Swine practitioners consider many factors when implementing antibiotic regimens, including labeled pathogens, clinical breakpoints or minimum inhibitory concentrations, cost, ease of implementation and withdrawal times, explained Sarah Lutz, a DVM student at Auburn University, during the 2023 Allen D. Leman Swine Conference. Another important factor to consider is duration of therapy, especially with today’s challenges in labor.
In other words, how quickly does it work?
“During my Swine Veterinary Internship Program (SVIP) summer internship, I had the opportunity to go on several herd visits with my mentor, Dr. Doug Powers. During our windshield time, we discussed diseases of different aged pigs, including Streptococcus suis. Since I was a Zoetis intern, I reached out to my mentor Dr. Micah Jansen about Excede as a treatment for Strep Suis,” Lutz said.
She shared the pharmacokinetics data with me, and we noticed that the first time point on previously published data for Excede – ceftiofur crystalline free acid (CCFA) – was at one hour post injection. At one hour, plasma concentrations for Excede were 2.23 ug/mL, which was greater than the MIC90 value for Strep suis at 2.0 ug/mL. The pharmacokinetics of Excede at time periods less than one hour post injection was unknown, so it was unclear when plasma concentrations of Excede surpassed MIC90 levels for labeled pathogens.
Lutz said she wanted to understand how quickly Excede reaches concentrations at or above MIC values for targeted bacteria. The objective of her trial was to study the pharmacokinetics of Excede in the first hour after a single intramuscular dose.
A Closer Look at the Study
Three barrows and three gilts, for a total of six weaned-aged pigs, were weighed and enrolled into her study. A dose of 1 milliliter per 44 lb. was calculated for each pig in accordance with the swine label for Excede.
Blood was collected immediately prior to administering an intramuscular injection of Excede. Blood was then collected at time points of 5, 10, 15, 30, 45 and 60 minutes for each pig. Blood was sampled into heparinized green top tubes, spun down via centrifuge and plasma collected.
A derivatization method and reversed phase high performance liquid chromatography (HPLC) was used to determine the concentration of ceftiofur and its active metabolite, desfuroylceftiofur (DFC) in plasma.
“The results of my study indicated that at 15 minutes, the mean plasma concentration of ceftiofur crystalline free acid was 2.44 ug/mL, which was greater than the MIC90 level for Strep suis (2 ug/mL). The range of plasma concentrations across the six pigs showed that at 15 minutes, the lowest plasma concentration recorded was 1.97 ug/mL, which is close to the MIC90 for Strep suis. By 30 minutes, the mean was 3.83 ug/mL and the range indicated that every pig had achieved plasma concentration levels above the MIC90 level for Strep suis,” Lutz said.
The key takeaway from her study was that Excede achieved therapeutic plasma concentrations for Strep suis in all pigs by 30 minutes post injection, with five out of six pigs reaching it by 15 minutes.
“Producers and practitioners can be confident that Excede not only has a long duration of therapy, but also reaches therapeutic concentrations rapidly,” Lutz said.
Lutz was one of the seven students competing for the 2023 Morrison Swine Innovator Prize.
Read More:
Highlights from the 2023 Allen D. Leman Swine Conference
Bates Wins 2023 Morrison Swine Innovator Prize with E. Coli Research
