Prevalence and characterization of Staphylococcus aureus isolated from patients with aerobic vaginitis in Shenzhen, Southern China.

BACKGROUND: Aerobic vaginitis (AV), characterized by vaginal inflammation and elevated pH, is associated with severe complications such as preterm delivery. Staphylococcus aureus (S. aureus) is a predominant pathogen in AV, but its molecular epidemiology, virulence profiles, and antimicrobial resistance in vaginal infections remain poorly defined. METHODS: Between August 2023 and August 2024, 38 S. aureus isolates from AV patients were analyzed for antimicrobial susceptibility, multilocus sequence typing (MLST), spa typing, accessory gene regulator (Agr) typing, PCR-based detection of virulence, hemolysin, and efflux pump genes, as well as their biofilm formation potential. RESULTS: A total of 38 S. aureus isolates were obtained from the vaginal samples of 38 AV patients, including 14 aged 20–30 years and 24 aged ≥ 31 years, of whom 13 were parturients. Penicillin resistance was highest (68.4%), followed by erythromycin and clindamycin (15.8% each); two MRSA strains carried mecA and pvl but lacked tsst. Resistance genes were frequent, with sepA (97.4%), norA (71.1%), and mepA (63.2%), and norA/mepA and mdeA/mepA combinations were linked to Fuyan Jie (FJ) resistance (P < 0.05). Detergent resistance rates were 55.3% (FJ), 44.7% (Metronidazole Chlorhexidine Detergent, MCD), and 31.6% (Honghe Fuyan Jie, HFJ). Virulence factors included sea (57.9%), tsst (47.4%), and hld (100%). Biofilm assays using the 96-well microtiter plate method showed strong biofilm formation in 72.2% of isolates, particularly among clonal complex (CC) 55 and AgrⅢ strains. MLST identified 12 STs, with ST188 predominant (21.1%) and four novel STs (ST9745, ST9746, ST9747, ST9749); CC1 was most common (42.1%), spa type t189 (26.3%) was dominant, and AgrⅠ (60.5%) prevailed. CONCLUSIONS: These findings highlight S. aureus genetic diversity, hemolysin and virulence gene prevalence, and resistance phenotypes in AV, providing insights for targeted therapy.