Association between SCC<i>mec</i> types and antimicrobial resistance in clinical MRSA isolates

Abstract

Background: Methicillin resistant Staphylococcus aureus (MRSA) is the causative agent of serious infections. MRSA isolates carry mecA gene which confers resistance to all β-lactams, markedly limiting the therapeutic options. Staphylococcal Chromosomal Cassette mec (SCCmec) typing enables strain-based MRSA identification.  Aim: This study aimed to identify the prevalent SCCmec types among clinical MRSA isolates in Alexandria, Egypt, and their association with antibiotic resistance. Methods: One hundred MRSA clinical isolates were phenotypically and genotypically identified and tested for susceptibility to different classes of antibiotics. Subsequently, SCCmec typing was done using both conventional and SYBR Green PCR. Results: Typeability was 75 %, SCCmec type V was the most predominant (45.3%), with significant association with pyogenic lesions (53%, ^MCp <0.001).  Staphylococcal Chromosomal Cassette mec type IV was significantly associated with nasal colonizers (50%, ^MCp < /em> 0.049).  Staphylococcal Chromosomal Cassette mec type II was the most prominent in blood stream infection (33 %). Various antibiotic resistance patterns were detected. SCCmec types II and III displayed the highest resistance, while SCCmec type IV showed the least resistance. There was a significant association between SCCmec types and antibiotic resistance (p < /em> = 0.02-0.001). Conclusions: The only SCCmec types detected by PCR were SCCmec II-VI, with high resistance to gentamicin among all types. SCCmec type V was the most prevalent and was of relatively low resistance to antibiotics. SCCmec type IV was the least prevalent and showed the least resistance to antibiotics. There was a significant association between SCCmec types II and III and resistance to fluoroquinolones. Macrolides resistance was significantly associated with SCCmec type II. Tetracyclines resistance was significantly associated with SCCmec type III.