[Molecular epidemiology and antibiotic resistance of Pseudomonas aeruginosa isolated from blood in a hospital in Shandong Province from 2014 to 2021]

Objective: To identify the antibiotic resistance, virulence genes, and sequence types of Pseudomonas aeruginosa (P. aeruginosa) strains isolated from blood. Methods: From November 2014 to December 2021, a total of 94 nonrepetitive P. aeruginosa isolates were obtained from blood samples of patients at the First Affiliated Hospital of Shandong First Medical University in Shandong Province, China. The bacteria were identified using matrix-assisted laser desorption ionization time of flight mass spectrometry. Antibiotic resistance of the P. aeruginosa isolates was detected using Vitek 2 Compact system. Polymerase chain reaction (PCR) was conducted for the 18 virulence genes, and multi locus sequence typing (MLST) was performed to identify the sequence types of the P. aeruginosa strains. The resistance rates and distributions of virulence genes between carbapenem resistant pseudomonas aeruginosa (CRPA) and carbapenem susceptible pseudomonas aeruginosa (CSPA) isolates were compared using the Chi-square test. Results: Among 94 P. aeruginosa isolates, 19 (20.2%) isolates were found to be multidrug resistant (MDR) bacteria, of which 17 were CRPA isolates and 2 were CSPA isolates. All strains contained more than 10 virulence genes. Except for exoU gene, the detection rate of other genes was above 83%. MLST analysis revealed a total of 66 different STs, including 59 existing STs and 7 novel STs. Among them, ST244 (n=11, 11.7%) and ST270 (n=7, 7.4%) were the dominant STs. Although these two types of isolates harbored the same virulence genes, the resistance rates to carbapenem were different. 54.5% (6/11) ST244 isolates were CRPA but all 7 ST270 isolates were CSPA. Conclusion: Although the resistance rates of P. aeruginosa strains isolated from blood were at a low level, some MDR and CRPA isolates were detected. As the high virulence gene detection rates and genetic diversity were found for P. aeruginosa strains isolated from blood, close attention should be paid to avoid transmission and outbreaks.

[Preliminary study on the etiological characteristics and clinical treatment of medication-related osteonecrosis of the jaws]

Objective: To summarize the etiological characteristics and clinical treatment effects of 17 patients with medication-related osteonecrosis of the jaw (MRONJ). Methods: The clinical data of 17 patients with MRONJ admitted to the Department of Oral and Maxillofacial Surgery, the First People's Hospital of Jinzhong, Shanxi Province, from July 2016 to December 2019 were retrospectively analyzed, including 9 males and 8 females, aged (63.6±9.6) years old (43-82 years old). Descriptive analysis of the primary disease, onset factors, site of disease, clinical manifestations, treatment methods, and treatment effects was conducted through follow-up for at least 1 year. Results: Among the primary diseases of the 17 cases, 12 were malignant tumors, and 5 were osteoporosis. There were 13 cases with a history of a trigger event (tooth extraction or unsuited removable denture). Six cases occurred in the maxilla, 10 cases occurred in the mandible, and 1 case involved both the upper and lower jaws. For the most common medication used, bisphosphonate was used in 16 cases including 5 cases with concomitant use of angiogenesis-inhibiting drugs. There was 1 case resulted from receptor activator of NF-κB ligand (RANKL) monoclonal antibody application. The duration of medication application was (10.1±3.9) months (3-18 months). All 17 cases were treated surgically. Totally 15 patients healed well after surgical treatment and the other 2 patients, who had poor soft tissue healing after surgery, healed well after a second operation. Conclusions: Tooth extraction might be a major trigger factor for the onset of MRONJ in the mandible. The disease was more possibly occured in the mandible than in the maxilla. Appropriate surgical treatment could achieve a good clinical outcome.

[Antibiotic analysis and whole genome sequencing of two nocardia farcinica strains causing joint infection]

Objective: To analyze the molecular characteristics and antibiotic susceptibility of two strains of Nocardia farcinica isolated from patients with joint infection using whole genome sequencing. Methods: Two strains of Nocardia farcinica causing knee-joint infections in two elderly patients were collected in January 2020. Whole genome sequencing was used to determine the nocardia species. Drug sensitivity test was performed using the micro-broth dilution and E-test method according to CLSI M24 guideline. ABRicate was used to analyze drug resistance and virulence genes. Snippy and other bioinformatic tools were used for genomic comparison, and to construct SNP homologous tree. Results: The clinical isolates in this study were both Nocardia farcinica. Antimicrobial susceptibility test showed the isolates were resistant to ceftriaxone, cefepime, cefotaxime and trimethoprim/sulfamethoxazole (TMP/SMX). Imipenem, linezolid and amoxicillin-clavulanic acid showed good activity. Four antibiotic resistance genes including class A β-lactamase gene far-1, RNA polymerase binding protein gene RbpA, multi-drug resistance efflux pump transcription activator gene MtrA and regulatory transcription factor gene vanR-O were identified in the Nocardia farcinica genomes, which conferred resistance to beta-lactams, rifampicin, macrolides and vancomycin respectively. No acquired TMP/SMX resistance genes were identified. There are multiple missense mutations in the dihydrofolate reductase family genes. Four virulence genes of icl, mbtH, phoP, and relA that are homologous to Mycobacterium tuberculosis were found. SNP homologous tree analysis showed the two Nocardia strains were closely related, and there were only ten SNP sites, six compound substitutions and one deletion mutation between them. Conclusions: Whole genome sequencing technology is helpful to explore the molecular characteristics and resistance mechanisms of Nocardia species. Nocardia farcinica has a trend of spreading in China. Resistance to TMP/SMX is worthy of attention. The mutation of genes involved in the metabolic pathway of dihydrofolate might be one of multiple TMP/SMX resistance mechanisms.

Refocusing of backscattered microwaves in target detection by using LHM flat lens

When microwave emitted from a point source is focused on a target by using a left-handed metamaterial (LHM) flat lens, microwave backscattered from the target will be refocused by the LHM lens in the vicinity of the point source. Numerical simulations with two-dimensional (2D) finite-difference time-domain (FDTD) method demonstrate that, even for flat LHM lens of material losses to the order as that reported in some LHM microwave experiments and simulations, the refocusing of backscattered microwave will yield a sub-wavelength lateral resolution and remarkable enhancement of the backscattered microwave, which will benefit the detection and imaging of small target.

Relation between the therapeutic effect of moxibustion in treating arthralgia and SP and enkephalin in nervous tissues

Moxibustion can accelerate the relief of arthralgia of rats suffering from adjuvant arthritis. At the same time, it promotes the recovery of SP in the sciatic nerve, and maintains SP and leu-enkephalin at a higher level in the lumbar spinal cord. The results show that the therapeutic effect of moxibustion in treating arthralgia bears some relation to activating the spinal enkephalin system and modulating the function of primary afferent neurons.