Comparison of phenotype,genotype and drug resistance genes of Acinetobacter baumunnii isolated from clinic
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. 
 
Key words: 
Acinetobacter baumannii; Drug resistance,multiple; Phenotype ; Genotype; Genes