Co-detection of antimicrobial resistance and virulence-associated determinants in Staphylococcus aureus isolated from radicular cysts in a post-disaster region of Türkiye

Abstract Background Radicular cysts are among the most common chronic odontogenic lesions, yet the molecular mechanisms of resistance and virulence of their microbial flora remain incompletely defined. Following the 2023 earthquakes in Hatay, Türkiye, medical facilities were severely disrupted, creating a post-disaster clinical setting. This cross-sectional, isolate-based study descriptively evaluated antimicrobial resistance phenotypes and selected virulence-associated genes among S. aureus isolates recovered from radicular cyst infections in this setting. Methods A total of 225 clinical S. aureus isolates were recovered from surgically excised radicular cysts. Antimicrobial susceptibility testing was performed by disk diffusion according to CLSI guidelines. Eleven selected targets, including mecA and virulence-associated genes ( hla, hlb, pvl, fnbA, fnbB, clfA, cna, ebpS, bbp ), together with 16S rRNA for species confirmation, were detected by PCR. Pairwise and higher-level co-occurrence analyses were used to describe gene co-detection patterns. Associations between resistance categories and gene positivity were evaluated using Fisher’s exact test or chi-square test, as appropriate. Results Resistance to one, two, and three or more antimicrobial classes was observed in 45.3%, 32.9%, and 21.8% of isolates, respectively. MecA positivity was more frequent in isolates with higher resistance categories, increasing from 4.9% in single-class-resistant isolates to 30.6% in multidrug-resistant (MDR) isolates ( p < 0.001). Among the selected virulence-associated genes, fnbA (58.7%), hla (52.9%), and cna (45.8%) were most frequently detected. MDR isolates showed higher detection frequencies of hla (85.7%), fnbA (81.6%), and cna (73.5%) than lower resistance categories. Although pvl was detected in only 8.0% of isolates overall, it was more frequently detected among MDR isolates. Co-occurrence analysis identified recurrent gene co-detection patterns involving adhesion- and hemolysin-associated genes, most commonly fnbA-cna, hla-fnbA , and hla-cna . Higher-order gene combinations (≥ 4 genes) were uncommon and reflected isolates that simultaneously carried multiple virulence-associated genes. Conclusions In this isolated collection, multidrug resistance was associated with more frequent detection of selected virulence-associated genes in cyst-derived S. aureus isolates. The results may be relevant for the combined use of phenotypic susceptibility testing and molecular detection of major resistance markers, particularly mecA , in laboratory characterization of isolates. Because the study lacked a pre-disaster comparator and external control group, the recorded patterns cannot be attributed to the disaster context; rather, they provide descriptive baseline data from a post-disaster clinical setting.