Emergence of Aminoglycoside Resistance Due to armA methylase in Multi-drug Resistant Acinetobacter Baumannii Isolates in a University Hospital in Nepal

Abstract

Abstract Background: The  emergence  of  multidrug-resistant  Acinetobacter  baumannii  associated  with  hospital-acquired infections  has  been  increasingly  reported  worldwide.  16S  rRNA   methylase  producing  Gram-negative  bacteria  are highly  resistant  to  all  clinically  important  aminoglycosides. We  analyzed A.  baumannii  clinical  isolates  resistant  to aminoglycosides from hospitalized patients. The objective of this study was to investigate the emergence of armA in A.baumannii species associated with nosocomial infection in a university hospital in Nepal. Â

 Methods: This was a cross-sectional study conducted at the department of Clinical Microbiology, Tribhuvan University Teaching Hospital (TUTH), from December 2013 to December 2014. A total of 246 Acinetobacter species were isolated from different patients were screened for MDR A. baumannii. Identification at the species level was confirmed by 16S rRNA sequencing. Drug susceptibility testing was performed by Kirby- Bauer disc diffusion method and minimum inhibitory  concentrations  (MICs)  were  determined  using  the  guidelines  of  the  Clinical  and  Laboratory  Standards Institute (CLSI). Screening for 16S rRNA methylase-production was done for the isolates resistant to gentamicin and amikacin. Detection of 16S rRNA methylase gene was done by PCR.

Results:  All 122 multidrug-resistant A. baumanniiisolates were resistant to majority of the antibiotics used except polymyxin and tigecycline. Ninty-six MDR A. baumannii isolates had MICs of > 512 mg/L to amikacin and arbekacin indicating  their  high  resistance  to  aminoglycosides.Of  the  96  pan-aminoglycoside  resistant  isolates,  75  isolates  had 16SrRNAmethylasewith all isolates harboring armA gene.

Conclusions:  This  is  the  first  report  describing  multidrug-resistant A.  baumannii  strains  harboring  armA  from hospitalized patients in Nepal. A methylase gene (armA), conferring high level of resistance to aminoglycosides, was detected in majority of our isolates.

Keywords: Acinetobacterbaumannii; aminoglycosideresistance; 16S rRNAmethylase; multidrug-resistant.