Epidemiology and characteristics of the dengue outbreak in Guangdong, Southern China, in 2014.

Dengue is a rapidly spreading mosquito-borne disease caused by the dengue virus (DENV) and has emerged as a severe public health problem around the world. Guangdong, one of the southern Chinese provinces, experienced a serious outbreak of dengue in 2014, which was believed to be the worst dengue epidemic in China over the last 20 years. To better understand the epidemic, we collected the epidemiological data of the outbreak and analyzed 14,594 clinically suspected dengue patients from 25 hospitals in Guangdong. Dengue cases were then laboratory-confirmed by the detection of DENV non-structural protein 1 (NS1) antigen and/or DENV RNA. Afterwards, clinical manifestations of dengue patients were analyzed and 93 laboratory-positive serum specimens were chosen for the DENV serotyping and molecular analysis. Our data showed that the 2014 dengue outbreak in Guangdong had spread to 20 cities and more than 45 thousand people suffered from dengue fever. Of 14,594 participants, 11,387 were definitively diagnosed. Most manifested with a typical non-severe clinical course, and 1.96 % developed to severe dengue. The strains isolated successfully from the serum samples were identified as DENV-1. Genetic analyses revealed that the strains were classified into genotypes I and V of DENV-1, and the dengue epidemic of Guangdong in 2014 was caused by indigenous cases and imported cases from the neighboring Southeast Asian countries of Malaysia and Singapore. Overall, our study is informative and significant to the 2014 dengue outbreak in Guangdong and will provide crucial implications for dengue prevention and control in China and elsewhere.

A functional genomic analysis of type 3 Streptococcus pneumoniae virulence.

Streptococcus pneumoniae remains a serious cause of morbidity and mortality in humans, but relatively little is known about the molecular basis of its pathogenesis. We used signature-tagged mutagenesis together with an analysis of S. pneumoniae genome sequence to identify and characterize genes required for pathogenesis. A library of signature-tagged mutants was created by insertion-duplication mutagenesis, and 1786 strains were analysed for their inability to survive and replicate in murine models of pneumonia and bacteraemia. One hundred and eighty-six mutant strains were identified as attenuated, and 56 were selected for further genetic characterization based on their ability to excise the integrated plasmid spontaneously. The genomic DNA inserts of the plasmids were cloned in Escherichia coli and sequenced. These sequences were subjected to database searches, including the S. pneumoniae genome sequence, which allowed us to examine the chromosomal regions flanking these genes. Most of the insertions were in probable operons, but no pathogenicity islands were found. Forty-two novel virulence loci were identified. Five strains mutated in genes involved in gene regulation, cation transport or stress tolerance were shown to be highly attenuated when tested individually in a murine respiratory tract infection model. Additional experiments also suggest that induction of competence for genetic transformation has a role in virulence.

Plants and animals share functionally common bacterial virulence factors.

By exploiting the ability of Pseudomonas aeruginosa to infect a variety of vertebrate and nonvertebrate hosts, we have developed model systems that use plants and nematodes as adjuncts to mammalian models to help elucidate the molecular basis of P. aeruginosa pathogenesis. Our studies reveal a remarkable degree of conservation in the virulence mechanisms used by P. aeruginosa to infect hosts of divergent evolutionary origins.

Insertion of the LINE retrotransposon MGL causes a conidiophore pattern mutation in Magnaporthe grisea.

We obtained three Magnaporthe grisea morphological mutants that had the LINE transposon MGL inserted into the ACR1 locus. Sequence analysis revealed that ACR1 is homologous to medA, a developmental regulator of Aspergillus nidulans conidiation. These results demonstrated that MGL elements could transpose and cause insertional mutagenesis in M. grisea.

Acropetal: a genetic locus required for conidiophore architecture and pathogenicity in the rice blast fungus.

Fungal spores are a primary means of dissemination and are the major sources of inoculum in pathogenic species. Sporulation in the rice blast fungus Magnaporthe grisea involves the production of three-celled conidia, borne sympodially on an aerial conidiophore. A disease cycle initiates when spores are dispersed and attach to the rice plant surface. Using insertional mutagenesis we have identified a major regulator of conidiophore morphogenesis in M. grisea. A null mutation in the acropetal (ACR1) locus causes a hypermorphic conidiation phenotype where indeterminate growth of the conidial tip cell results in the production of head-to-tail (acropetal) arrays of spores. acropetal mutants are nonpathogenic and fail to undergo infection-related morphogenesis. The ACR1 locus encodes a spore-specific transcript and acr1(-) mutants fail to turn off the expression of the hydrophobin encoding gene MPG1 in dormant spores. We propose that ACR1 is a stage-specific negative regulator of conidiation that is required to establish a sympodial pattern of spore formation. Interestingly a failure to establish the correct pattern of sporulation in M. grisea results in the production of spores that cannot progress through the disease cycle. Studies of Acropetal suggest that the diverse patterns of spore ontogeny in conidial fungi arose through alterations in major genes controlling spore-specific gene expression.

Immunohistological localization of regulatory peptides in the midgut of the female mosquito Aedes aegypti.

The midgut of the female mosquito Aedes aegypti was studied immunohistologically with antisera to various regulatory peptides. Endocrine cells immunoreactive with antisera to perisulfakinin, RFamide, bovine pancreatic polypeptide, urotensin 1, locustatachykinin 2 and allatostatins A1 and B2 were found in the midgut. Perisulfakinin, RFamide and bovine pancreatic polypeptide all react with the same, about 500 endocrine cells, which were evenly distributed throughout the posterior midgut, with the exception of its most frontal and caudal regions. In addition, these antisera recognized three to five neurons in each ingluvial ganglion and their axons, which ran longitudinally over the anterior midgut, as well as axons innervating the pyloric sphincter. The latter axons appear to be derived from neurons located in the abdominal ganglia. Antisera to two different allatostatins recognized about 70 endocrine cells in the most caudal area of the posterior midgut and axons in the anterior midgut whose cell bodies were probably located in either the brain or the frontal ganglion. Antiserum to locustatachykinin 2 recognized endocrine cells present in the anterior midgut and the most frontal part of the posterior midgut, as well as about 50 cells in the most caudal region of the posterior midgut. Urotensin 1 immunoreactivity was found in endocrine cells in the same region as the perisulfakinin-immunoreactive cells, but no urotensin-immunoreactive axons were found in the midgut. Double labeling experiments showed that the urotensin and perisulfakinin immunoreactivities were located in different cells. Such experiments also showed that the locustatachykinin and allatostatin immunoreactivities in the most caudal area of the posterior midgut were present in different cells. No immunoreactivity was found in the mosquito midgut when using antisera to corazonin, allatropin or leucokinin IV. Since these peptides have either been isolated from, or can reasonably be expected to be present in mosquitoes, it was concluded that these peptides are not present in the mosquito midgut.