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Infection and Immunity, August 2009, p. 3188-3195, Vol. 77, No. 8
0019-9567/09/$08.00+0     doi:10.1128/IAI.00296-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Most Environmental Isolates of Cryptococcus neoformans var. grubii (Serotype A) Are Not Lethal for Mice{triangledown}

Anastasia P. Litvintseva and Thomas G. Mitchell*

Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina

Received 13 March 2009/ Returned for modification 16 April 2009/ Accepted 26 May 2009

Most cases of cryptococcosis are caused by Cryptococcus neoformans var. grubii (serotype A), which is widespread in the environment, where it is primarily associated with pigeon excreta. A number of molecular epidemiological studies indicate that many environmental and clinical isolates of serotype A are indistinguishable. However, the murine virulence of environmental strains of C. neoformans has not been thoroughly evaluated. We used the murine intranasal model of cryptococcosis to compare the lethality of clinical and environmental strains of serotype A that possessed identical genotypes as determined by amplified fragment length polymorphisms (AFLP) and multilocus sequence typing (MLST). Eleven environmental strains were tested, and only one caused disease within 60 days postinfection, at which time the experiments were terminated. Conversely, 7 of 10 clinical isolates were lethal for mice at median times of 19 to 40 days. Passing environmental isolates in mice (up to three times) did not significantly increase their lethality. In follow-up studies, we developed a new genotyping technique based on hybridization with TCN2 and TCN4 retrotransposon-specific probes. Although the retrotransposon banding patterns were unstable after prolonged incubation in the laboratory, this method was able to differentiate clinical and environmental strains that had the same AFLP/MLST genotypes.

* Corresponding author. Mailing address: Box 3803, Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710. Phone: (919) 684-5792. Fax: (919) 684-2790. E-mail: tom.mitchell{at}duke.edu

{triangledown} Published ahead of print on 1 June 2009.

Editor: A. Casadevall

Infection and Immunity, August 2009, p. 3188-3195, Vol. 77, No. 8
0019-9567/09/$08.00+0     doi:10.1128/IAI.00296-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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