Fosfomycin concentrations in epithelial lining fluid in weaning piglets.

Respiratory diseases are one of the most important problems in modern intensive swine production (Gardner and Hird, 1990). These diseases are a common cause of morbidity and mortality in weaning pigs (Gardner and Hird, 1990; Galina et al., 1994; Dos̆en et al., 2007). The concentrations of antibiotics in epithelial lining fluid (ELF) reflect the antimicrobial activity for extracellular pathogens involved in respiratory diseases (Schentag & Ballow, 1991; Kiem & Schentag, 2008; Ross, 2006). Fosfomycin is a hydrosoluble bactericidal broad-spectrum antibiotic used in Central and South America and various Asian countries. Although fosfomycin showed clinical efficacy in the treatment of pulmonary diseases, concentrations in ELF have not still been established in any species. Assuming that the determination of fosfomycin concentration in ELF (biophase) represents the key parameter for establishing efficacy of antibiotics, the objective of this work was to characterize the penetrating capacity of fosfomycin in ELF and its relationship with serum concentrations in weaning piglets. Six weaning piglets (three males and three females), clinically healthy 25–28 days old, were used in this trial. To minimize the stress and facilitate blood sampling, a permanent long catheter was placed in each piglet in the left external jugular vein according to the method of Soraci et al. (2010). Serum concentrations of disodium-fosfomycin were evaluated following a single i.m. dose of 15 mg ⁄kg in the gluteus muscle. The disodium-fosfomycin was supplied by Bedson S.A. Laboratories, Pilar, Buenos Aires, Argentina. It was dissolved in a 10% sodium citrate solution that yielded a pH of 6.8. The study was carried out following the rules of ethical approval by the experimental ethics committee of Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Argentina. To obtain the bronchoalveolar lavage fluid (BALF), a flexible fiber optic bronchoscope (Olympus BF-P20D) was used. The bronchoscope was pushed into the bronchus trachealis which leads into the right cranial lung lobe (Shields & Riedler, 2000; Baltes et al., 2001; Scollo et al., 2011). Seven milliliters of sterile 0.9% saline (prewarmed to 30 C) was introduced and recovered by using a vacuum pump aspiration with a maximum of 15 kPa (Shields & Riedler, 2000; Baltes et al., 2001). This washing was repeated three times and a range between 15 and 18 mL was obtained (Shields & Riedler, 2000). The procedure of instillation and collection was completed in <1 min (the average dwell time was about 50 ± 10 sec) (Baughman et al., 1983; Dohn & Baughman, 1985; Rennard et al., 1986; Grigg et al., 1991; Lamer et al., 1993; Baughman, 1997; Mombarg et al., 2002). The aliquots were pooled for analysis. Blood and BALF samples were collected at the same time after fosfomycin i.m. administration: 1, 2, 4, 6, 8, and 12 h. The serum was separated immediately by centrifugation at 2000 g for 15 min and frozen at )20 C until analysis. The lavage sample was centrifuged immediately at 400 g for 10 min, and the supernatant was separated from the pellets. Fosfomycin concentrations in serum and dilute solution of BALF were measured using a highperformance liquid chromatography–mass-mass spectrometry (HPLC-MS ⁄MS) according to the method determined by Soraci et al. (2011). Estimation of the amount of ELF sampled by BALF was performed using the urea dilution method (Taylor et al., 1956; Theodore et al., 1975; Rennard et al., 1986). The urea content was measured in BALF and serum according to the urea test kit instructions (Urea testkit; Sigma Chemical, St Louis, MO, USA). The AUCs of fosfomycin in ELF and serum were calculated by the trapezoidal rule when multiple measurements were available. A nonparametric paired data test (Wilcoxon signed rank test) was used to compare pharmacokinetics data by using a SAS software package (SAS Institute Inc., Cary, NC, USA). A P J. vet. Pharmacol. Therap. 35, 406–409. doi: 10.1111/j.1365-2885.2011.01344.x. SHORT COMMUNICATION