Kim Joo-Sung, Carver Donna K, Kathariou Sophia
Department of Food Science, North Carolina State University, Raleigh, NC 27695-7624, USA.
Appl Environ Microbiol. 2006 Feb;72(2):1316-21. doi: 10.1128/AEM.72.2.1316-1321.2006.
Erythromycin resistance in Campylobacter coli from meat animals is frequently encountered and could represent a substantial barrier to antibiotic treatment of human infections. Erythromycin resistance in this organism has been associated with a point mutation (A2075G) in the 23S rRNA gene. However, the mechanisms responsible for possible dissemination of erythromycin resistance in C. coli remain poorly understood. In this study, we investigated transformation-mediated acquisition of erythromycin resistance by genotypically diverse C. coli strains from turkeys and swine, with total genomic DNA from erythromycin-resistant C. coli of either turkey or swine origin used as a donor. Overall, transformation to erythromycin resistance was significantly more frequent in C. coli strains from turkeys than in swine-derived strains (P < 0.01). The frequency of transformation to erythromycin resistance was 10(-5) to 10(-6) for turkey-derived strains but 10(-7) or less for C. coli from swine. Transformants harbored the point mutation A2075G in the 23S rRNA gene, as did the erythromycin-resistant strains used as DNA donors. Erythromycin resistance was stable in transformants following serial transfers in the absence of the antibiotic, and most transformants had high MICs (>256 microg/ml), as did the C. coli donor strains. In contrast to the results obtained with transformation, spontaneous mutants had relatively low erythromycin MICs (32 to 64 microg/ml) and lacked the A2075G mutation in the 23S rRNA gene. These findings suggest that natural transformation has the potential to contribute to the dissemination of high-level resistance to erythromycin among C. coli strains colonizing meat animals.
在肉类动物的空肠弯曲菌中，红霉素耐药性屡见不鲜，这可能成为人类感染抗生素治疗的重大障碍。该菌的红霉素耐药性与23S rRNA基因中的一个点突变（A2075G）有关。然而，空肠弯曲菌中红霉素耐药性可能传播的机制仍知之甚少。在本研究中，我们调查了来自火鸡和猪的基因多样的空肠弯曲菌菌株通过转化介导获得红霉素耐药性的情况，使用来自火鸡或猪源的红霉素耐药空肠弯曲菌的全基因组DNA作为供体。总体而言，来自火鸡的空肠弯曲菌菌株转化为红霉素耐药性的频率显著高于猪源菌株（P < 0.01）。火鸡源菌株转化为红霉素耐药性的频率为10^(-5)至10^(-6)，但猪源空肠弯曲菌的频率为10^(-7)或更低。转化体在23S rRNA基因中携带点突变A2075G，用作DNA供体的红霉素耐药菌株也是如此。在无抗生素条件下连续传代后，转化体中的红霉素耐药性稳定，大多数转化体的最低抑菌浓度（MIC）较高（>256微克/毫升），空肠弯曲菌供体菌株也是如此。与转化结果相反，自发突变体的红霉素MIC相对较低（32至64微克/毫升），并且在23S rRNA基因中缺乏A2075G突变。这些发现表明，自然转化有可能导致在定殖于肉类动物的空肠弯曲菌菌株中传播对红霉素的高水平耐药性。
