Temperature affects the susceptibility of Cryptococcus neoformans biofilms to antifungal agents

Robin Pettit, Kimberly K. Repp, Kevin C. Hazen

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


The fungal opportunist Cryptococcus neoformans forms biofilms in vitro and in vivo. C. neoformans has an unusual ability to grow over a wide range of temperatures, and is one of only two species in the genus able to grow at 37°C. The optimum growth temperature in the laboratory is 30°C, but Clinical and Laboratory Standards Institute (CLSI) planktonic susceptibility testing is performed at 35°C. We investigated whether these growth temperatures affected C. neoformans biofilm formation and drug resistance. Biofilms of 30 strains of C. neoformans were grown at 30°C or 35°C, and antifungal susceptibilities evaluated at 30°C or 35°C using minimum biofilm eradication endpoints. At 35°C, biofilms from 40% of the strains were more susceptible to flucytosine, 30% were more susceptible to nystatin, 27% were more susceptible to amphotericin, and 20% were more susceptible to fluconazole, as compared to 30°C. The reverse, that is an increased susceptibility at 30°C, only occurred with a single strain using nystatin or fluconazole. For the remaining strains, biofilm susceptibility was equivalent at the two temperatures. Biofilm colony forming units (CFU)s, as measured indirectly by 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5- carboxanilide (XTT) reduction, were greater at 35°C than at 30°C for the majority of the strains. Thus, growth temperature does affect C. neoformans biofilm properties, but factors other than relative biofilm CFUs/ml must be involved in the increased drug susceptibility at 35°C.

Original languageEnglish (US)
Pages (from-to)421-426
Number of pages6
JournalMedical Mycology
Issue number2
StatePublished - 2010


  • Biofilm
  • Cryptococcus neoformans
  • XTT susceptibility

ASJC Scopus subject areas

  • Infectious Diseases


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