Staphylococcus epidermidis strains are diverse in their pathogenicity; some are invasive and cause seri-ous nosocomial infections, whereas others are non-pathogenic commensal organisms, To analyse the implications of different virulence factors in Staphylo-coccus epidermidis infections, the complete genome of Staphylococcus epidermidis strain ATCC 12228, a non-biofilm forming, non-infection associated strain used for detection of residual antibiotics in food prod-ucts, was sequenced, This strain showed low viru-lence by mouse and rat experimental infections, The genome consists of a single 2499 279 bp chromosome and six plasmids. The chromosomal G+C content is 32.1% and 2419 protein coding sequences (CDS) are predicted, among which 230 are putative novel genes. Compared to the virulence factors in Staphylococcus aureus, aside from δ-haemolysin and 13-haemolysin, other toxin genes were not found. In contrast, the majority of adbesin genes are intact in ATCC 12228. Most strikingly, the ica operon coding for the enzymes synthesizing interbacterial cellular polysaccharide is missing in ATCC 12228 and rearrangements of adja-cent genes are shown. No mec genes, IS256, IS257, were found in ATCC 12228. It is suggested that the absence of the ica operon is a genetic marker in com-mensal Staphylococcus epidermidis strains which are less likely to become invasive.

We have sequenced the genome of Shigella-exneri serotype 2a, the most prevalent species and serotype that causes bacillary dysentery or shigellosis in man. The whole genome is composed of a 4 607 203 bp chromosome and a 221 618 bp virulence plasmid, designated pCP301. While the plasmid shows minor divergence from that sequenced in serotype 5a, striking characteristics of the chromosome have been revealed. The S-exneri chromosome has, astonishingly, 314 IS elements, more than 7-fold over those possessed by its close relatives, the non-pathogenic K12 strain and enterohemorrhagic O157:H7 strain of Escherichia coli. There are 13 translocations and inversions compared with the E.coli sequences, all involve a segment larger than 5 kb, and most are associated with deletions or acquired DNA sequences, of which several are likely to be bacteriophage-transmitted pathogenicity islands. Furthermore, S-exneri, resembling another human-restricted enteric pathogen, Salmonella typhi, also has hundreds of pseudogenes compared with the E.coli strains. All of these could be subjected to investigations towards novel preventative and treatment strategies against shigellosis.

目的 检测福氏志贺菌喹诺酮类耐药临床分离株DNA旋转酶gyrA和拓扑异构酶ⅣparC基因的突变情况，探讨GyrA和ParC氨基酸改变与喹诺酮类耐药的相关性。方法 根据药敏实验结果选取47株福氏志贺菌临床分离菌，对其gyrA、parC喹诺酮耐药决定区（QRDR）进行聚合酶链反应（PCR）扩增和测序分析，并采用SAS（V8.2）软件分析GyrA和ParC改变和喹诺酮类耐药性的关联程度。结果 44株喹诺酮类耐药菌在gyrA、parC基因QRDR均发生有义突变，gyrA83位密码子突变（TCG→TTG）最为常见，存在于43株耐药菌。混合模型分析结果显示GyrA83位、ParC80位氨基酸改变与萘啶酸的耐药性密切相关（P<0.01，R2=0.999），GyrA83、87位氨基酸改变与环丙沙星的耐药性密切相关（P<0.05，R2=0.872）。结论 GyrASer83→Leu突变是导致福氏志贺菌临床株对喹诺酮类耐药的关键突变，此单位点突变即可介导福氏志贺菌对萘啶酸的耐药，但对环丙沙星耐药需同时存在GyrA和/或ParC多个位点突变或其他耐药机制。

目的：研究两种不同的IL-15真核表达质粒对乙肝蛋白疫殁苗诱导的免殁应答的影响。方法：构建IL-15真核表达质粒（简称pIL-15）和含有IL-12信号肽的IL-15真核表达质粒（简称pIL-2s-15），CfLL-2细胞增殖实验验证两种质粒真核表达产物的生物学活性。将这两种质粒分别与HBsAg共免疫BALB/C小鼠，用ELISA法检测小鼠血清抗-HBsigG及igGl、igG2a亚类的效价。结果：与HBsAg蛋白疫苗共免疫时，pIL-15可使FIBsAg诱导的抗-HBslgG效价升高，显著高于载体pcDNA3.l与HB-sAg共免疫对照组，pIL-2s-15对HBsAg诱导抗-HBslgG效价没有明显影响。与HBsAg+pcDNA3.l组相比，FIBsAg+pIL-2s-15组和HBsAg+piL-15组诱生的抗HBsigG2a亚类均升高，但前者igG2a/lgGl比值最高，与HBsAg+pcDNA3.l组相比差别有显著性；HBsAg+pIL-15组igG2a/lgGl比值与HBsAg+pcDNA3.l组相比差别无显著性。结论：piL-15真核表达质粒可增强蛋白疫苗诱导的体液免疫应答，pIL-2s-15真核表达质粒则主要使免疫应答趋向Thl型。

目的 研究鸭IFN-γ（DuIFN-γ）在感染及控制病毒过程中的作用和机制。方法 基于βarlln的高度保守序列设计引物，通过RT-PCR方法获得了β-actin的郭分cDNA为看家基因，然后构建DuIFN-γ靶片段的竞争性内参照，建立检测DuIFN-γ基因转录的半定量竞争性RT-PCR方法。结果 建立了检测DuIFN-γ基因转录的半定量竞争性RT-PCR方法，并检测了在PHA刺激下鸭外周血单核细胞IFN-γmRNA动态变化，结果表明PHA刺激24～36h，DuIFN-γmRNA转录量最高。以此方法对用DHBvpresDNA或与IFN-γDNA共免疫DHBv感染鸭进行了测定，结果表明IFN-γ表达质粒作为DNA免疫佐剂。可以增强宿主IFN-γ的应答。结论 IFN-γ表达质粒为DNA疫苗的有效佐剂。DuJFN-γ基因转录的半定量竞争性RT-PCR方法为研究鸭IFN-γ在DHBv感染及清除中的作用和机制奠定了基础。