香港养殖海鲷弧菌致病菌药物敏感性及耐药质粒研究

从发病海鲷(Sparus sarba)中共分离到51株弧菌(%Vibrio)%,经API20E细菌快速鉴定系统及Alsina和Blanch关键生理生化特性分析鉴定为7个种，它们分别是：溶藻胶弧菌(%V.alginolyticus)(24株)，创伤弧菌(V.vulnificus)(12株)和副溶血弧菌(V.parahaemolyticus)(7株),火神弧菌(V.logei)(4株),远洋弧菌Ⅱ菌(V.pelagius Ⅱ)(2株),河弧菌(V.fluvialis)(1株)和地中海弧菌(V.mediterranei)(1株)%。其中3种优势菌溶藻胶弧菌创伤弧菌和副溶血弧菌证实对海鲷有致病性。另外采用平板稀释法检测了51株菌对16种抗菌素的敏感性。发现所有菌株对ceftriaxone,链霉素，萘啶酮酸和利福霉素敏感，几乎所有菌株对ceftazidime, netilimicin,氯霉素和sulfamethoxazole敏感.大部分菌株对氨苄青霉素(60.8%),cefuroxime(667%),丁胺卡那霉素(55%)，卡那霉素(588%)和三甲氧苄氨嘧啶(765%)等具有较强的耐药性。通过对菌株中所含有的耐药质粒进行分析，发现15株菌株含有1～4个质粒，分子量范围为9～123kb之间，对12株既含有较大分子量质粒又具有耐药性的菌株进行了质粒转化试验，结果其中9株菌的质粒具有转化能力，转化率为１０－１１～１０－９，表明所分离的菌株的抗药性是由于细菌染色体相关突变造成的。

ANTIBIOTIC RESISTANCE AND PLASMID PROFILES OF VIBRIO ISOLATESFROM CULTURED SPARUS SARBA

A total of 51 potential pathogenic vibrios were isolated from moribund silver seabream Sparus sarba, which were collected from local fish farms of Hong Kong. All the isolates were classified and identified as 7 species by the API 20 E system and the scheme of Alsina & Blanch. These species were Vibrio alginolyticus (24 strains), Vibrio vulnificus (12 strains), Vibrio parahaemolyticus(7 strains), Vibrio logei(4 strains), Vibrio pelagius II(2 strains), Vibrio fluvialis (1 strains) and Vibrio meditterranei (1 strains). Among these isolates, the three predominant species (V. alginolyticus, V. vulnificus and V. parahaemolyticus) were confirmed to be virulent to sea bream by experimental challenge. All isolates were also screened for plasmid DNA by agarose gel electrophoresis and tested for susceptibility to 16 antimicrobial agents by the agar dilution method. Of the 51 isolates examined, all strains were sensitive to ceftriaxone, streptomycin, nalidixic acid and rifampicin, and almost all were sensitive to ceftazidime, netilimicin, chloramphenicol and sulfamethoxazole except one or two strains. Most isolates were resistant to ampicillin (60. 8%), cefuroxime (66.7%), amikacin(55%), kanamycin(58.8%) and trimethoprinm (76.5%). Fifteen of the 51 isolates harboured 1-4 plasmids, with sizes ranging from 9 to 123 kb. Both the plasmids and the associated antimicrobial resistance (ampicillin, cefuroxime and trimethoprim) of 9 isolates could be transferred to recipient by single-step conjugation, however, the frequencies were very low, ranging from 10(-11) to 10(-9). The present results indicate that resistance to these antibiotics is chromosomal.