Centre for Microbiology Research, Kenya Medical Research Institute, PO Box 43640, Nairobi, Kenya.
BMC Microbiol. 2009 Dec 29;9:275. doi: 10.1186/1471-2180-9-275.
Over the last decade, cholera outbreaks in parts of Kenya have become common. Although a number of recent studies describe the epidemiology of cholera in Kenya, there is paucity of information concerning the diversity and occurrence of mobile genetic elements in Vibrio cholerae strains implicated in these outbreaks. A total of 65 Vibrio cholerae O1 El Tor serotype Inaba isolated between 1994 and 2007 from various outbreaks in Kenya were investigated for mobile genetic elements including integrons, transposons, the integrating conjugative elements (ICEs), conjugative plasmids and for their genotypic relatedness.
All the strains were haemolytic on 5% sheep blood and positive for the Vibrio cholerae El Tor-specific haemolysin toxin gene (hylA) by PCR. They all contained strB, sulII, floR and the dfrA1 genes encoding resistance to streptomycin, sulfamethoxazole, chloramphenicol and trimethoprim respectively. These genes, together with an ICE belonging to the SXT/R391 family were transferable to the rifampicin-resistant E. coli C600 en bloc. All the strains were negative for integron class 1, 2 and 3 and for transposase gene of transposon Tn7 but were positive for integron class 4 and the trpM gene of transposon Tn21. No plasmids were isolated from any of the 65 strains. All the strains were also positive for all V. cholera El Tor pathogenic genes except the NAG- specific heat-stable toxin (st) gene. None of the strains were positive for virulence genes associated with the V. cholerae classical biotype. All the strains were positive for El Tor-specific CTXphi bacteriophage rstrR repressor gene (CTXETPhi) but negative for the Classical, Calcutta, and the Environmental repressor types. Pulse Field Gel Electrophoresis (PFGE) showed that regardless of the year of isolation, all the strains bearing the SXT element were clonally related.
This study demonstrates that the V. cholerae O1 strains carrying an SXT/R391-like element implicated in recent cholera outbreaks in Kenya has not changed significantly between 1994 and 2007 and are clonally related.
在过去的十年中，肯尼亚部分地区的霍乱爆发已变得很常见。尽管最近有许多研究描述了肯尼亚霍乱的流行病学，但有关参与这些暴发的霍乱弧菌菌株中移动遗传元件的多样性和发生情况的信息却很少。本研究共检测了 1994 年至 2007 年间从肯尼亚各种暴发中分离出的 65 株霍乱弧菌 O1 型 El Tor 血清型 Inaba 菌株的移动遗传元件，包括整合子、转座子、整合性 conjugative 元件（ICEs）、接合质粒，并对其基因型相关性进行了研究。
所有菌株在 5%绵羊血平板上均呈溶血，PCR 检测霍乱弧菌 El Tor 特异性溶血素毒素基因（hylA）均为阳性。它们均含有 strB、sulII、floR 和 dfrA1 基因，分别编码对链霉素、磺胺甲恶唑、氯霉素和甲氧苄啶的耐药性。这些基因与属于 SXT/R391 家族的 ICE 一起可转移至利福平耐药的大肠杆菌 C600 中。所有菌株均未检测到整合子 1、2 和 3 类和转座子 Tn7 的转座酶基因，但均检测到整合子 4 类和转座子 Tn21 的 trpM 基因。未从 65 株菌中分离出质粒。所有菌株均为霍乱弧菌 El Tor 致病基因阳性，除 NAG 特异性热稳定毒素（st）基因外。所有菌株均未检测到与霍乱弧菌古典生物型相关的毒力基因。所有菌株均为霍乱弧菌 El Tor 特异性 CTXphi 噬菌体 rstrR 阻遏基因（CTXETPhi）阳性，但经典、加尔各答和环境阻遏型均为阴性。脉冲场凝胶电泳（PFGE）显示，无论分离年份如何，携带 SXT 元件的所有菌株均具有克隆相关性。
本研究表明，在肯尼亚最近的霍乱暴发中涉及的携带 SXT/R391 样元件的霍乱弧菌 O1 菌株在 1994 年至 2007 年期间没有明显变化，并且具有克隆相关性。
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