Identification of Paecilomyces variotii in clinical samples and settings.

Paecilomyces variotii is a commonly occurring species in air and food, but it is also associated with many types of human infections and is among the emerging causative agents of opportunistic mycoses in immunocompromised hosts. Paecilomyces can cause hyalohyphomycosis, and two species, Paecilomyces lilacinus and P. variotii, are the most frequently encountered organisms. In the present study, a set of 34 clinical isolates morphologically identified as P. variotii or P. lilacinus were formally identified by sequencing intergenic transcribed spacer regions 1 and 2 (including 5.8S rDNA) and a part of the beta-tubulin gene. Three isolates were identified as P. lilacinus, and five of the presumptive P. variotii isolates did not belong to the genus Paecilomyces but were identified as Talaromyces eburneus (anamorph, Geosmithia argillacea) or Hamigera avellanea (anamorph, Merimbla ingelheimense). Applying the most recent taxonomy, we found that the clinical P. variotii isolates could be identified as P. variotii sensu stricto (14 strains), P. formosus (11 strains), and P. dactylethromorphus (1 strain). These data indicate that P. formosus occurs in clinical samples as commonly as P. variotii. Susceptibility tests showed that the antifungal susceptibility profiles of P. variotii, P. formosus, and P. dactylethromorphus are similar and that all strains tested were susceptible to amphotericin B in vitro. P. lilanicus, T. eburneus, and H. avellanea had different susceptibility profiles; and flucytosine and voriconazole were the least active of the antifungal drugs tested against these species. Our results indicate that correct species identification is important to help guide appropriate antifungal therapy.

Possible environmental origin of resistance of Aspergillus fumigatus to medical triazoles.

We reported the emergence of resistance to medical triazoles of Aspergillus fumigatus isolates from patients with invasive aspergillosis. A dominant resistance mechanism was found, and we hypothesized that azole resistance might develop through azole exposure in the environment rather than in azole-treated patients. We investigated if A. fumigatus isolates resistant to medical triazoles are present in our environment by sampling the hospital indoor environment and soil from the outdoor environment. Antifungal susceptibility, resistance mechanisms, and genetic relatedness were compared with those of azole-resistant clinical isolates collected in a previous study. Itraconazole-resistant A. fumigatus (five isolates) was cultured from the indoor hospital environment as well as from soil obtained from flower beds in proximity to the hospital (six isolates) but never from natural soil. Additional samples of commercial compost, leaves, and seeds obtained from a garden center and a plant nursery were also positive (four isolates). Cross-resistance was observed for voriconazole, posaconazole, and the azole fungicides metconazole and tebuconazole. Molecular analysis showed the presence of the dominant resistance mechanism, which was identical to that found in clinical isolates, in 13 of 15 environmental isolates, and it showed that environmental and clinical isolates were genetically clustered apart from nonresistant isolates. Patients with azole-resistant aspergillosis might have been colonized with azole-resistant isolates from the environment.

Emergence of azole resistance in Aspergillus fumigatus and spread of a single resistance mechanism.

BACKGROUND: Resistance to triazoles was recently reported in Aspergillus fumigatus isolates cultured from patients with invasive aspergillosis. The prevalence of azole resistance in A. fumigatus is unknown. We investigated the prevalence and spread of azole resistance using our culture collection that contained A. fumigatus isolates collected between 1994 and 2007. METHODS AND FINDINGS: We investigated the prevalence of itraconazole (ITZ) resistance in 1,912 clinical A. fumigatus isolates collected from 1,219 patients in our University Medical Centre over a 14-y period. The spread of resistance was investigated by analyzing 147 A. fumigatus isolates from 101 patients, from 28 other medical centres in The Netherlands and 317 isolates from six other countries. The isolates were characterized using phenotypic and molecular methods. The electronic patient files were used to determine the underlying conditions of the patients and the presence of invasive aspergillosis. ITZ-resistant isolates were found in 32 of 1,219 patients. All cases were observed after 1999 with an annual prevalence of 1.7% to 6%. The ITZ-resistant isolates also showed elevated minimum inhibitory concentrations of voriconazole, ravuconazole, and posaconazole. A substitution of leucine 98 for histidine in the cyp51A gene, together with two copies of a 34-bp sequence in tandem in the gene promoter (TR/L98H), was found to be the dominant resistance mechanism. Microsatellite analysis indicated that the ITZ-resistant isolates were genetically distinct but clustered. The ITZ-sensitive isolates were not more likely to be responsible for invasive aspergillosis than the ITZ-resistant isolates. ITZ resistance was found in isolates from 13 patients (12.8%) from nine other medical centres in The Netherlands, of which 69% harboured the TR/L98H substitution, and in six isolates originating from four other countries. CONCLUSIONS: Azole resistance has emerged in A. fumigatus and might be more prevalent than currently acknowledged. The presence of a dominant resistance mechanism in clinical isolates suggests that isolates with this mechanism are spreading in our environment.

Nationwide survey of in vitro activities of itraconazole and voriconazole against clinical Aspergillus fumigatus isolates cultured between 1945 and 1998.

The isolates in a collection of 170 Aspergillus fumigatus isolates recovered from 114 patients and 21 different medical centers in The Netherlands over a period of 53 years were tested for the presence of resistance to itraconazole and voriconazole according to the guidelines of NCCLS document M38-P and by the E-test. Three isolates were highly resistant to itraconazole, and voriconazole MICs were low for all isolates.