Detection Of 16S RRNA Methylases Gene In Gram-negative Bacteria

Objective: To investigate the prevalence of 16S rRNA methylases gene, armA and rmtB, which mediate high level aminoglycoside antibiotics resistance, in Gram-negative bacteria from 2 hospitals of Dalian and study it's mechanism of the resistance.Methods: A total of 134 non-replicate clinical isolates (56 A.baumannii, 29 E.coli, 35 K.pneumoniae, 4 P.aeruginosa,3 E.areogenes, 2 E.cloacae,5 S.marcescens)of amikacin resistance in Gram-negative bacteria were collected. Two 16S rRNA methylases gene, armA and rmtB, were detected by PCR-based assays. PCR products were sequenced. armA and rmtB gene mappings were proformed by plasmid extraction, conjugation and transformation. The minimal inhibitory concentrations (MIC) of the positives isolates, the transconjugations and the product of the trans- formation to amikacin, gentamycin and tobramycin were determinated using ager dilution.Results: Over all, 21(37.5%) armA-positive Acinetobacter baumannii, 5 (17.2%) rmtB-positive Escherichia coli and 5 (14.3%) rmtB-positive Klebsiella pneumoniae isolates were identified. Plasmid extraction and Conjugation experiments were only successful for 7 rmtB-positive isolates that produced ESBLs. Transconjugation and DH5a(pMDarmA) exhibited high-level resistance aminoglycoside (MIC≥1024mg/L).Conclusions: The 16S rRNA methylases gene, armA and rmtB had been existing in Dalian. armA is in Acinetobacter baumannii . rmtB gene is located on Escherichia coli and Klebsiella pneumoniae plasmid. armA and rmtB can induce high-level resistance to aminoglycosides.