Reliability of the MS-2 system in detecting methicillin-resistant Staphylococcus aureus.

The MS-2 system (Abbott Diagnostics, Division of Abbott Laboratories, Dallas, Tex.) is an automated system capable of rapid antimicrobial susceptibility testing. However, the short incubation periods used by the device may adversely affect its ability to detect slowly growing resistant organisms. Shortly after the introduction of the MS-2 system into the University of Mississippi Medical Center clinical microbiology laboratory, we noted discrepancies between the MS-2 and the disk diffusion susceptibility reports when methicillin-resistant Staphylococcus aureus isolates were tested. Subsequently, we determined the susceptibilities of 75 such isolates by the MS-2 and Kirby-Bauer disk diffusion methods and measured the minimum inhibitory concentrations of methicillin, oxacillin, and cephalothin for 33 of the 75 isolates by standardized agar dilution techniques. There was only 47% overall agreement between the MS-2 and disk diffusion methods when methicillin was tested and 15% agreement when cephalothin was the test drug. There was 93% or more overall agreement between the two methods when other antimicrobial agents were tested. The minimum inhibitory concentration of methicillin was greater than or equal to 16 micrograms/ml for all 33 isolates evaluated by the agar dilution method. A comparison of the MS-2 and agar dilution results revealed an overall agreement of 49% when the susceptibilities to methicillin were determined. The MS-2 system reported that multiple methicillin-resistant S. aureus isolates obtained from a single patient were either resistant, intermediate, or sensitive to methicillin. Inconsistent results were also obtained when a single isolate was tested simultaneously in 10 cuvette cartridges. We conclude that the MS-2 system does not reliably detect methicillin and cephalothin resistance among S. aureus.     

Ultra-Deep Genomic Sequencing of HCV NS5A Resistance-Associated Substitutions in HCV/HIV Coinfected Patients

Background and Aims

The prevalence of naturally occurring HCV-NS5A resistance-associated substitutions (RAS) to DAA drugs might affect the response to treatment in HCV/HIV coinfected subjects. There are limited data on the frequency of HCV-NS5A naturally occurring drug-RAS at baseline in HCV/HIV coinfected patients when ultra-deep sequencing methodologies are applied.

Methods

HCV-NS5A-RAS were evaluated among 25 subjects in each group. Patients were matched by age, gender, and hepatic fibrosis stage category to control for selection bias.

Results

Within subtype 1a, RAS were observed in 28% of HCV monoinfected and 48% of HCV/HIV coinfected subjects. More patients in the HCV/HIV coinfected group had clinically relevant mutations to DAA directed at NS5A.

Conclusion

While the clinical significance of this observation may be limited in highly drug adherent populations, some HCV/HIV coinfected persons may be at greater risk of viral resistance if suboptimal dosing occurs.

     

胃肠胰胰岛淀粉样多肽的定位和表达

胰岛淀粉样多肽(islet armyloid polypeptide,IAPP)是1986年瑞典学者Westermarket al[1,2 ]从胰岛素瘤患者的瘤组织,糖尿病猫及Ⅱ型糖尿病患者胰岛淀粉样沉积物中分离出来的一种多肽,几乎在同时,英国生物化学家Cooper et al[3,4]也从Ⅱ型糖尿病患者的胰岛淀粉样沉积物中分离出该肽.IAPP又称为amylin.对IAPP的分子结构、基因表达和生理作用等已有许多报道[5].近年来,在IAPP定位、表达及胃肠胰IAPP免疫反应(immunoreactive,IR)细胞定位、发生、发育方面的研究报道,为探讨IAPP的生理作用及疾病状态下的改变,提供了形态学依据,现综述如下.     

灰色数列预测模型在成骨细胞体外培养中的应用

目的：灰色模型是运用一定的数学方法使信息不完全明确的系统经数据处理后能得到较明确结果的一种数学预测模型，体外细胞培养的影响因素较多，属于信息不完全明确的灰色系统，故运用灰色GM（1，1）模型对成骨细胞增殖、分化的变化规律进行预测，验证模型在体外细胞培养中的可应用性。方法：实验于2005—11／2006—03在广东医学院药理教研室完成。①实验过程：应用酶序列消化分离培养法培养新生大鼠颅骨成骨细胞；用MTT法测定体外培养成骨细胞在不含血清培养液A值，以了解成骨细胞的增殖情况；对硝基苯磷酸盐法观察体积分数为0．01的胎牛血清培养液对体外培养成骨细胞分泌碱性磷酸酶活性的影响，代表成骨细胞的分化情况。②灰色GM（1，1）模型建立：运用灰色系统理论，通过SAS8．1软件对体外培养成骨细胞MTT值和碱性磷酸酶OT值进行分析和预测。结果：运用灰色系统理论的后验差检验方法对模型进行检验，MTT这一指标的平均相对误差为4．4％，碱性磷酸酶这一指标的平均相对误差为7．04％，后验差比值为0．048和0．315，综合评定该模型为“好”。结论：灰色GM（1，1）模型对体外培养成骨细胞MTT值和碱性磷酸酶的OT值变化的预测精度高，结果可靠。体外培养成骨细胞MTT值和碱性磷酸酶的OT值的变化可用灰色GM（1，1）模型进行预测。     

Pathway analysis of gene signatures predicting metastasis of node-negative primary breast cancer

Background  

Published prognostic gene signatures in breast cancer have few genes in common. Here we provide a rationale for this observation by studying the prognostic power and the underlying biological pathways of different gene signatures.     

The capsule is a virulence determinant in the pathogenesis of Pasteurella multocida M1404 (B:2)

Capsules from a range of pathogenic bacteria are key virulence determinants, and the capsule has been implicated in virulence in Pasteurella multocida. We have previously identified and determined the nucleotide sequence of the P. multocida M1404 (B:2) capsule biosynthetic locus (J. D. Boyce, J. Y. Chung, and B. Adler, Vet. Microbiol. 72:121-134, 2000). The cap locus consists of 15 genes, which can be grouped into three functional regions. Regions 1 and 3 contain genes proposed to encode proteins involved in capsule export, and region 2 contains genes proposed to encode proteins involved in polysaccharide biosynthesis. In order to construct a mutant impaired in capsule export, the final gene of region 1, cexA, was disrupted by insertion of a tetracycline resistance cassette by allelic replacement. The genotype of the tet(M) OmegacexA mutant was confirmed by Southern hybridization and PCR. The acapsular phenotype was confirmed by immunofluorescence, and the strain could be complemented and returned to capsule production by the presence of a cloned uninterrupted copy of cexA. Wild-type, mutant, and complemented strains were tested for virulence by intraperitoneal challenge of mice; the presence of the capsule was shown to be a crucial virulence determinant. Following intraperitoneal challenge of mice, the acapsular bacteria were removed efficiently from the blood, spleen, and liver, while wild-type bacteria multiplied rapidly. Acapsular bacteria were readily taken up by murine peritoneal macrophages, but wild-type bacteria were significantly resistant to phagocytosis. Both wild-type and acapsular bacteria were resistant to complement in bovine and murine serum.     

Patterns of avian seroprevalence to western equine encephalomyelitis and Saint Louis encephalitis viruses in California, USA

Temporal and spatial changes in the enzootic activity of western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses were monitored at representative wetland study sites in the Coachella, San Joaquin, and Sacramento valleys of California from 1996 to 1998 using three methods: (1) virus isolation from pools of 50 host-seeking Culex tarsalis Coquillett females, (2) seroconversions in flocks of 10 sentinel chickens, and (3) seroprevalence in wild birds collected by mist nets and grain baited traps. Overall, 74 WEE and one SLE isolates were obtained from 222,455 Cx. tarsalis females tested in 4,988 pools. In addition, 133 and 40 seroconversions were detected in 28 chicken flocks, and 143 and 27 of 20,192 sera tested from 149 species of wild birds were positive for antibodies to WEE and SLE, respectively. WEE was active in all three valleys, whereas SLE only was detected in Coachella Valley. Seroconversions in sentinel chickens provided the most sensitive indication of enzootic activity and were correlated with seroprevalence rates in wild birds. Avian seroprevalence rates did not provide an early warning of pending enzootic activity in chickens, because positive sera from after hatching year birds collected during spring most probably were the result of infections acquired during the previous season. Few seroconversions were detected among banded recaptured birds collected during spring and early summer. Age and resident status, but not sex, were significant risk factors for wild bird infection, with the highest seroprevalence rates among after hatching year individuals of permanent resident species. Migrants (with the exception of mourning doves) and winter resident species rarely were positive. House finches, house sparrows, Gambel's quail, California quail, common ground doves, and mourning doves were most frequently positive for antibodies. The initial detection of enzootic activity each summer coincided closely with the appearance of hatching year birds of these species in our study areas, perhaps indicating their role in virus amplification. Bird species most frequently positive roosted or nested in elevated upland vegetation, sites where Cx. tarsalis host-seeking females hunt most frequently. These serosurveys provided important background information for planned host competence and chronic infection studies.