Sequence analysis showed three mutant spots in mar OR of clinical strain LC 1. Conclusion There does exist mar mechanism in clinical isolated Escherichia coli resistant to fluoroquinolone. PCR扩增及DNA序列分析发现,临床株LC1的marOR基因存在3处突变。结论对氟喹诺酮类耐药的临床分离大肠杆菌中存在Mar耐药机制。