How do host population dynamics impact Lyme disease risk dynamics in theoretical models?

Lyme disease is the most common wildlife-to-human transmitted disease reported in North America. The study of this disease requires an understanding of the ecology of the complex communities of ticks and host species involved in harboring and transmitting this disease. Much of the ecology of this system is well understood, such as the life cycle of ticks, and how hosts are able to support tick populations and serve as disease reservoirs, but there is much to be explored about how the population dynamics of different host species and communities impact disease risk to humans. In this study, we construct a stage-structured, empirically-informed model with host dynamics to investigate how host population dynamics can affect disease risk to humans. The model describes a tick population and a simplified community of three host species, where primary nymph host populations are made to fluctuate on an annual basis, as commonly observed in host populations. We tested the model under different environmental conditions to examine the effect of environment on the interactions of host dynamics and disease risk. Results show that allowing for host dynamics in the model reduces mean nymphal infection prevalence and increases the maximum annual prevalence of nymphal infection and the density of infected nymphs. Effects of host dynamics on disease measures of nymphal infection prevalence were nonlinear and patterns in the effect of dynamics on amplitude in nymphal infection prevalence varied across environmental conditions. These results highlight the importance of further study of the effect of community dynamics on disease risk. This will involve the construction of further theoretical models and collection of robust field data to inform these models. With a more complete understanding of disease dynamics we can begin to better determine how to predict and manage disease risk using these models.

Mutualisms in a warming world.

Predicting the impacts of global warming on mutualisms poses a significant challenge given the functional and life history differences that usually exist among interacting species. However, this is a critical endeavour since virtually all species on Earth depend on other species for survival and/or reproduction. The field of thermal ecology can provide physiological and mechanistic insights, as well as quantitative tools, for addressing this challenge. Here, we develop a conceptual and quantitative framework that connects thermal physiology to species' traits, species' traits to interacting mutualists' traits and interacting traits to the mutualism. We first identify the functioning of reciprocal mutualism-relevant traits in diverse systems as the key temperature-dependent mechanisms driving the interaction. We then develop metrics that measure the thermal performance of interacting mutualists' traits and that approximate the thermal performance of the mutualism itself. This integrated approach allows us to additionally examine how warming might interact with resource/nutrient availability and affect mutualistic species' associations across space and time. We offer this framework as a synthesis of convergent and critical issues in mutualism science in a changing world, and as a baseline to which other ecological complexities and scales might be added.

Continent-wide tree fecundity driven by indirect climate effects.

Indirect climate effects on tree fecundity that come through variation in size and growth (climate-condition interactions) are not currently part of models used to predict future forests. Trends in species abundances predicted from meta-analyses and species distribution models will be misleading if they depend on the conditions of individuals. Here we find from a synthesis of tree species in North America that climate-condition interactions dominate responses through two pathways, i) effects of growth that depend on climate, and ii) effects of climate that depend on tree size. Because tree fecundity first increases and then declines with size, climate change that stimulates growth promotes a shift of small trees to more fecund sizes, but the opposite can be true for large sizes. Change the depresses growth also affects fecundity. We find a biogeographic divide, with these interactions reducing fecundity in the West and increasing it in the East. Continental-scale responses of these forests are thus driven largely by indirect effects, recommending management for climate change that considers multiple demographic rates.

Safety and Efficacy of Segmental Yttrium-90 Radioembolization for Hepatocellular Carcinoma after Transjugular Intrahepatic Portosystemic Shunt Creation.

PURPOSE: To evaluate safety and efficacy of segmental yttrium-90 (Y90) radioembolization for hepatocellular carcinoma (HCC) after transjugular intrahepatic portosystemic shunt (TIPS) placement. The hypothesis was liver sparing segmental Y90 for HCC after TIPS would provide high antitumor response with a tolerable safety profile. MATERIALS AND METHODS: This single-arm retrospective study included 39 patients (16 women, 23 men) with ages 49-81 years old who were treated with Y90. Child-Pugh A/B liver dysfunction was present in 72% (28/39) with a median Model for End-stage Liver Disease score of 18 (95% confidence interval, 16.4-19.4). Primary outcomes were clinical and biochemical toxicities and antitumor imaging response by World Health Organization (WHO) and European Association for the Study of the Liver (EASL) criteria. Secondary outcomes were orthotopic liver transplantation (OLT), time to progression (TTP), and overall survival (OS) estimates by the Kaplan-Meier method. RESULTS: The 30-day mortality was 0%. Grade 3+ clinical adverse events and grade 3+ hyperbilirubinemia occurred in 5% (2/39) and 0% (0/39), respectively. Imaging response was achieved in 58% (22/38, WHO criteria) and 74% (28/38, EASL criteria), respectively. Median TTP was 16.1 months for any cause and 27.5 months for primary index lesions. OLT was completed in 88% (21/24) of listed patients at a median time of 6.1 months (range, 0.9-11.7 months). Median OS was 31.6 months and 62.9 months censored and uncensored to OLT, respectively. CONCLUSIONS: Segmental Y90 for HCC appears safe and efficacious in patients after TIPS. Preserved transplant eligibility suggests that Y90 is a useful tool for bridging these patients to liver transplantation.

Trends and Transitions in 150 Years of The American Naturalist.

The American Naturalist recently passed its sesquicentennial. Throughout this long history, it regularly encountered moments of introspection and debate over its goals, mission, identity, and audience. Here, we chronicle the history of those debates and transitions at critical moments. The Naturalist began as a popular magazine for amateur naturalists in the late 1860s. In the late 1870s, it transitioned to an increasingly academic journal for professional scientists from all branches of the natural sciences. By the turn of the century, academic specialization led to increasing fragmentation of the sciences into a multitude of societies and journals, creating an identity crisis for the once-broad-reaching American Naturalist. This identity crisis was resolved when the journal pivoted around 1910 to focus on fundamental advances in the newly emerging field of genetics. In the 1960s, the journal underwent a remarkably rapid transition to its present focus on evolution and ecology. The profound shifts in the journal's contents over this time are a reflection of the historical changes in science as a whole: from amateur naturalists, to polymath professionals, to increasingly specialized academics. This chronicle reveals the ways in which The American Naturalist has left its mark on many disciplines, many of which are today only loosely affiliated with the journal, if at all.

A Case of Drug-Induced Liver Injury Secondary to Natalizumab.

A 33-year-old Caucasian female with relapsing-remitting multiple sclerosis presented with abdominal pain, nausea, and vomiting and was found to have acute liver injury. After thorough investigation, she was diagnosed with drug-induced liver injury (DILI) thought secondary to redosing of Natalizumab therapy.

Case Series of 10 Patients with Cirrhosis Undergoing Emergent Repair of Ruptured Umbilical Hernias: Natural History and Predictors of Outcomes.

OBJECTIVES: Ascites represents an important event in the natural history of cirrhosis, portending increased 1-year mortality. Umbilical herniation with rupture is an uncommon complication of large-volume ascites that is associated with significant morbidity and mortality. The aim of this study was to describe predictors of outcomes in patients undergoing emergent repair for spontaneous umbilical hernia rupture. MATERIALS AND METHODS: We report a case series of 10 patients with decompensated cirrhosis (mean age 66 ± 9 years, mean Model for End-Stage Liver Disease score of 21 ± 7) who presented with a ruptured umbilical hernia and had emergent repair. RESULTS: Thirty percent (3/10) of patients died or required liver transplant. Factors associated with death or transplant included the development of bacterial peritonitis (P = .03) and the presurgical 30-day Mayo Clinic Postoperative Mortality Risk in Patient with Cirrhosis Score (P = .03). CONCLUSIONS: Emergent repair after umbilical hernia rupture in patients with decompensated cirrhosis carries a poor prognosis with 30% of patients developing poor postsurgical outcomes.

Procalcitonin, and cytokines document a dynamic inflammatory state in non-infected cirrhotic patients with ascites.

AIM: To quantitate the simultaneous serum and ascitic fluid levels of procalcitonin and inflammatory markers in cirrhotics with and without ascites. METHODS: A total of 88 consecutive severe cirrhotic patients seen in a large city hospital liver clinic were studied and divided into two groups, those with and without ascites. Group 1 consisted of 41 cirrhotic patients with massive ascites, as demonstrated by necessity for therapeutic large-volume paracentesis. Group 2 consisted of 47 cirrhotic patients without any clinically documented ascites to include either a recent abdominal computed tomography scan or ultrasound study. Serum and ascitic fluid levels of an array of inflammatory markers, including procalcitonin, were measured and compared to each other and a normal plasma panel (NPP). RESULTS: The values for inflammatory markers assayed in the serum of Groups 1 and 2, and ascitic fluid of the Group 1. The plasma levels of the inflammatory cytokines interleukin (IL)-2, IL-4, IL-6, IL-8, interferon gamma (IFNγ) and epidermal growth factor (EGF) were all significantly greater in the serum of Group 1 as compared to that of the serum obtained from the Group 2 subjects (all P < 0.05). There were significantly greater serum levels of IL-6, IL-8, IL-10, monocyte chemoattractant protein-1, tumor necrosis factor-α, vascular endothelial growth factor and EGF when comparing Group 2 to the NPP. There was no significant difference for IL-1A, IL-1B, IL-2, IL-4 and IFNγ levels between these two groups. Serum procalcitonin levels were increased in cirrhotics with ascites compared to cirrhotics without ascites, but serum levels were similar to ascites levels within the ascites group. Furthermore, many of these cytokines, but not procalcitonin, demonstrate an ascites-to-serum gradient. Serum procalcitonin does not demonstrate any significant difference segregated by liver etiology in the ascites group; but ascitic fluid procalcitonin is elevated significantly in cardiac cirrhosis/miscellaneous subgroup compared to the hepatitis C virus and alcoholic cirrhosis subgroups. CONCLUSION: Procalcitonin in the ascitic fluid, but not in the serum, differentiates between cirrhotic subgroup reflecting the dynamic interplay of ascites, bacterial translocation and the peri-peritoneal cytokine.

Cirrhotic ascites review: Pathophysiology, diagnosis and management.

Ascites is a pathologic accumulation of peritoneal fluidcommonly observed in decompensated cirrhotic states.Its causes are multi-factorial, but principally involve significant volume and hormonal dysregulation in the setting of portal hypertension. The diagnosis of ascites is considered in cirrhotic patients given a constellation of clinical and laboratory findings, and ultimately confirmed, with insight into etiology, by imaging and paracentesis procedures. Treatment for ascites is multi-modal including dietary sodium restriction, pharmacologic therapies, diagnostic and therapeutic paracentesis, and in certain cases transjugular intra-hepatic portosystemic shunt. Ascites is associated with numerous complications including spontaneous bacterial peritonitis, hepato-hydrothorax and hepatorenal syndrome. Given the complex nature of ascites and associatedcomplications, it is not surprising that it heralds increased morbidity and mortality in cirrhotic patients and increased cost-utilization upon the health-care system. This review will detail the pathophysiology of cirrhotic ascites, common complications derived from it, and pertinent treatment modalities.

Colonic diffuse large B-cell lymphoma in a liver transplant patient with historically very low tacrolimus levels.

Posttransplant lymphoproliferative disorders (PTLDs) comprise a wide spectrum of hematologic malignancies that are found increasingly in orthotopic liver transplant (OLT) patients given the rising frequency of these surgeries and their long-term success. PTLDs are highly correlated with both the Epstein-Barr virus (EBV) infection and the degree of immunosuppression involved. Herein is reported a case of a 53-year-old male with successfully treated hepatitis C virus genotype 4 and hepatocellular carcinoma who underwent OLT and developed symptoms of weakness and poor appetite 4 years later while on tacrolimus 3 mg b.i.d. with historically very low plasma levels. He was found to be anemic and colonoscopy revealed a 4.5 cm cecal diffuse large B-cell lymphoma (DLBCL). Further workup revealed mesenteric lymph node enlargement consistent and nodal DLBCL dissemination. He was treated with cyclophosphamide-hydroxyldaunorubicin-oncovin-prednisone-rituximab (CHOP-R) chemotherapy and his tacrolimus dose was lowered. Additionally, he manifested PTLD-associated cryoglobulinemia leading to acute kidney injury. After a prolonged hospitalization he was discharged with close followup.

Community-associated and healthcare-associated methicillin-resistant Staphylococcus aureus virulence toward Caenorhabditis elegans compared.

Community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged as major human pathogens. CA-MRSA virulence appears to be distinct from healthcare-associated (HA) MRSA with several factors [α-hemolysin (Hla), Panton-Valentine leukocidin (PVL), α-type phenol soluble modulins (PSMα) and SCCmec IV] postulated to enhance virulence or fitness. Using the Caenorhabditis elegans infection model, we compared the virulence of clinical and laboratory isolates of CA-MRSA and HA-MRSA and explored the contribution of CA-MRSA associated virulence factors to nematode killing. All CA-MRSA strains were highly pathogenic to nematodes, while HA-MRSA strains demonstrated variable nematode killing. Nematode killing by isogenic mutants of hla or the loci for PVL, PSMα, PSMß, PSMδ or SCCmec IV was not different than the parental strains. These results demonstrate that CA-MRSA is highly virulent, shows some strains of HA-MRSA are equally virulent toward nematodes and suggests CA-MRSA virulence in C. elegans is not linked to a single virulence factor.

Fungal infections: their diagnosis and treatment in transplant recipients.

Systemic fungal infections typically occur in individuals who are seriously ill with recognized risk factors such as those frequently found in transplant recipients. Unfortunately, they are often diagnosed late, when the efficacy of the available treatments is low, often less than 50%, and the cost in terms of lives lost, hospital length of stay, and total hospital costs is substantially increased. The application of antifungal therapies associated with reported efficacy rates greater than 50% are those used prophylactically. When used prophylactically, these infections are reduced in greater than 95% of the expected cases. The choice of a prophylactic agent should be based upon its ease of administration, lack of adverse effects, reduced likelihood of potential drug interactions, and its efficacy in patients with established risk factors and comorbid disease processes that include renal, hepatic, and chronic pulmonary disease. The indications for the use of currently available antifungal agents, their adverse effects, drug interactions, ease of dosing, and applicability in patients with preexisting disease states, and especially in liver transplant recipients, are presented in this paper.

Consensus interferon used to treat prior partial-responders to pegylated interferon plus ribavirin.

BACKGROUND: The response to pegylated interferon (peg-IFN) plus ribavirin therapy remains less than ideal with 40-50% of treated subjects failing to clear the virus. Moreover, retreatment is only minimally effective. Consensus interferon (c-IFN) has been shown to be efficacious in HCV genotype 1 patients who have failed therapy with peg-IFN. AIM: To evaluated the response to re-treatment of peg-IFN plus ribavirin partial-responders with c-IFN plus ribavirin. METHODS: Forty-two subjects who had previously failed to clear virus after treatment with peg-IFN plus ribavirin were treated with c-IFN (15 µg/day) plus ribavirin (800-1,200 mg/day) until 12 months of therapy or a total of six consecutive months of PCR negativity was achieved. RESULTS: The study population consisted predominantly of males (71%), Caucasians (76%), with African Americans comprising the remaining 24%, subjects with HCV genotype 1 infection (81%) and 21% had cirrhosis by liver biopsy. The overall SVR rate was 29%. The only pretreatment variable that distinguished responders from partial-responders was the serum triglyceride level. CONCLUSIONS: The use of c-IFN plus ribavirin in the retreatment of prior peg-IFN plus ribavirin partial responders is essentially twice that achieved in prior re-treatment regimens consisting of a second course of peg-IFN plus ribavirin. These results will need to be evaluated against the use of triple therapy consisting of a peg-IFN plus ribavirin and a protease inhibitor. More studies utilizing c-IFN plus ribavirin with either a protease inhibitor or polymerase inhibitor need to be performed as well.

Continuous peritoneal drainage of large-volume ascites.

BACKGROUND: With the increasing population of individuals with cirrhosis, many of whom are not liver transplant candidates, large volume paracentesis as a medical therapy for ascites resistant to diuretic therapy has become increasingly utilized. AIM: To determine the safety and efficacy of continuous peritoneal drainage of large-volume ascites in Child Class-C cirrhosis. Subjects with no current clinical or laboratory findings of spontaneous bacterial ascites were studied. Each had a complete medical evaluation to document the etiology and severity of their liver disease as well as the identification of any confounding medical illness. A triple-phase abdominal CT of the abdomen was obtained in each individual to rule out any hepatoma. Upon completion of the above, a pericardiocentesis catheter was placed in the abdomen using the Seldinger technique and the ascites was drained continuously (to gravity) until no additional ascitic fluid could be removed or the total time of drainage was 72 h. The patient's weight, volume of ascitic fluid removed, ascitic fluid cell counts, ascitic fluid cultures, complete blood count and comprehensive metabolic profile were obtained immediately before and after the peritoneal catheter was removed. RESULTS: HCV cirrhosis accounted for 12 cases and alcoholic liver disease accounted for 8 cases (half the total of 40 cases), with 6 other diseases accounting for the remaining half. The ascitic fluid was drained continuously for 2.5 ± 0.08 days, with a removal of 13.3 ± 0.5 l of ascitic fluid. No clinically significant change in the serum creatinine or ascitic fluid cells count occurred as a result of the procedure. The adverse effects of the procedure were minimal. 63% of the patients experienced some mild discomfort at the catheter insertion site, or local abdominal pain just prior to the removal of the catheter. Two patients developed a small abdominal wall hematoma that required no therapy. No patients experienced peritoneal hemorrhage, infection or renal dysfunction. CONCLUSION: (1) Continuous large-volume peritoneal drainage by gravity is safe and effective; (2) if the procedure is limited 72 h, no cases of ascitic fluid contamination/infection occur; and (3) it reduces the time between subsequent paracentesis based upon historical data.

Risk factors for Burkholderia cepacia complex bacteremia among intensive care unit patients without cystic fibrosis: a case-control study.

BACKGROUND: The Burkholderia cepacia complex is associated with colonization or disease in patients with cystic fibrosis (CF). For patients without CF, this complex is poorly understood apart from its presence in occasional point source outbreaks. OBJECTIVE: To investigate risk factors for B. cepacia bacteremia in hospitalized, intensive care unit patients without CF. METHODS: We identified patients with 1 or more blood cultures positive for B. cepacia between May 1, 1996, and March 31, 2002, excluding those with CF. Control patients were matched to case patients by ward, duration of hospitalization, and onset date of bacteremia. Matched analyses were used to identify risk factors for B. cepacia bacteremia. RESULTS: We enrolled 40 patients with B. cepacia bacteremia into the study. No environmental or other point source for B. cepacia complex was identified, although horizontal spread was suspected. Implementation of contact precautions was effective in decreasing the incidence of B. cepacia bacteremia. We selected 119 matched controls. Age, sex, and race were similar between cases and controls. In multivariable analysis, renal failure that required dialysis, recent abdominal surgery, 2 or more bronchoscopic procedures before detection of B. cepacia bacteremia, tracheostomy, and presence of a central line before detection of B. cepacia bacteremia were independently associated with development of B. cepacia bacteremia, whereas presence of a percutaneous feeding tube was associated with a lower risk of disease. CONCLUSIONS: B. cepacia complex is an important emerging group of nosocomial pathogens in patients with and patients without CF. Nosocomial spread is likely facilitated by cross-transmission, frequent pulmonary procedures, and central venous access. Infection control measures appear useful for limiting the spread of virulent, transmissible clones of B. cepacia complex.

X-ray volumetric imaging in image-guided radiotherapy: the new standard in on-treatment imaging.

PURPOSE: X-ray volumetric imaging (XVI) for the first time allows for the on-treatment acquisition of three-dimensional (3D) kV cone beam computed tomography (CT) images. Clinical imaging using the Synergy System (Elekta, Crawley, UK) commenced in July 2003. This study evaluated image quality and dose delivered and assessed clinical utility for treatment verification at a range of anatomic sites. METHODS AND MATERIALS: Single XVIs were acquired from 30 patients undergoing radiotherapy for tumors at 10 different anatomic sites. Patients were imaged in their setup position. Radiation doses received were measured using TLDs on the skin surface. The utility of XVI in verifying target volume coverage was qualitatively assessed by experienced clinicians. RESULTS: X-ray volumetric imaging acquisition was completed in the treatment position at all anatomic sites. At sites where a full gantry rotation was not possible, XVIs were reconstructed from projection images acquired from partial rotations. Soft-tissue definition of organ boundaries allowed direct assessment of 3D target volume coverage at all sites. Individual image quality depended on both imaging parameters and patient characteristics. Radiation dose ranged from 0.003 Gy in the head to 0.03 Gy in the pelvis. CONCLUSIONS: On-treatment XVI provided 3D verification images with soft-tissue definition at all anatomic sites at acceptably low radiation doses. This technology sets a new standard in treatment verification and will facilitate novel adaptive radiotherapy techniques.

Virulence associated with outbreak-related strains of Burkholderia cepacia complex among a cohort of patients with bacteremia.

The Burkholderia cepacia complex includes 9 genomovars. The relative virulence of each is unknown. Host and pathogen features associated with mortality were evaluated among patients with B. cepacia complex bacteremia. Cases were ascertained through review of blood culture results for the period of May 1996 through May 2002. Isolates were identified to species level with 16S rDNA and recA-based species-specific polymerase chain reaction analyses and recA restriction fragment-length polymorphism. Strain typing was performed with pulsed-field gel electrophoresis. Fifty-three patients with B. cepacia complex bacteremia were identified; only 9 (17%) had cystic fibrosis. Twenty-five patients (47%) died within 14 days of bacteremia. After controlling for comorbid conditions and therapeutic interventions, 2 outbreak-related strains of Burkholderia cenocepacia (genomovar III) were associated with 14-day mortality (odds ratio, 5.5; 95% confidence interval, 1.20-25.02). B. cenocepacia is an emerging nosocomial pathogen. Certain strains are associated with an enhanced capacity for interpatient spread and poor outcome.

Increasing rates of cardiac device infections among Medicare beneficiaries: 1990-1999.

BACKGROUND: Although cardiac devices have been found to reduce symptoms and mortality rates in appropriate patient populations, the implications of certain important risks, such as infection, are incompletely understood. The purpose of this study was to use a large population-based database to define the population that is at risk for cardiac device infections, determine the prevalence of device infections, and study changes in the rates of cardiac device implantation and infection in the past decade. METHODS: Patients with cardiac device implantations and infections were identified with claims files from the Health Care Finance Administration for Medicare beneficiaries from January 1, 1990, through December 31, 1999. Rates of implantation of cardiac devices were determined. Time trend analyses were performed to determine the significance of the observed change in rates. RESULTS: Cardiac device implantation rates increased from 3.26 implantations per 1000 beneficiaries in 1990 to 4.64 implantations per 1000 beneficiaries in 1999, which represents an increase of 42% in 10 years (P for trend <.001). Cardiac device infections showed a larger increase, from 0.94 device infections per 1000 beneficiaries in 1990 to 2.11 device infections per 1000 beneficiaries in 1999, which represents an increase of 124% during the study period (P for trend <.001). CONCLUSIONS: During the previous decade, there was a significant increase in both cardiac device implantations and infections in elderly patients, although the increase in the rates of device infections was substantially higher. Additional studies are needed to better understand the relationship and timing between cardiac device implantation and infection.