Staphylococcus aureus is a common pathogen that can cause pneumonia and a variety of skin diseases. Skin injuries have a high risk of colonization by S. aureus, which increases morbidity and mortality. Due to the emergence of multidrug-resistant strains, antimicrobial peptides are considered to be among the best alternatives to antibiotics due to their unique mechanism of action and other characteristics. MPX is an antibacterial peptide extracted from wasp venom that has antibacterial activity against a variety of bacteria. This study revealed that MPX has good bactericidal activity against S. aureus and that its minimum inhibitory concentration (MIC) is 0.08 μM. MPX (4×MIC) can kill 99.9% of bacteria within 1 h, and MPX has good stability. The research on the bactericidal mechanism found that MPX could destroy the membrane integrity, increase the membrane permeability, change the membrane electromotive force, and cause cellular content leakage, resulting in bactericidal activity. Results from a mouse scratch model experiment results show that MPX can inhibit colonization by S. aureus, which reduces the wound size, decreases inflammation, and promotes wound healing. This study reports the activity of MPX against S. aureus and its mechanism and reveals the ability of MPX to treat S. aureus infection in mice, laying the foundation for the development of new drugs for bacterial infections.

Summary: Enrichment and propagation of gonocytes or spermatogonial stem cells (SSCs) from cryopreserved testicular tissue is essential to applySSCs‐related techniques in large domestic animals. We previously reported the cryopreservation of adult bovine testicular tissue. Here, we conducted the enrichment and culture of putative gonocytes from cryopreserved testicular tissues of post‐natal 1‐day‐old bulls. The testicular structure was well maintained after freezing and thawing. HighermRNAlevels of gonocyte/SSCs markers (PLZF,GFRα1, andUCHL‐1) than those of pluripotency genes (Oct4,Sox2, andNanog) were detected in the frozen–thawed sex cords.GFRα1 was specifically detected in the membrane and cytoplasm of gonocytes by immunostaining. Differential plating provided 40–50% enrichment of putative gonocytes. They were single, paired‐, aligned‐cells, or grape cluster‐like colonies in minimum essential medium (MEM) containing 2.5%FBS + 2 mM glutamine + 100 IU/mLpenicillin‐streptomycin + 40 μg/mLgentamycin + 15 mM HEPES + 10 mM β‐mercaptoethanol + 0.1 mM non‐essential amino acids + 1 mM sodium pyruvate. On day 3, gonocyte progeny increased and the contaminated somatic cells spread and concurrently divided slowly. On day 5, gonocyte progeny proliferated continuously and typical intercellular bridges formed by incomplete cytokinesis in paired‐cells or aligned‐cysts were observed. Immunochemically, they were stillGFRα1 andPLZFpositive. These cells expressed significantly higher gonocyte/SSCs markermRNAs than pluripotency genemRNAs, concomitant with a higher level of differentiated spermatogonia markerc‐kit. With time, gonocyte progeny colonies appeared in varied sizes and expanded dramatically on day 7. After cultured for 9–10 days, however, large colonies collapsed and dispersed as some single cells and small syncytial cysts. Together,MEMcontaining 10% dimethyl sulfoxide + 2.5% newborn calf serum provides efficient cryoprotection for the testicular tissue from 1‐day‐old neonatal bulls. Putative gonocytes enriched from these nascent tissues present robust proliferation capacity, conserved gonocyte/SSCs markers, andSSCs‐like in vitro features.