Evaluating synergy between marbofloxacin and gentamicin in Pseudomonas aeruginosa strains isolated from dogs with otitis externa

The aim of this study was to determine antimicrobial susceptibility of Pseudomonas aeruginosa strains to marbofloxacin and gentamicin, and investigate the possible synergistic, additive, indifferent or antagonistic effects between the two agents. P. aeruginosa strains can develop resistance quickly against certain antibiotics if used alone, thus the need emerges to find synergistic combinations. A total of 68 P. aeruginosa strains isolated from dogs were examined. In order to describe interactions between marbofloxacin and gentamicin the checkerboard microdilution method was utilized. The MICs (minimum inhibitory concentrations) for marbofloxacin and gentamicin were in the range 0.25–64 mg/L and 0.25–32 mg/L, respectively. The combination of marbofloxacin and gentamicin was more effective with a MIC range of 0.031–8 mg/L and a MIC90 of 1 mg/L, compared to 16 mg/L for marbofloxacin alone and 8 mg/L for gentamicin alone. The FIC (fractional inhibitory concentration) indices ranged from 0.0945 (pronounced synergy) to 1.0625 (indifference). Synergy between marbofloxacin and gentamicin was found in 33 isolates. The mean FIC index is 0.546, which represents a partial synergistic/additive effect close to the full synergy threshold. In vitro results indicate that marbofloxacin and gentamicin as partially synergistic agents may prove clinically useful in combination therapy against P. aeruginosa infections. Although marbofloxacin is not used in the human practice, the interactions between fluoroquinolones and aminoglycosides may have importance outside the veterinary field

A fully validated microbiological assay for daptomycin injection and comparison to HPLC method

abstract Daptomycin (DPT) was the first lipopeptide antibiotic available for commercialization. It is active against gram-positive bacteria, including resistant strains. This work aimed to develop and validate a turbidimetric microbiologic assay to determine daptomycin in an injectable form. A 3x3 design was employed, at concentrations of 1, 2 and 4.0 µg/mL. The microorganism test used was Staphylococcus aureus ATCC 6538p, and Antibiotic Medium 3 was used as the culture medium. Method validation demonstrated that the bioassay was linear (r=0.9995), precise (RSD=2.58%), accurate (recovery 100.48± 2.11%), and robust. Degradation kinetics was also performed in an alkaline medium, indicating that daptomycin degradation follows first order kinetics under these conditions. The analyses of degraded solutions showed that daptomycin degradation products do not possess bactericidal activity. The bioassay was compared to HPLC method that was previously developed and no significant difference was found between them (p>0.05). The method proved to be appropriate for daptomycin injection quality control

Platinum-group elements and gold in komatiitic rocks from the Agrilia Formation, Othrys ophiolite complex, Greece

Highly magnesian lavas (32 wt.% MgO) from the Agrilia Formation, Othrys ophiolite complex, central Greece, were analyzed for major and trace elements. Average platinum-group elements (PGE) concentrations (all in ppb) are: Os 3.6, Ir 0.68, Ru 4, Pt 1.2, Pd 8.5, Rh < 0.5 and Au 19. Although the studied lavas from the Agrilia Formation have unusually high Mg, Cr and Ni contents, they differ from boninites in respect to the dominance of olivine phenocrysts, the lack of orthopyroxene and primary hornblende and the preferential association of chromite with groundmass. The higher Pd than Pt concentrations and the lack of detectable Rh appear to be characteristic of the Agrilia ultramafic lavas. The PGE concentrations, the relatively low values of Pd/Ir ratios (∼ 12), the chondrite-normalized PGE patterns - which are almost flat, with exception of a Pt anomaly - and the mineral chemistry of the studied lavas are comparable to typical komatiites, suggesting that these lavas may represent primitive magmas. The derived parental magma for the studied lavas (in equilibrium with Fo90.5) contains ∼ 17 wt.% MgO and is similar to those which gave rise to modern analogues of the Archean komatiites from Gorgona island, Colombia. However, the variation in Ti/V and Ti/Sc ratios in Agrilia lavas and the enrichment in some incompatible elements (Sr, Rb, Ba, La) may indicate a modification of the magma composition in the mantle source region by a subduction component. The occurrence of the Triassic komatiitic (and boninitic) lavas in combination with tholeiitic lavas with mid-ocean ridge basalt (MORB) affinities of the Othrys complex, may suggest changes in the geotectonic setting during the development of the Othrys complex from a fore-arc (formation of the highly magnesian lavas) to back-arc tectonic setting (formation of the main complex). © 1989