Staphylococcus haemolyticus attenuates the antibacterial effect of teicoplanin via aggregates and biofilms

Staphylococcus pseudintermedius ST2660 isolated from a cat has strong biofilm-forming ability and increases biofilm formation at cat's normal body temperature

Staphylococcus pseudintermedius has been isolated from dogs, cats, and horses and is also known as an emergent zoonotic agent. We administered orbifloxacin, a fluoroquinolone, to treat bacterial infections of cutaneous wounds caused by excessive grooming of the skin in contact with the subcutaneous port of the subcutaneous ureteral bypass (SUB) system in a cat. However, after 80 days of treatment, a severe abscess was observed in the wound and fluoroquinolone-resistant S. pseudintermedius was isolated from the abscess. The isolate was identified as a novel sequence type (ST) 2660 and contained genes for leukocidins (lukS and lukF), exfoliative toxin (siet), and biofilm regulation (icaA and icaD). The isolate was resistant to macrolide, lincosamide, fluoroquinolone, and tetracycline classes. In addition, the isolate had strong biofilm-forming ability which significantly increased with culturing at 39 °C compared with that at 37 °C, suggesting that the isolate prefers a cats' body temperature as the optimal biofilm growth condition. Notably, the biofilms were increased in the presence of doxycycline with culturing at 39 °C. This study is the first report in Japan on the new sequence type of S. pseudintermedius isolated from a companion animal and clarifies the distinctive virulence of S. pseudintermedius.

Ginkgo biloba L. exocarp petroleum ether extract inhibits methicillin-resistant Staphylococcus aureus by modulating ion transport, virulence, and biofilm formation in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

As reported in the Ancient Chinese Medicinal Books, Ginkgo biloba L. fruit has been used as a traditional Chinese medicine for the treatment asthma and cough or as a disinfectant. Our previous study demonstrated that G. biloba exocarp extract (GBEE), an extract of a traditional Chinese herb, inhibits the formation of methicillin-resistant Staphylococcus aureus (MRSA) biofilms. However, GBEE is a crude extract that contains many components, and the underlying mechanisms of purified GBEE fractions extracted with solvents of different polarities are unknown.

AIM OF THE STUDY

This study aimed to investigate the different components in GBEE fractions extracted with solvents of different polarities and their antibacterial effects and mechanisms against MRSA and Staphylococcus haemolyticus biofilms both in vitro and in vivo.

METHODS

The components in different fractions were detected by high-performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS). Microbroth dilution assays and time growth curves were used to determine the antibacterial effects of the fractions on 15 clinical bacterial isolates. Crystal violet staining, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to identify the fractions that affected bacterial biofilm formation. The potential MRSA targets of the GBEE fraction obtained with petroleum ether (PE), denoted GBEE-PE, were screened by transcriptome sequencing, and the gene expression profile was verified by quantitative polymerase chain reaction (qPCR).

RESULTS

HPLC-HRMS analysis revealed that the four GBEE fractions (extracted with petroleum ether, ethyl acetate, n-butanol, and water) contained different ginkgo components, and the antibacterial effects decreased as the polarity of the extraction solvent increased. The antibacterial activity of GBEE-PE was greater than that of the GBEE fraction extracted with ethyl acetate (EA). GBEE-PE improved H. illucens survival and reduced MRSA colonization in model mouse organs. Crystal violet staining and SEM and TEM analyses revealed that GBEE-PE inhibited MRSA and S. haemolyticus biofilm formation. Transcriptional analysis revealed that GBEE-PE inhibits MRSA biofilms by altering ion transport, cell wall metabolism and virulence-related gene expression. In addition, the LO2 cell viability and H. illucens toxicity assay data showed that GBEE-PE at 20 mg/kg was nontoxic.

CONCLUSION

The GBEE fractions contained different components, and their antibacterial effects decreased with increases in the polarity of the extraction solvent. GBEE-PE limited MRSA growth and biofilm formation by affecting ion transport, cell wall synthesis, and virulence-related pathways. This research provides a more detailed overview of the mechanism by which GBEE-PE inhibits MRSA both in vitro and in vivo and suggests that GBEE-PE is a new prospective antimicrobial with the potential to be used in MRSA therapeutics in the future.