Real-time detection of response regulator phosphorylation dynamics in live bacteria.

Bacteria utilize two-component system (TCS) signal transduction pathways to sense and adapt to changing environments. In a typical TCS, a stimulus induces a sensor histidine kinase (SHK) to phosphorylate a response regulator (RR), which then dimerizes and activates a transcriptional response. Here, we demonstrate that oligomerization-dependent depolarization of excitation light by fused mNeonGreen fluorescent protein probes enables real-time monitoring of RR dimerization dynamics in live bacteria. Using inducible promoters to independently express SHKs and RRs, we detect RR dimerization within seconds of stimulus addition in several model pathways. We go on to combine experiments with mathematical modeling to reveal that TCS phosphosignaling accelerates with SHK expression but decelerates with RR expression and SHK phosphatase activity. We further observe pulsatile activation of the SHK NarX in response to addition and depletion of the extracellular electron acceptor nitrate when the corresponding TCS is expressed from both inducible systems and the native chromosomal operon. Finally, we combine our method with polarized light microscopy to enable single-cell measurements of RR dimerization under changing stimulus conditions. Direct in vivo characterization of RR oligomerization dynamics should enable insights into the regulation of bacterial physiology.

Increased Incidence of Pseudotumor Cerebri Syndrome Among Users of Tetracycline Antibiotics.

BACKGROUND: To determine whether the use of a tetracycline-class antibiotic is associated with an increased risk of developing pseudotumor cerebri syndrome (PTCS). METHODS: We identified patients in the University of Utah Health system who were prescribed a tetracycline-class antibiotic and determined what percentage of those individuals were subsequently diagnosed with PTCS secondary to tetracycline use. We compared this calculation to the number of patients with PTCS unrelated to tetracycline use. RESULTS: Between 2007 and 2014, a total of 960 patients in the University system between the ages of 12 and 50 were prescribed a tetracycline antibiotic. Among those, 45 were diagnosed with tetracycline-induced PTCS. We estimate the incidence of tetracycline-induced PTCS to be 63.9 per 100,000 person-years. By comparison, the incidence of idiopathic intracranial hypertension (IIH) is estimated to be less than one per 100,000 person-years (Calculated Risk Ratio = 178). CONCLUSIONS: Although a causative link between tetracycline use and pseudotumor cerebri has yet to be firmly established, our study suggests that the incidence of pseudotumor cerebri among tetracycline users is significantly higher than the incidence of IIH in the general population.

Evaluation of a D-Dimer Protocol for Detection of Venous Thromboembolism.

BACKGROUND: The use of venous duplex ultrasonography (VDU) for confirmation of deep venous thrombosis in neurosurgical patients is costly and requires experienced personnel. We evaluated a protocol using D-dimer levels to screen for venous thromboembolism (VTE), defined as deep venous thrombosis and asymptomatic pulmonary embolism. METHODS: We used a retrospective bioinformatics analysis to identify neurosurgical inpatients who had undergone a protocol assessing the serum D-dimer levels and had undergone a VDU study to evaluate for the presence of VTE from March 2008 through July 2017. The clinical risk factors and D-dimer levels were evaluated for the prediction of VTE. RESULTS: In the 1918 patient encounters identified, the overall VTE detection rate was 28.7%. Using a receiver operating characteristic curve, an area under the curve of 0.58 was identified for all D-dimer values (P = 0.0001). A D-dimer level of ≥2.5 µg/mL on admission conferred a 30% greater relative risk of VTE (sensitivity, 0.43; specificity, 0.67; positive predictive value, 0.27; negative predictive value, 0.8). A D-dimer value of ≥3.5 µg/mL during hospitalization yielded a 28% greater relative risk of VTE (sensitivity, 0.73; specificity, 0.32; positive predictive value, 0.24; negative predictive value, 0.81). Multivariable logistic regression showed that age, male sex, length of stay, tumor or other neurological disease diagnosis, and D-dimer level ≥3.5 µg/mL during hospitalization were independent predictors of VTE. CONCLUSIONS: The D-dimer protocol was beneficial in identifying VTE in a heterogeneous group of neurosurgical patients by prompting VDU evaluation for patients with a D-dimer values of ≥3.5 µg/mL during hospitalization. Refinement of this screening model is necessary to improve the identification of VTE in a practical and cost-effective manner.

Outcomes Associated With Stage 2 Pressure Injuries Among Surgical Critical Care Patients: A Retrospective Cohort Study.

BACKGROUND: Hospital-acquired pressure injuries are a serious problem among critical care patients. Although most hospital-acquired pressure injuries are stage 2 (partial-thickness skin loss with exposed dermis), no studies have examined outcomes of stage 2 pressure injuries among critical care patients. OBJECTIVES: To examine outcomes of stage 2 hospital-acquired pressure injuries among critical care patients and identify factors associated with nonhealing stage 2 hospital-acquired pressure injuries. METHODS: Electronic health record data were used to identify surgical critical care patients with stage 2 hospital-acquired pressure injuries at a level I trauma center. Univariate Cox regressions were used to identify factors associated with healed stage 2 hospital-acquired pressure injuries. RESULTS: Of 6376 surgical critical care patients, 298 (4.7%) developed stage 2 hospital-acquired pressure injuries; complete data were available for 253 patients. Of these 253 patients, 160 (63%) had unhealed pressure injuries at hospital discharge. Factors inversely related to the presence of a healed hospital-acquired pressure injury were older age (hazard ratio, 0.98; 95% CI, 0.97-0.99; P = .003), elevated serum lactate (hazard ratio, 0.85; 95% CI, 0.75-0.96; P = .01), elevated serum creatinine (hazard ratio, 0.87; 95% CI, 0.77-0.98; P = .02), and lower oxygenation (hazard ratio, 0.64; 95% CI, 0.41-1.00; P = .05). CONCLUSIONS: Stage 2 hospital-acquired pressure injuries were not healed at discharge in 63% of the patients in our sample. Nurses should be especially vigilant in treating pressure injury patients who are older, have altered oxygenation or perfusion (elevated serum lactate level or decreased oxygenation), or have evidence of renal compromise.

Predicting Pressure Injury in Critical Care Patients: A Machine-Learning Model.

BACKGROUND: Hospital-acquired pressure injuries are a serious problem among critical care patients. Some can be prevented by using measures such as specialty beds, which are not feasible for every patient because of costs. However, decisions about which patient would benefit most from a specialty bed are difficult because results of existing tools to determine risk for pressure injury indicate that most critical care patients are at high risk. OBJECTIVE: To develop a model for predicting development of pressure injuries among surgical critical care patients. METHODS: Data from electronic health records were divided into training (67%) and testing (33%) data sets, and a model was developed by using a random forest algorithm via the R package "randomforest." RESULTS: Among a sample of 6376 patients, hospital-acquired pressure injuries of stage 1 or greater (outcome variable 1) developed in 516 patients (8.1%) and injuries of stage 2 or greater (outcome variable 2) developed in 257 (4.0%). Random forest models were developed to predict stage 1 and greater and stage 2 and greater injuries by using the testing set to evaluate classifier performance. The area under the receiver operating characteristic curve for both models was 0.79. CONCLUSION: This machine-learning approach differs from other available models because it does not require clinicians to input information into a tool (eg, the Braden Scale). Rather, it uses information readily available in electronic health records. Next steps include testing in an independent sample and then calibration to optimize specificity.

Outcomes Associated With Stage 1 Pressure Injuries: A Retrospective Cohort Study.

BACKGROUND: Approximately half of hospital-acquired pressure injuries identified among critical care patients are stage 1. Although stage 1 injuries are common, outcomes associated with them among critical care patients have not been examined. OBJECTIVES: To examine the outcomes of stage 1 pressure injuries among critical care patients and to identify factors associated with worsening of pressure injuries. METHODS: Electronic health records were used to determine which surgical critical care patients at a level I trauma center and academic medical center had stage 1 pressure injuries. Competing risk survival analysis was used to identify factors associated with worsening of pressure injuries. RESULTS: Review of 6377 patient records indicated that 259 patients (4.1%) experienced stage 1 injuries. The injuries persisted until discharge from the hospital in 92 patients (35.5%), worsened into injuries of stage 2 or greater in 84 (32.4%), and healed in 83 (32.0%). Patients whose pressure injuries worsened were more likely to be older (subdistribution hazard ratio [SHR], 1.02; 95% CI, 1.01-1.03; P = .002), or to have higher levels of serum lactate (SHR, 1.06; 95% CI, 1.02-1.10; P = .007), lower levels of hemoglobin (SHR, 0.82; 95% CI, 0.71-0.96; P = .01), or decreased oxygen saturation by pulse oximetry (< 90%; SHR, 1.50; 95% CI, 1.00-2.25; P = .05). CONCLUSIONS: Stage 1 pressure injuries worsen in about one-third of patients (32.4%). Nurses should consider maximal treatment for patients who are older or who experience alterations in oxygen delivery or perfusion.

In vivo performance of a visible wavelength optical sensor for monitoring intestinal perfusion and oxygenation.

Traumatic injury resulting in hemorrhage is a prevalent cause of death worldwide. The current standard of care for trauma patients is to restore hemostasis by controlling bleeding and administering intravenous volume resuscitation. Adequate resuscitation to restore tissue blood flow and oxygenation is critical within the first hours following admission to assess severity and avoid complications. However, current clinical methods for guiding resuscitation are not sensitive or specific enough to adequately understand the patient condition. To better address the shortcomings of the current methods, an approach to monitor intestinal perfusion and oxygenation using a multiwavelength (470, 560, and 630 nm) optical sensor has been developed based on photoplethysmography and reflectance spectroscopy. Specifically, two sensors were developed using three wavelengths to measure relative changes in the small intestine. Using vessel occlusion, systemic changes in oxygenation input, and induction of hemorrhagic shock, the capabilities and sensitivity of the sensor were explored in vivo. Pulsatile and nonpulsatile components of the red, blue, and green wavelength signals were analyzed for all three protocols (occlusion, systemic oxygenation changes, and shock) and were shown to differentiate perfusion and oxygenation changes in the jejunum. The blue and green signals produced better correlation to perfusion changes during occlusion and shock, while the red and blue signals, using a new correlation algorithm, produced better data for assessing changes in oxygenation induced both systemically and locally during shock. The conventional modulation ratio method was found to be an ineffective measure of oxygenation in the intestine due to noise and an algorithm was developed based on the Pearson correlation coefficient. The method utilized the difference in phase between two different wavelength signals to assess oxygen content. A combination of measures from the three wavelengths provided verification of oxygenation and perfusion states, and showed promise for the development of a clinical monitor.

Comparison of Empiric Antibiotics for Acute Osteomyelitis in Children.

OBJECTIVES: Broad-spectrum antibiotics are commonly used for the empiric treatment of acute hematogenous osteomyelitis and often target methicillin-resistant Staphylococcus aureus (MRSA) with medication-associated risk and unknown treatment benefit. We aimed to compare clinical outcomes among patients with osteomyelitis who did and did not receive initial antibiotics used to target MRSA. METHODS: A retrospective cohort study of 974 hospitalized children 2 to 18 years old using the Pediatric Health Information System database, augmented with clinical data. Rates of hospital readmission, repeat MRI and 72-hour improvement in inflammatory markers were compared between treatment groups. RESULTS: Repeat MRI within 7 and 180 days was more frequent among patients who received initial MRSA coverage versus methicillin-sensitive S aureus (MSSA)-only coverage (8.6% vs 4.1% within 7 days [P = .02] and 12% vs 5.8% within 180 days [P < .01], respectively). Ninety- and 180-day hospital readmission rates were similar between coverage groups (9.0% vs 8.7% [P = .87] and 10.9% vs 11.2% [P = .92], respectively). Patients with MRSA- and MSSA-only coverage had similar rates of 72-hour improvement in C-reactive protein values, but patients with MRSA coverage had a lower rate of 72-hour white blood cell count normalization compared with patients with MSSA-only coverage (4.2% vs 16.4%; P = .02). CONCLUSIONS: In this study of children hospitalized with acute hematogenous osteomyelitis, early antibiotic treatment used to target MRSA was associated with a higher rate of repeat MRI compared with early antibiotic treatment used to target MSSA but not MRSA. Hospital readmission rates were similar for both treatment groups.

In-silico and in-vitro investigation of a photonic monitor for intestinal perfusion and oxygenation.

The quantification of visceral organ oxygenation after trauma-related systemic hypovolemia and shock is critical to enable effective resuscitation. In this work, a photoplethysmography-based (PPG) sensor was specifically designed for probing the perfusion and oxygenation condition of intestinal tissue with the ultimate goal to monitor patients post trauma to guide resuscitation. Through Monte Carlo modeling, suitable optofluidic phantoms were determined, the wavelength and separation distance for the sensor was optimized, and sensor performance for the quantification of tissue perfusion and oxygenation was tested on the in-vitro phantom. In particular, the Monte Carlo simulated both a standard block three-layer model and a more realistic model including villi. Measurements were collected on the designed three layer optofluidic phantom and the results taken with the small form factor PPG device showed a marked improvement when using shorter visible wavelengths over the more conventional longer visible wavelengths. Overall, in this work a Monte Carlo model was developed, an optofluidic phantom was built, and a small form factor PPG sensor was developed and characterized using the phantom for perfusion and oxygenation over the visible wavelength range. The results show promise that this small form factor PPG sensor could be used as a future guide to shock-related resuscitation.

Midrange Braden Subscale Scores Are Associated With Increased Risk for Pressure Injury Development Among Critical Care Patients.

PURPOSE: The purpose of the current study was to examine the relationship between pressure injury development and the Braden Scale for Pressure Sore Risk subscale scores in a surgical intensive care unit (ICU) population and to ascertain whether the risk represented by the subscale scores is different between older and younger patients. DESIGN: Retrospective review of electronic medical records. SUBJECTS AND SETTING: The sample comprised patients admitted to the ICU at an academic medical center in the Western United States (Utah) and Level 1 trauma center between January 1, 2008 and May 1, 2013. Analysis is based on data from 6377 patients. METHODS: Retrospective chart review was used to determine Braden Scale total and subscale scores, age, and incidence of pressure injury development. We used survival analysis to determine the hazards of developing a pressure injury associated with each subscale of the Braden Scale, with the lowest-risk category as a reference. In addition, we used time-dependent Cox regression with natural cubic splines to model the interaction between age and Braden Scale scores and subscale scores in pressure injury risk. RESULTS: Of the 6377 ICU patients, 214 (4%) developed a pressure injury (stages 2-4, deep tissue injury, or unstageable) and 516 (8%) developed a hospital-acquired pressure injury of any stage. With the exception of the friction and shear subscales, regardless of age, individuals with scores in the intermediate-risk levels had the highest likelihood of developing pressure injury. CONCLUSION: The relationship between age, Braden Scale subscale scores, and pressure injury development varied among subscales. Maximal preventive efforts should be extended to include individuals with intermediate Braden Scale subscale scores, and age should be considered along with the subscale scores as a factor in care planning.

Effectiveness of Fundoplication or Gastrojejunal Feeding in Children With Neurologic Impairment.

BACKGROUND AND OBJECTIVES: Gastroesophageal reflux (GER), aspiration, and secondary complications lead to morbidity and mortality in children with neurologic impairment (NI), dysphagia, and gastrostomy feeding. Fundoplication and gastrojejunal (GJ) feeding can reduce risk. We compared GJ to fundoplication using first-year postprocedure reflux-related hospitalization (RRH) rates. METHODS: We identified children with NI, dysphagia requiring gastrostomy tube feeding and GER undergoing initial GJ placement or fundoplication from January 1, 2007 to December 31, 2012. Data came from the Pediatric Health Information Systems augmented by laboratory, microbiology, and radiology results. GJ placement was ascertained using radiology results and fundoplication by International Classification of Diseases, Ninth Revision, Clinical Modification codes. Subjects were matched within hospital using propensity scores. The primary outcome was first-year postprocedure RRH rate (hospitalization for GER disease, other esophagitis, aspiration pneumonia, other pneumonia, asthma, or mechanical ventilation). Secondary outcomes included failure to thrive, death, repeated initial intervention, crossover intervention, and procedural complications. RESULTS: We identified 1178 children with fundoplication and 163 with GJ placement, matching 114 per group. Matched sample RRH incident rate per child-year (95% confidence interval) for GJ was 2.07 (1.62-2.64) and for fundoplication 1.67 (1.28-2.18), P = .19. Odds of death were similar between groups. Failure to thrive, repeat of initial intervention, and crossover intervention were more common in the GJ group. CONCLUSIONS: In children with NI, GER, and dysphagia: fundoplication and GJ feeding have similar RRH outcomes. Either intervention can reduce future aspiration risk; the choice can reflect non-RRH-related complication risks, caregiver preference, and clinician recommendation.