Dual-functional bioactive silk sericin for osteoblast responses and osteomyelitis treatment.

Sericin, a natural protein from silk cocoon, has been reported for various biological properties in the biomaterials field. Modified forms of sericin have been studied for bone tissue engineering, while its unmodified form has been scarcely reported. Therefore, the purpose of this study was to evaluate physical and biological properties of unmodified sericin for potential use in bone surgery. Sericin was extracted from silk cocoons using a chemical-free boiling method. Sericin extract showed distinct bands with molecular weight ranging from 25 to 42 kDa including smear bands. Fourier transform infrared spectra presented characteristic peaks of amide I, II, and III, confirming the chemical composition of sericin. Based on biological activity, sericin extract at a concentration of 40 µg/mL increased the proliferation of osteoblast cells up to 135%, compared with the untreated control. Moreover, increase in antibacterial activity against Staphylococcus aureus, both clinical isolates and the reference strain ATCC 29213, was demonstrated for sericin extract with normal saline, while no antibacterial activity was observed for sericin with broth. It was found that sericin with normal saline showed higher zeta potential than sericin without normal saline, indicating higher system stability. This was confirmed by the average particle size of sericin extract with NaCl (3,249.3±226.1 nm) showing approximately 10 times smaller than sericin solution (29,015.9 ± 8,085.6 nm). Furthermore, sericin extract at the minimal inhibitory concentration significantly reduced the biofilm formation of S. aureus up to 95%. The study indicates biological activities of sericin, which could be applied as a dual-functional bioactive material to support bone regeneration and treat bone infections.

The prevalence and antibiotic susceptibility of Staphylococcus spp. on ocular surfaces of fighting bulls (Bos indicus) in Thailand.

Background and Aim: fighting bulls have a high risk of eye injuries, and opportunistic conjunctival bacterial flora may cause subsequent eye diseases. There is little information about the ocular health care of fighting bulls in Thailand. Thus, this study aimed to estimate the prevalence of Staphylococcus spp. from the eyes of fighting bulls and investigate their antimicrobial susceptibility. Materials and Methods: The samples were collected from the right conjunctival sacs of 105 fighting bulls. Biochemical tests and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were used to identify bacteria to genus and species levels. Antimicrobial susceptibility was tested by agar disk diffusion. Results: Staphylococcus spp. (36.84%, 56/152) were the most detected bacteria. The most prevalent Staphylococcus spp. was Staphylococcus chromogenes (37.50%, 21/56). The susceptibility test revealed that all isolates were susceptible to sulfamethoxazole/trimethoprim (56/56, 100%) and most were susceptible to chloramphenicol and gentamicin (54/56, 96.43%). The highest resistance rates were seen for tetracycline and doxycycline (23.21%, 13/56) followed by erythromycin (19.64%, 11/56). In addition, S. chromogenes isolates were evaluated for their ability to produce biofilms by a quantitative biofilm production assay. A total of 21 isolates exhibited biofilm production, independent of their antimicrobial susceptibility. Three multidrug-resistant isolates were found, including two Staphylococcus epidermidis isolates and a single S. chromogenes isolate. Conclusion: As antimicrobial resistant bacteria were detected on the eye surface, veterinarians should always conduct antimicrobial susceptibility testing before using antimicrobial agents. The results from this study will help to improve the standard of eye treatment for fighting bulls in Thailand.