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

Extracellular carbonic anhydrase facilitates carbon dioxide availability for photosynthesis in the marine dinoflagellate prorocentrum micans

This study investigated inorganic carbon accumulation in relation to photosynthesis in the marine dinoflagellate Prorocentrum micans. Measurement of the internal inorganic carbon pool showed a 10-fold accumulation in relation to external dissolved inorganic carbon (DIC). Dextran-bound sulfonamide (DBS), which inhibited extracellular carbonic anhydrase, caused more than 95% inhibition of DIC accumulation and photosynthesis. We used real-time imaging of living cells with confocal laser scanning microscopy and a fluorescent pH indicator dye to measure transient pH changes in relation to inorganic carbon availability. When steady-state photosynthesizing cells were DIC limited, the chloroplast pH decreased from 8.3 to 6.9 and cytosolic pH decreased from 7.7 to 7.1. Re-addition of HCO3- led to a rapid re-establishment of the steady-state pH values abolished by DBS. The addition of DBS to photosynthesizing cells under steady-state conditions resulted in a transient increase in intracellular pH, with photosynthesis maintained for 6 s, the amount of time needed for depletion of the intracellular inorganic carbon pool. These results demonstrate the key role of extracellular carbonic anhydrase in facilitating the availability of CO2 at the exofacial surface of the plasma membrane necessary to maintain the photosynthetic rate. The need for a CO2-concentrating mechanism at ambient CO2 concentrations may reflect the difference in the specificity factor of ribulose-1,5 bisphosphate carboxylase/oxygenase in dinoflagellates compared with other algal phyla.