Mutations in AcrR and RNA Polymerase Confer High-Level Resistance to Psoralen-UVA Irradiation.

DNA interstrand cross-links, such as those formed by psoralen-UVA irradiation, are highly toxic lesions in both humans and bacteria, with a single lesion being lethal in Escherichia coli. Despite the lack of effective repair, human cancers and bacteria can develop resistance to cross-linking treatments, although the mechanisms of resistance remain poorly defined. Here, we subjected E. coli to repeated psoralen-UVA exposure to isolate three independently derived strains that were >10,000-fold more resistant to this treatment than the parental strain. Analysis of these strains identified gain-of-function mutations in the transcriptional regulator AcrR and the alpha subunit of RNA polymerase that together could account for the resistance of these strains. Resistance conferred by the AcrR mutation is mediated at least in part through the regulation of the AcrAB-TolC efflux pump. Resistance via mutations in the alpha subunit of RNA polymerase occurs through a still-uncharacterized mechanism that has an additive effect with mutations in AcrR. Both acrR and rpoA mutations reduced cross-link formation in vivo. We discuss potential mechanisms in relation to the ability to repair and survive interstrand DNA cross-links. IMPORTANCE Psoralen DNA interstrand cross-links are highly toxic lesions with antimicrobial and anticancer properties. Despite the lack of effective mechanisms for repair, cells can become resistant to cross-linking agents through mechanisms that remain poorly defined. We derived resistant mutants and identified that two gain-of-function mutations in AcrR and the alpha subunit of RNA polymerase confer high levels of resistance to E. coli treated with psoralen-UVA. Resistance conferred by AcrR mutations occurs through regulation of the AcrAB-TolC efflux pump, has an additive effect with RNA polymerase mutations, acts by reducing the formation of cross-links in vivo, and reveals a novel mechanism by which these environmentally and clinically important agents are processed by the cell.

Mpox among Public Festival Attendees, Chicago, Illinois, USA, July-August 2022.

We investigated an mpox outbreak after a 2022 LGBTQ event in Chicago, Illinois, USA. Among case-patients, 38% had received 1 dose of mpox vaccine, none 2 doses; most reported sexual activity during the probable exposure period. Among other preventive measures, persons at risk should complete mpox vaccination 14 days before an event.

RecBCD, SbcCD and ExoI process a substrate created by convergent replisomes to complete DNA replication.

The accurate completion of DNA replication on the chromosome requires RecBCD and structure specific SbcCD and ExoI nucleases. However, the substrates and mechanism by which this reaction occurs remains unknown. Here we show that these completion enzymes operate on plasmid substrates containing two replisomes, but are not required for plasmids containing one replisome. Completion on the two-replisome plasmids requires RecBCD, but does not require RecA and no broken intermediates accumulate in its absence, indicating that the completion reaction occurs normally in the absence of any double-strand breaks. Further, similar to the chromosome, we show that when the normal completion reaction is prevented, an aberrant RecA-mediated recombination process leads to amplifications that drive most of the instabilities associated with the two-replisome substrates. The observations imply that the substrate SbcCD, ExoI and RecBCD act upon in vivo is created specifically by two convergent replisomes, and demonstrate that the function of RecBCD in completing replication is independent of double-strand break repair, and likely promotes joining of the strands of the convergent replication forks.

Management of Keratoacanthoma: 157 Tumors Treated With Surgery or Intralesional Methotrexate.

BACKGROUND: Keratoacanthomas (KAs) are common tumors of squamous cell origin that grow rapidly and may regress; however, differentiation from an aggressive squamous cell carcinoma is problematic. OBJECTIVE: To report the authors' experience in managing KA with intralesional methotrexate (MTX) or surgical excision. MATERIALS AND METHODS: The authors collected data on 157 tumors (136 patients) over 6 months from a single institution. RESULTS: There were 73 tumors (54 patients) treated with intralesional MTX. There were 9 tumors that did not resolve with intralesional MTX (88% cure). Nonresolving tumors were excised with no recurrences or complications. In all 9 cases, the nonresolving tumors were of the same size or smaller after MTX. Of the 73 tumors treated with MTX, 29 tumors (11 patients) were multiple KAs. All 29 tumors resolved (100% tumor clearance). There were no complications in any of the MTX-treated patients. Tumor clearance was defined by clinical resolution for a minimum of 6 weeks without a recurrence. There were 84 tumors (83 patients) treated with surgical excision. There were no complications and no recurrences (100% cure) with surgery. CONCLUSION: Intralesional MTX may be considered as the initial treatment for solitary KA, multiple KA, or in poor surgical candidates.

Superluminous supernovae at redshifts of 2.05 and 3.90.

A rare class of 'superluminous' supernovae that are about ten or more times more luminous at their peaks than other types of luminous supernova has recently been found at low to intermediate redshifts. A small subset of these events have luminosities that evolve slowly and result in radiated energies of up to about 10(51) ergs. Therefore, they are probably examples of 'pair-instability' or 'pulsational pair-instability' supernovae with estimated progenitor masses of 100 to 250 times that of the Sun. These events are exceedingly rare at low redshift, but are expected to be more common at high redshift because the mass distribution of the earliest stars was probably skewed to high values. Here we report the detection of two superluminous supernovae, at redshifts of 2.05 and 3.90, that have slowly evolving light curves. We estimate the rate of events at redshifts of 2 and 4 to be approximately ten times higher than the rate at low redshift. The extreme luminosities of superluminous supernovae extend the redshift limit for supernova detection using present technology, previously 2.36 (ref. 8), and provide a way of investigating the deaths of the first generation of stars to form after the Big Bang.

COVID-19 Clusters and Outbreaks Among Non-Health Care, Noncongregate Workers in Chicago, Illinois: Surveillance Through the First Omicron Wave.

OBJECTIVE: To describe COVID-19 investigations by a large urban health department among non-health care, noncongregate workplaces and the utility of surveillance methods over time. METHODS: Frequencies of workplace-associated clusters and outbreaks are described by workplace type, workforce size, and method of identification over time. RESULTS: From April 2020 through January 2022, 496 COVID-19 investigations identified 442 clusters (89%) and 54 outbreaks (11%). Frontline essential workplaces comprised 36% of investigations before versus 15% after vaccine eligibility. Pre-Omicron, most investigations (84%) were identified through case interviews. During Omicron predominance, case interviews decreased dramatically and identified 10% of investigations. Offices (41%) and bars and restaurants (36%) were overrepresented, and only one outbreak was identified, given decreases in confirmatory testing. CONCLUSIONS: Findings suggest that vaccine prioritization reduced COVID-19 burden among highest-risk workplaces, but surveillance methods likely became less representative over time.

Probiotics for the Management of Infantile Colic: A Systematic Review.

BACKGROUND: Colic is defined as periods of inconsolable crying, fussing, or irritability that have no apparent cause and present in healthy infants under 5 months of age. Although colic is a benign and self-limiting condition, it can be distressing to parents and there are few robust treatment interventions. This systematic review explored the evidence for administration of probiotics to prevent or decrease symptoms of colic. METHODS: Literature searches were conducted in PubMed, CINAHL (Cumulative Index to Nursing and Allied Health Literature), Cochrane Library, and Web of Science. SAMPLE: Twenty articles were included: 15 randomized controlled trials and 5 meta-analyses. RESULTS: Based on the evidence in this systematic review, the oral administration of probiotics to breastfed infants with colic resulted in at least a 50% reduction in crying time compared with placebo. Efficacy of probiotics to reduce colic symptoms in formula-fed infants needs further study. In this review, we did not find evidence to support or refute efficacy of probiotics to prevent infantile colic. Clinical Implication: Probiotics (especially the strain Lactobacillus reuteri DSM 17938) can safely be recommended if parents desire a treatment option for their infants with colic.