He Tao, Shen Jianzhong, Schwarz Stefan, Wu Congming, Wang Yang
National Center for Veterinary Drug Safety Evaluation, College of Veterinary Medicine, China Agricultural University, Beijing 100193, P. R. China.
Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut (FLI), Höltystr. 10, 31535 Neustadt-Mariensee, Germany.
J Antimicrob Chemother. 2015 Apr;70(4):1031-6. doi: 10.1093/jac/dku491. Epub 2014 Dec 4.
To characterize the chromosomally encoded novel floR gene variant floRv from Stenotrophomonas maltophilia of porcine origin and elucidate the gene order and content of the floRv-flanking regions in an MDR genomic island (GI).
Whole genome sequencing was used to identify the unknown florfenicol resistance gene in S. maltophilia strain GZP-Sm1. The candidate gene was cloned into pMD19-T and Escherichia coli transformants carrying this vector were tested for phenicol MICs. Flanking sequences of the florfenicol resistance gene were identified by a de novo assembly and a primer walking strategy.
GZP-Sm1 carried a floR gene variant, designated floRv. E. coli clones carrying this gene were resistant to chloramphenicol and florfenicol. The deduced 404 amino acid FloRv protein showed 84.1%-91.8% amino acid identity to various FloR proteins. The gene floRv was located in an MDR region within a 40 226 bp GI region. Six resistance genes, including floRv (phenicol resistance), tetR-tetA(A) (tetracycline resistance), strA/strB (streptomycin resistance), sul1 (sulphonamide resistance) and aadA2 (streptomycin/spectinomycin resistance), were located in this MDR region. PCR analysis revealed that the GI was not stable and could be excised from the chromosome as a circular intermediate.
The floRv gene was identified in a porcine S. maltophilia isolate. Six resistance genes including floRv were located in a novel GI. As an opportunistic pathogen in animals and humans, S. maltophilia might act as a resistance gene reservoir in farm environments. Its contribution to the spread of resistance genes to other pathogens should be monitored.
鉴定猪源嗜麦芽窄食单胞菌中染色体编码的新型氟苯尼考抗性基因变体floRv，并阐明多药耐药基因组岛（GI）中floRv侧翼区域的基因顺序和内容。
采用全基因组测序来鉴定嗜麦芽窄食单胞菌菌株GZP-Sm1中未知的氟苯尼考抗性基因。将候选基因克隆到pMD19-T中，并对携带该载体的大肠杆菌转化体进行酚类抗生素最低抑菌浓度（MIC）测试。通过从头组装和引物步移策略鉴定氟苯尼考抗性基因的侧翼序列。
GZP-Sm1携带一个名为floRv的floR基因变体。携带该基因的大肠杆菌克隆对氯霉素和氟苯尼考具有抗性。推导的404个氨基酸的FloRv蛋白与各种FloR蛋白的氨基酸同一性为84.1%-91.8%。基因floRv位于一个40226 bp的GI区域内的多药耐药区域。六个抗性基因，包括floRv（酚类抗生素抗性）、tetR-tetA(A)（四环素抗性）、strA/strB（链霉素抗性）、sul1（磺胺类抗性）和aadA2（链霉素/壮观霉素抗性），位于该多药耐药区域。PCR分析表明，该GI不稳定，可以作为环状中间体从染色体上切除。
在猪源嗜麦芽窄食单胞菌分离株中鉴定出floRv基因。包括floRv在内的六个抗性基因位于一个新型GI中。作为动物和人类中的机会致病菌，嗜麦芽窄食单胞菌可能在农场环境中充当抗性基因库。应监测其对抗性基因向其他病原体传播的贡献。
