Virulence determinants, drug resistance and mobile genetic elements of Laribacter hongkongensis: a genome-wide analysis

Background

Laribacter hongkongensis is associated with community-acquired gastroenteritis and traveler's diarrhea. In this study, we performed an in-depth annotation of the genes in its genome related to the various steps in the infective process, drug resistance and mobile genetic elements.

Results

For acid and bile resistance, L. hongkongensis possessed a urease gene cassette, two arc gene clusters and bile salt efflux systems. For intestinal colonization, it possessed a putative adhesin of the autotransporter family homologous to those of diffusely adherent Escherichia coli (E. coli) and enterotoxigenic E. coli. To evade from host defense, it possessed superoxide dismutase and catalases. For lipopolysaccharide biosynthesis, it possessed the same set of genes that encode enzymes for synthesizing lipid A, two Kdo units and heptose units as E. coli, but different genes for its symmetrical acylation pattern, and nine genes for polysaccharide side chains biosynthesis. It contained a number of CDSs that encode putative cell surface acting (RTX toxin and hemolysins) and intracellular cytotoxins (patatin-like proteins) and enzymes for invasion (outer membrane phospholipase A). It contained a broad variety of antibiotic resistance-related genes, including genes related to β-lactam (n = 10) and multidrug efflux (n = 54). It also contained eight prophages, 17 other phage-related CDSs and 26 CDSs for transposases.

Conclusions

The L. hongkongensis genome possessed genes for acid and bile resistance, intestinal mucosa colonization, evasion of host defense and cytotoxicity and invasion. A broad variety of antibiotic resistance or multidrug resistance genes, a high number of prophages, other phage-related CDSs and CDSs for transposases, were also identified.     

Proinflammatory cytokine responses induced by influenza A (H5N1) viruses in primary human alveolar and bronchial epithelial cells

Background

Fatal human respiratory disease associated with influenza A subtype H5N1 has been documented in Hong Kong, and more recently in Vietnam, Thailand and Cambodia. We previously demonstrated that patients with H5N1 disease had unusually high serum levels of IP-10 (interferon-gamma-inducible protein-10). Furthermore, when compared with human influenza virus subtype H1N1, the H5N1 viruses in 1997 (A/Hong Kong/483/97) (H5N1/97) were more potent inducers of pro-inflammatory cytokines (e.g. tumor necrosis factor-a) and chemokines (e.g. IP-10) from primary human macrophages in vitro, which suggests that cytokines dysregulation may play a role in pathogenesis of H5N1 disease. Since respiratory epithelial cells are the primary target cell for replication of influenza viruses, it is pertinent to investigate the cytokine induction profile of H5N1 viruses in these cells.

Methods

We used quantitative RT-PCR and ELISA to compare the profile of cytokine and chemokine gene expression induced by H5N1 viruses A/HK/483/97 (H5N1/97), A/Vietnam/1194/04 and A/Vietnam/3046/04 (both H5N1/04) with that of human H1N1 virus in human primary alveolar and bronchial epithelial cells in vitro.

Results

We demonstrated that in comparison to human H1N1 viruses, H5N1/97 and H5N1/04 viruses were more potent inducers of IP-10, interferon beta, RANTES (regulated on activation, normal T cell expressed and secreted) and interleukin 6 (IL-6) in primary human alveolar and bronchial epithelial cells in vitro. Recent H5N1 viruses from Vietnam (H5N1/04) appeared to be even more potent at inducing IP-10 than H5N1/97 virus.

Conclusion

The H5N1/97 and H5N1/04 subtype influenza A viruses are more potent inducers of proinflammatory cytokines and chemokines in primary human respiratory epithelial cells than subtype H1N1 virus. We suggest that this hyper-induction of cytokines may be relevant to the pathogenesis of human H5N1 disease.     

Chemical and viral transformation of cultured skin fibroblasts from patients with familial polyposis coli

Treatment of skin fibroblasts from an FPC patient with 4NQO or MNNG followed by sequential passaging caused morphological changes of the cells, which showed characteristics of transformed cells such as a high frequency of colony formation in agarose, increased growth ability, and chromosomal abnormalities. This and other fibroblast lines from 5 of 12 FPC patients had an increased susceptibility to 4NQO cytotoxicity, which was caused by enhanced 4NQO-reductase activity rather than by reduced DNA repair. However, the susceptibility to cytotoxicity of MNNG and repair of MNNG-damaged DNA were normal in FPC cells. The tumor promoters TPA and DHTB enhanced the frequency of chemical transformation of the FPC fibroblasts, and protease inhibitors suppressed the promoter-enhanced transformation. The skin fibroblasts from many FPC patients exhibited increased susceptibility to transformation by murine sarcoma viruses. Analysis of the viral DNA and RNA after infection revealed that the increased susceptibility is determined at an early stage of transformation. Two out of 5 MNNG-transformed clones of FPC fibroblasts, isolated from agarose, had increased expression of c-Ki-ras or c-Ha-ras, and 4 of 4 MSV-transformed clones showed high expression of viral Ki-ras. These clones grew further after isolation from agarose, but were mortal and did not form tumors in nude mice. The present results suggest that additional changes in morphologically transformed FPC fibroblasts are required for malignant transformation.     

Strand breaks of mammalian mitochondrial DNA induced by carcinogens.

Closed circular mitochondrial DNA in mammalian cells was degradated to the open circular form by exposure of the cells to the carcinogens N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 4-nitroquinoline 1-oxide (4NQO). MNNG caused more strand scission of mitochondrial DNA than 4NQO at the same concentration. The action of the carcinogens on mitochondrial DNA did not parallel that with nuclear DNA which was damaged by 4NQO more markedly than by MNNG. Mitochondrial DNA damaged by carcinogens was not repaired during 4-20 h of post-treatment incubation of the cells. Incorporation of labeled thymidine into the closed circular mitochondrial DNA, decreased by the treatment of cells with carcinogens, recovered during post-treatment incubation.     

UV-induced imbalance of the deoxyribonucleoside triphosphate pool in E. coli

The effect of UV irradiation on the intracellular DNA precursor pool in E. coli was investigated. UV irradiation of E. coli, followed by post-incubation for 1-1.5 h, altered the relative sizes of the deoxyribonucleoside triphosphate (dNTP) pool. The total amount of dNTPs increased: both dATP and dTTP increased several-fold, dCTP about twofold, while dGTP remained almost unchanged. In recA- and umuC- strains, which are defective in UV-induced mutagenesis, the pattern of nucleotide pool alterations was similar to that of wild-type strains.     

Late Pleistocene divergence and postglacial expansion in the Brazilian Atlantic Forest: multilocus phylogeography of Rhopias gularis (Aves: Passeriformes)

In the last decade, phylogeographic studies have revealed a complex evolutionary history of the Brazilian Atlantic Forest (AF) biota. Here, we investigated the evolutionary history of Rhopias gularis, an endemic bird of the AF, based on sequences of two mitochondrial genes and three nuclear introns from 64 specimens from 15 localities. We addressed three main questions: (1) Does the genetic diversity of R. gularis exhibit a distribution pattern congruent with the refuge hypothesis postulated for the AF? (2) Is the population genetic structure of R. gularis congruent with those observed in other AF species? (3) What were the possible historical events responsible for the population structure of this species? Our mtDNA data revealed two phylogroups: (1) phylogroup central‐south, with samples from the central and southern parts of the range; (2) and phylogroup north, which included individuals from southern Bahia. Nevertheless, nuclear loci did not reveal any evidence of population structure. Bottleneck tests indicated that the central‐south lineage experienced demographic expansion, starting around 20 kya, which coincides with the end of the last glacial maximum. However, there was no evidence of population growth in phylogroup north. Isolation with migration analysis indicated that these phylogroups split c.a. 304 kya, with limited gene flow among them. Palaeodistribution models indicated that R. gularis had a reduced distribution in the south and central AF during the last glacial maximum. Our results support a diversification scenario that is in accordance with proposed Pleistocene refugia. The phylogeographic results from our study exhibited spatial and temporal concordances and discordances with previous studies of organisms from the AF. Differences in habitat requirements of these species could be behind this complex scenario. Future studies correlating variables of the niche of these species with the observed phylogeographic patterns may help understand why there are congruent and incongruent results.     

A Guyon's canal ganglion presenting as occupational overuse syndrome: A case report

We report a case of severe weight loss secondary to anorexia nervosa causing bilateral superficial peroneal nerve entrapment in a young female patient who was treated successfully by bilateral surgical decompression.