RESUMEN
It has been long appreciated that expression of the Yersinia type-III secretion system (T3SS) in culture is associated with growth arrest. Here we sought to understand whether this impacts expression of ribosomal protein genes, which were among the most highly abundant transcripts in exponential phase Yersinia pseudotuberculosis based on RNA-seq analysis. To visualize changes in ribosomal protein expression, we generated a fluorescent transcriptional reporter with the promoter upstream of rpsJ /S10 fused to a destabilized gfp variant. We confirmed reporter expression significantly increases in exponential phase and decreases as cells transition to stationary phase. We then utilized a mouse model of systemic Y. pseudotuberculosis infection to compare T3SS and S10 reporter expression during clustered bacterial growth in the spleen, and found that cells expressing high levels of the T3SS had decreased S10 levels, while cells with lower T3SS expression retained higher S10 expression. In bacteriological media, growth inhibition with T3SS induction and a reduction in S10 expression were observed in subsets of cells, while cells with high expression of both T3SS and S10 were also observed. Loss of T3SS genes resulted in rescued growth and heightened S10 expression. To understand if clustered growth impacted bacterial gene expression, we utilized droplet-based microfluidics to encapsulate bacteria in spherical agarose droplets, and also observed growth inhibition with high expression of T3SS and reduced S10 levels that better mirrored phenotypes observed in the mouse spleen. Finally, we show that T3SS expression is sufficient to promote tolerance to the ribosome-targeting antibiotic, gentamicin. Collectively, these data indicate that the growth arrest associated with T3SS induction leads to decreased expression of ribosomal protein genes, and this results in reduced antibiotic susceptibility. Author Summary: Slow-growing bacterial cells have reduced antibiotic susceptibility, rendering them very difficult to eliminate during antibiotic treatment. However, for many key virulence factors (bacterial factors required to promote infection), it remains unclear whether expression is sufficient to slow bacterial growth and impact antibiotic susceptibility. Using Yersinia pseudotuberculosis , we found ribosomal protein expression fluctuated based on growth rate, and we generated a fluorescent reporter construct to detect altered ribosomal protein expression within individual bacterial cells. We then asked if expression of a key virulence factor in Yersinia , the type-III secretion system (T3SS), is sufficient to lower ribosomal protein expression, since it has been well established that T3SS induction results in growth arrest. We found high levels of T3SS expression promotes slowed growth and antibiotic tolerance, and bacterial cells that survive treatment with a ribosome-targeting antibiotic, gentamicin, have heightened levels of T3SS and lower levels of S10 expression.
RESUMEN
OBJECTIVE: Managing hospitalized patients on ambulatory U-500 insulin is challenging because of limited guidance on how to safely adjust insulin doses during admission. We sought to evaluate glycemic outcomes in relation to inpatient insulin doses in patients receiving U-500 prior to hospitalization. METHODS: Retrospective study of hospitalized patients on ambulatory U-500 seen consecutively from January 2015 to December 2019. Primary outcomes were inpatient hypoglycemia, hyperglycemia, and normoglycemia at different insulin dosages expressed as weight-based (unit/kg/d) inpatient total daily dose (TDD) and ratio of inpatient to outpatient TDD. RESULTS: We identified 66 admissions of 46 unique patients. The median (interquartile range) body mass index was 41.0 kg/m2 (35.1, 46.8), home TDD 212 units (120, 300), and home insulin dose 1.6 units/kg/d (1.1, 2.2). The median (interquartile range) inpatient insulin dose was 0.7 unit/kg/d (0.3, 1.0) and the ratio of inpatient to outpatient TDD was 0.4 (0.2, 0.8). Hyperglycemia persisted throughout the hospitalization. For the outcomes of hyperglycemia and normoglycemia, we found no association between increased levels of insulin dosages. For the outcome of hypoglycemia, significantly higher odds were observed when non-fasting patients received an inpatient TDD that was either > 40% of their home TDD or > 0.6 unit/kg/d of insulin. CONCLUSION: Patients on ambulatory U-500 have significant hyperglycemia during admission. Inpatient insulin doses of 40% of home TDD or ≤ 0.6 unit/kg were not associated with increased hypoglycemia risk. Further prospective studies are needed to determine effective doses in these high-risk patients.
Asunto(s)
Insulina , Humanos , Estudios Retrospectivos , Insulina/uso terapéuticoRESUMEN
Cellular differentiation is a fundamental strategy used by cells to generate specialized functions at specific stages of development. The bacterium Caulobacter crescentus employs a specialized dimorphic life cycle consisting of two differentiated cell types. How environmental cues, including mechanical inputs such as contact with a surface, regulate this cell cycle remain unclear. Here, we find that surface sensing by the physical perturbation of retracting extracellular pilus filaments accelerates cell-cycle progression and cellular differentiation. We show that physical obstruction of dynamic pilus activity by chemical perturbation or by a mutation in the outer-membrane pilus secretin CpaC stimulates early initiation of chromosome replication. In addition, we find that surface contact stimulates cell-cycle progression by demonstrating that surface-stimulated cells initiate early chromosome replication to the same extent as planktonic cells with obstructed pilus activity. Finally, we show that obstruction of pilus retraction stimulates the synthesis of the cell-cycle regulator cyclic diguanylate monophosphate (c-di-GMP) through changes in the activity and localization of two key regulatory histidine kinases that control cell fate and differentiation. Together, these results demonstrate that surface contact and sensing by alterations in pilus activity stimulate C. crescentus to bypass its developmentally programmed temporal delay in cell differentiation to more quickly adapt to a surface-associated lifestyle.