Introduction: Accurate diagnosis of von Willebrand disease (VWD) enables effective patient management. von Willebrand factor (VWF) multimer analysis provides useful information regarding VWF multimer structure, thereby aiding VWD subtyping and management; however, historically technically challenging assays have had limited utility. This study evaluates the Sebia Hydrasys Hydragel-11 semi-automated VWF multimer assay and further validates the Hydragel-5 gel system, as primarily pertaining to VWD diagnostics and monitoring of therapy. Methods: Provisionally diagnosed (via a reference assay test panel) archived patientsamples and prospective test patient samples, including those undergoing desmopressin trial or therapy monitoring, along with commercial and in-house control material and various external quality assessment (EQA) samples, were analysed. VWF multimers were evaluated for presence, loss or partial loss of high molecular weight (HMWM) and intermediate molecular weight (IMWM) multimers by both visual inspection and densitometric scanning, and comparison with reference assay results. Results: All anticipated multimer patterns were reproduced, with patients generally showing multimer profiles matching expected patterns according to VWD type based on reference test panel 'diagnosis'. Occasional discrepancies were resolved by retesting. The increase in plasma VWF following desmopressin therapy was also clearly demonstrated. Multimer profiles of EQA samples complemented reference test panel results and matched EQA targets. There were some 'technical' limitations noted. Conclusion: This easy to use, standardised, semi-automated multimer analysis system can demonstrate the multimer profile of VWD patients, thus representing an additional laboratory tool for improved diagnosis, thereby facilitating appropriate patient management. K E Y W O R D S desmopressin, Hydragel, Multimers, von Willebrand disease, von Willebrand factor | 763 OLIVER Et aL.

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Linear B-cell epitopes of the Rhodococcus equi virulence-associated protein (VapA) were mapped using a synthetic peptide bank in this study. The peptides were screened in an enzyme-linked immunosorbent assay (ELISA) with a total of 70 sera from foals with current R. equi disease (51 sera), as well as from foals that had either recovered from R. equi infection 10 months previously (3 sera) or that had no known history of R. equi disease (16 sera). An epitope with the sequence NLQKDEPNGRA was identified and was universally recognized by all 51 sera from foals with R. equi disease and was not recognized by any of the other sera. There was poor reactivity between all sera and peptides relating to other areas of the VapA protein. It is proposed that an ELISA based upon a defined peptide epitope may be used in an improved serological diagnostic test for R. equi infection in foals.

The antimicrobial properties of olive leaf extract (OLE) have been well recognized in the Mediterranean traditional medicine. Few studies have investigated the antimicrobial properties of OLE. In this preliminary study, commercial OLE and its major phenolic secondary metabolites were evaluated in vitro for their antimicrobial activities against Escherichia coli and Staphylococcus aureus, both individually and in combination with ampicillin. Besides luteolin 7-O-glucoside, OLE and its major phenolic secondary metabolites were effective against both bacteria, with more activity on S. aureus. In combination with ampicillin, OLE, caffeic acid, verbascoside and oleuropein showed additive effects. Synergistic interaction was observed between ampicillin and hydroxytyrosol. The phenolic composition of OLE and the stability of olive phenols in assay medium were also investigated. While OLE and its phenolic secondary metabolites may not be potent enough as stand-alone antimicrobials, their abilities to boost the activity of co-administered antibiotics constitute an imperative future research area.