Detection of Plasmid-Mediated 16S rRNA Methylase Conferring High-Level Resistance to Aminoglycosides in Gram negative bacilli from Egypt

Background: Recently, production of 16S rRNA methylases by Gram-negative bacilli has emerged as a novel mechanism for high-level resistance to aminoglycosides by these organisms in a variety of geographic locations. Therefore, the spread of high-level aminoglycoside resistance determinants has become a great concern. Objective: to determine the prevalence of the occurrence of 16S rRNA methylases genes in aminoglycosideresistant gram-negative bacteria isolates. Methods: 30 Gram-negative bacilli amikacin resistant isolates were collected from inpatients and outpatients at Theodor Bilharz Research Institute (TBRI). Biochemical identification of bacterial species was performed with API 20E system. Antimicrobial susceptibilities of amikacin, gentamicin, tobramycin, neomycin, kanamycin, and netilmicin, were determined by the disk diffusion method and the MICs of amikacin were detected by the E test method. PCR was used to identify 16S rRNA methylas armA and rmtB genes. Result: E.coli, (15/30; 50%), Klebsiella pneumonia (7/30; 23.3%), Pseudomonas aeruginosa (4/30; 13.3%), Enterobacter cloaca and Acinetobacter baumanii (2/30; 6.7% each) were isolated. Extended spectrum β-lactamases (ESBLs) were detected in 7 (23.6%) isolates. Among the 30 isolates, 13 (43.3%) isolates showed a high level of resistance to amikacin. Seven out of 30 (23.3%) amikacin-resistant isolates were positive for 16S rRNA methylase genes. Six isolates (20%) were positive for rmtB gene and one (3.3%) Enterobacter cloaca ESBLs producer isolate was positive for armA gene. rmtB was detected in one (3.3%) Pseudomonas aeruginosae isolate and five (16.7%) E. coli isolates, in which, 3 of them were ESBLs producers. ArmA and rmtB genes were not detected simultaneously. Conclusions: 16S rRNA methylase genes were detected in gram negative bacilli in TBRI. RmtB was found to be more prevalent than armA. There was correlation between the detection of methylase genes and the production of ESBLs. [Aisha Abu Aitta; Manal El Said, Ehab El Dabaa; Mohamed Abd El Salam and Hesham Mohamed Mahdy. Detection of Plasmid-Mediated 16S rRNA Methylase Conferring High-Level Resistance to Aminoglycosides in Gram negative bacilli from Egypt. Life Sci J 2012;9(4):2472-2479]. (ISSN: 1097-8135). http://www.lifesciencesite.com. 365

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