Abstract: Abstract Objective To investigate the prevalence of 16SrRNA methylase genes and the rate of drug resistance in Acinetobacter baumannii isolates in Tianjin District.Methods A total of 152 strains of Acinetobacter baumannii were collected from clinical specimens in Tianjin District from August 1st,2010 to December 31st,2010.The primary antimicrobial susceptibility testing was performed by either Broth dilution or Kirby-Bauer Disk diffusion;Seven 16SrRNA methylase genes (armA、rmtA、rmtB、rmtC、rmtD、rmtE、npmA) were amplified by polymerase chain reaction(PCR) and sequenced.Results Polymyxin resistance rate (1.97%) among 152 strains is the lowest,followed are Cefoperazone/sulbactam(15.79%) and Levofloxacin(36.84%). The resistance rates to Aminoglycoside、Cephalosporin、 Carbapenem are above 55%.73 of the 83 resistance to Aminoglycoside strains were armA genes positive(87.95%).account for 48,03% of all the experimental strains. No rmtA、rmtB、rmtC、rmtD、rmtE、npmA were found.Except the Polymyxin,the rates of resistance to the rest 13 antibiaotics were significantly higher in armA gene positive strains than in armA gene negative strains.(P<0.05).Multidrug-resistance Acinetobacter baumannii (MDRAb) and Pandrug-resistance Acinetobacter baumannii(PDRAb) were also higher in armA gene positive strains (100% and 69.86% respectively) than in armA gene negative strains(21.52% and 11.39% respectively) .Conclusion The rate of 16SrRNA methylase genes (armA) were firstly reported in Tianjin district.armA gene is widely existed in Acinetobacter baumannii strains. No other six genes were found in Acinetobacter baumannii.The rate of drug resistance in armA positive strains were higher than in armA negative ones.The number of MDRAb and PDRAb are significantly larger in armA gene positive strains than in armA negative ones.Also armA positive strains are all MDRAb.Further research was needed to confirm wether the armA gene positive strains can be treated as MDRAb in clinical therapy by collecting more strains.

Key words: Aminoglycoside antibiotics, Acinetobacter baumannii, 16SrRNA methylase genes