Noroviruses as a Cause of Diarrhea in Immunocompromised Pediatric Hematopoietic Stem Cell and Solid Organ Transplant Recipients.

Case reports describe significant norovirus gastroenteritis morbidity in immunocompromised patients. We evaluated norovirus pathogenesis in prospectively enrolled solid organ (SOT) and hematopoietic stem cell transplant (HSCT) patients with diarrhea who presented to Texas Children's Hospital and submitted stool for enteric testing. Noroviruses were detected by real-time reverse transcription polymerase chain reaction. Clinical outcomes of norovirus diarrhea and non-norovirus diarrhea patients, matched by transplanted organ type, were compared. Norovirus infection was identified in 25 (22%) of 116 patients, more frequently than other enteropathogens. Fifty percent of norovirus patients experienced diarrhea lasting ≥14 days, with median duration of 12.5 days (range 1-324 days); 29% developed diarrhea recurrence. Fifty-five percent of norovirus patients were hospitalized for diarrhea, with 27% requiring intensive care unit (ICU) admission. One HSCT recipient developed pneumatosis intestinalis. Three HSCT patients expired ≤6 months of norovirus diarrhea onset. Compared to non-norovirus diarrhea patients, norovirus patients experienced significantly more frequent ICU admission (27% vs. 0%, p = 0.02), greater serum creatinine rise (median 0.3 vs. 0.2 mg/dL, p = 0.01), and more weight loss (median 1.6 vs. 0.6 kg, p < 0.01). Noroviruses are an important cause of diarrhea in pediatric transplant patients and are associated with significant clinical complications.

Defining acute renal dysfunction as a criterion for the severity of Clostridium difficile infection in patients with community-onset vs hospital-onset infection.

BACKGROUND: Acute renal dysfunction can be used to define severe Clostridium difficile infection (CDI). The Society for Healthcare Epidemiology of America (SHEA) and Infectious Disease Society of America (IDSA) guidelines define acute renal dysfunction as serum creatinine (SrCr) ≥1.5 times the premorbid level. AIM: To determine the ability to assess premorbid SrCr in hospitalized patients with CDI, stratified into community-onset CDI (CO-CDI) and hospital-onset CDI (HO-CDI); and to evaluate differing definitions for premorbid SrCr as a criterion for acute renal dysfunction. METHODS: Hospitalized patients with CDI were stratified into CO-CDI and HO-CDI. The ability to assess premorbid SrCr was determined, and the incidence of acute renal dysfunction and the severity of CDI were compared using varying definitions of premorbid SrCr. FINDINGS: In total, 293 patients with CDI were evaluated; of these, 135 (46%) had CO-CDI and 158 (54%) had HO-CDI. Premorbid SrCr data were not available for 37 (27%) patients with CO-CDI and one (<1%) patient with HO-CDI (P < 0.0001). Depending on the definition of premorbid SrCr used, acute renal dysfunction ranged from 17% to 24% for patients with CO-CDI (P = 0.26), and from 13% to 14% for HO-CDI (P = 0.81). The severity of CDI could not be determined for 43 out of 293 (15%) patients, primarily due to the lack of premorbid SrCr data (N = 38). CONCLUSION: Assessment of acute renal dysfunction and the severity of CDI was not possible for many patients with CO-CDI using the current SHEA/IDSA guidelines. Given the increasing incidence of CO-CDI, an alternative definition of acute renal dysfunction may be required.

Disseminated histoplasmosis manifesting as a soft-tissue chest wall mass in a heart transplant recipient.

Soft-tissue masses are rarely associated with Histoplasma capsulatum infection. We describe a heart transplant patient who presented with a large right-sided chest wall mass as a manifestation of disseminated histoplasmosis. A successful clinical outcome was achieved upon recognition of the fungal pathogen.

Sequence and analysis of chromosome 1 of the plant Arabidopsis thaliana.

The genome of the flowering plant Arabidopsis thaliana has five chromosomes. Here we report the sequence of the largest, chromosome 1, in two contigs of around 14.2 and 14.6 megabases. The contigs extend from the telomeres to the centromeric borders, regions rich in transposons, retrotransposons and repetitive elements such as the 180-base-pair repeat. The chromosome represents 25% of the genome and contains about 6,850 open reading frames, 236 transfer RNAs (tRNAs) and 12 small nuclear RNAs. There are two clusters of tRNA genes at different places on the chromosome. One consists of 27 tRNA(Pro) genes and the other contains 27 tandem repeats of tRNA(Tyr)-tRNA(Tyr)-tRNA(Ser) genes. Chromosome 1 contains about 300 gene families with clustered duplications. There are also many repeat elements, representing 8% of the sequence.

Sequence and analysis of chromosome 2 of the plant Arabidopsis thaliana.

Arabidopsis thaliana (Arabidopsis) is unique among plant model organisms in having a small genome (130-140 Mb), excellent physical and genetic maps, and little repetitive DNA. Here we report the sequence of chromosome 2 from the Columbia ecotype in two gap-free assemblies (contigs) of 3.6 and 16 megabases (Mb). The latter represents the longest published stretch of uninterrupted DNA sequence assembled from any organism to date. Chromosome 2 represents 15% of the genome and encodes 4,037 genes, 49% of which have no predicted function. Roughly 250 tandem gene duplications were found in addition to large-scale duplications of about 0.5 and 4.5 Mb between chromosomes 2 and 1 and between chromosomes 2 and 4, respectively. Sequencing of nearly 2 Mb within the genetically defined centromere revealed a low density of recognizable genes, and a high density and diverse range of vestigial and presumably inactive mobile elements. More unexpected is what appears to be a recent insertion of a continuous stretch of 75% of the mitochondrial genome into chromosome 2.