Detection of tetracycline resistance genes, aminoglycoside modifying enzymes, and coagulase gene typing of clinical isolates of Staphylococcus aureus in the Southwest of Iran

Objective(s): The aim of the present study was to determine the aminoglycoside modifying enzymes (AMEs) encoded genes, tetracycline resistance genes, and the coa based typing of Staphylococcus aureus isolates in the Southwest of Iran. Materials and Methods: Antimicrobial susceptibility of isolates was carried out by agar disk diffusion methods. Two sets of multiplex PCR mixture were used for detection of AME genes and tet genes.  All of the isolates were typed with the coagulase gene typing method. Of the ۱۲۱ isolates, ۲۹.۷۵% and ۴۷.۹۳% were resistant to at least one aminoglycosides and tetracyclines, respectively. Results: The aac(۶')-Ie-aph(۲'') was the most frequent gene (۹۷.۲۲%), and aph (۳')-IIIa and ant (۴')-Ia genes were detected in ۶۱.۱۱% and ۱۱.۱۱% of aminoglycoside resistant isolates, respectively. The tetK and tetM genes were detected in ۸۲.۷۵% and ۵۶.۹% of tetracycline resistant isolates, respectively. Overall ۳۱.۴% of isolates were MRSA. Totally ۱۷ distinct coa gene RFLP patterns, numbered C۱ to C۱۷, were observed.  The C۵ was the most frequent coa type with ۳۱ isolates. Conclusion: The aac(۶')-Ie-aph(۲'') and aph (۳')-IIIa genes were the most important genes contributing to aminoglycosides resistance, while resistance to tetracyclines was mediated by tetK and tetM genes. Interestingly all S. aureus with C۵ as the most prevalent coa-type were resistant to at least one of the aminoglycoside antibiotics and tetracycline simultaneously. Moreover, ۳۰ out of ۳۱ isolates with this coa type were MRSA, indicating the importance of the C۵ coa-type in MRSA strains and also in isolates that were resistant to aminoglycosides and tetracycline.

Keywords:

Aminoglycoside resistance , Aminoglycoside modifying enzymes , Coagulase gene typing , Staphylococcus aureus , Tetracycline resistance