Central nervous system (CNS) nocardiosis is a rare disease entity caused by the filamentous bacteria Nocardia species. We present a case series of 5 patients from our hospital and a review of the cases of CNS nocardiosis reported in the literature from January 2000 to December 2011. Our results indicate that CNS nocardiosis can occur in both immunocompromised and immunocompetent individuals and can be the result of prior pulmonary infection or can exist on its own. The most common predisposing factors are corticosteroid use (54% of patients) and organ transplantation (25%). Presentation of the disease is widely variable, and available diagnostic tests are far from perfect, often leading to delayed detection and initiation of treatment. The optimal therapeutic approach is still undetermined and depends on speciation, but lower mortality and relapse rates have been reported with a combination of targeted antimicrobial treatment including trimethoprim/sulfomethoxazole (TMP-SMX) for more than 6 months and neurosurgical intervention.

ABSTRACTPathogenic fungi are capable of switching between different phenotypes, each of which has a different biological advantage. In the most prevalent human fungal pathogen,Candida albicans, phenotypic transitions not only improve its adaptation to a continuously changing host microenvironment but also regulate sexual mating. In this report, we show thatCandida tropicalis, another important human opportunistic pathogen, undergoes reversible and heritable phenotypic switching, referred to as the “white-opaque” transition. Here we show thatN-acetylglucosamine (GlcNAc), an inducer of white-to-opaque switching inC. albicans, promotes opaque-cell formation and mating and also inhibits filamentation in a number of naturalC. tropicalisstrains. Our results suggest that host chemical signals may facilitate this phenotypic switching and mating ofC. tropicalis, which had been previously thought to reproduce asexually. Overexpression of theC. tropicalis WOR1gene inC. albicansinduces opaque-cell formation. Additionally, an intermediate phase between white and opaque was observed inC. tropicalis, indicating that the switching could be tristable.