Biomedical subjects

Michael Pfaller

Publications and source records attributed to Michael Pfaller.

5 recordsLinked to original sources

PubMed2006

Candida albicans and Candida glabrata clinical isolates exhibiting reduced echinocandin susceptibility.

A recognized hotspot for mutations conferring reduced echinocandin susceptibility (RES) is residue S645 of Candida albicans Gsc1(Fks1). We report that the mutation F641Y is associated with RES in a C. albicans isolate. The analogous Fks2 residue is mutated F to V in a Candida glabrata RES isolate; the introduction of this mutation into susceptible C. glabrata confirmed its role in RES. Y641-equivalent Fks residues were identified in intrinsically RES Fusarium species and Candida guilliermondii.

Amino Acid Sequence↗

PubMed2005

Disk diffusion testing using Candida sp. colonies taken directly from CHROMagar Candida medium may decrease time required to obtain results.

We compared results of disk diffusion antifungal susceptibility testing from Candida sp. strains passaged on CHROMagar and on potato dextrose agar. The overall categorical agreements for fluconazole and voriconazole disk testing were 95% and 98% with 0% and 0.5% very major errors, respectively. Disk diffusion testing by the CLSI (formerly NCCLS) M44-A method can be performed accurately by taking inocula directly from CHROMagar.

Agar↗

PubMed2003

Attributable mortality of nosocomial candidemia, revisited.

We reexamined the attributable mortality of nosocomial candidemia 15 years after a retrospective cohort study performed at our hospital demonstrated an attributable mortality of 38%. For all episodes of nosocomial candidemia between 1 July 1997 and 30 June 2001, we matched control patients with case patients by age, sex, date of hospital admission, underlying disease(s), length of time at risk, and surgical procedure(s). We analyzed 108 matched pairs. There were no statistically significant differences in age, sex, underlying disease(s), time at risk, surgical procedure, or vital signs at admission between cases and controls. The crude mortality among case patients was 61% (66 of 108 patients), compared with 12% (13 of 108) among control patients, for an attributable mortality of 49% (95% CI, 38%-60%). Nosocomial candidemia is still associated with an extremely high crude and attributable mortality--much higher than that expected from underlying disease alone.

Age Factors↗

PubMed2003

Drug resistance is not directly affected by mating type locus zygosity in Candida albicans.

Recently, evidence was presented that in a collection of fluconazole-resistant strains of Candida albicans there was a much higher proportion of homozygotes for the mating type locus (MTL) than in a collection of fluconazole-sensitive isolates, suggesting the possibility that when cells become MTL homozygous they acquire intrinsic drug resistance. To investigate this possibility, an opposite strategy was employed. First, drug susceptibility was measured in a collection of isolates selected for MTL homozygosity. The majority of these isolates had not been exposed to antifungal drugs. Second, the level of drug susceptibility was compared between spontaneously generated MTL-homozygous progeny and their MTL-heterozygous parent strains which had not been exposed to antifungal drugs. The results demonstrate that naturally occurring MTL-homozygous strains are not intrinsically more drug resistant, supporting the hypotheses that either the higher incidence of MTL homozygosity previously demonstrated among fluconazole-resistant isolates involved associated homozygosity of a drug resistance gene linked to the MTL locus, or that MTL-homozygous strains may be better at developing drug resistance upon exposure to the drug than MTL-heterozygous strains. Furthermore, the results demonstrate that a switch by an MTL-homozygous strain from the white to opaque phenotype, the latter functioning as the facilitator of mating, does not notably alter drug susceptibility.

Candida albicans↗

PubMed2002

Ca3 fingerprinting of Candida albicans bloodstream isolates from the United States, Canada, South America, and Europe reveals a European clade.

It was previously demonstrated by a cluster analysis that 26 unrelated U.S. isolates of Candida albicans separated into three distinct groups (groups I, II, and III) while South African isolates separated into four distinct groups (groups I, II, III, and SA). To verify the absence or underrepresentation of SA isolates in North America, and to identify which groups are represented in Europe and South America, collections of bloodstream isolates from each geographical locale were analyzed by cluster analyses based on genetic fingerprinting with the Ca3 probe. The results verify that North America is almost devoid of SA isolates (2%). However, the results reveal a new clade, designated group E, relatively specific to Europe. While 26% of a European collection of 46 isolates was composed of group E isolates, only 2% of the 164 North American isolates, 5% of 22 South American isolates, and 1% of 361 South African isolates were composed of group E isolates. The North American collection proved to be the least-diverse collection in regard to group representation. In a comparison of collections from the Northeast, Midwest, and Southwest regions of the United States, Canada, and South America, it was demonstrated that both the U.S. Southwest and the South American collections were devoid of group II isolates. Together these results identify for the first time a European-specific clade and demonstrate clear distinctions in the representations of the five demonstrated clades (groups I, II, III, SA, and E) in different geographical locales.

Blood↗