Abstract
Background
Next to the high prevalence of methicillin-resistant Staphylococcus aureus (MRSA), S.aureus isolates are now resistant to some other antibiotics, such as aminoglycosides. The aim of this study was to determine the aminoglycoside resistance and aminoglycoside-modifying enzyme (AMEs) genes among S.aureus isolated from patients referred to the Children’s Medical Center, Tehran, Iran.
Methods
A total of 333 S. aureus clinical isolates were collected and tested by disk diffusion for susceptibility testing. Aminoglycoside-resistant S. aureus isolates were screened for the presence of the three AMEs genes.
Results
A total of 149 isolates (45%) were of aminoglycoside-resistant, of which 142 isolates (95%) were amikacin-resistant isolates and 27 (18%) were gentamicin-resistant isolates. Among 149 isolates, aac(6′)-Ie-aph(2″) resistance gene was detected in 65 isolates (44%). The aph(3′)-IIIa resistance gene and ant (4′)-Ia resistance gene were found in 55 isolates (37%) and 27 isolates (18%), respectively. Concurrent of aph(3′)-IIIa and ant(4′)-Ia genes was seen in 16 isolates (11%). Moreover, aph(3′)-IIIa and aac(6′)-Ie-aph(2″) were observed in 49 (33%) isolates, simultaneously. Concurrent ant(4′)-Ia and aac(6′)-Ie-aph(2″) genes were detected in 16 isolates (11%). Simultaneous presence of all three genes aph (3′)-IIIa and ant (4′)-Ia and aac(6′)-Ie-aph(2″) was observed in 14 (9%) of the isolates. Among amikacin-resistant isolates, concurrent of aph(3′)-IIIa and aac(6′)-Ie-aph(2″) genes were seen in 44 isolates (31%), while it was found in 70% of gentamicin-resistant S. aureus (19 isolates).
Conclusion
Since high frequency of aminoglycoside resistance and AME genes were found in S. aureus strain isolated from hospitalized children in our hospital, the monitoring of aminoglycoside resistance and AMEs genes is highly recommended to limit the spread of aminoglycoside resistance among S. aureus isolates.