Frequency of the Genes Encoding Aminoglycoside Modifying Enzymes in Staphylococcus Aureus Isolated from Hospitalized Burn Patients

Background and Staphylococcus aureus is one of the most common nosocomial pathogens especially among burn patients. Aminoglycoside is usually used in combination with other antibiotics for treatment of serious S. aureus infections. Resistance to aminoglycoside antibiotics is one of the most important problems in treatment of S.aureus infections. The aim of the present study was to determine the frequency of aminoglycoside resistance genes in S. aureus isolated from burn patients.
a total of 81 isolates of S.aureus were collected from burn wounds of patients hospitalized in Taleghani hospital in Ahvaz, Iran. Conventional laboratory tests were used for identification of S. aureus at species level and then confirmed by detection of nucA gene. Antimicrobial susceptibility pattern was tested against 11 different antibiotics by Disc Agar Diffusion Method. Frequency of aminoglycoside resistance genes (aac(6’)-Ie-aph(2’’)-I, aph(3’)-IIIa, and ant(4’)-Ia) were evaluated by multiplex-PCR method.
Highest rate of resistance were observed against Penicillin (97.53%), Erythromycin (77.78%) and Ciprofloxacin (76.54%). None of the isolates were resistant to Vancomycin. MRSA detection rate was 87.65%. In isolates that showed resistance to Aminoglycosides, 28.57% have only aac(6’)-Ie-aph(2’’)-I gene and 46.03% have both aac(6’)-Ie-aph(2’’)-I and aph(3’)-IIIa genes simultaneously. None of the isolates were positive for ant(4’)-Ia gene.
Considering the high prevalence of MRSA isolates and also aminoglycoside resistance gene in S. aureus, continuous surveillance in infection control policy is necessary in hospitals to prevent resistant bacteria spreading.