Accuracy of the VITEK® 2 system for a rapid and direct identification and susceptibility testing of Gramnegative rods and Gram-positive cocci in blood samples.

The performance of the VITEK® 2 system for direct rapid identification and antimicrobial susceptibility testing of the bacteria responsible for blood infections was determined. The isolates studied included 166 Gram-negative rods and 74 Gram-positive cocci from inpatients. Specially treated monomicrobial samples from positive blood culture bottles were directly inoculated into the VITEK 2 system and the results were compared with those from cards inoculated with standardized bacterial suspensions. Compared with the standard method, 95.8% of Gram-negative rods were correctly identified by VITEK 2 and the overall level of agreement between the two methods in susceptibility testing was 92.0%. For Gram-positive bacteria, 89.2% were correctly identified by VITEK 2 and susceptibility testing revealed an overall agreement rate of 91.3%. These results suggest that VITEK 2 cards inoculated with fluids sampled directly from positive blood culture bottles are suitable for speedy identification and susceptibility testing of Gram-negative bacilli and Gram-positive cocci.

Accuracy of the VITEK 2 system for a rapid and direct identification and susceptibility testing of Gram-negative rods and Gram-positive cocci in blood samples

The performance of the VITEK 2 system for direct rapid identification and antimicrobial susceptibility testing of the bacteria responsible for blood infections was determined.The isolates studied included 166 Gram-negative rods and 74 Gram-positive cocci from inpatients.Specially treated monomicrobial samples from positive blood culture bottles were directly inoculated into the VITEK 2 system and the results were compared with those from cards inoculated with standardized bacterial suspensions.Compared with the standard method,95.8% of Gram-negative rods were correctly identified by VITEK 2 and the overall level of agreement between the two methods in susceptibility testing was 92.0%.For Gram-positive bacteria,89.2% were correctly identified by VITEK 2 and susceptibility testing revealed an overall agreement rate of 91.3%.These results suggest that VITEK2 cards inoculated with fluids sampled directly from positive blood culture bottles are suitable for speedy identification and susceptibility testing of Gram-negative bacilli and Gram-positive cocci

La performance du systeme VITEK 2 pour une identification et un test de sensibilite aux antimicrobiens rapides et directs des bacteries responsables d'infections sanguines a ete mesuree.Les isolats etudies concernaient 166 batonnets a gram negatif et 74 cocci a gram positif preleves sur des patients hospitalises.Des echantillons monomicrobiens issus de flacons d'hemoculture positifs ayant ete soumis a un traitement special ont ete directement inocules dans le systeme VITEK 2 et les resultats ont ete compares avec ceux issus de cartes inoculees a I'aide de suspensions bacteriennes standards.Par comparaison avec la methode standard,95,8 % des batonnets a gram negatif ont ete correctement identifies par VITEK 2 etle niveau de concordance global entre les deux methodes en matiere de test de sensibilite etait de 92,0 %.Pour les bacteries a gram positif,89,2 % ont ete correctement iclentifiees par VITEK2 etle testdesensibilite a revele un tauxde concordance de 91,3 %.Ces resultats suggerentque les cartes VITEK 2 inoculees a I'aide de liquides preleves directement dans des flacons d'hemoculture positifs sont adaptees a une identification eta un testde sensibilite rapides des bacilles a gram negatif et des cocci a gram positif

[Relation between plasma membrane redox activity and extracellular carbonic anhydrase activity in marine phytoplankton].

Exofacial ferricyanide reduction at the plasma membrane of intact cells, and the link between plasma membrane redox activity, inorganic carbon status of the cells and extracellular carbonic anhydrase (CAext) activity were assayed using 10 marine phytoplankton species. In species Chaetocceros compressus, Cocolithus pelagicus and Gephyrocapsa ocetanica with no extracellular CA activity under carbon-limited or carbon-replete conditions, barely detectable ferricyanide reduction was observed. Species Skeletonema costatum, Melosira sp., Thalassiosira rotula, Thalassiosira weisflogi and Pleurochrysis carterae in which extracellular CA activity was only detected under carbon-limited conditions showed high rates of exofacial ferricyanide reduction. Western blotting and immunolocalization showed the presence of enzyme protein under carbon-limited and replete conditions at the cell surface, even though the CA activity could only detected when inorganic carbon was limiting, which suggests that the development of extracellular CA in response to carbon limitation is an activation of a preexisting protein rather than de novo synthesis. The results suggest that inorganic carbon limitation in the light increases plasma membrane redox activity and promotes proton extrusion, which result in the protonation and activation of the extracellular CA.

Carbon dioxide-concentrating mechanism and the development of extracellular carbonic anhydrase in the marine picoeukaryote Micromonas pusilla.

A range of marine photosynthetic picoeukaryote phytoplankton species grown in culture were screened for the presence of extracellular carbonic anhydrase (CAext ), a key enzyme in inorganic carbon acquisition under carbon- limiting conditions in some larger marine phytoplankton species. Of the species tested, extracellular carbonic anhydrase was detected only in Micromonas pusilla Butcher. The rapid, light-dependent development of CAext when cells were transferred from carbon-replete to carbon-limiting conditions was regulated by the available free- CO2 concentration and not by total dissolved inorganic carbon. Kinetic studies provided support for a CO2 - concentrating mechanism in that the K0.5 [CO2 ] (i.e. the CO2 concentration required for the half-maximal rate of photosynthesis) was substantially lower than the Km [CO2 ] of Rubisco from related taxa, whilst the intracellular carbon pool was at least seven fold greater than the extracellular DIC concentration, for extracellular DIC values ⩽1.0 mm. It is proposed that when the flux of CO2 into the cell is insufficient to support the photosynthetic rate at an optimum photon irradiance, the development of CAext increases the availability of CO2 at the plasma membrane. This ensures rapid acclimation to environmental change and provides an explanation for the central role of M. pusilla as a carbon sink in oligotrophic environments.

Ethanolic dehydration and its effect on membrane-bound enzymes of Chlorogloeopsis fritschii and Chlorella pyrenoidosa.

Ethanolic dehydration (20% to 70%) of the thylakoid membranes of Chlorogloeopsis fritschii resulted in an 8% to 58% loss of glutamine synthetase activity. In Chlorella pyrenoidosa, hydroxypyruvate reductase and fumarase, marker enzymes of the peroxisomes and mitochondria, respectively, diffused from the organelles on dehydration.

The presence of glycollate oxidase and dehydrogenase in Dunaliella primolecta.

Homogenates of Dunaliella primolecta, D. salina and D. tertiolecta were assayed for glycollate oxidase and glycollate dehydrogenase. Both D. primolecta and D. salina but not D. tertiolecta showed substantial glycollate-dependent O2-uptake which is characteristic of glycollate oxidase. L-Lactate was an alternative substrate and both glycollate- and L-lactate-dependent O2 uptake were insensitive to 2 mM cyanide. Glycollate dehydrogenase, measured by following the glycollate-dependent reduction of 2,6-dichlorophenolindophenol under aerobic conditions, was present in D. primolecta, D. salina and D. tertiolecta. In the presence of glycollate and D-lactate, rates were additive so both glycollate and D-lactate dehydrogenases are present in the homogenates. Glycollate and D-lactate oxidation were both inhibited by 2 mM cyanide. Organelles released from phototrophically grown cells of D. primolecta were separated by isopycnic centrifugation on sucrose gradients. Glycollate oxidase was present in the peroxisome fraction at an equilibrium density of 1.25 g/cm(3), while the major peak of glycollate dehydrogenase activity was in the mitochondrial fraction at an equilibirium density of 1.22 g/cm(3).

The intracellular localization of glycolate oxidoreductase in Escherichia coli.

Distribution of glycolate oxidoreductase in cell-free extracts of E. coli grown in mineral medium containing sodium glycolate has been studied. The enzyme was found to be largely associated with the cytoplasmic membranes. Homologous antiserum to the membranes inhibited the enzyme activity completely after the solubilization of the intact membranes with Triton X-100. Results on the effect of pronase on glycolate oxidoreductase activity confirmed that part of the enzyme is exposed to the surface of the membrane.

Localization of glycollate dehydrogenase in Dunaliella salina.

Glycollate dehydrogenase of the halotolerant green alga Dunaliella salina, isolated from a brine pond, was found associated with the membrane fraction which exhibited complete photosynthetic activity. Highest enzyme activity was found in cells grown in the presence of 5% NaCl. Any increase in NaCl concentration led to a decrease in specific enzyme activity.