Trace analysis of antibacterial tylosin A, B, C and D in honey by liquid chromatography-electrospray ionization-mass spectrometry.

A new LC-ESI-MS method was developed for the determination of residues of the antibacterial tylosins A, B, C and D in honey. The procedure employed an SPE on polymeric cartridges for the isolation of tylosins from diluted honey. Chromatographic separation of the tylosins was performed on a C18 column (150 x 4.60 mm2 ID, 5 microm) using a ternary gradient made of formic acid 1% in water (solvent A), methanol (solvent B) and ACN (solvent C) as mobile phase, at 30 degrees C and at a flow rate of 0.8 mL/min. Average analyte recoveries for the studied compounds ranged from 89 to 106% in replica sets of fortified honey samples. The detection limits for the four drugs studied were between 2 and 3 microg/kg. The developed method has been applied to the analysis of tylosin residues in honey from veterinarian treated beehives fed with the technical product, which contains the four compounds and is a new candidate antibiotic to treat American foulbrood disease of honey bee colonies.

Efficacy of ampicillin combined with ceftriaxone and gentamicin in the treatment of experimental endocarditis due to Enterococcus faecalis with no high-level resistance to aminoglycosides.

OBJECTIVE: This study tests the usefulness of ceftriaxone combined with ampicillin as an alternative to ampicillin plus gentamicin for the treatment of experimental endocarditis due to Enterococcus faecalis without high-level resistance to aminoglycosides. It also determines whether adding ceftriaxone to ampicillin and gentamicin increases the effectiveness against experimental enterococcal endocarditis resulting from E. faecalis. METHODS: Animals with catheter-induced endocarditis were infected intravenously with 108 cfu of the EF91 strain of E. faecalis and were treated for 3 days with ampicillin 2 g every 4 h administered as 'human-like' (H-L) pharmacokinetics, plus gentamicin 1 mg/kg every 8 h H-L, or ceftriaxone 2 g every 12 h H-L alone or combined with gentamicin 6 mg/kg every 24 h administered subcutaneously. RESULTS: The results of therapy for experimental endocarditis resulting from EF91 showed that the combination of ampicillin plus ceftriaxone was as effective as ampicillin plus gentamicin. The triple combination did not improve on the overall efficacies of the two-drug combinations. CONCLUSIONS: Because of its lower nephrotoxicity, ampicillin plus ceftriaxone may be a useful alternative therapy for E. faecalis endocarditis in selected patients.