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. 2017 Dec;33(12):587-593.
doi: 10.1016/j.kjms.2017.08.001. Epub 2017 Aug 26.

Distribution of genes encoding resistance to aminoglycoside modifying enzymes in methicillin-resistant Staphylococcus aureus (MRSA) strains

Azar Dokht Khosravi  1 , Atefeh Jenabi  2 , Effat Abbasi Montazeri  3
Affiliations

Distribution of genes encoding resistance to aminoglycoside modifying enzymes in methicillin-resistant Staphylococcus aureus (MRSA) strains

Azar Dokht Khosravi et al. Kaohsiung J Med Sci. 2017 Dec.

Abstract

Today Methicillin-Resistant Staphylococcus aureus (MRSA) have acquired multiple resistance to a wide range of antibiotics including aminoglycosides. So, this study was aimed to investigate the rate of aminoglycoside resistance and the frequency of aminoglycoside resistance mediated genes of aac(Ia)-2, aph(3)-IIIa and ant(4')-Ia among MRSA strains. A total of 467 staphylococci isolates were collected from various clinical samples. S. aureus strains were identified by standard culture and identification criteria and investigating of presence of 16S rRNA and nuc genes. Cefoxitin disk diffusion, and oxacillin-salt agar screening methods were used to detect the MRSA strains with subsequent molecular identification for the presence of mecA gene. Antibiotic susceptibility of MRSA strains against aminoglycoside antibiotics was evaluated by using agar disk diffusion method. Multiplex PCR for the presence of aac(Ia)-2, aph(3)-IIIa and ant(4')-Ia encoding genes for aminoglycosides were performed for MRSA strains. From total staphylococci tested isolates, 262 (56.1%) were identified as S. aureus, of which 161 (61.45%) were detected as MRSA and all comprised mecA gene. The resistance pattern of MRSA strains to aminoglycoside antibiotics were: gentamicin 136 (84.5%); amikacin 125 (77.6%); kanamycin 139 (86.3%); tobramycin 132 (82%); and neomycin 155 (96.3%). The frequency of aac(Ia)-2, aph(3)-IIIa, and ant(4')-Ia genes among MRSA strains, were 64%, 42% and 11.8% respectively. In conclusion, as MRSA strains are of great concern in human infections, the results of present study could provide a useful resource for health sectors for choosing appropriate antibiotics for the effective treatment of infections due to MRSA strains.

Keywords: Aminoglycoside; Drug susceptibility test; MRSA; Staphylococcus aureus; mecA gene.

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Figures

Figure 1
Figure 1
Distribution of MRSA isolates according to the hospitals wards. NICU: Neonatal Intensive Care Unit; OPD: Outpatient Department; N/S: Neuro Surgery.
Figure 2
Figure 2
Antibiotic resistance pattern of MRSA blood isolates against aminoglycoside antibiotics.
Figure 3
Figure 3
The frequency of AME genes among MRSA strains.
See this image and copyright information in PMC

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