关键词: 猪葡萄球菌；分离鉴定；表皮脱落毒素；药物敏感性试验

Abstract: To investigate the causative agent of exudative epidermitis in 7?day?old suckling piglets on a large? scale pig farm in Jiangmen，Guangdong Province in April 2026，skin scabs and exudates from affected piglets were collected. The isolate was subjected to systematic identification，including isolation and culture，morphological observation，biochemical identification，16S rRNA and gap gene sequencing，and antimicrobial susceptibility testing. The carriage of six exfoliative toxin genes（ExhA，ExhB，ExhC，ExhD，ShetA，ShetB）was also examined. The results showed that the isolate exhibited no hemolysis on blood agar plates，appeared as Gram positive cocci arranged in typical grape like clusters under microscopic examination，and displayed biochemical characteristics consistent with Staphylococcus hyicus. Sequence analysis of the 16S rRNA and gap genes revealed that the isolate shared 100.0% identity with reference strains of Staphylococcus hyicus，and 95.3%–97.0% identity with other staphylococci，such as Staphylococcus aureus；notably，the gap gene exhibited 99.9%–100.0% identity with representative Staphylococcus hyicus strains of both porcine and human origin. Based on these results，the isolate was preliminarily identified as Staphylococcus hyicus and designated strain GDjm 202604. Antimicrobial susceptibility testing showed that the isolate was susceptible to 11 agents， including cefazolin， ceftriaxone， enrofloxacin， novobiocin， and gentamicin； intermediately susceptible to amoxicillin，neomycin sulfate，and ampicillin sulbactam；and resistant to 12 agents， including ampicillin，lincomycin，doxycycline，and trimethoprim. Detection of exfoliative toxin genes revealed that only ExhC was positive，while the other five were negative；the ExhC gene sequence shared 100.0% identity with a strain isolated from Zhaoqing and 99.0%–99.8% identity with other domestic and international strains，indicating that ExhC exfoliative toxin is the major virulence factor of this strain. This study provides reference data for the etiological diagnosis，rational clinical antimicrobial use，and integrated prevention and control of exudative dermatitis in piglets in the Guangdong Province.

Key words: Staphylococcus hyicus；Isolation and identification；exfoliative toxin；Drug sensitivity test