ObjectiveTo investigate the isolation trends of common pathogenic bacteria in healthcareassociated infection(HAI) in a hospital,evaluate the changes in antimicrobial resistance to quinolones and antimicrobial resistance mechanisms, and guide rational antimicrobial use.MethodsBacterial identification and antimicrobial susceptibility test were performed by Vitek32 system and KirbyBauer method respectively, and antimicrobial susceptibility test results were evaluated based on standard of US Clinical and Laboratory Standards Institute (CLSI).ResultsFrom January 2006 to December 2010, a total of 10 606 pathogenic bacteria isolates were detected, the top 5 pathogens were Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii, distribution of pathogens of each year varied little. Antimicrobial susceptibility test results showed that antimicrobial resistance of these 5 pathogens to quinolones increased year by year, Escherichia coli and Klebsiella pneumoniae increased most rapidly,the resistant rate to ciprofloxacin increased from 48.72% and 48.33% in 2006 to 89.06% and 81.53% in 2010 respectively (P<0.005), the resistance to levofloxacin increased from 48.84% and 39.77% in 2006 to 80.14% and 80.64% in 2010 respectively (P<0.005); the resistant rate of Pseudomonas aeruginosa to ciprofloxacin, levofloxacin, and pefloxacin also increased year by year (P<0.005). Antimicrobial resistant rate of grampositive cocci to quinolones increased slowly.ConclusionIn the past five years, resistance of common pathogens in HAI to quinolones were increasing, monitoring on bacterial resistance should be strengthened; clinical antimicrobial use should be based on antimicrobial susceptibility test result.