Endogenous Acquisition Research Articles

Persistent Urinary Tract Infection in Association with Community-Acquired NDM-5 Escherichia coli Clonal Group Following COVID-19 Infection - Beijing Municipality, China, 2023.

The hospital-acquired infections caused by New Delhi metallo-beta-lactamase (NDM)-producing strains are typically attributed to a single clonal lineage. In this study, we encountered a unique case of community-acquired NDM-5 Escherichia coli urinary tract infection (UTI) following coronavirus disease 2019 (COVID-19). The UTI persisted for a duration of at least 45 days. Genomic analyses revealed the presence of two NDM-5 strains, both sharing an identical chromosomal background but distinct, homologous, and recombined plasmids. This case suggests that a diverse range of resistance genes may be present within the human body, with drug-resistant strains undergoing continuous evolution during infection. The intestinal tract may have been its drug-resistant gene pool. The observations presented in this case indicate that the endogenous acquisition of drug-resistant genes may also be an issue in managing multidrug-resistant organisms (MDRO). It is possible for continuous recombination to occur within carbapenem-resistant Enterobacteriaceae (CRE) during infection. In contrast to exogenously-acquired resistance, greater attention should be placed on the endogenous factors that contribute to the development of CRE within healthcare settings.

Media Competition and Social Disagreement

We study the competitive provision and endogenous acquisition of political information. Our main result identifies a natural equilibrium channel through which a more competitive market decreases the efficiency of policy outcomes. A critical insight we put forward is that competition among information providers leads to informational specialization: firms provide relatively less information on issues that are of common interest and relatively more information on issues on which agents' preferences are heterogeneous. This enables agents to acquire information about different aspects of the policy, specifically, those that are particularly important to them. This leads to an increase in social disagreement, which has negative welfare implications. We establish that, in large enough societies, competition makes every agent worse off by decreasing the utility that she derives from the policy outcome. Furthermore, we show that this decline cannot be compensated by the decrease in prices resulting from competition.

Endogenous Acquisition of Multi-Dimensional Information in a Strategic Trading Model

We analyze a strategic trading model with endogenous acquisition of multi-dimensional costly private information. We find that integer constraints on the number of informed traders, coupled with the interactions among different types of informed traders, lead to multiplicity and nonexistence of equilibria in the information market. Multiplicity stems either from information substitutability or from information complementarity, and nonexistence stems from the combined effect of information substitutability and information complementarity. Integer constraints also lead to asymmetric equilibria even when the model setup is symmetric. Under integer constraints, the fixed point theorem is no longer applicable and new methodologies are developed to prove the existence of equilibria as well as to find specific solutions for equilibria.

Mathematical modelling of vancomycin-resistant enterococci transmission during passive surveillance and active surveillance with contact isolation highlights the need to identify and address the source of acquisition

BackgroundClinical studies and mathematical simulation suggest that active surveillance with contact isolation is associated with reduced vancomycin-resistant enterococci (VRE) prevalence compared to passive surveillance. Models using pre- and post-intervention data that account for the imperfect observation and serial dependence of VRE transmission events can better estimate the effectiveness of active surveillance and subsequent contact isolation; however, such analyses have not been performed.MethodsA mathematical model was fitted to surveillance data collected pre- and post-implementation of active surveillance with contact isolation in the haematology-oncology ward. We developed a Hidden Markov Model to describe undetected and observed VRE colonisation/infection status based on the detection activities in the ward. Bayesian inference was used to estimate transmission rates. The effectiveness of active surveillance was assumed to be via increased detection and subsequent contact isolation of VRE positive patients.ResultsWe estimated that 31% (95% credible interval: 0.33–85%) of the VRE transmissions were due to cross-transmission between patients. The ratio of transmission rates from patients with contact isolation versus those without contact isolation was 0.33 (95% credible interval: 0.050–1.22).ConclusionsThe majority of the VRE acquisitions in the haematology-oncology ward was estimated to be due to background rates of VRE, rather than within ward patient to patient acquisition. The credible interval for cross-transmission was wide which results in a large degree of uncertainty in the estimates. Factors that could account for background VRE acquisition include endogenous acquisition from antibiotic selection pressure and VRE in the environment. Contact isolation was not significantly associated with reduced VRE transmission in settings where the majority of VRE acquisition was due to background acquisition, emphasising the need to identify and address the source of acquisition. As the credible interval for the ratio of VRE transmission in contact isolated versus non-contact isolated patients crossed 1, there is a probability that the transmission rate in contact isolation was not lower. Our finding highlights the need to optimise infection control measures other than active surveillance for VRE and subsequent contact isolation to reduce VRE transmission. Such measures could include antimicrobial stewardship, environmental cleaning, and hand hygiene.

Costly information acquisition under horizontal competition

We analyze endogenous acquisition of costly information for two firms that sell homogeneous products. Prior to determining its production quantity, either firm has an opportunity to acquire a costly forecast. There exists a correlation between errors in the acquired forecasts. We model the problem as a two-stage game in which the firms first decide whether to acquire their respective forecasts and then decide their production quantities. We derive the equilibrium outcome on information acquisition and production quantity.

Bayesian Persuasion with Costly Information Acquisition

A sender who chooses a signal to reveal to a receiver can often influence the receiver’s subsequent actions. Is persuasion more difficult when the receiver has her own sources of information? Does the receiver benefit from having additional information sources? We consider a Bayesian persuasion model extended to a receiver’s endogenous acquisition of information under an entropy-based cost commonly used in rational inattention. A sender’s optimal signal can be computed from standard Bayesian persuasion subject to an additional constraint: the receiver never gathers her own costly information. We further determine a finite set of the sender’s signals satisfying the additional constraint in which some optimal signal must be contained. The set is characterized by linear conditions using the receiver’s utility and information cost parameters. The new method is also applicable to a standard Bayesian persuasion model and can simplify, sometimes dramatically, the search for a sender’s optimal signal (as opposed to a standard concavification technique used to solve these models). We show that the ‘threat’ of additional learning weakly decreases the sender’s expected equilibrium payoff. However, the outcome can be worse not only for the sender, but also for the receiver.

What You See is All There is

In the contexts of social networks and the news media alike, people often select into environments in which they are predominantly exposed to information that confirms their prior beliefs, hence introducing a selection problem into the belief formation process. This paper shows experimentally that many people do not take into account how their own prior decisions shape their informational environment, but rather largely base their views on their local information sample. In consequence, beliefs excessively depend on people’s priors and tend to be too extreme, akin to popular concerns about echo chambers driving irrational belief polarization across social groups. The distribution of individuals’ naivete follows a pronounced bimodal structure – people either fully account for the selection problem or do not adjust for it at all. Allowing for interaction between these heterogeneous updating types induces little learning: neither the endogenous acquisition of advice nor exogenously induced dissent lead to a convergence of beliefs across types, suggesting that the belief heterogeneity induced by selected information may persist over time. Finally, the paper also sheds light on the cognitive mechanisms underlying selection neglect as well as its relationship to neglecting double-counting problems.

Identical Biofilm Forming Strains of Pseudomonas aeruginosa Occur in Lung Allograft BAL and Gastric Juice from CF Patients with Gastro Oesophageal Reflux

Purpose Gastro-oesophageal reflux and aspiration is known to occur frequently in patients with cystic fibrosis (CF) before and after lung transplantation and early re-establishment of Pseudomonas aeruginosa (Pa) in the allograft is associated with injury and loss of function. We hypothesised that the upper gastrointestinal tract could represent a reservoir of microorganisms relevant to lung injury in patients with evidence of reflux. Methods and Materials We evaluated twelve lung allograft recipients with and without CF, determining gastric juice and lung (BAL, sputum) microbiology. All patients were treated with proton pump inhibitors. Bacterial DNA (RAPD) typing was performed on all Pa isolated from gastric juice and compared where available, to isolates of Pa from pre and post transplant sputa and BAL for each patient. Objective measurements of reflux were performed by pH-impedance. Results In lung transplant patients treated with proton pump inhibitors abnormal levels of reflux persisted in the majority of the patients investigated. Reflux reached the top of the oesophagus to an abnormal extent in 7 out of 12 patients with and without CF. This indicated the potential for extra oesophageal reflux and lung microaspiration. Of five patients with CF, three had Pa recovered from samples of gastric juice. In two of these patients identical strains of Pseudomonas aeruginosa were found in bronchoalveolar lavage (BAL), gastric juice and pre and post transplant sputa. Conclusions Our data suggests the potential for the endogenous acquisition of microorganisms through reflux and aspiration including biofilm forming Pa, in CF patients. In principle, our data indicates that the lungs of CF patients might be vulnerable to infection from aspiration of Pa colonising the gastrointestinal tract.

The Evolution of Influence Through Endogenous Link Formation

Marketing researchers and practitioners are interested in targeting individuals in social networks who may have disproportionately higher levels of influence over others in their network. While the extant literature suggests individual characteristics or network position as proxies for relative influence, our study bridges these two streams by investigating the endogenous acquisition of network position as a function of exogenous individual characteristics. Specifically, do those with higher expertise achieve higher influence when people endogenously choose those to whom they listen? Using an agent-based modeling simulation framework, we model the dynamics of two types of individuals, i.e., independents with exogenous information and imitators. Over the course of multiple diffusions, agents choose whom to “listen to” for information; dropping less useful ties and adding new ones. We find that independents can have less influence (out-degree) than imitators who collect information from multiple sources. Furthermore, this effect is exacerbated by homophily. Noise in communication channels, on the other hand, moderates these effects, yet can increase penetration rates. We show that our results are robust to alternative dynamic network structures. Our research suggests that marketers should consider the environment, community characteristics, communication medium, and product domains when assessing the relative influence of individuals. Data and the online appendix are available at https://doi.org/10.1287/mksc.2017.1077 .

The Evolution of Endogenous Influence

Marketing researchers and practitioners are interested in targeting individuals in social networks who may have disproportionately higher level of influence over others in their network. While the extant literature suggests either individual characteristics and/or network position may explain one’s relative influence, our study bridges these two streams of work by investigating the endogenous acquisition of network position as a function of exogenous individual characteristics. Specifically, do those with higher expertise attain higher influence when people choose who they listen to endogenously? Using an agent-based modeling (ABM) simulation framework, we model the dynamics of two types of individuals: experts with exogenous information and non-experts who listen to others' information. Over the course of multiple diffusions, agents choose whom to “listen to” for information; dropping less useful ties and adding new ones. We find that experts can have less influence (out-degree) than non-experts who collect information from multiple sources. Furthermore, homophily amongst experts decreases their influence. However, noise in communication channels moderates these effects be- cause non-experts also aggregate errors. We show our results are robust to alternative dynamic networks. Our research suggests that marketers should consider the envi- ronment, community characteristics, communication medium, and product domains to maximize the spread of information.

Endogenous Acquisition of Information and the Equity Home Bias

This paper investigates the extent to which differences in information costs can explain the equity home bias puzzle. In a model where information costs are higher for the Foreign asset than for the Home asset, I show that, if cost functions are convex and the assets have identical return characteristics, the expected size of the home bias in terms of differences in expected demands is positive and increasing in expected excess returns and risk, but decreasing in risk aversion. However, a calibration to US data suggests that information costs can explain only a small fraction of the observed home bias.

Buying Back Subcontractors: The Strategic Limits of Backward Integration

In a model where a monopolistic downstream firm (assembler) negotiates simultaneously with each of its n subcontractors the prices of the complementary components which enter its product, we show that backward integration is limited by a strategic negative effect: the prices and profits of independent suppliers increase when a merger reduces their number. Mergers are profitable only if the downstream firm buys at least two thirds of its suppliers. In an endogenous acquisition game à la Kamien and Zang (1990) the only merged equilibrium occurs when there is only one subcontractor. In a sequential acquisition game full integration is not an equilibrium when the number of suppliers is at least five.

Multidrug-Resistant Gram-Negative Bacteria among Patients Who Require Chronic Hemodialysis

Multidrug-resistant gram-negative bacteria are rapidly spreading throughout the world. The epidemiology of multidrug-resistant gram-negative bacteria in patients who require chronic hemodialysis has not been previously studied. A prospective cohort study of an outpatient hemodialysis unit was conducted. Serial surveillance cultures for multidrug-resistant gram-negative bacteria, vancomycin-resistant enterococci, and methicillin-resistant Staphylococcus aureus were collected from patients who were undergoing chronic hemodialysis. Nineteen (28%) of the 67 enrolled patients were colonized with one or more antimicrobial-resistant bacteria at study enrollment. Eleven (16%), nine (13%), and three (5%) patients were colonized with multidrug-resistant gram-negative bacteria, vancomycin-resistant enterococci, and methicillin-resistant Staphylococcus aureus, respectively. Independent risk factors associated with harboring multidrug-resistant gram-negative bacteria at enrollment were residence in a long-term care facility and antibiotic exposure for > or = 7 d in the previous 3 mo. Twenty-two (40%) of 55 patients who had follow-up cultures acquired at least one antimicrobial-resistant bacterium. A total of 20, 15, and 13% of patients acquired multidrug-resistant gram-negative bacteria, vancomycin-resistant enterococci, and methicillin-resistant Staphylococcus aureus, respectively. Antibiotic exposure was the only independent risk factor for multidrug-resistant gram-negative bacteria acquisition. Endogenous multidrug-resistant gram-negative bacteria acquisition was detected among 69% of acquired multidrug-resistant gram-negative bacterial strains. The prevalence and acquisition of multidrug-resistant gram-negative bacteria surpassed that of vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus. Endogenous acquisition, as opposed to patient-to-patient spread, was the predominant mechanism of acquisition. Residence in a long-term care facility and antibiotic exposure may be important factors promoting the spread of multidrug-resistant gram-negative bacteria among this patient population.

Endogenous Acquisition of Information and the Equity Home Bias

This paper investigates the extent to which differences in information costs can explain the equity home bias puzzle. In a model where information costs are higher for the Foreign asset than for the Home asset, we show that - if cost functions are convex and the assets have identical return characteristics - the expected size of the home bias in terms of differences in expected demands is positive and increasing in expected excess returns and risk, but decreasing in risk aversion. However, a calibration to US data suggests that information costs can explain only a small fraction of the observed home bias.

Asymmetric Vertical Integration

We examine vertical backward integration in a reduced-form model of successive oligopolies. Our key findings are: (i) There may be asymmetric equilibria where some firms integrate and others remain separated, even if firms are symmetric initially; (ii) Efficient firms are more likely to integrate vertically. As a result, integrated firms also tend to have a large market share. The driving force behind these findings are demand/mark-up complementarities in the product market. We also identify countervailing forces resulting from strong vertical foreclosure, upstream sales and endogenous acquisition costs.

Prospective study of nosocomial colonization and infection due to Pseudomonas aeruginosa in mechanically ventilated patients.

To investigate the respective contribution of endogenous and exogenous transmission of Pseudomonas aeruginosa in the colonization of lungs in the mechanically ventilated patient, to estimate the role of P. aeruginosa colonization in the occurrence of severe infections, and to extrapolate appropriate control measures for the prevention of P. aeruginosa ventilator-associated pneumonia. Prospective study of the presence of P. aeruginosa (in stomach fluid, throat specimens, stool, and sputum) on admission, twice a week throughout the patient's stay, and in their environment. O-serotyping, pulsed-field gel electrophoresis, and arbitrarily-primed polymerase chain reaction were used to characterize the strains. The two intensive care units (ICUs 1 and 2) of a university hospital. During a 6-month period, 59 patients were included (21 in ICU 1 and 38 in ICU 2). P. aeruginosa was isolated in 26 patients, including ten pneumonia cases and seven colonizations on admission. The incidence of acquired colonization was statistically different between the two ICUs: 5.5 and 20.5 per 1000 days of mechanical ventilation, in ICUs 1 and 2, respectively. Endogenous acquisition was the main origin of P. aeruginosa colonization (21 of 26 patients) and the upper respiratory tract was the main bacterial reservoir in broncho-pulmonary colonization and infection. However, during the 6-month period of the study, a multidrug-resistant strain of P. aeruginosa O:11, isolated in the sink of the room of 12 patients, was found responsible for two colonizations (1 digestive, 1 throat/lungs) and one pneumonia. As a whole, from 26 cases of colonization/infection with P. aeruginosa, 5 were related to an exogenous contamination (environmental reservoir in 4 patients and cross-contamination in one patient). These results emphasize the need for applying various infection control measures to prevent colonization of patients with P. aeruginosa, including strategies to limit the potential of sinks from acting as a source or reservoir for this bacterium.

Molecular epidemiology of Enterobacter aerogenes acquisition: one-year prospective study in two intensive care units.

To evaluate the respective contributions of patient-to-patient transmission and endogenous acquisition of Enterobacter aerogenes isolates, we conducted a prospective epidemiologic study in two intensive care units (ICUs) between May 1994 and April 1995. We collected a total of 185 E. aerogenes isolates: 130 from 51 patients in a surgical ICU (SICU), 45 from 26 patients in a medical ICU (MICU), and 10 from the environments in these two ICUs. All isolates were typed by random amplification of polymorphic DNA and enterobacterial repetitive intergenic consensus PCR. Among the 175 clinical isolate, we observed 40 different profiles by random amplification of polymorphic DNA and 36 different profiles by enterobacterial repetitive intergenic consensus PCR. We identified a ubiquitous and prevalent clone, corresponding to 58% of SICU and 41% of MICU clinical isolates. Three epidemiologically related strains were specific to each ICU and represented 17% of SICU and 24% of MICU clinical isolates; unique type strains represented 17 and 29% of SICU and MICU clinical isolates, respectively, and E. aerogenes strains which were spread to a limited degree and which were isolated less than five times during the 1-year study period represented 8 and 6% of SICU and MICU clinical isolates, respectively. Our results show that E. aerogenes is acquired in the ICU in three different ways: patient-to-patient spread of a prevalent or an epidemiologically related strain, acquisition de novo of a strain from patients' own flora, and acquisition of a nonendemic strain followed by occasional patient-to-patient transmission. The findings point out the importance of patient-to-patient transmission in E. aerogenes acquisition and suggest that changes in E. aerogenes ecology in the hospital have taken place during the past decade.

Exogenous or endogenous reservoirs of nosocomial Pseudomonas aeruginosa and Staphylococcus aureus infections in a surgical intensive care unit.

A 4 month prospective study was performed to assess the incidence and routes of endogenous or exogenous colonization and nosocomial infection caused by Staphylococcus aureus and Pseudomonas aeruginosa in surgical critically ill patients. A total of 4634 specimens were obtained. Patient's nasal, scalp, and rectal swabs as well as tracheal secretion (TS) were cultured every second day beginning on the day of admission. Nasal swabs and hand cultures of the personnel as well as cultures from gowns were also taken. All isolates of S. aureus were phage typed and 116 of these isolates were also plasmid typed. P. aeruginosa isolates were sero- and pyocin typed. Resistance patterns were determined in all isolates. The study was carried out in the surgical intensive care unit (SICU) of an teaching hospital. During the study period each patient (a total of 153 patients) admitted to the SICU entered the study. P. aeruginosa and S. aureus colonisation rate on admission were 5% and 36.5% respectively. Only 10 patients (6.5%) were colonized with P. aeruginosa during hospitalization, and only 7 patients (4.5%) acquired S. aureus in the surgical intensive care unit (SICU). The most common primary colonisation site of P. aeruginosa was the rectum, whereas S. aureus was predominantly found in nasal cultures. Horizontal transmission of S. aureus occurred in only 2 patients. The study suggests that colonisation with P. aeruginosa and S. aureus occurs from endogenous rather than from exogenous sources and that the endogenous acquisition of both bacteria play a more important role in development of nosocomial infections than the exogenous route of transmission.

Characterization of the sequence of colonization and nosocomial candidemia using DNA fingerprinting and a DNA probe

The objective of this hospital-based study was to determine the relationship between colonizing and infecting strains of Candida species and Torulopsis glabrata. Surveillance cultures from high-risk patients were paired with subsequent bloodstream isolates. Organisms were typed by using restriction endonuclease digestion of chromosomal DNA with BstNI and EcoRI, followed by Southern hybridization with a DNA probe (pBD4) derived from Saccharomyces cerevisiae. Sixteen patients for whom documented colonization preceded documented bloodstream infection were identified. The mean time between obtainment of surveillance isolates and obtainment of bloodstream isolates was 8 days, with a range of 1 to 423 days. For 15 (94%) of 16 patients, the DNA fingerprint pattern (using BstNI) of the surveillance isolate was identical to that of the bloodstream isolate. Isolates from 13 (81%) of 16 patients were unique to those patients. Typing by Southern hybridization with the pBD4 probe was less discriminating. We conclude that for a well-defined subset of hospitalized patients who were colonized by Candida species before developing nosocomial candidemia, the colonizing and infecting strains were identical, suggesting endogenous acquisition of infection. Restriction endonuclease digestion of chromosomal DNA was shown to be a discriminating and reproducible typing method for Candida species and T. glabrata.

Informed Speculation with Imperfect Competition

Competitive rational expectations models have the unsatisfactory property, dubbed the problem by Hellwig, that each trader takes the equilibrium price as given despite the fact that he influences that price. An examination of information aggregation in a non-competitive rational expectations model using a Nash equilibrium in demand functions shows that the schizophrenia problem is avoided by having each trader take into account the effect his demand has on the equilibrium price. Given a distribution of private information across traders, prices reveal less information than in the competition equilibrium, and prices no longer become fully informative in the limit as noise trading vanishes or as traders become risk neutral. With small traders, the model may become one of monopolistic competition, not perfect competition. In contrast to the competitive model, a reasonable model of endogenous acquisition of costly private information is obtained, even when traders are risk-neutral.