Culture Collection of Antimicrobial Resistant Microbes, Department of Biology, Seoul Women's University, Seoul, Korea.
Microb Drug Resist. 2010 Sep;16(3):231-9. doi: 10.1089/mdr.2010.0039.
Erythromycin-resistant Campylobacter organisms were isolated from swine, and their resistance to the antibiotic was characterized. One hundred fourteen Campylobacter organisms were isolated from 572 swine intestinal samples. All isolates were identified as Campylobacter coli by sequence analysis of 16S rRNA gene and polymerase chain reactions with primers specific to hippuricase gene in Campylobacter jejuni and aspartokinase gene in C. coli. Minimal inhibitory concentrations (MICs) of erythromycin were determined by using the agar dilution method, and 80 isolates were found to be resistant to erythromycin (MIC ≥ 4 μg/ml). Of these, 31 isolates had low-level resistance (MIC =4-16 μg/ml), and 49 isolates had high-level resistance (HLR, MIC ≥ 32 μg/ml). The HLR isolates carried a point mutation at position A2075 → G in domain V of the 23S rRNA gene, whereas the low-level resistance isolates carried no mutation. These 49 HLR isolates were characterized by pulsed-field gel electrophoresis and multilocus sequence typing to study their genetic diversity. Pulsed-field gel electrophoresis identified 16 distinct types with 50% genetic similarity as the cutoff. On the other hand, 28 different sequence types (STs), including 10 new STs, were identified with multilocus sequence typing. Forty-six of 49 erythromycin HLR isolates showed crossresistance to 6 macrolide derivatives. The correlation between the inhibitory activity of carbonyl cyanide m-chlorophenylhydrazone and the existence of cmeB, which is responsible for efflux in HLR isolates, was found to be low. Erythromycin resistance was transferred from 38 of the 43 HLR isolates to susceptible C. coli by natural transformation, with a frequency of 1.217 x 10(-8)-4.618 x 10(-5) per recipient cell. All transformants were erythromycin resistant and had A2075 → G mutation in at least one of three copies of the 23S rRNA gene. Results indicate that variable genotypes of HLR C. coli coexist in swine and high-level erythromycin resistance can be transferred to other strains.
从猪中分离出红霉素耐药的弯曲杆菌属微生物，并对其抗生素耐药性进行了特征分析。从 572 份猪肠样本中分离出 114 株弯曲杆菌属微生物。所有分离株均通过 16S rRNA 基因序列分析和针对空肠弯曲杆菌 hippuricase 基因和大肠弯曲杆菌 aspartokinase 基因的聚合酶链反应鉴定为大肠弯曲杆菌。通过琼脂稀释法测定红霉素的最小抑菌浓度（MIC），发现 80 株对红霉素耐药（MIC≥4μg/ml）。其中，31 株为低水平耐药（MIC=4-16μg/ml），49 株为高水平耐药（HLR，MIC≥32μg/ml）。HLR 分离株在 23S rRNA 基因 V 区 2075 位的 A2075→G 点突变，而低水平耐药分离株无突变。对这 49 株 HLR 分离株进行脉冲场凝胶电泳和多位点序列分型，以研究其遗传多样性。脉冲场凝胶电泳鉴定出 16 种不同的类型，以 50%的遗传相似性作为截断值。另一方面，通过多位点序列分型鉴定出 28 种不同的序列型（ST），包括 10 种新的 ST。49 株红霉素 HLR 分离株中 46 株对 6 种大环内酯衍生物表现出交叉耐药性。羰基氰化物 m-氯苯腙的抑制活性与 HLR 分离株中负责外排的 cmeB 的存在之间的相关性较低。HLR 分离株的红霉素耐药性通过自然转化从 43 株中的 38 株转移到敏感的大肠弯曲杆菌中，每受体细胞的频率为 1.217×10（-8）至 4.618×10（-5）。所有转化子均对红霉素耐药，至少有一个 23S rRNA 基因的三个拷贝中存在 A2075→G 突变。结果表明，猪中存在不同基因型的 HLR 大肠弯曲杆菌，高水平的红霉素耐药性可转移到其他菌株。
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