Biclonality among tst -positive MRSA in a tertiary hospital in Algeria: predominance of ST22 and detection of a multidrug-resistant ST39 strain

AIMS: Methicillin-resistant Staphylococcus aureus (MRSA) remains a major public health concern due to its antibiotic resistance and virulence potential. This study aimed to characterizes tst-positive MRSA strains identified among 150 clinical isolates collected between 2020 and 2023 at Mustapha Bacha Hospital, Algiers, Algeria. METHODS AND RESULTS: Antimicrobial susceptibility testing was performed according to CLSI guidelines. The methicillin resistance genes (mecA and mecC) and virulence gene tst were detected by PCR. In addition, whole genome sequencing (WGS) was conducted on all tst-positive isolates to determine their multilocus sequence types (MLST), antimicrobial resistance and virulence gene profiles, and single nucleotide polymorphisms (SNPs), in order to determine clonal relatedness. Among the 150 isolates tested, 143 carried the mecA gene, while the remaining seven were negative. The mecC gene was not detected. Eight MRSA (5.3%) carried the tst gene encoding toxic shock syndrome toxin-1 (TSST-1). The predominant clone was ST22-MRSA-IV, detected in seven isolates, while one strain belonged to ST39-MRSA-II. CONCLUSIONS: This study reports the detection of tst-positive ST22-MRSA (Gaza epidemic clone) and a multidrug-resistant ST39-MRSA isolates at Mustapha Bacha Hospital, underscoring the need for ongoing genomic surveillance to monitor their occurrence and potential spread.