Proliferation of Streptococcus zooepidemicus and Pseudomonas aeruginosa within a simulated subpalpebral lavage flushed with equine serum.

This research investigated whether administering equine serum via a simulated subpalpebral lavage system (SPL) can support the growth of bacteria Streptococcus zooepidemicus or Pseudomonas aeruginosa within the tubing. The findings indicate that these bacteria do not proliferate within silicone tubing infused with equine serum, suggesting that topical serum can be safely administered in clinical cases.

Research Methodology

• The researchers simulated a subpalpebral lavage (SPL) system—an eyelid fluid washing system for horses—by securing a silicone tube with an inserted sterile i.v. catheter with injection cap to an elevated platform. The platform was designed to mimic the dorsal conjunctival fornix, the area of the horse’s eye where SPL is typically performed.
• The tip of the tube was placed into a vial containing a culture medium inoculated with one of two types of bacteria: Streptococcus zooepidemicus or Pseudomonas aeruginosa. These bacteria were used due to their known occurrence in clinical equine diseases.
• The tubing was infused twice daily with equine serum (a type of blood fluid), sterile saline as a negative control, or culture medium as a positive control, followed by air. The infusions were designed to mimic the administration of medication through SPL in real-world scenarios.
• The experiment was incubated under temperatures of 25 or 37 degrees Celsius to imitate different possible environmental conditions, and it was performed three times to consolidate the results.

Key Findings and Conclusion

• The results showed that both types of bacteria were isolated from 100% of the tubing tips, indicating their presence at the interaction point with the microbial culture.
• However, the mid-section of the tubing and the i.v. catheter tip did not show bacterial growth, except for one instance of Streptococcus zooepidemicus found in the mid-section flushed with culture medium at 37 degrees Celsius. This suggests that the bacteria did not spread or multiply within the silicone tubing when it was infused with equine serum.
• The study concludes that Streptococcus zooepidemicus and Pseudomonas aeruginosa did not proliferate within silicone tubing infused with equine serum. The findings imply that the practice of using equine serum through a subpalpebral lavage system in clinical procedures does not lead to bacterial contamination and holds up safe.