This study determined the impact of porcine reproductive and respiratory syndrome virus (PRRSV) and Streptococcus suis coinfection on the pharmacokinetic (PK) profile of ceftiofur hydrochloride in pigs after intramuscular (i.m.) injection. Eighteen clinically normal crossbred gilts were assigned by weight into a challenge group (10 pigs) and control group (eight pigs). Pigs in both groups received a single i.m. injection of ceftiofur hydrochloride (Excenel RTU Sterile Suspension; Zoetis) at a 5 mg/kg BW dose. Serial blood samples were collected to characterize the plasma concentration curve. After a 10 days drug washout period, the challenge group was inoculated with 2 mL of PRRSV isolate VR-2385 (10(5.75) 50% tissue culture infective doses per mL) intranasally and 8 days later inoculated S. suis. When clinical disease was evident, the second PK assessment began in both challenge and control groups. Coinfected pigs demonstrated lower values of AUC and CMAX , but higher values of Cl/F and Vz/F indicating drug kinetics were altered by infection. The data from this study have implications on ceftiofur treatment regimens in diseased pigs.

The pharmacokinetics of intramuscularly administered ceftiofur crystalline-free acid (CCFA) were determined in pigs that were clinically healthy (n = 8), vaccinated with a Porcine reproductive and respiratory syndrome modified live virus (PRRS MLV) (n = 10), challenged with wild-type porcine reproductive and respiratory syndrome virus (PRRSv) VR-2385 (n = 10), or vaccinated with PRRS MLV and later challenged with wild-type PRRSv VR-2385 (n = 10). Animals were given a single dose of CCFA intramuscularly at 5 mg/kg body weight. Blood was collected at 0 (pretreatment), 0.25, 0.5, 1, 6, 12, 24, 48, 96, 144, 192, and 240 h postinjection. Plasma was analyzed using liquid chromatography-mass spectrometry. Plasma concentration-time curves for each group were evaluated with noncompartmental modeling. When compared to control animals, those receiving the PRRSv wild-type challenge only had a lower AUC , higher Cl/F, and higher Vz/F. The PRRSv wild-type challenge only group had the longest T . The C did not differ among all four treatments. Control animals had no statistically significant differences from animals vaccinated with PRRS MLV alone or animals vaccinated with PRRS MLV and later challenged with wild-type PRRSv. Our results suggest that PRRSv wild-type infection has the potential to alter CCFA pharmacokinetics and PRRS MLV vaccination may attenuate those changes.

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In this trial sampling technique did impact levels of bacterial contamination present in synovial fluid. The differences in contamination levels were highly variable between sampling techniques, ranging from no bacteria present to bacterial concentrations of 10^6. Needle aspiration proceeded by skinning of the joint resulted in the lowest level of contamination in samples indicating the skin is a major source of contamination and the use of needle aspiration over swab collection significantly reduces contamination levels.