Clonal diversity, antimicrobial resistance, and genome features among nonfermenting gram-negative bacteria isolated from patients with cystic fibrosis in Russia.

Nonfermenting gram-negative (NFGN) bacteria were isolated from cystic fibrosis (CF) patients and subjected to susceptibility testing and whole-genome sequencing. Among 170 enrolled CF patients, 112 (65.9%) were colonized with at least 1 key NFGN species. The species-specific infection rate was highest for Pseudomonas aeruginosa (40.6%) followed by Stenotrophomonas maltophilia (14.1%), Achromobacter spp. (9.4%), and Burkholderia cepacia complex (Bcc, 8.2%) demonstrating a significant age-dependent increase for P. aeruginosa and Achromobacter spp., but not for S. maltophilia or Bcc. P. aeruginosa sequence types (STs) related to high-risk epidemic and global CF clones were carried by 12 (7.1%) and 13 (7.6%) patients, respectively. In total, 47% NFGN isolates, predominantly P. aeruginosa, harbored at least 1 plasmid-borne resistance gene; 5 ST235 isolates carried blaVIM2. Pathogenicity island-borne virulence genes were harbored by 9% NFGN isolates. These findings in conjunction with frequent early colonization by Bcc raised serious concerns regarding infection control in Russian CF centers.

A case of localized paranasal sinusitis associated with Burkholderia cenocepacia ST 1880 in a cystic fibrosis patient.

Burkholderia cepacia complex (Bcc) bacteria are considered to be very dangerous players in cystic fibrosis (CF) pathogenesis and are a criterion for negative prognosis in CF cases. In this report, a pediatric case of paranasal sinusitis caused by Burkholderia cenocepacia in a CF patient is described. This is an unusual case, since the paranasal sinuses were the only colonization locus of B. cenocepacia in this patient for 5 years (2015-2020). The lungs remained microbiologically clear with no clinical or radiological signs of pulmonary function decrease during this time period. The paranasal sinuses were sanitized by endoscopic sinus surgery on the left side (2020). Although having no local or systemic antibiotic treatment from the time of surgery to 2022, no B. cenocepacia were detected in the samples. The case shows the possibility of a prolonged remission of Bcc-associated paranasal sinusitis in the absence of systemic antibiotic therapy.

Influence of Bi doping on the electronic structure of (Ga,Mn)As epitaxial layers.

The influence of the addition of Bi to the dilute ferromagnetic semiconductor (Ga,Mn)As on its electronic structure as well as on its magnetic and structural properties has been studied. Epitaxial (Ga,Mn)(Bi,As) layers of high structural perfection have been grown using low-temperature molecular-beam epitaxy. Post-growth annealing of the samples improves their structural and magnetic properties and increases the hole concentration in the layers. Hard X-ray angle-resolved photoemission spectroscopy reveals a strongly dispersing band in the Mn-doped layers, which crosses the Fermi energy and is caused by the high concentration of Mn-induced itinerant holes located in the valence band. An increased density of states near the Fermi level is attributed to additional localized Mn states. In addition to a decrease in the chemical potential with increasing Mn doping, we find significant changes in the valence band caused by the incorporation of a small atomic fraction of Bi atoms. The spin-orbit split-off band is shifted to higher binding energies, which is inconsistent with the impurity band model of the band structure in (Ga,Mn)As. Spectroscopic ellipsometry and modulation photoreflectance spectroscopy results confirm the valence band modifications in the investigated layers.