Objective To investigate the prevalence of 16S rRNA methylase gene armA and to analyze their effect on the drug resistance in multi drug-resistant strains of Acinetobacter baumannii . Methods A total of 72 Acinetobacter baumannii isolates were collected from the Second Xiangya Hospital from Jan. 2008 to Dec. 2008. The size of inhibitory zone of these strains to gentamycin, tobramycin and amikacin were determinate using Kirby-Bauer( K-B) method. The 16S rRNA methylase genes armA were detected by PCR. PCR products were purified and sequenced. Then we used randomly amplified polymorphic DNA method (RAPD) genotyping technology for the establishment of DNA fingerprinting. In addition, we compared drug sensitivity test with RAPD technology. Results Twenty isolates of 72 strains were armA positive and the resistance rates of the strains with armA gene to gentamycin, tobramycin, amikacin were 90.0% , 90.0% and 90. 0% , respectivily. armA positive stains were divided into 7 types using RAPD technology. A genotype was the advantage type. Conclusion The study showed that 16S rRNA methylases gene armA was prevalent in Acinetobacter baumannii which could lead to resistant to almost all aminoglycosides at a high level. And the main form of armA gene prevalence in our hospital was the spread of the same clone strain inside and outside of clinic department.

Objective To investigate the genotypes and encoding resistance genes differences of Acinetobacter baumannii and analyze their interrelations with multi-drug resistance.Methods A total of 77strains Acinetobacter baumannii were collected random from the second Xiangya Hospital during September 2008 to September 2009.The K-B method which was WHO recommended was adopted to Acinetobacter baumannii drug sensitivity test to 15 kinds of antibiotics to establish susceptibility spectrum.At the same time,random amplified polymorphic DNA(RAPD)technique was used to establish DNA fingerprinting.The genes of β-lactamase(TEM-1,IMP,OXA-23,OXA-24,AmpC),aminoglycoside-modifying enzymes[aac(3')-Ⅰ ,aac(6')-Ⅰ ,ant(3")-Ⅰ]and 16S rRNA methylase(armA,rmtA,rmtB)were detected by PCR and sequenced,and find the relationship between the gene encoding and multi-drug resistance.In addition,we compared the rates of resistance genes of Acinetobacter baumannii and the relations with the genotype and the multi-resistance.Results Thirty-one sensitive strains and 46 multi-drug resistance strains(10 Pan-drug resistances)were isolated.Seventeen types from A to Q were separated using RAPD technique.E genotype widely popular in the ICU was the advantage type in multi-drug resistance strains,and the rate was 47.1%.While the various types scattered in sensitive strains.The positive rates of TEM-1,IMP,OXA-23,OXA-24,AmpC,aac(3')-Ⅰ ,aac(6')-Ⅰ ,ant(3")-Ⅰ ,armA in the multi-drug resistance strains and the sensitive strains were 95.7%,39.1%,84.8% ,54.3%,87.0%,89.1%,84.8%,45.7%,63.0% and 58.1%,9.7%,32.3%,48.4%,48.4%,29.0%,45.2%,12.9%,9.7%,respectively,and there was significant difference except for OXA-24 using the X2 test(P ＜ 0.05).All isolates were negative for rmtA gene and rmtB gene.Drug susceptibility analysis showed that the resistant rate was significantly higher of the strains carrying resistant genes than that of the resistance negative strains.When the strains were resistant to gentamicin and amikacin,the rate of three aminoglycoside genes positive was 34.8%.The trains containing all the measured β-lactamase genes were all resistant strains.Conclusion Compared with the sensitive Acinetobacter baumannii strains,a broad resistance spectrum and a high drug resistance rate were showed in multidrug resistance strains isolated from clinic,which harboring many kinds of β-lactamase genes and aminoglycosides genes with a high separation rate,and the same clone of multiple drug-resistant strains may be transmitted in and among wards.