Distribution of florfenicol resistance genes fexA and cfr among chloramphenicol-resistant Staphylococcus isolates
Distribution of florfenicol resistance genes fexA and cfr among chloramphenicol-resistant Staphylococcus isolates
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DOI：
10.1128/aac.50.4.1156-1163.2006
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发表时间：
2006-04-01
影响因子：
4.9
通讯作者：
Schwarz, S
中科院分区：
文献类型：
--
作者：
Kehrenberg, C;Schwarz, S
共筛选了302株氯霉素耐药葡萄球菌，以确定是否存在氟苯尼考/氯霉素耐药基因fexA和cfr及其在移动的遗传元件上的定位。在来自人类的114株分离株中，只有一株金黄色葡萄球菌分离株对氟苯尼考的MIC升高，但不携带已知的耐药基因cfr或fexA。相比之下，188株来自动物源的葡萄球菌中有11株被认为是氟苯尼考耐药的，并携带cfr（1株分离株）、fexA（5株分离株）或两种耐药基因（5株分离株）。在9个案例中，我们证实这些基因携带在质粒上。五种不同类型的质粒可以根据它们的大小、限制性图谱和抗性基因来区分。先前已被证明是非接合转座子Tn 558的一部分的基因fexA在来自动物的11个耐药分离株中的10个中被鉴定。开发了PCR测定来检测该转座子的不同部分以及它们的物理连接。Tn 558的完整拷贝被发现在五个不同的分离株，并通过反向PCR显示功能活性。Tn 558的截短拷贝，其中tnpA-tnpB区域由于整合了包括基因cfr的4，674-bp片段和新的2，446-bp IS 21样插入序列而部分缺失，在存在于三个葡萄球菌分离株中的质粒中观察到。
A total of 302 chloramphenicol-resistant Staphylococcus isolates were screened for the presence of the florfenicol/chloramphenicol resistance genes fexA and cfr and their localization on mobile genetic elements. Of the 114 isolates from humans, only a single Staphylococcus aureus isolate showed an elevated MIC to florfenicol, but did not carry either of the known resistance genes, cfr or fexA. In contrast, 11 of the 188 staphylococci from animal sources were considered florfenicol resistant and carried either cfr (one isolate), fexA (five isolates), or both resistance genes (five isolates). In nine cases we confirmed that these genes were carried on a plasmid. Five different types of plasmids could be differentiated on the basis of their sizes, restriction patterns, and resistance genes. The gene fexA, which has previously been shown to be part of the nonconjugative transposon Tn558, was identified in 10 of the 11 resistant isolates from animals. PCR assays were developed to detect different parts of this transposon as well as their physical linkage. Complete copies of Tn558 were found in five different isolates and shown by inverse PCR to be functionally active. Truncated copies of Tn558, in which the tnpA-tnpB area was in part deleted by the integration of a 4,674-bp segment including the gene cfr and a novel 2,446-bp IS21-like insertion sequence, were seen in a plasmid present in three staphylococcal isolates.