Normally saprobic cryptococci isolated from Cryptococcus neoformans infections

Abstract

We report two cases in which Cryptococcus laurentii was isolated from surgically resected pulmonary lesions but the cryptococcal cells in tissue reacted positively with a specific fluorescent antibody (FA) conjugate for Cryptococcus neoformans. Both patients had no apparent host defense defects. In both cases, multiple cryptococcal isolates were obtained from tissue, and yeastlike cells consistent with C. neoformans were seen in direct histology. The isolates were identified by assimilation patterns and standard procedures including phenoloxidase reactions. Since C. laurentii was consistently isolated by using stringent procedures, it was considered unlikely that the fungus represented surgical or laboratory contamination. Its presence may be the result of dual infection not detected by FA, but other possible explanations exist. The results show the value of the FA test in diagnostic mycology and call into question previous reports of cryptococci other than C. neoformans as agents of infection. There have been numerous reports over the years of Cryptococcus species other than C. neoformans causing human infection (Table 1). Isolates in these cases have most often been obtained from body sites which characteristically have been associated with C. neoformans infection. For example, in 6 of 12 published cases, isolates were obtained from cerebrospinal fluid (Table 1) while in 3 other cases, non-C. neoformans isolates were recovered from pulmonary sources. In 11 of the 12 cases, the species isolated was either C. albidus or C. Iaurentii, both of which are commonly isolated from normal skin (14, 17) and indoor and outdoor air (20, 31). Recently, we investigated two cases strongly suggestive of pulmonary infection by C. laurentii. In both instances, while multiple isolates of C. laurentii were obtained from surgically resected lung tissue, C. neoformans was not isolated. Fluorescent antibody staining (FA) techniques, however, indicated that the fungus present in the tissues was C. neoformans. These unusual findings suggest that a reassessment of the literature with respect to infections supposedly caused by Cryptococcus species other than C. neoformans is in order and that the clinical ecology of such infections requires clarification. CASE REPORTS Case 1. Over a 2-year period prior to admission, a 54-yearold woman resident of Ontario, Canada, experienced four

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