Distribution of Aminoglycoside Resistance Mediated by 16S rRNA Methylation among IraqI Isolates of Escherichia coli and Pseudomonas aeruginosa

Abstract

One hundred   clinical isolates  of Escherichia coli and Pseudomonas aeruginosa (58 , 42 isolates respectively ) were obtained  from patients   suffering from  different infections at Baghdad \Iraq  teaching  hospital . These isolates were diagnosed using api 20E  .Results of primary screening test for aminoglycoside resistance using determination the minimum inhibitory concentration  revealed that all the isolates conferring multidrug resistance and the highest resistance was against kanamycin, while the lowest  was against amikacin .Phenotypic detection of Extended spectrum ?–lactamase ( ES?Ls) was preformed and the results showed that 84% of the isolates gave positive results. Highly resistant isolates (20 for each ) were selected for the genetic study using polymerase chain reaction technique (PCR) to determine  aminoglycoside resistance mediated by methylation 16S rRNA  beside detection blaCTX –M gene responsible for ESBLs production .Seven 16S rRNA methylase genes were amplified ,the ArmA (846 bp), RmtA(635bp), RmtB(584bp), RmtC(711bp), RmtD (500 bp), RmtF(453bp) and npmA (641bp) beside amplifying blaCTX –M gene ( 550bp) .Out of 20 E.coli isolates ,16(80%)gave positive results for ArmA gene, while non of P.aeruginosa harboured this gene. Only one isolates out of 20(5%) harboured  RmtB methylation gene in E.coli isolates, while 3 isolates out of 20(15%) contains RmtC gene and 1 isolates(5%) harboured  RmtD gene in E.coli isolates while in P.aeruginosa showed 3 isolates out of  20 (15%) positive results in this gene. The sixth methylation gene was npmA was detected in only one isolate (5%) out of 20. For blaCTX –M gene , it was detected in all E.coli isolates  (100%) while  it was  detected in 17(85%)  of  P.aeruginosa. This is the first report in Iraq for the emergence of 16S rRNA methylases  among  E.coli and P.aeruginosa in correlation with ES?Ls  production .

Key words: Aminoglycoside resistance, 16S rRNA methylation genes, and ES?Ls  blaCTX –M genes.