Levofloxacin susceptibility testing for Helicobacter pylori in China: comparison of E-test and disk diffusion method.

BACKGROUND: The aims of this study were to compare disk diffusion with E-test method for levofloxacin susceptibility testing of Helicobacter pylori and standardized breakpoints for disk diffusion as a stable and reliable method for determining qualitative levofloxacin susceptibility. MATERIALS AND METHODS: We determined the levofloxacin susceptibility of 45 H. pylori strains isolated from Chinese patients by the E-test method. Disk diffusion was evaluated as an alternative method to determine susceptibility and compared with the E-test results by linear regression analysis. RESULTS: The minimum inhibitory concentration (MIC) values tested by E-test method ranged from 0.047 to 32 µg/mL. Resistance to levofloxacin was detected in 16 (35.6%) isolates. The levofloxacin disk zone sizes obtained by disk diffusion method correlated well (r² = .877) with the MICs obtained by E-test method. As a consequence of regression analysis, isolates with inhibition diameters < 12 mm were considered resistant to levofloxacin. There was 100% agreement between the two methods for levofloxacin, applying the regression-based breakpoints. CONCLUSIONS: The disk diffusion method is equivalent to the E-test method for testing levofloxacin susceptibility of H. pylori strains; it is more practical and inexpensive, and it is suitable for the analysis of a small number of isolates compared with the E-test method.

[Influence of interferon gamma treatment on expression of TGF-beta1 and its receptors in liver fibrosis of mice with schistosomiasis japonica].

OBJECTIVE: To investigate the effect of interferon-gamma (IFN-gamma) on the expression of TGF-beta1 and its two membrane receptors--TGF-beta receptor I (TbetaRI), TGF-beta receptor II (TbetaRII), and observe the expression of TGF-beta1, TbetaRI and TbetaRII during the development of liver fibrosis in BALB/c mice infected by Schistosoma japonicum. METHODS: BALB/c mice, aged 6-8 weeks, were infected with cercariae of S. japonicum. The infected mice were divided randomly into three groups 16 week after infection: model group, praziquantel group and praziquantel combined with IFN-gamma group. Liver specimen were obtained at 8, 12, 16 week and at the end of treatment. Pathological examination, immunohistochemistry and RT-PCR were used to evaluate the pathological change, the expression of TGF-beta1, TbetaRI and TbetaRII and the mRNA level respectively. RESULTS: The expression of TGF-beta1, TbetaRI, and TbetaRII can be detected in infected mice, while the expression around egg granulomas enhanced along with the progress of the disease. With the therapy of IFN-gamma, the reduction of egg granulomas, and of the expression of TGF-beta1, TbetaRI and TbetaRII was observed. From the transcription level, it was found that TGF-beta1 mRNA increased at 12 week and peaked at model group, then decreased to the normal level after treatment with IFN-gamma combined with praziquantel. The level of TbetaRII mRNA reduced at 8 and 16 week and returned to normal at the end of treatment. More interestingly, TbetaRI mRNA remained at the normal level on the whole course both in the development of fibrogenesis and the period of treatment. CONCLUSION: The up regulation of TGF-beta1 and down regulation of TbetaRII mRNA may induce liver fibrogenesis and IFN-gamma might suppress TGF-beta1 to reverse fibrosis. The mechanism of the suppression is mediated by down regulation of expression of its two receptors at protein level but not by influencing the mRNA expression.

[Studies on Smads at transcription level in liver fibrosis of mice with Schistosomiasis japonica].

OBJECTIVE: To study Smads involved in TGF-beta signal transduction at the transcription level during the development of liver fibrosis in BALB/c mice infected by Schistosoma japonicum. METHODS: BALB/c mice infected with cercariae of S. japonicum were used as liver fibrosis models. Liver specimens were harvested at 8, 12, 16 and 24 weeks after infection and normal control were sacrificed at the 24th week. A part of the liver specimens were preserved for pathologic examination and the other part was frozen for the detection of mRNA level of Smad 2, Smad 3, Smad 4 and Smad 7. RESULTS: The level of Smad 3 mRNA was significantly higher than that of control at the later stage, while the mRNA level of Smad 2 decreased at 12 and at 24 weeks, respectively. No significant difference in the mRNA level of Smad 4 and Smad 7 was observed between the infection group and the control. CONCLUSION: Smad 3 may induce the development of liver fibrosis in mice infected by S. japonicum while Smad 2 may induce the development of liver fibrosis at early stage and inhibit it at later stage.

Telomere attrition and chromosome instability via downregulation of TRF2 contributes to arsenic trioxide-induced apoptosis of human T-Cell leukemia cell line molt-4 cells.

Overexpression of human telomere repeat binding factor 2 (TRF2), which may play an important role in the fate of cancer cells, has been observed in adult T-cell leukemia. Previous reports have shown that the inhibition of TRF2 results in the apoptosis of cancer cells. In this study, we demonstrated that arsenic trioxide (As2O3) induced in vitro growth inhibition and/or apoptosis of human T-cell leukemia cell line Molt-4 in a caspase-independent manner. Telomerase activity was not inhibited, although the level of the reverse transcriptase subunit of the human telomerase gene (hTERT) mRNA expression was down regulated during the early times and then recovered to the level found in untreated controls about 48 hours after treatment with As2O3. Furthermore, a remarkable telomere shortening related to exposure of As2O3 was observed in 50 population doubling. Inc ontrast, the alteration of telomere length did not occur after exposure to higher concentration of As2O3 (10 microM) for 24 hours and 48 hours, respectively, suggesting that the shortening of telomeres induced by As2O3 is dependent of a series of cell division cycles. Chromosomal analysis showed that As2O3 exposure caused chromosomal end-to-end fusion in human T-cell leukemia cells while downregulation of TRF2 was observed. Finally, the inhibition of TRF2 protein expression and the sensitivity to As2O3 in a panel of leukemia cell lines were checked. The data revealed that inhibition of TRF2 rendered leukemia cells more susceptible to As2O3. In conclusion, the downregulation of TRF2 by As2O3 contribute to chromosomal end-to-end fusion, and apoptosis in leukemia cells, suggesting that TRF2 could be an attractive target for new therapies of leukemia.