The H-mshi antigen is conserved among standard BALB/cBy, C57BL/6J, and wild-derived CAST/Ei and SPRET/Ei inbred strains of mice

 The recessive male sterility and histoincompatibility mutation (mshi) arose spontaneously in the standard inbred mouse strain BALB/cBy. In addition to generating sterility in homozygous males, mshi controls the loss of a minor histocompatibility antigen designated H-mshi. To determine whether the H-mshi antigen normally expressed by the BALB/cBy strain (H-mshi^c) is the same as or different from the antigen (H-mshi^x) expressed by the standard inbred C57BL/6J strain or the wild-derived CAST/Ei and SPRET/Ei strains, animals heterozygous for the mutant antigen-loss allele (H-mshi ^– ) and H-mshi ^x were grafted with tail skin from BALB/cBy mice. The long-term retention of grafts by these hosts indicates that the H-mshi antigen encoded by the BALB/cBy, C57BL/6J, CAST/Ei, and SPRET/Ei strains is histogenically identical. Conservation of this minor histocompatibility antigen among these evolutionarily diverse strains suggests that H-mshi encodes a functionally important cellular product(s). Received: 1 August 1998 / Accepted: 26 October 1998     

Population genomics of the pathogenic yeast Candida tropicalis identifies hybrid isolates in environmental samples

Candida tropicalis is a human pathogen that primarily infects the immunocompromised. Whereas the genome of one isolate, C. tropicalis MYA-3404, was originally sequenced in 2009, there have been no large-scale, multi-isolate studies of the genetic and phenotypic diversity of this species. Here, we used whole genome sequencing and phenotyping to characterize 77 isolates of C. tropicalis from clinical and environmental sources from a variety of locations. We show that most C. tropicalis isolates are diploids with approximately 2–6 heterozygous variants per kilobase. The genomes are relatively stable, with few aneuploidies. However, we identified one highly homozygous isolate and six isolates of C. tropicalis with much higher heterozygosity levels ranging from 36–49 heterozygous variants per kilobase. Our analyses show that the heterozygous isolates represent two different hybrid lineages, where the hybrids share one parent (A) with most other C. tropicalis isolates, but the second parent (B or C) differs by at least 4% at the genome level. Four of the sequenced isolates descend from an AB hybridization, and two from an AC hybridization. The hybrids are MTLa/α heterozygotes. Hybridization, or mating, between different parents is therefore common in the evolutionary history of C. tropicalis. The new hybrids were predominantly found in environmental niches, including from soil. Hybridization is therefore unlikely to be associated with virulence. In addition, we used genotype-phenotype correlation and CRISPR-Cas9 editing to identify a genome variant that results in the inability of one isolate to utilize certain branched-chain amino acids as a sole nitrogen source.     

Inapparent genital infection with Chlamydia trachomatis and its potential role in the genesis of Reiters syndrome.

An infectious etiology has been suggested for Reiter's syndrome (RS) because the disease has often been observed to follow episodes of urethritis or dysentery. Despite demonstrations of bacterial antigens in the synovial tissues of RS patients, it is not clear whether viable organisms are present in the synovium in any particular stage of this disease. Furthermore, it is not clear how either viable organisms or their product(s) might reach the joints. Infection with the bacterium Chlamydia trachomatis is the most common sexually transmitted disease in the United States, and as such this organism has emerged as a primary pathogen associated with RS. Previous work from our group has shown that synovial biopsy tissues from a majority of RS patients studied show significant levels of apparently intact chlamydial RNA, even when synovial or urethral cultures from the same patients are unequivocally negative for the organism. We show here that inapparent urethral infection with chlamydia occurs with high prevalence in men, and that inapparent cervical infection with the organism occurs at high prevalence in women. These data provide an important link in the relationship between initial chlamydial infection and possible subsequent genesis of RS, and they may give useful insight into mechanisms by which chlamydial infection can lead to development of this disease. Our data argue further that inapparent infection may be a significant factor in pathogenesis for all chlamydia-related diseases, and they suggest that, contrary to current ideas, C. trachomatis can generate disseminated infection.     

An Outbreak of Cryptosporidium parvum across England & Scotland Associated with Consumption of Fresh Pre-Cut Salad Leaves,May 2012

BackgroundWe report a widespread foodborne outbreak of Cryptosporidium parvum in England and Scotland in May 2012. Cases were more common in female adults, and had no history of foreign travel. Over 300 excess cases were identified during the period of the outbreak. Speciation and microbiological typing revealed the outbreak strain to be C. parvum gp60 subtype IIaA15G2R1.MethodsHypothesis generation questionnaires were administered and an unmatched case control study was undertaken to test the hypotheses raised. Cases and controls were interviewed by telephone. Controls were selected using sequential digit dialling. Information was gathered on demographics, foods consumed and retailers where foods were purchased.ResultsSeventy-four laboratory confirmed cases and 74 controls were included in analyses. Infection was found to be strongly associated with the consumption of pre-cut mixed salad leaves sold by a single retailer. This is the largest documented outbreak of cryptosporidiosis attributed to a food vehicle.     

Evaluation of the National Notifiable Diseases Surveillance System for Dengue Fever in Taiwan, 2010–2012

BackgroundIn Taiwan, around 1,500 cases of dengue fever are reported annually and incidence has been increasing over time. A national web-based Notifiable Diseases Surveillance System (NDSS) has been in operation since 1997 to monitor incidence and trends and support case and outbreak management. We present the findings of an evaluation of the NDSS to ascertain the extent to which dengue fever surveillance objectives are being achieved.MethodologyWe extracted the NDSS data on all laboratory-confirmed dengue fever cases reported during 1 January 2010 to 31 December 2012 to assess and describe key system attributes based on the Centers for Disease Control and Prevention surveillance evaluation guidelines. The system’s structure and processes were delineated and operational staff interviewed using a semi-structured questionnaire. Crude and age-adjusted incidence rates were calculated and key demographic variables were summarised to describe reporting activity. Data completeness and validity were described across several variables.Conclusions/SignificanceThe NDSS for dengue fever surveillance is a robust, well maintained and acceptable system that supports the collection of complete and valid data needed to achieve the surveillance objectives. The simplicity of the system engenders compliance leading to timely and accurate reporting. Completeness of hospitalization information could be further improved to allow assessment of severity of illness. To minimize misclassification, an algorithm to accurately classify travel cases should be established.