Clinical efficacy of local administration of ceftiofur in a Staphylococcus aureus infection in tissue cages in ponies.

The study explores the effects of a locally administered antibiotic, ceftiofur, in ponies who have been experimentally infected with a type of bacteria known as Staphylococcus aureus. The results suggest that while ceftiofur can significantly reduce bacteria counts, it is not capable of completely eliminating an infection on its own.

Study Design

• The researchers studied eight ponies, each implanted with tissue cages (TCs) on both sides of their neck.
• One of the TCs in each pony was inoculated with 150 mg of ceftiofur, an antibiotic, without any infection. Fluid samples were then collected to measure the concentration of ceftiofur.
• After a week, the other TC was infected with S. aureus, a type of bacteria causing various infections in animals and humans, and then treated with the same dose of ceftiofur for 21 days.
• During the treatment, fluid samples were collected to determine both the concentration of ceftiofur and the count of bacteria in the tissue cage fluid (TCF).

Findings

• The concentration of ceftiofur in the tissue fluid did not significantly vary between the infected and uninfected environments when a single dose of 150 mg of ceftiofur was administered.
• The level of ceftiofur was well above the minimum inhibitory concentration (MIC), which is the lowest concentration of an antibiotic that can prevent bacterial growth, for the particular strain of S. aureus used in the study.
• The count of viable bacteria in TCF decreased markedly after the antibiotic treatment. However, the infection was not completely eliminated and abscesses formed in five out of seven ponies.

Implications

• The findings suggest that locally administering ceftiofur alone is insufficient to completely eradicate S. aureus infections in sequestered sites in horses.
• Based on these results, the authors recommend using ceftiofur, not as a standalone treatment, but as an adjunct therapy alongside other treatments to effectively manage S. aureus infections.