Delivery of therapeutic agents into the brain is a major challenge in central nervous system drug development. The blood–brain barrier (BBB) prevents access of biotherapeutics to their targets in the central nervous system and, therefore, prohibits the effective treatment of many neurological disorders. To find blood–brain barrier shuttle peptides that could target therapeutics to the brain, we applied a phage display technology on a primary endothelial rat cellular model. Two identified peptides from a 12 mer phage library, GLHTSATNLYLH and VAARTGEIYVPW, were selected and their permeability was validated using the in vitro BBB model. The permeability of peptides through the BBB was measured by ultra-performance liquid chromatography-tandem mass spectrometry coupled to a triple-quadrupole mass spectrometer (UHPLC-MS/MS). We showed higher permeability for both peptides compared to N–C reversed-sequence peptides through in vitro BBB: for peptide GLHTSATNLYLH 3.3 × 10⁻⁷ cm/s and for peptide VAARTGEIYVPW 1.5 × 10⁻⁶ cm/s. The results indicate that the peptides identified by the in vitro phage display technology could serve as transporters for the administration of biopharmaceuticals into the brain. Our results also demonstrated the importance of proper BBB model for the discovery of shuttle peptides through phage display libraries.

Staphylococcus spp. is the most common cause of mastitis, with a significantly low cure rate. Bacterial characteristics like adhesion and biofilm formation, as well as extracellular factors, can affect the pathogenesis of staphylococcal mastitis. The study’s objectives were to confirm S. aureus, assess their antibiotic resistance, identify methicillin resistance genes, verify biofilm formation, and detect biofilm-associated genes from bovine mastitis samples using multiplex PCR (mPCR). From 215 milk samples, six were confirmed as S. aureus. Most isolates were sensitive to all measured antibiotics. One isolate was identified as an inducible form of MLSB resistance (macrolides, lincosamides, and streptogramin B resistance), while the other two isolates were resistant to penicillins and carboxypenicillins. In S. aureus cultures used for methicillin resistance genotypic analysis by PCR, the mecA and mecC genes were not found. Biofilm formation phenotypes were determined in four strains. An mPCR analysis revealed that all strains of S. aureus carried icaABCD, agrA, srtA, fnbA, clfA, and clfB genes. Only in one isolate was the fnbB gene detected; the bap gene was not detected in any of the isolates. This emphasizes the importance of using appropriate treatment and continuous monitoring of S. aureus to prevent the spread of antibiotic-resistant strains in dairy cow farms.

Staphylococcus aureus is an important human pathogen known for its versatility and ability to cause a wide range of infections. The aim of this study was to isolate and identify S. aureus from skin lesions from human patients, to determine antimicrobial resistance and biofilm formation potential at phenotypic and genotypic levels, as well as to verify the activity of efflux pump production. Out of 51 samples collected from skin lesions of various etiologies, 13 isolates were identified as S. aureus. All isolates showed the ability to form biofilms, which correlated with the presence of the icaABCD, agrA, srtA, clfAB, and fnbAB genes, while the bap gene was absent. The highest rates of resistance were observed for ampicillin (69.2%) and gentamicin (46.2%), as well as for erythromycin and clindamycin (38.5%). The mecA gene was present in two isolates, but phenotypic resistance to methicillin was confirmed in only one of them, suggesting possible heterogeneous expression or regulated activity of resistance mechanisms. The mecC gene was not present in any isolate. Efflux pump production was observed in only three isolates, showing weak to intermediate levels. These findings indicate the high biofilm potential and variable antimicrobial resistance of S. aureus clinical isolates, which pose a challenge for the treatment of emerging skin infections.