Fluorogenic Probes of the Mycobacterial Membrane as Reporters of Antibiotic Action.

The genus Mycobacterium includes species such as Mycobacterium tuberculosis, which can cause deadly human diseases. These bacteria have a protective cell envelope that can be remodeled to facilitate their survival in challenging conditions. Understanding how such conditions affect membrane remodeling can facilitate antibiotic discovery and treatment. To this end, we describe an optimized fluorogenic probe, N-QTF, that reports on mycolyltransferase activity, which is vital for cell division and remodeling. N-QTF is a glycolipid probe that can reveal dynamic changes in the mycobacterial cell envelope in both fast- and slow-growing mycobacterial species. Using this probe to monitor the consequences of antibiotic treatment uncovered distinct cellular phenotypes. Even antibiotics that do not directly inhibit cell envelope biosynthesis cause conspicuous phenotypes. For instance, mycobacteria exposed to the RNA polymerase inhibitor rifampicin release fluorescent extracellular vesicles (EVs). While all mycobacteria release EVs, fluorescent EVs were detected only in the presence of RIF, indicating that exposure to the drug alters EV content. Macrophages exposed to the EVs derived from RIF-treated cells released lower levels of cytokines, suggesting the EVs moderate immune responses. These data suggest that antibiotics can alter EV content to impact immunity. Our ability to see such changes in EV constituents directly results from exploiting these chemical probes.

Targeted protein degradation in mycobacteria uncovers antibacterial effects and potentiates antibiotic efficacy.

Proteolysis-targeting chimeras (PROTACs) represent a new therapeutic modality involving selectively directing disease-causing proteins for degradation through proteolytic systems. Our ability to exploit targeted protein degradation (TPD) for antibiotic development remains nascent due to our limited understanding of which bacterial proteins are amenable to a TPD strategy. Here, we use a genetic system to model chemically-induced proximity and degradation to screen essential proteins in Mycobacterium smegmatis (Msm), a model for the human pathogen M. tuberculosis (Mtb). By integrating experimental screening of 72 protein candidates and machine learning, we find that drug-induced proximity to the bacterial ClpC1P1P2 proteolytic complex leads to the degradation of many endogenous proteins, especially those with disordered termini. Additionally, TPD of essential Msm proteins inhibits bacterial growth and potentiates the effects of existing antimicrobial compounds. Together, our results provide biological principles to select and evaluate attractive targets for future Mtb PROTAC development, as both standalone antibiotics and potentiators of existing antibiotic efficacy.

Short-Term Strategies for Augmenting the National Radiologist Workforce.

The current radiology landscape has an imbalance between the rising demand for radiology services and the national radiologist workforce available. More vacant radiology positions exist than graduating radiology trainees. The origins of this problem are complex and require long-term solutions. Rather than working longer and/or faster, radiologists can work smarter. In this article, we present multiple short-term strategies to increase the effective radiologist workforce and/or increase workforce efficiency, to alleviate the current workload challenges. These strategies are derived from an analysis of possible practice-level changes in personnel, process, and physical plant. The impacts of the potential changes are estimated. No single change addresses the mismatch between supply and demand for radiology services. By creating an inventory of potential solutions, practices can choose the potential mechanism(s) to address the workforce shortage that best fit their needs and local environment.

Genetically encoded transcriptional plasticity underlies stress adaptation in Mycobacterium tuberculosis.

Transcriptional regulation is a critical adaptive mechanism that allows bacteria to respond to changing environments, yet the concept of transcriptional plasticity (TP) - the variability of gene expression in response to environmental changes - remains largely unexplored. In this study, we investigate the genome-wide TP profiles of Mycobacterium tuberculosis (Mtb) genes by analyzing 894 RNA sequencing samples derived from 73 different environmental conditions. Our data reveal that Mtb genes exhibit significant TP variation that correlates with gene function and gene essentiality. We also find that critical genetic features, such as gene length, GC content, and operon size independently impose constraints on TP, beyond trans-regulation. By extending our analysis to include two other Mycobacterium species -- M. smegmatis and M. abscessus -- we demonstrate a striking conservation of the TP landscape. This study provides a comprehensive understanding of the TP exhibited by mycobacteria genes, shedding light on this significant, yet understudied, genetic feature encoded in bacterial genomes.

The 2021 ACR/RBMA Workforce Survey: Practice Types, Employment Trends, and Hiring Needs.

PURPOSE: The aim of this study was to analyze current radiology practice types, specific subspecialty needs, employment trends, and retirement trends. METHODS: ACR members, nonmembers, and Radiology Business Management Association members were surveyed using predominantly structured closed-ended questions about a variety of current and recent radiology practice characteristics. Responses were group practice deduplicated and weighted. RESULTS: Of 1,702 survey respondents, 64% were men, with a median age of 51 years. In 2021, 62% of responding practices hired radiologists, with the average practice hiring 2 radiologists and academic practices on average hiring the most (3.5). Most radiologists (87%) were hired for full-time positions, with independent practices hiring the largest proportion of part-time positions. Body and breast imagers represented the largest numbers of hired radiologists (17% each). Practices anticipated similar hiring patterns in 2022, prioritizing breast (37%) and body (35%) imaging. Of all practice types, academic groups were least likely to prioritize general radiologist hiring. A large majority (82%) of radiology practices permit remote work (teleradiology), more common at academic than other practices. Of currently employed radiologists, 16% plan to seek new employment in the next year; early-career radiologists indicated the highest likelihood (92%) and academic radiologists the lowest (66%) of remaining in the same practice for at least 5 years. A large majority of practices (80%) reported no radiologist retirements in 2021. Of those retiring, the average age was 75 years, and 66% worked full-time until retirement. CONCLUSIONS: Radiologist recruiting remains robust. Current information on practice characteristics may help inform radiology practice leaders seeking to right-size their groups.

Reducing the risks of nuclear war - The role of health professionals.

No abstract available.

Development of an Engineered Mycobacterium tuberculosis Strain for a Safe and Effective Tuberculosis Human Challenge Model.

Human challenge experiments could greatly accelerate the development of a tuberculosis (TB) vaccine. Human challenge for tuberculosis requires a strain that can both replicate in the host and be reliably cleared. To accomplish this, we designed Mycobacterium tuberculosis (Mtb) strains featuring up to three orthogonal kill switches, tightly regulated by exogenous tetracyclines and trimethoprim. The resultant strains displayed immunogenicity and antibiotic susceptibility similar to wild-type Mtb under permissive conditions. In the absence of supplementary exogenous compounds, the strains were rapidly killed in axenic culture, mice and nonhuman primates. Notably, the strain that contained three kill switches had an escape rate of less than 10 -10 per genome per generation and displayed no relapse in a SCID mouse model. Collectively, these findings suggest that this engineered Mtb strain could be a safe and effective candidate for a human challenge model.