Armandina Garza

Development and validation of an algorithm to recalibrate mental models and reduce diagnostic errors associated with catheter-associated bacteriuria.

BackgroundOvertreatment of catheter-associated bacteriuria is a quality and safety problem, despite the availability of evidence-based guidelines. Little is known about how guidelines-based knowledge is integrated into clinicians’ mental models for diagnosing catheter-associated urinary tract infection (CA-UTI). The objectives of this research were to better understand clinicians’ mental models for CA-UTI, and to develop and validate an algorithm to improve diagnostic accuracy for CA-UTI.MethodsWe conducted two phases of this research project. In phase one, 10 clinicians assessed and diagnosed four patient cases of catheter associated bacteriuria (n= 40 total cases). We assessed the clinical cues used when diagnosing these cases to determine if the mental models were IDSA guideline compliant. In phase two, we developed a diagnostic algorithm derived from the IDSA guidelines. IDSA guideline authors and non-expert clinicians evaluated the algorithm for content and face validity. In order to determine if diagnostic accuracy improved using the algorithm, we had experts and non-experts diagnose 71 cases of bacteriuria.ResultsOnly 21 (53%) diagnoses made by clinicians without the algorithm were guidelines-concordant with fair inter-rater reliability between clinicians (Fleiss’ kappa = 0.35, 95% Confidence Intervals (CIs) = 0.21 and 0.50). Evidence suggests that clinicians’ mental models are inappropriately constructed in that clinicians endorsed guidelines-discordant cues as influential in their decision-making: pyuria, systemic leukocytosis, organism type and number, weakness, and elderly or frail patient. Using the algorithm, inter-rater reliability between the expert and each non-expert was substantial (Cohen’s kappa = 0.72, 95% CIs = 0.52 and 0.93 between the expert and non-expert #1 and 0.80, 95% CIs = 0.61 and 0.99 between the expert and non-expert #2).ConclusionsDiagnostic errors occur when clinicians’ mental models for catheter-associated bacteriuria include cues that are guidelines-discordant for CA-UTI. The understanding we gained of clinicians’ mental models, especially diagnostic errors, and the algorithm developed to address these errors will inform interventions to improve the accuracy and reliability of CA-UTI diagnoses.

Ethnicity affects the postprandial regulation of glycogenolysis

We investigated the effect of nutrient intake on glucose metabolism in normal Mexican-Americans (n = 6) and European-Americans (n = 6). Subjects were studied after an 18-h fast and after 5-6 h of ingestion of hourly meals that supplied 6.35 or 12.75 micromol glucose. kg(-1). min(-1). Endogenous glucose production (EGP), gluconeogenesis (GNG), and glycogenolysis (GLY) were estimated by mass isotopomer analysis with [U-(13)C]glucose infusions. Fasting EGP, GNG, and GLY did not differ between the groups. Food ingestion lowered the molar rate of GNG by only 31%. However, while consuming the lower quantity of nutrients, Mexican-Americans had higher plasma glucose (P < 0.05), a 39% higher rate of EGP (P < 0.05), and a 68% (P < 0.025) higher rate of GLY than the European-Americans. At the higher intake, EGP and GLY were suppressed completely in both groups. There was a linear relationship between insulin concentrations, EGP, and GLY in both groups, but the slope of the line was significantly (P < 0.05) greater in the European-Americans. We conclude that the sensitivity of GLY to nutrient intake differs between ethnic groups and that this may play a role in the increased predisposition of Mexican-Americans to type II diabetes.

Substance P causes seizures in neurocysticercosis.

Neurocysticercosis (NCC), a helminth infection of the brain, is a major cause of seizures. The mediators responsible for seizures in NCC are unknown, and their management remains controversial. Substance P (SP) is a neuropeptide produced by neurons, endothelial cells and immunocytes. The current studies examined the hypothesis that SP mediates seizures in NCC. We demonstrated by immunostaining that 5 of 5 brain biopsies from NCC patients contained substance P (SP)-positive (+) cells adjacent to but not distant from degenerating worms; no SP+ cells were detected in uninfected brains. In a rodent model of NCC, seizures were induced after intrahippocampal injection of SP alone or after injection of extracts of cysticercosis granuloma obtained from infected wild type (WT), but not from infected SP precursor-deficient mice. Seizure activity correlated with SP levels within WT granuloma extracts and was prevented by intrahippocampal pre-injection of SP receptor antagonist. Furthermore, extracts of granulomas from WT mice caused seizures when injected into the hippocampus of WT mice, but not when injected into SP receptor (NK1R) deficient mice. These findings indicate that SP causes seizures in NCC, and, suggests that seizures in NCC in humans may be prevented and/or treated with SP-receptor antagonists.

Accuracy of a urinary catheter surveillance protocol

BACKGROUND Many hospitals are increasing surveillance for catheter-associated urinary tract infections, which requires documentation of urinary catheter device-days. However, device-days are usually obtained by chart review or nursing reports. The aim of this study was to demonstrate that chart review can provide accurate urinary catheter data compared with physical inspection of the urinary catheter at the bedside. METHODS We compared 2 methods for collecting urinary catheter data over a 6-month period on 10 wards at our VA hospital. For the chart reviews, we created a daily bed-occupancy roster from the electronic medical record. Catheter data were extracted from the daily progress notes for each patient using a standardized review process. Bedside reviews were conducted by visiting the ward and verifying the presence and type of urinary catheters. Agreement between the 2 methods was calculated. RESULTS We obtained urinary catheter data by both methods in 621 cases. The presence or type of urinary catheter differed between chart and bedside review in only 10 cases (1.6%). Chart review had a sensitivity of 100%, a specificity of 97.7%, raw agreement of 98.4%, and a κ value of 0.96. CONCLUSIONS Individual chart review in the electronic medical record provided very accurate data on urinary catheter use.

Substance P signaling contributes to granuloma formation in taenia crassiceps infection, a murine model of cysticercosis

Cysticercosis is an infection with larval cysts of the cestode Taenia solium. Through pathways that are incompletely understood, dying parasites initiate a granulomatous reaction that, in the brain, causes seizures. Substance P (SP), a neuropeptide involved in pain-transmission, contributes to inflammation and previously was detected in granulomas associated with dead T. crassiceps cysts. To determine if SP contributes to granuloma formation, we measured granuloma-size and levels of IL-1β, TNF-α, and IL-6 within granulomas in T. crassiceps-infected wild type (WT) mice and mice deficient in SP-precursor (SPP) or the SP-receptor (neurokinin 1, NK1). Granuloma volumes of infected SPP- and NK1-knockout mice were reduced by 31 and 36%, respectively, compared to WT mice (P < .05 for both) and produced up to 5-fold less IL-1β, TNF-α, and IL-6 protein. Thus, SP signaling contributes to granuloma development and proinflammatory cytokine production in T. crassiceps infection and suggests a potential role for this mediator in human cystercercosis.

Substance P Receptor Antagonism for Treatment of Cryptosporidiosis in Immunosuppressed Mice

Cryptosporidiosis, caused by the protozoan parasite Cryptosporidium parvum, causes self-limited diarrhea in normal hosts but can cause life-threatening diarrhea for immunosuppressed patients. There is an urgent need for new drugs to treat this chronic disease. Cryptosporidium parvum infection is associated with intestinal structural and pathophysiologic changes, including villi blunting and glucose malabsorption. Substance P (SP), a neuropeptide and pain transmitter, is associated with the gastrointestinal tract and is elevated in humans and macaques after experimental C. parvum challenge. To examine the relevance of SP in the pathogenesis of cryptosporidiosis, and to determine if SP receptor antagonism can be employed for treatment of cryptosporidiosis in immunosuppressed hosts, we used an immunosuppressed murine model (dexamethasone-immunosuppressed mice) that is frequently utilized for examining chemotherapeutic potential of drugs. Quantitative ELISA was used to measure intestinal SP levels in immunosuppressed mice with, and without, C. parvum infection. Intestinal physiological alterations, as studied by the Ussing chamber technique, plus weight change, fecal oocyst shedding, and villi measurements, were compared in infected mice with, and without, SP receptor antagonist (aprepitant) treatment. Immunosuppressed mice infected with C. parvum demonstrated increased SP levels as well as physiological alterations (glucose malabsorption), weight loss, fecal oocyst shedding, and structural alterations (increased intestinal villi blunting) compared to uninfected mice. Each of these defects was significantly inhibited by aprepitant treatment. These studies demonstrate the potential of SP receptor antagonism for treatment of pathogenesis of cryptosporidiosis in immunosuppressed hosts.

ABSENCE OF THE SP/SP RECEPTOR CIRCUITRY IN THE SUBSTANCE P-PRECURSOR KNOCKOUT MICE OR SP RECEPTOR, NEUROKININ (NK)1 KNOCKOUT MICE LEADS TO AN INHIBITED CYTOKINE RESPONSE IN GRANULOMAS ASSOCIATED WITH MURINE TAENIA CRASSICEPS INFECTION

Abstract Neurocysticercosis, caused by the cestode Taenia solium, is the most common parasitic infection of the human central nervous system that leads to seizures. Taenia crassiceps cysticercosis in mice is an experimental model for Taenia solium cysticercosis. Similar to the human infection, live parasites cause little or no granulomatous inflammation. Dying parasites initiate a granulomatous reaction. The neuropeptide substance P (SP) stimulates T-helper (Th) 1 cytokine production. In the current study, we determined whether absence of SP/SP receptor circuitry in the SP-precursor, preprotachykinin, knockout or SP-receptor, neurokinin (NK)1, knockout mice affected granuloma cytokine production. We hence compared the levels of Th1 cytokines interleukin (IL)-2 and interferon (IFN)-γ and levels of Th2/immunoregulatory cytokines IL-4 and IL-10 by enzyme-linked immunosorbent assay in T. crassiceps-induced granulomas derived from infected C57BL/6 wild-type (WT) versus SP-precursor knockout and NK1 knockout mice. We found that mean levels of IL-2, IFN-γ, IL-4, and IL-10 in infected WT-derived granulomas were significantly higher than those of granulomas derived from infected SP-precursor knockout or the NK1 receptor (NK1R) knockout mice. Levels of Th2/immunoregulatory cytokines IL-4 and IL-10 were higher in early stage granulomas (histologically staged on basis of evidence of parasite remnants) versus late stage granulomas (no parasite remnants) of both knockouts, whereas the reverse was noted in WT-derived granulomas. This study established that the absence of an SP/SP receptor circuitry in the SP-precursor knockout mice or NK1 receptor knockout mice led to an inhibited cytokine response.

Substance P receptor antagonist reverses intestinal pathophysiological alterations occurring in a novel ex‐vivo model of Cryptosporidium parvum infection of intestinal tissues derived from SIV‐infected macaques

Background  Cryptosporidium infection leads to life‐threatening diarrhea in AIDS patients. Pathogenesis of cryptosporidiosis is due to intestinal physiological alterations. We devised an ex‐vivo model using ex‐vivo Cryptosporidium parvum infection of jejunal tissues derived from SIV‐infected macaques and studied the role of substance P (SP) in the pathogenesis of cryptosporidiosis.

Infection of immunocompetent mice with acid-water-pretreated Cryptosporidium parvum results in weight loss, and intestinal (structural and physiological) alterations.

Cryptosporidiosis, caused by Cryptosporidium, causes self-limited diarrhea in normal hosts but may cause life-threatening diarrhea in immunocompromised persons. Cryptosporidium-induced manifestations, including weight-loss and intestinal physiological alterations are not noted in adult immunocompetent mice. So far, studies that have been used to test the therapeutic efficacy of drugs have been performed using various immunocompromised animal models. There is an urgent need of an immunocompetent small animal model that portrays Cryptosporidium-induced manifestations. In the current studies, we have compared two Cryptosporidium parvum pretreatment methods, we have hence used sodium hypochlorite or acidic water to treat Cryptosporidium parvum, followed by infection by oral gavage in adult immunocompetent C57BL6 mice. We demonstrated manifestations such as weight loss, intestinal structural and physiological alterations such as intestinal, villi blunting, and glucose malabsorption (as studied by the Ussing chamber technique) only in response to infection with C. parvum that has been treated with acidic water and not with sodium hypochlorite. These novel studies reveal that acidic water treatment of C. parvum results in manifestations of cryptosporidiosis in otherwise resistant immunocompetent mice. The current studies open up possibilities of using the normal immunocompetent mice model to test therapeutic drugs against cryptosporidiosis.