ABSTRACT
VITEK 2 is an automated identification system for diverse bacterial and fungal species. A new card (the Neisseria-Haemophilus [NH] card) for the identification of Neisseria spp., Haemophilus spp., and other fastidious gram-negative or gram-variable microorganisms has been developed, but its performance in a routine clinical laboratory has not yet been evaluated. In this study, a total of 188 bacterial strains belonging to the genera Actinobacillus, Campylobacter, Capnocytophaga, Cardiobacterium, Eikenella, Gardnerella, Haemophilus, Kingella, Moraxella, and Neisseria were investigated. The NH card was able to identify 171 strains (91%) correctly without the need for extra tests; one strain (0.5%) was misidentified, and five strains (2.7%) could not be classified. Eleven strains (5.8%) were identified with a low level of discrimination, and simple additional tests were required to increase the correct-identification rate to 96.8%. The results were available within 6 h. Based on these results, the new VITEK 2 NH card appears to be a good method for the identification of diverse groups of fastidious organisms, which would otherwise require testing with multiple systems. However, more work is needed to evaluate the performance of VITEK 2 with regard to Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella bacteria because of the insufficient number of strains tested in this study. Moreover, further reduction of the detection time would be desirable.
Subject(s)
Haemophilus/isolation & purification , Neisseria/isolation & purification , Bacterial Typing Techniques , Gram-Negative Bacteria/classification , Gram-Negative Bacteria/isolation & purification , Time FactorsABSTRACT
The ascomycete Candida albicans is the most common fungal pathogen in immunocompromised patients . Its ability to change morphology, from yeast to filamentous forms, in response to host environmental cues is important for virulence . Filamentation is mediated by second messengers such as cyclic adenosine 3',5'-monophosphate (cAMP) synthesized by adenylyl cyclase . The distantly related basidiomycete Cryptococcus neoformans is an encapsulated yeast that predominantly infects the central nervous system in immunocompromised patients . Similar to the morphological change in C. albicans, capsule biosynthesis in C. neoformans, a major virulence attribute, is also dependent upon adenylyl cyclase activity . Here we demonstrate that physiological concentrations of CO2/HCO3- induce filamentation in C. albicans by direct stimulation of cyclase activity. Furthermore, we show that CO2/HCO3- equilibration by carbonic anhydrase is essential for pathogenesis of C. albicans in niches where the available CO2 is limited. We also demonstrate that adenylyl cyclase from C. neoformans is sensitive to physiological concentrations of CO2/HCO3-. These data demonstrate that the link between cAMP signaling and CO2/HCO3- sensing is conserved in fungi and reveal CO2 sensing to be an important mediator of fungal pathogenesis. Novel therapeutic agents could target this pathway at several levels to control fungal infections.
