医学微生物学：第9章 弧菌属

1、第九章 弧菌属(Vibrio)第一节 霍乱弧菌第二节 副溶血性弧菌弧菌属（Vibrio）细菌是一大群菌体短小，弯曲成弧形、一端有单鞭毛的革兰阴性菌，运动极活泼。分布广泛，多存在于水中。对人有致病性主要为霍乱弧菌(V. cholerae)和副溶血弧菌(V. parahaemolyticus )。第一节 霍乱弧菌霍乱弧菌（V.cholera）是人类霍乱的病原体。霍乱是一种古老且流行广泛的烈性传染病之一。曾在世界上引起多次大流行，主要表现为剧烈的呕吐，腹泻，失水，死亡率甚高。属于国际检疫传染病。 中华人民共和国国境卫生检疫法第一章 总 则第三条 本法规定的传染病是指检疫传染病和监测传染病。检疫传染病

2、，是指鼠疫、霍乱、黄热病以及国务院确定和公布的其他传染病。监测传染病，由国务院卫生行政部门确定和公布。History and spread of epidemic choleraCholera has smoldered in an endemic fashion on the Indian subcontinent for centuries.There are references to deaths due to dehydrating diarrhea dating back to Hippocrates and Sanskrit writings. The mode of trans

3、mission of cholera by water was proven in 1849 by John Snow, a London physician. In 1883, Robert Koch successfully isolated the cholera vibrio from the intestinal discharges of cholera patients and proved conclusively that it was the agent of the disease.Vibrio cholerae O1 has two biotypes, namely,

4、classical and El Tor. The first long-distance spread of cholera to Europe and the Americas began in 1817, such that by the early 20th century, six waves of cholera had spread across the world in devastating epidemic fashion. Since then, until the 1960s, the disease contracted, remaining present only

5、 in southern Asia. In 1961, the El Tor biotype (distinguished from classic biotypes by the production of hemolysins) reemerged and produced a major epidemic in the Philippines to initiate a seventh global pandemic. Since then, this biotype has spread across Asia, the Middle East, Africa, and parts o

6、f Europe. There are several characteristics of the El Tor strain that confer upon it a high degree of epidemic virulence allowing it to spread across the world as previous strains have done. First, the ratio of cases to carriers is much less than in cholera due to classic biotypes (1: 30-100 for El

7、Tor vs. 1: 2 - 4 for classic biotypes). Second, the duration of carriage after infection is longer for the El Tor strain than the classic strains. Third, the El Tor strain survives for longer periods in the extraintestinal environment. Between 1969 and 1974, El Tor replaced the classic strains in th

8、e heartland of endemic cholera, the Ganges River Delta of India. Differences in whole-genome expression patterns between the classical and El Tor biotypes of Vibrio cholerae O1 were determined under conditions that induce virulence gene expression in the classical biotype. A total of 524 genes (13.5

9、% of the genome) were found to be differentially expressed in the two biotypes. The expression of genes encoding proteins required for biofilm formation, chemotaxis, and transport of amino acids, peptides, and iron was higher in the El Tor biotype. These gene expression differences may contribute to

10、 the enhanced survival capacity of the El Tor biotype in environmental reservoirs. The expression of genes encoding virulence factors was higher in the classical than in the El Tor biotype. A large fraction (20.8%) of the genes that are differentially expressed in the classical versus the El Tor bio

11、type are controlled by VieA in the classical biotype. Thus, VieA is a major regulator of genes in the classical biotype under virulence gene-inducing conditions. Sinem Beyhan, Anna D. Tischler, Andrew Camilli, and Fitnat H. Yildiz. Differences in Gene Expression between the Classical and El Tor Biot

12、ypes of Vibrio cholerae O1.Infection and Immunity, June 2006, p. 3633-3642, Vol. 74, No. 6霍乱弧菌的疫源地霍乱是一种烈性肠道传染病，有3个疫源地： 印度恒河三角洲：O1群, 古典生物型：前六次世界性大流行，始于1817年； 印尼苏拉威西岛：O1群, 埃托生物型(EL-Tor bio-type) ：第七次世界大流行，始于1961年，累及140多个国家； 孟加拉湾（O139，Bengal）：始于1992年，危害相同。WHO规定：疑为霍乱病例，三种同时检测。V cholerae O139 appears to

13、have been derived from the pandemic El Tor biotype but has lost the characteristic O1 somatic antigen; it has gained the ability to produce a polysaccharide capsule; it produces the same cholera enterotoxin; and it seems to have retained the epidemic potential of O1 strains. Last cholera outbreak da

14、tes December 2006 in Angola The physical map of the two replicons of classical V. cholerae strain 395. The circles represent the I-CeuI (Inner) and SfiI (Outer) maps. The order of genes within each SfiI fragment are arbitrary. (A) Replicon I. (B) Replicon II.Proc Natl Acad Sci U S A. 1998 November 2

15、4; 95(24): 1446414469. 一、生物学性状形态染色G弧菌，单鞭毛，穿梭样动力，鱼群状排列，有菌毛，个别有荚膜，无芽胞培养特性兼性厌氧，氧气充分生长良好；营养要求不高，故用pH8-9碱性培养基，耐碱不耐酸（pH7.4-9.6），形成光滑透明湿润的“水滴样”菌落，分离（选择）能在无盐培养基中生长（区别其它弧菌）。霍乱弧菌在硫代硫酸钠-柠檬酸钠-胆盐-蔗糖(TCBS)琼脂平板上的生长状况霍乱弧菌发酵蔗糖产酸，菌落呈黄色 生化反应：触酶、氧化酶（+），硝酸盐还原（+），靛基质（+）抗原分型： 有200多个血清群，其中O1群、O139群可引起霍乱，其余不致病或仅引起胃肠炎等， O1群包

16、括两个生物型：古典生物型和埃托生物型（E1-Tor）抵抗力：较弱怕干干燥时易死亡，水环境中可存活两周（水源性传 播，水性爆发）怕酸正常胃酸4min不耐热100，1-2min对消毒剂、抗生素敏感。Antigenic Variation in V choleraeAntigenic variation plays an important role in the epidemiology and virulence of cholera. The flagellar antigens of V. cholerae are shared with many water vibrios and the

17、refore are of no use in distinguishing strains causing epidemic cholera. O antigens do distinguish strains of V. cholerae into 139 known serogroups. There are three distinct O1 serotypes, named Ogawa, Inaba and Hikojima, and each serotype may display the classical or El Tor biotypes. The Bengal stra

18、in (O139) is a new serological strain with a unique O-antigen which partly explains the lack of residual immunity. 二、致病性与免疫性致病物质侵袭力鞭毛与黏液素酶鞭毛运动 有利于细菌穿过黏膜表面黏液层黏液素酶液化黏液菌毛使细菌定植于小肠霍乱肠毒素最强烈的致泻毒素其致病机制与ETEC的LT相似，但作用强烈得多霍乱肠毒素的作用机制霍乱肠毒素的作用机制毒素由A和B两个亚单位组成，A亚单位又分为A1和A2两个肽链，两者依靠二硫链连接。A亚单位为毒性单位，其中A1肽链具有酶活性，A2肽链与B

19、亚单位结合参与受体介导的内吞作用中的转位作用。B亚单位为结合单位，能特异地识别肠上皮细胞上的受体。1个毒素分子由一个A亚单位和5个B亚单位组成多聚体。霍乱肠毒素作用于肠细胞膜表面上的受体（由神经节苷脂GM1组成），其B亚单位与受体结合，使毒素分子变构，A精致单位进入细胞，A1肽链活化，进而激活腺苷环化酶（AC），使三磷酸腺苷（ATP）转化为环磷酸腺苷（cAMP），细胞内 cAMP浓度增高，导致肠粘膜细胞分泌功能大为亢进，使大量体液和电解质进入肠腔而发生剧烈吐泻，由于大量脱水和失盐，可发生代谢性酸中毒，血循环衰竭，甚至休克或死亡。 所致疾病霍乱（甲类法定传染病02）传染源：病人粪便污染的水源或食

20、品传染途径：经口（暴饮暴食者）潜伏期：23d前驱期：不明显，少数有轻度吐泻、腹胀不适吐泻期：剧烈吐泻、米泔样，每日数十次，持续23天，失水12000ml脱水期：严重吐泻引起水电解质紊乱，脱水酸中毒，肾衰、循环衰竭、休克、死亡。表现：神志不安、淡漠“霍乱面容”呈脱水貌，眼窝下陷，舟状腹，肌痉挛等。恢复期：吐泻停止、紊乱纠正、症状消失、病程平均为37天。免疫力：病人愈后可获得牢固免疫。三、微生物学检查与防治 烈性传染病（发病率高、流行迅速、死亡率高），早期、快速、准确诊断（尤其首例）对防治蔓延意义重大。1.标本：“米泔样”便及呕吐物，专人护送，快速送检，指定实验室；2.直接涂片镜检 悬滴法或暗视野显微镜，观察穿梭样运动；3.分离培养鉴定；4.快速诊断：荧光菌球法，SPA协同凝集试验。免疫荧光菌球法 将粪标本直接接种于蛋白胨水中，此胨水中含有标记荧光素的O1群或O139群抗体，于37孵育46小时，此后或直接取培养液，或经离心后取沉淀物作标本在荧光显微镜下观察。如看到荧光菌球，表示试验阳性，可作可疑诊断。SPA协同凝集试验基本原理 由于SPA能与IgG的Fc片段非特异性结合，同时不影响Fab片段的活性,所以当带有SPA的金黄色葡萄球菌与抗体混合，再