ABSTRACT
Objective To analyze the aminoglycoside ( AG ) antibiotics resistance rate of carbapenem-resistant Klebsiella pneumoniae ( CRKP ) and its molecular mechanisms.Methods One hundred and four strains of CRKP isolated from 4 hospitals in Zhejiang Province from January 2013 to June 2014 were collected, including 56 strains from Sir Run Run Shaw Hospital , Zhejiang University School of Medicine ( S hospital ), 22 from the First Affiliated Hospital, Zhejiang University School of Medicine ( Z hospital), 13 from Yiwu TCM Hospitals (Y Hospital) and 13 from Fuyang First People's Hospital (F Hospital).VITEK 2 Compact method and K-B disk method were used to detect the susceptibility of commonly used antibiotics including three kinds of AGs (kanamycin, gentamycin and amikacin ).PCR and sequencing techniques were used to screen the aminoglycoside resistance -related 16S rRNA methylation genes (rmtA, rmtB and armA) and the aminoglycoside modified enzyme resistance gene [aac(6′)Ⅰb].The relationship between drug resistance and carrier status of drug resistance genes was analyzed .Homologous analysis of rmtB-positive strains was performed using PFGE to examine the epidemic spread of strains in each hospital.Results All 104 CRKP strains were multi-drug resistant and had high resistance to cephalosporins, fluoroquinolones ( ciprofloxacin, levofloxacin ) and nitrofurantoin.The resistance rates to gentamicin, kanamycin and amikacin were 73.1%(76/104), 64.4%(67/104) and 56.7%(59/104), respectively.The carrying rates of aminoglycoside-resistance genes were: rmtB 56.7%( 59/104 ), aac (6′)Ⅰb 17.3%(18/104), armA 1.9%(2/104); while no rmtA was detected.Thirty-seven strains did not carry the screened genes.Amikacin-resistant strains were resistant to both kanamycin and gentamicin, and both were rmtB-positive strains.The PFGE classification results showed that 104 strains were divided into 11 clonal populations, and there were scattered non-population clones in each hospital. There were seven major clonal populations (Ⅰ-Ⅶ) carrying rmtB genes, of which typeⅠ, typeⅢand typeⅤwere prevalent in S hospital ; typeⅡ, typeⅥand TypeⅦwere popular in Z hospital ; the distribution of strains in Y hospital was scattered ; F hospital had one independent clone type Ⅳ(3 strains).Conclusion AGs still have certain sensitivity to CRKP strains.The main mechanism of strain resistance to AGs is the rmtB gene-mediated 16S rRNA methylase.
ABSTRACT
OBJECTIVE To investigate the 16S rRNA methylases gene and AMEs of 30 strains multi-resistant Pseudomonas aeruginosa isolated from clinic work in our hospital.METHODS Collected 50 P.aeruginosa strains from two hospitals(30 strains of multi-resistant P.aeruginosa from Yantai,Shandong,20 strains of pan-drug resistant P.aeruginosa from Jiangsu),and analyzed 6 kinds of 16S rRNA methylases(armA,rmtA,rmtB,rmtC,rmtD and npmA) and 6 kinds of AMEs gene aac(3)-Ⅰ,aac(3)-Ⅱ,aac(6′)-Ⅰb,aac(6′)-Ⅱ,aac(3″)-Ⅰ,and aac(2″)-Ⅰ by PCR and sequence analysis.RESULTS Among 30 strains of multi-resistant P.aeruginosa from Yantai,the positive rate of 4 kinds of genes aac(3)-Ⅱ,aac(6′)-Ⅱ,aac(3″)-Ⅰ,and aac(2″)-Ⅰ was 20%(6/30),46.7%(14/30),36.7%(11/30) and 3.3%(1/30).The other 8 kinds genes were all negative.The total positive rate of AMEs gene was 46.7%(14/30).In 20 strains of pan-drug resistant P.aeruginosa,the positive rate of 6 kinds of genes rmtB,aac(3)-Ⅱ,aac(6′)-Ⅰb,aac(6′)-Ⅱ,aac(3″)-Ⅰ,and aac(2″)-Ⅰ was 55%(11/20),60%(12/20),35%(7/20),60%(12/20),50%(10/20) and 45%(9/20).The other 6 kinds genes were all negative.The total positive rate of AMEs gene was 95%(19/20).CONCLUSIONS It is the first report that 16S rRNA methylases gene is existed in P.aeruginosa;there is very high positive rate of AMEs genotypes in P.aeruginosa;there are differences in gene existing among two hospitals.