A general framework for developing computable clinical phenotype algorithms.

OBJECTIVE: Present a general framework providing high-level guidance to developers of computable algorithms for identifying patients with specific clinical conditions (phenotypes) through a variety of approaches, including but not limited to machine learning and natural language processing methods to incorporate rich electronic health record data. MATERIALS/METHODS: Drawing on extensive prior phenotyping experiences and insights derived from three algorithm development projects conducted specifically for this purpose, our team with expertise in clinical medicine, statistics, informatics, pharmacoepidemiology, and healthcare data science methods conceptualized stages of development and corresponding sets of principles, strategies, and practical guidelines for improving the algorithm development process. RESULTS: We propose five stages of algorithm development and corresponding principles, strategies, and guidelines: 1) assessing fitness-for-purpose, 2) creating gold standard data, 3) feature engineering, 4) model development, and 5) model evaluation. DISCUSSION/CONCLUSION: This framework is intended to provide practical guidance and serve as a basis for future elaboration and extension.

Challenges in Heart Failure Disease Management in Skilled Nursing Facilities: A Qualitative Study.

Clinical guidelines recommend clinicians in skilled nursing facilities (SNFs) monitor body weight and signs and symptoms related to heart failure (HF) and encourage a sodium restricted diet to improve HF outcomes; however, SNFs face considerable challenges in HF disease management (HF-DM). In the current study, we characterized the challenges of HF-DM with data from semi-structured, in-depth interviews with patients, caregivers, staff, and physicians from nine SNFs. Patients receiving skilled nursing care were interviewed together as a dyad with their caregiver. A data-driven, qualitative descriptive approach was used to understand the process and challenges of HF-DM. Coded text was categorized into descriptive themes. Interviews with five dyads (n = 10 individuals), SNF nurses and certified nursing assistants (n = 13), and physicians (n = 2) revealed that, among the sample, HF care was not prioritized above other competing health concerns. Staff operated in the challenging SNF environment largely without protocols or educational materials to prompt HF-DM. [Journal of Gerontological Nursing, 48(5), 13-17.].

Distinct carbon isotope fractionation during anaerobic degradation of dichlorobenzene isomers.

Chlorinated benzenes are ubiquitous organic contaminants found in groundwater and soils. Compound specific isotope analysis (CSIA) has been increasingly used to assess natural attenuation of chlorinated contaminants, in which anaerobic reductive dechlorination plays an essential role. In this work, carbon isotope fractionation of the three dichlorobenzene (DCB) isomers was investigated during anaerobic reductive dehalogenation in methanogenic laboratory microcosms. Large isotope fractionation of 1,3-DCB and 1,4-DCB was observed while only a small isotope effect occurred for 1,2-DCB. Bulk enrichment factors (εbulk) were determined from a Rayleigh model: -0.8 ± 0.1 ‰ for 1,2-DCB, -5.4 ± 0.4 ‰ for 1,3-DCB, and -6.3 ± 0.2 ‰ for 1,4-DCB. εbulk values were converted to apparent kinetic isotope effects for carbon (AKIE) in order to characterize the carbon isotope effect at the reactive positions for the DCB isomers. AKIE values are 1.005 ± 0.001, 1.034 ± 0.003, and 1.039 ± 0.001 for 1,2-DCB, 1,3-DCB, and 1,4-DCB, respectively. The large difference in AKIE values between 1,2-DCB and 1,3-DCB (or 1,4-DCB) suggests distinct reaction pathways may be involved for different DCB isomers during microbial reductive dechlorination by the methanogenic cultures.

Dehalogenation of chlorobenzenes, dichlorotoluenes, and tetrachloroethene by three Dehalobacter spp.

Three enrichment cultures containing Dehalobacter spp. were developed that dehalogenate each of the dichlorobenzene (DCB) isomers to monochlorobenzene (MCB), and the strains using 1,2-DCB (12DCB1) or 1,3-DCB (13DCB1) are now considered isolated, whereas the strain using 1,4-DCB (14DCB1) is considered highly enriched. In this study, we examined the dehalogenation capability of each strain to use chlorobenzenes with three or more chlorines, tetrachloroethene (PCE), or dichlorotoluene (DCT) isomers. Strain 12DCB1 preferentially dehalogenated singly flanked chlorines, but not doubly flanked or unflanked chlorines. It dehalogenated pentachlorobenzene to MCB with little buildup of intermediates. Strain 13DCB1, which could use either 1,3-DCB or 1,2-DCB, demonstrated the widest dehalogenation spectrum of electron acceptors tested, and dehalogenated every chlorobenzene isomer except 1,4-DCB. Notably, strain 13DCB1 dehalogenated the recalcitrant 1,3,5-trichlorobenzene isomer to MCB, and qPCR of 16S rRNA genes indicated that strain 13DCB1 grew. Strain 14DCB1 exhibited the narrowest range of substrate utilization, but was the only strain to dehalogenate para-substituted chlorines. Strains 12DCB1 and 13DCB1 dehalogenated PCE to cis-dichloroethene, and all strains dehalogenated 3,4-DCT to monochlorotoluene. These findings show that Dehalobacter spp., like Dehalococcoides spp., are versatile dehalogenators and should be considered when determining the fate of chlorinated organics at contaminated sites.

Airway obstruction due to unilateral vocal fold paralysis.

OBJECTIVES/HYPOTHESIS: Airway obstruction is an uncommon presentation of unilateral laryngeal paralysis. We have observed two mechanisms of obstruction: arytenoid prolapse and inappropriate adduction of the paralyzed vocal fold. We evaluated arytenoid abduction (AAb) and recurrent laryngeal nerve (RLN) reinnervation as treatments for airway obstruction in patients with unilateral laryngeal paralysis. STUDY DESIGN: Retrospective case series. METHODS: Seven patients with airway obstruction secondary to unilateral laryngeal paralysis were evaluated with flexible laryngoscopy and direct laryngoscopy. Patients with flaccid paralysis and a prolapsing arytenoid were treated with AAb. Airway obstruction due to inspiratory vocal fold adduction was managed by RLN transection and ansa reinnervation of the distal stump. RESULTS: In all cases, paralysis resulted from RLN injury during surgery: thyroidectomy or cervical spine surgery. AAb was performed in four patients with arytenoid prolapse, and all had significant airway improvement, including decannulation of the two patients who had been tracheotomy dependent. RLN reinnervation was performed in five patients, two of whom had inappropriate adduction detected after AAb. The site of RLN injury was identified at surgery in all four patients. Inspiratory stridor and laryngospasm were abolished immediately after RLN transection. CONCLUSIONS: Arytenoid prolapse and/or inappropriate laryngeal adduction can cause airway obstruction in patients with unilateral laryngeal paralysis. Treatment of airway obstruction should address the underlying pathophysiology. AAb and RLN transection with ansa reinnervation can be effective in selected patients.

Pathway-dependent isotope fractionation during aerobic and anaerobic degradation of monochlorobenzene and 1,2,4-trichlorobenzene.

Stable carbon isotope fractionation is a valuable tool for monitoring natural attenuation and to establish the fate of groundwater contaminants. In this study, we measured carbon isotope fractionation during aerobic and anaerobic degradation of two chlorinated benzenes: monochlorobenzene (MCB) and 1,2,4-trichlorobenzene (1,2,4-TCB). MCB isotope fractionation was measured in anaerobic methanogenic microcosms, while 1,2,4-TCB isotope experiments were carried out in both aerobic and anaerobic microcosms. Large isotope fractionation was observed in both the anaerobic microcosm experiments. Enrichment factors (ε) for anaerobic reductive dechlorination of MCB and 1,2,4-TCB were -5.0‰ ± 0.2‰ and -3.0‰ ± 0.4‰, respectively. In contrast, no significant isotope fractionation was found during aerobic microbial degradation of 1,2,4-TCB. The cleavage of a C-Cl σ bond occurs during anaerobic reductive dechlorination of MCB and 1,2,4-TCB, while no σ bond cleavage is involved during aerobic degradation via dioxygenase. The difference in isotope fractionation for aerobic versus anaerobic biodegradation of MCB and 1,2,4-TCB can be explained by the difference in the initial step of aerobic versus anaerobic biodegradation pathways.

A role for Dehalobacter spp. in the reductive dehalogenation of dichlorobenzenes and monochlorobenzene.

Previously, we demonstrated the reductive dehalogenation of dichlorobenzene (DCB) isomers to monochlorobenzene (MCB), and MCB to benzene in sediment microcosms derived from a chlorobenzene-contaminated site. In this study, enrichment cultures were established for each DCB isomer and each produced MCB and trace amounts of benzene as end products. MCB dehalogenation activity could only be transferred in sediment microcosms. The 1,2-DCB-dehalogenating culture was studied the most intensively. Whereas Dehalococcoides spp. were not detected in any of the microcosms or cultures, Dehalobacter spp. were detected in 16S rRNA gene clone libraries from 1,2-DCB enrichment cultures, and by PCR using Dehalobacter-specific primers in 1,3-DCB and 1,4-DCB enrichments and MCB-dehalogenating microcosms. Quantitative PCR showed Dehalobacter 16S rRNA gene copies increased up to 3 orders of magnitude upon dehalogenation of DCBs or MCB, and that nearly all of bacterial 16S rRNA genes in a 1,2-DCB-dehalogenating culture belonged to Dehalobacter spp. Dehalobacter 16S rRNA genes from DCB enrichment cultures and MCB-dehalogenating microcosms showed considerable diversity, implying that 16S rRNA sequences do not predict dehalogenation-spectra of Dehalobacter spp. These studies support a role for Dehalobacter spp. in the reductive dehalogenation of DCBs and MCB, and this genus should be considered for its potential impact on chlorobenzene fate at contaminated sites.

Using NMR metabolomics to investigate tricarboxylic acid cycle-dependent signal transduction in Staphylococcus epidermidis.

Staphylococcus epidermidis is a skin-resident bacterium and a major cause of biomaterial-associated infections. The transition from residing on the skin to residing on an implanted biomaterial is accompanied by regulatory changes that facilitate bacterial survival in the new environment. These regulatory changes are dependent upon the ability of bacteria to "sense" environmental changes. In S. epidermidis, disparate environmental signals can affect synthesis of the biofilm matrix polysaccharide intercellular adhesin (PIA). Previously, we demonstrated that PIA biosynthesis is regulated by tricarboxylic acid (TCA) cycle activity. The observations that very different environmental signals result in a common phenotype (i.e. increased PIA synthesis) and that TCA cycle activity regulates PIA biosynthesis led us to hypothesize that S. epidermidis is "sensing" disparate environmental signals through the modulation of TCA cycle activity. In this study, we used NMR metabolomics to demonstrate that divergent environmental signals are transduced into common metabolomic changes that are "sensed" by metabolite-responsive regulators, such as CcpA, to affect PIA biosynthesis. These data clarify one mechanism by which very different environmental signals cause common phenotypic changes. In addition, due to the frequency of the TCA cycle in diverse genera of bacteria and the intrinsic properties of TCA cycle enzymes, it is likely the TCA cycle acts as a signal transduction pathway in many bacteria.

Vancomycin-intermediate Staphylococcus aureus strains have impaired acetate catabolism: implications for polysaccharide intercellular adhesin synthesis and autolysis.

The most common mechanism by which Staphylococcus aureus gains resistance to vancomycin is by adapting its physiology and metabolism to permit growth in the presence of vancomycin. Several studies have examined the adaptive changes occurring during the transition to vancomycin-intermediate resistance, leading to a model of vancomycin resistance in which decreased cell wall turnover and autolysis result in increased cell wall thickness and resistance to vancomycin. In the present study, we identified metabolic changes common to vancomycin-intermediate S. aureus (VISA) strains by assessing the metabolic and growth characteristics of two VISA strains (vancomycin MICs of 8 microg/ml) and two isogenic derivative strains with vancomycin MICs of 32 microg/ml. Interestingly, we observed the parental strains had impaired catabolism of nonpreferred carbon sources (i.e., acetate), and this impairment became more pronounced as vancomycin resistance increased. To determine if acetate catabolism impairment is common to VISA strains, we assessed the ability of VISA and vancomycin-sensitive S. aureus (VSSA) clinical isolates to catabolize acetate. As expected, a significantly greater percentage of VISA strains (71%) had impaired acetate catabolism relative to VSSA (8%). This is an important observation because staphylococcal acetate catabolism is implicated in growth yield and antibiotic tolerance and in regulating cell death and polysaccharide intercellular adhesin synthesis.

Validity of maternal and perinatal risk factors reported on fetal death certificates.

We sought to estimate the accuracy, relative to maternal medical records, of perinatal risk factors recorded on fetal death certificates. We conducted a validation study of fetal death certificates among women who experienced fetal deaths between 1996 and 2001. The number of previous births, established diabetes, chronic hypertension, maternal fever, performance of autopsy, anencephaly, and Down syndrome had very high accuracy, while placental cord conditions and other chromosomal abnormalities were reported inaccurately. Additional population-based studies are needed to identify strategies to improve fetal death certificate data.

Error-prone polymerase, DNA polymerase IV, is responsible for transient hypermutation during adaptive mutation in Escherichia coli.

The frequencies of nonselected mutations among adaptive Lac(+) revertants of Escherichia coli strains with and without the error-prone DNA polymerase IV (Pol IV) were compared. This frequency was more than sevenfold lower in the Pol IV-defective strain than in the wild-type strain. Thus, the mutations that occur during hypermutation are due to Pol IV.