Identification of Determinants that Allow Maintenance of High-Level Fluoroquinolone Resistance in Acinetobacter baumannii

Acinetobacter baumannii is associated with multidrug resistant (MDR) infections in healthcare settings, with fluoroquinolones such as ciprofloxacin being currently ineffective. Clinical isolates largely harbor mutations in the GyrA and TopoIV fluoroquinolone targets, as well as mutations that increase expression of drug resistance-nodulation-division (RND) efflux pumps. Factors critical for maintaining fitness levels of pump overproducers are uncharacterized despite their prevalence in clinical isolates. We here identify proteins that contribute to the fitness of FQR strains overexpressing three known RND systems using high-density insertion mutagenesis. Overproduction of the AdeFGH efflux pump caused hypersensitization to defects in outer membrane homeostatic regulation, including lesions that reduced LOS biosynthesis and blocked production of the major A. baumannii porin. In contrast, AdeAB pump overproduction, which does not affect the outer membrane pump component, was relatively tolerant to loss of these functions, consistent with outer membrane protein overproduction being the primary disruptive component. Surprisingly, overproduction of proton-transporting efflux pumps had little impact on cytosolic pH, consistent with a compensatory response to pump activity. The most striking transcriptional changes were associated with AdeFGH pump overproduction, resulting in activation of the phenylacetate (PAA) degradation regulon. Disruption of the PAA pathway resulted in cytosolic acidification and defective expression of genes involved in protection from peroxide stress. These results indicate that the RND outer membrane protein overproduction is compensated by cytoplasmic buffering and maintenance of outer membrane integrity in A. baumannii to facilitate fitness of FQR isolates.

Gender Disparities Among Academic Vitreoretinal Specialists in the United States With Regard to Scholarly Impact and Academic Rank

Background and objective While men outnumber women in the specialty of ophthalmology in general, the subspecialty of vitreoretinal surgery in particular has the highest percentage of men across all ophthalmic subspecialties. This study aimed to analyze the gender disparities regarding the publication productivity and academic rank of academic vitreoretinal specialists in the United States (US). Methods This cross-sectional study evaluated 116 ophthalmology residency programs in the US participating in the 2022 San Francisco Match. The academic vitreoretinal faculty from each ophthalmology residency program was included. The information on gender, academic rank, and publication activity in terms of the h-index were collected from institutional websites, the Scopus database, and the National Library of Medicine PubMed website. Results A total of 467 academic vitreoretinal specialists were identified. Among them, 345 (73.9%) were men, and 122 (26.1%) were women (p<0.001). When the academic ranks were analyzed, a higher number of men (43.8%) were found to hold the rank of full professor as compared to women. Furthermore, a higher number of women (47.5%) were found to hold the rank of assistant professor as compared to their male colleagues. Regarding the number of publications, in all academic rank categories, women had a significantly lower number of publications compared to men (p<0.001). Men also had a higher publication productivity or scholarly impact [h-index=15.2 ± 0.82 standard error of the mean (SEM)] compared to women (h-index=12.8 ± 0.99 SEM) (p=0.0004). Higher h-index correlated with higher academic rank, from assistant professor through full professor (p<0.001). Conclusion The field of vitreoretinal surgery has significantly fewer women compared to men, with women producing fewer publications and having less scholarly impact. H-index and total number of publications are also associated with a higher academic rank. Furthermore, full professors are more likely to be men, while assistant professors are more likely to be women. Future efforts should be aimed at reducing the gender disparity in vitreoretinal surgery.

The impact of primary repair timing on longitudinal visual outcomes after open globe injury

BACKGROUND

The urgency with which to repair open globe injuries is a debated topic that lacks grounding in longitudinal visual outcomes data. We aim to test the association between primary repair timing and visual recovery potential following OGI.

SUBJECTS/METHODS

We performed a retrospective cohort study of medical records from a US academic medical center (7/2017 to 11/2021). We included all patients with a principal diagnosis of OGI, a documented date and time of injury, presentation, repair, and ≥ 3 months of complete follow-up data on visual outcomes. We excluded those with prior OGI in the same eye. We also tested the correlation of injury to repair time (ITR) in hours with best corrected visual acuity (BCVA, in logMAR units) at last follow-up in the general cohort and select subpopulations and the impact of repair delay on visual improvement over the follow-up period.

RESULTS

One hundred twenty-nine patients with OGI were analyzed (91 patients with ≥ 3 months of follow-up). The majority were male (105/129, 81%) with a median age of 45 years. Most OGI involved zone 1 (57%), followed by zone 3 (24%), and zone 2 injuries (19%). Median ocular trauma score (OTS) was 60 (IQR 37-70); mean presenting BCVA was logMAR 1.9 (median 2.3, IQR 1.0-2.7). Median ITR was 22 h (IQR 15-30 h, range 5-199 h). ITR time did not significantly correlate with final BCVA (n = 91, β = - 0.003, 95% CI - 0.009-0.002, P = 0.233), nor did it significantly increase the odds of developing ocular complications or requiring secondary ocular surgeries (OR 0.985, 95% CI 0.967-1.002, P = 0.085). Additionally, the rate of BCVA improvement over subsequent months of follow-up did not significantly differ based on ITR time. Presenting BCVA (R² = 0.701, P < 0.001) and OTS (R² = 0.477, P < 0.001) significantly correlated with final BCVA, independent of repair delays.

CONCLUSIONS

In this cohort of OGI patients, repair timing does not significantly correlate with final BCVA, and delays beyond 24 h do not significantly correlate with worse visual recovery potential. Repair time alone should be emphasized to a lesser extent as a prognosticator of visual potential, in favor of significant predictors such as the ocular trauma score and presenting visual acuity.

Preformation and epigenesis converge to specify primordial germ cell fate in the early Drosophila embryo

A critical step in animal development is the specification of primordial germ cells (PGCs), the precursors of the germline. Two seemingly mutually exclusive mechanisms are implemented across the animal kingdom: epigenesis and preformation. In epigenesis, PGC specification is non-autonomous and depends on extrinsic signaling pathways. The BMP pathway provides the key PGC specification signals in mammals. Preformation is autonomous and mediated by determinants localized within PGCs. In Drosophila, a classic example of preformation, constituents of the germ plasm localized at the embryonic posterior are thought to be both necessary and sufficient for proper determination of PGCs. Contrary to this longstanding model, here we show that these localized determinants are insufficient by themselves to direct PGC specification in blastoderm stage embryos. Instead, we find that the BMP signaling pathway is required at multiple steps during the specification process and functions in conjunction with components of the germ plasm to orchestrate PGC fate.

Proper specification of primordial germ cells (PGCs) is crucial as PGCs serve as the precursors of germline stem cells. To specify PGC fate, invertebrates rely upon cell autonomous preformation involving maternally deposited germ plasm. In Drosophila melanogaster, to insulate newly formed PGCs from the adverse effects of the cell-cell signaling pathways, germ plasm determinants silence transcription and attenuate the cell cycle. However, our data on the BMP signaling pathway challenge this long-held view of PGC specification and suggest that appropriate specification of embryonic PGCs is sensitive to the BMP ligand, decapentaplegic (dpp), and its cognate receptor, thickveins. We find that PGCs are not only capable of responding to BMP signals from the soma, but also that these signals impact the proper determination of the germ cells. Based on these unanticipated similarities between mammals and flies, we propose a model integrating contribution of both the cell-autonomous (preformation) and non-autonomous (epigenesis) pathways during PGC determination. Consistent with the model, we have observed dominant genetic interactions between, oskar, the maternal determinant of PGC fate, and the BMP pathway ligand dpp.

Initial Post-Operative Visit Absenteeism is Associated with Worse Amputation-Free Survival after Tibial Angioplasty

OBJECTIVES

Tibial revascularization is often performed in the setting of critical limb ischemia and tissue loss requiring close patient monitoring in the early post-operative period for worsening gangrene and/or ischemia. Multiple studies have shown loss to follow-up (LTF) is an independent risk factor for poor outcomes in several vascular procedures. Therefore, we evaluated the risk factors relating to LTF against outcomes in patients undergoing tibial endovascular procedures with the hypothesis that poor post-operative visit compliance is associated with decreased amputation-free survival rates.

METHODS

We performed a single-institution retrospective chart review of patients who underwent therapeutic endovascular tibial revascularization between 2014-2018. Patient follow-up and outcomes of death or major amputation (trans-tibial/trans-femoral) were followed up to 36-months post-operatively. Patients who had undergone previous infra-geniculate interventions or reached mortality/major amputation within 30-days post-operatively were excluded from analysis.

RESULTS

We identified 89 patients who met inclusion criteria. The overall rate of attendance at less than <1 month, 1-6 months, 6-15 months and 15-36 months post-operatively were 60%, 64%, 60 and 40% respectively. 16% of patients had complete loss to follow-up. Patients without tissue loss (≤ Rutherford 4) were less likely to attend early <1 month and 1-6 month follow-up intervals. Notably, absenteeism from the first immediate post-operative visit was a significant risk factor for further absenteeism at 1-6 months (51% vs 26%; p=.01) and at greater than 6 month follow-up (48% vs 31%; p=.05). Compared to the cohort of all patients, failure to follow-up within 1 month was associated with a decrease in attendance from 64% to 26% at 1-6 months and 63% to 31% at more than 6 months. Missing the first post-operative visit was also associated with decreased amputation-free survival (p=.04).

CONCLUSIONS

Absenteeism from the first post-operative visit is associated with worse amputation-free survival and a significant risk factor for further absenteeism from post-operative care. Given these results, ensuring close immediate post-operative follow up is essential to improving outcomes in patients undergoing tibial revascularization.

Antibiotic susceptibility signatures identify potential antimicrobial targets in the Acinetobacter baumannii cell envelope

A unique, protective cell envelope contributes to the broad drug resistance of the nosocomial pathogen Acinetobacter baumannii. Here we use transposon insertion sequencing to identify A. baumannii mutants displaying altered susceptibility to a panel of diverse antibiotics. By examining mutants with antibiotic susceptibility profiles that parallel mutations in characterized genes, we infer the function of multiple uncharacterized envelope proteins, some of which have roles in cell division or cell elongation. Remarkably, mutations affecting a predicted cell wall hydrolase lead to alterations in lipooligosaccharide synthesis. In addition, the analysis of altered susceptibility signatures and antibiotic-induced morphology patterns allows us to predict drug synergies; for example, certain beta-lactams appear to work cooperatively due to their preferential targeting of specific cell wall assembly machineries. Our results indicate that the pathogen may be effectively inhibited by the combined targeting of multiple pathways critical for envelope growth.

Reactive oxygen species signaling in primordial germ cell development in Drosophila embryos

REDOX mechanisms that induce biosynthesis of the reactive oxygen species (ROS) have attracted considerable attention due to both the deleterious and beneficial responses elicited by the reactive radical. In several organisms including Drosophila melanogaster, modulation of ROS activity is thought to be crucial for the maintenance of cell fates in developmental contexts. Interestingly, REDOX mechanisms have been shown to be involved in maintaining progenitor fate of stem cells as well as their proliferation and differentiation. Here, we have explored the possible functions of ROS during proper specification and developmental progression of embryonic primordial germ cells (PGCs). Indicating its potential involvement in these processes, ROS can be detected in the embryonic PGCs and the surrounding somatic cells from very early stages of embryogenesis. Using both "loss" and "gain" of function mutations in two different components of the REDOX pathway, we show that ROS levels are likely to be critical in maintaining germ cell behavior, including their directed migration. Altering the activity of a putative regulator of ROS also adversely influences the ability of PGCs to adhere to one another in cellular blastoderm embryos, suggesting potential involvement of this pathway in orchestrating different phases of germ cell migration.

Functional magnetic resonance imaging during emotion recognition in social anxiety disorder: an activation likelihood meta-analysis

Background: Social anxiety disorder (SAD) is characterized by abnormal fear and anxiety in social situations. Functional magnetic resonance imaging (fMRI) is a brain imaging technique that can be used to demonstrate neural activation to emotionally salient stimuli. However, no attempt has yet been made to statistically collate fMRI studies of brain activation, using the activation likelihood-estimate (ALE) technique, in response to emotion recognition tasks in individuals with SAD. Methods: A systematic search of fMRI studies of neural responses to socially emotive cues in SAD was undertaken. ALE meta-analysis, a voxel-based meta-analytic technique, was used to estimate the most significant activations during emotional recognition. Results: Seven studies were eligible for inclusion in the meta-analysis, constituting a total of 91 subjects with SAD, and 93 healthy controls. The most significant areas of activation during emotional vs. neutral stimuli in individuals with SAD compared to controls were: bilateral amygdala, left medial temporal lobe encompassing the entorhinal cortex, left medial aspect of the inferior temporal lobe encompassing perirhinal cortex and parahippocampus, right anterior cingulate, right globus pallidus, and distal tip of right postcentral gyrus. Conclusion: The results are consistent with neuroanatomic models of the role of the amygdala in fear conditioning, and the importance of the limbic circuitry in mediating anxiety symptoms.