Intramuscular injection of tetracycline decreased gut microbial diversity in mouse.

Antibiotics contribute a lot to human beings and can kill bacteria effectively. However, more and more studies show that antibiotics can disturb the intestinal microbial community. It has been widely reported that oral antibiotics can reduce the diversity of intestinal microflora, but the effect of intramuscular injection on intestinal microflora is less studied. In this study, we sequenced the intestinal microflora of mice treated with tetracycline by 16SrRNA method, and found that intramuscular injection of tetracycline (TET) can also reduce the intestinal microbial richness of mice. In addition, the results showed that within a certain range (3 mg), with the increase of TET injection concentration, the wind of intestinal microflora in mice decreased significantly. When the injection concentration reached saturation, although the amount of TET injection was increased, the degree of intestinal flora affected was not increased. The results showed that the degree of diversity decrease was in direct proportion to the amount of tetracycline injection in the saturated concentration, but not positively related to the high amount of TET injection after exceeding the saturated concentration.

[Effect of dexamethasone contamination in drinking water on intestinal flora in mice].

OBJECTIVE: To evaluate the effect of water pollution with dexamethasone on intestinal flora in mice. METHODS: Twenty Balb/c mice were randomly divided into control group and low-, moderate- and high-dose dexamethasone groups. The mice in dexamethasone groups were exposed to dexamethasone sodium phosphate in drinking water at doses of 0.035, 0.225, and 2.25 ng for 36 days. The changes in behaviors, fur condition, and feces of the mice were observed daily. All the mice were sacrificed at 36 days and the tissues in the ileocecal region was collected for denaturant gradient gel electrophoresis (DGGE) of 16S rDNA V6 variable regions of microbes and sequence analysis with BLAST. RESULTS: The mice in the 3 dexamethasone groups all showed aggressive behaviors. Cluster analysis of DGGE graph showed relatively stable floras in the ileocecal region in all the mice, but principal component analysis identified differences in the dominating flora among the groups. Diversity analysis of the flora revealed significantly increased amount and types of bacteria in the intestinal flora in all the 3 dexamethasone groups (P<0.05 or 0.01) compared with the control group. Sequence analysis of 16S rDNA V6 regions showed 15 common bacterial species and 2 differential species between the dexamethasone groups and the control group with changes in the type and proportion of the dominating bacterium in the dexamethasone groups. Lactobacillus colonization was detected in the control group but not in moderate- and high-dose dexamethasone groups, and Shigella species were found in the latter two groups. CONCLUSIONS: Water contamination with dexamethasone can affect the nervous system of mice, cause changes in the types and amounts of intestinal bacteria and the dominating bacteria, and inhibit the colonization of probiotics in the intestinal floras to increase the risk of invasion by intestinal pathogenic bacteria.

Morphological and physiological comparison of taxa comprising the Sporothrix schenckii complex.

Based on recent molecular data, it has been suggested that Sporothrix globosa is the main causal agent of sporotrichosis in China. The objective of this study was to compare the morphology, growth characteristics, patterns of carbon source usage, and susceptibility to antifungal agents among Sporothrix strains. A total of 15 clinical strains confirmed to be S. globosa, from three different regions of China, and 11 ex-type strains from the CBS-KNAW biodiversity center were obtained. The elongated conidia of S. pallida, S. variecibatus, S. schenckii, and S. schenckii luriei were clearly different from the subglobose and globose conidia of S. globosa strains. S. schenckii is able to assimilate sucrose, raffinose, and ribitol. Susceptibility profiles of these Sporothrix species were evaluated by measuring minimum inhibitory concentrations (MICs). Fluconazole, itraconazole, terbinafine, and amphotericin B showed good activity against most S. globosa clinical isolates from China. Potassium iodide also showed a low MIC against S. pallida, while fluconazole showed a high MIC for S. mexicana, S. humicola, S. globosa, S. schenckii, and S. inflata; these strains might be considered tolerant. The species showed differences in susceptibility to antifungal drugs and should therefore be properly identified during diagnosis prior to designing therapeutic strategies.

A homolog of glyceraldehyde-3-phosphate dehydrogenase from Riemerella anatipestifer is an extracellular protein and exhibits biological activity.

Riemerella anatipestifer is the causative agent of septicemia anserum exsudativa in ducks. Its pathogenesis and virulence factors are still unclear. The glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), an anchorless and multifunctional protein on the surface of several pathogenic microorganisms, is involved in virulence and adhesion. Whether homologs of GAPDH exist, and display similar characteristics in R. anatipestifer (RaGAPDH) has not been determined. In our research, the RaGAPDH activity from various R. anatipestifer isolates was confirmed. Twenty-two gapdh genes from genomic DNA of R. anatipestifer isolates were cloned and sequenced for phylogenetic analysis. The distribution of RaGAPDH in R. anatipestifer CZ2 strain was confirmed by antisera to recombinant RaGAPDH. The ability of purified RaGAPDH to bind host proteins was analyzed by solid-phase ligand-binding assay. Results revealed that all R. anatipestifer isolates showed different levels of GAPDH activity except four strains, which contained a gapdh-like gene. The gapdh of R. anatipestifer, which is located phylogenetically in the same branch as enterohemorrhagic Escherichia coli (EHEC), belonged to class I GAPDH, and encoded a 36.7-kDa protein. All RaGAPDH-encoding gene sequences from field isolates of R. anatipestifer displayed 100% homology. The RaGAPDH localized on the extracellular membrane of several R. anatipestifer strains. Further, it was released into the culture medium, and exhibited GAPDH enzyme activity. We also confirmed the binding of RaGAPDH to plasminogen and fibrinogen. These results demonstrated that GAPDH was present in R. anatipestifer, although not in all strains, and that RaGAPDH might contribute to the microorganism's virulence.

Upregulation and lysosomal degradation of AQP4 in rat brains with bacterial meningitis.

Brain edema is among the major complications in children with bacterial meningitis. Aquaporins are integral membrane pore proteins that form channels to regulate cellular water content. Aquaporin-4 (AQP4), which is enriched in parts of astrocytic membranes that are apposed to pial or perivascular basal laminae, is the predominant aquaporin in the central nervous system. Dystroglycan is among the proteins that are responsible for the site-specific anchorage of AQP4. To elucidate the role of AQP4 in the development of brain edema induced by meningitis, a model of bacterial meningitis was established by injecting group B ß-hemolytic Streptococci into the cerebrospinal fluid of three-week-old rats. The brain water content increased in this model compared with that in the control group. The expression of AQP4 and dystroglycan was examined by Western blot and the degradation route of AQP4 was investigated by double immunofluorescence labeling. Western blot results showed that the expression of AQP4 and dystroglycan in rat brain increased in the meningitis model. Meanwhile, AQP4 was co-localized with the marker of lysosome in this model, indicating that the lysosome is involved in AQP4 degradation.

Mutant spectrum of dengue type 1 virus in the plasma of patients from the 2006 epidemic in South China.

The aim of the present study was to explore the mutant spectrum of dengue type 1 virus (DENV-1) within individuals during the 2006 dengue epidemic in South China. A 513-bp fragment including most of domain III of the envelope (E) gene was amplified directly from clinical samples, then cloned and sequenced. A total of 89 clones from six patients (range 11-17 clones per patient) were sequenced. Genetic diversity was calculated using MEGA 4 package. The total number of nucleotide mutations was 113 (3.7%) within the sequenced 513-bp E gene, with a range of 15 (3%) to 24 (4.7%) within individual viral populations, harboring more non-synonymous than synonymous mutations. The extent of sequence diversity varied among patients, with the mean diversity ranging from 0.19% to 0.32%, and the mean pairwise p-distance ranging from 0.34% to 0.65%. No genome-defective virus was detected in any clone in this study. Purifying selection may be the main driving force for the intrahost evolution: the mean dN/dS ratio was 0.532. Our findings contribute to the understanding of the genetic variation of DENV-1 in South China.

[Establishment of cellular hypoxia model and its effects on biological behavior of gastric cancer cell line SGC-7901].

BACKGROUND & OBJECTIVE: Hypoxia is an elementary characteristic of tumor microenvironment. Establishing hypoxia microenvironment in vitro will be of help in studying the effects of hypoxia on tumor cells. Previous methods of establishing hypoxic cell culture model are fussy, and researches on the effects of hypoxia on gastric cancer cells are rare. This study was to establish hypoxia microenvironment with GasPaK method in vitro, and observe the effects of hypoxia on biological features of gastric cancer cell line SGC-7901. METHODS: The hypoxia microenvironment was established by GasPaK method; the changes of PO2, PCO2, and pH in RPMI-1640 were monitored by blood gas analysis. The effect of hypoxia on cell cycle of SGC-7901 cells was analyzed by flow cytometry (FCM). The morphology of SGC-7901 cells was observed under light microscope and transmission electron microscope. Live cells were counted with trypan blue staining. The adhesiveness of SGC-7901 cells was detected by MTT assay; migration ability of SGC-7901 cells was assessed by movement experiment. RESULTS: GasPaK formed hypoxia microenvironment in 0.5-48 h with stable PO2, PCO2, and pH. When cultured in hypoxia for 16 h, no significant change in cell cycle of SGC-7901 cells was observed; morphology of some SGC-7901 cells was changed; the number of live cells didn't significantly decreased; the adhesiveness and migration ability of SGC-7901 cells were significantly enhanced. CONCLUSIONS: GasPaK method can stably establish hypoxia microenvironment with good repetition. Hypoxia has slight effect on SGC-7901 cells, and may induce morphologic change of SGC-7901 cells.