Identification of two major direct repeat unit clusters, 8i and 11ce, among methicillin resistant Staphylococcus aureus strains: the emergence of novel dru types and repeats

Background: The changing epidemiology and decreasing susceptibility to first-line antibiotics, such as vancomycin and linezolid, leave clinicians with few therapeutic options for MRSA infections. This study aimed to conduct an epidemiology study and characterize MRSA isolates. Methods: A total of 150 MRSA isolates were collected from clinical specimens. Antimicrobial susceptibility was determined using the disk diffusion method. Resistance and major virulence genes were screened using the polymerase chain reaction. The SCCmec and dru typing were used to conduct molecular epidemiology. The BioNumerics tandem-repeat sequence typing plug-in tool was utilized for dru type cluster analysis. We constructed a minimum spanning tree using the similarity matrix of the DSI model. Results: We discovered 24 dru types among the 55 dru sequenced MRSA isolates. Additionally, eight new dru types were discovered and added to the dru typing database. Two dru clusters (8i, 11ce) and nine single dru types were identified in 55 dru sequenced MRSA isolates. The two dru clusters, 8i and 11ce, accounted for 46 MRSA isolates (83.63%). The most common one of the nine singles dru types in this study was dt9bd, which belonged to the SCCmec types of IX. Conclusions: Given that two clusters account for the majority of strains in our study, we can conclude that the genetic origin of these strains is the same. Therefore, the spread of these strains can be prevented with effective MRSA monitoring in hospitals and communities.