified model to each client and uses labeled samples for training. However, in most cases, clients are equipped with different devices and are exposed to a variety of situations. There are great differences between clients in storage, computing, communication, and other resources, which makes unified deep models used in traditional FL cannot fit clients’ personalized resource conditions. Furthermore, a great deal of labeled data is needed in traditional FL, whereas data labeling requires a great investment of time and resources, which is hard to do for individual clients. As a result, clients only have a vast amount of unlabeled data, which goes against the federated learning needs. To address the aforementioned two issues, we propose Semi-HFL, a semi-supervised federated learning approach for heterogeneous devices, which divides a deep model into a series of small submodels by inserting early exit branches to meet the resource requirements of different devices. Furthermore, considering the availability of labeled data, Semi-HFL introduces semi-supervised techniques for training in the above heterogeneous learning process. Specifically, two training phases are included in the semi-supervised learning process, unsupervised learning on clients and supervised learning on the server, which makes full use of clients’ unlabeled data. Through image classification, text classification, next-word prediction, and multi-task FL experiments based on five kinds of datasets, it is verified that compared with the traditional homogeneous learning method, Semi-HFL not only achieves higher accuracies but also significantly reduces the global resource overhead

Ocean oil pollution mapping with ERS synthetic aperture radar imagery

International Geoscience and Remote Sensing Symposium (IGARSS)1212-214IGRS