Clonal Diversity and Genetic Landscape of mecC-Positive S. aureus in Human Samples from Iran: First Report of CC/ST423/t742.

BACKGROUND

The emergence of mecC-carrying Staphylococcus aureus strains is a serious concern in public health. Our study investigated the clonal diversity, genetic characteristics, antimicrobial resistance, virulence determinants, biofilm-forming ability, and molecular epidemiology of mecC-positive Staphylococcus aureus isolates obtained from hospitalized patients in Iran.

METHODS

We analyzed 45 mecC-carrying S. aureus strains isolated from 1,590 S. aureus samples collected from different clinical sources. The characterization included antimicrobial susceptibility tests, assessment of biofilm formation, spa typing, multilocus sequence typing (MLST), and PCR analysis to detect resistance, biofilm-related, and virulence genes.

RESULTS

Our results showed that 17.8%, 17.8%, and 64.4% of the isolates were classified as weak, intermediate, and strong biofilm producers, respectively. The prevalence of the ant(4΄)-Ia and tet(M) was found in 80% and 73.3% of the isolates, respectively. MLST revealed that the 45 isolates belonged to four clonal complexes: CC8 (44.4%), CC130 (24.5%), CC121 (17.8%), and CC425 (13.3%). The majority of S. aureus isolates belonged to the CC8/ST239 lineage (44.4%). Also, tst-positive strains belonged to CC121/ST599/t5930 (17.8%) and CC8/ST239/t037 (11.1%), while eta-positive isolates belonged to CC/ST130/t843 (15.6%). Fusidic acid-resistant S. aureus isolates primarily belonged to CC8/ST239/t037 lineage (11.1%), followed by CC8/ST239/t7688 (6.7%), both carrying the fusB gene. Vancomycin-intermediate S. aureus strains were classified into CC/ST599/t5930 (6.7%) and CC/ST130/t843 (4.4%) clones.

CONCLUSION

This study highlights the need for close and continuous monitoring of the genetic diversity and characteristics of the mecC-carrying S. aureus strains. Besides, urgent measures are required to prevent the transmission of these strains and to effectively treat associated infections.