Rapid identification of moulds and arthroconidial yeasts from positive blood cultures by MALDI-TOF mass spectrometry

Moulds and arthroconidial yeasts are potential life-threatening agents of fungemia in immunocompromised patients. Fast and accurate identification (ID) of these pathogens hastens initiation of targeted antifungal therapy, thereby improving the patients' prognosis. We describe a new strategy that enabled the identification of moulds and arthroconidial yeasts directly from positive blood cultures by MALDI-TOF mass spectrometry (MS). Positive blood cultures (BCs) with Gram staining showing hyphae and/or arthroconidia were prospectively selected and submitted to an in-house protein extraction protocol. Mass spectra were obtained by Vitek MS™ system, and identifications were carried out with in the research use only (RUO) mode with an extended database (SARAMIS™ [v.4.12] plus in-house database). Fusarium solani, Fusarium verticillioides, Exophiala dermatitidis, Saprochaete clavata, and Trichosporon asahii had correct species ID by MALDI-TOF MS analysis of positive BCs. All cases were related to critically ill patients with high mortality fungemia and direct ID from positive BCs was helpful for rapid administration of targeted antifungal therapy.

Trichosporon inkin as an Emergent Pathogen in Patients With Severe Pemphigus

IMPORTANCE

To our knowledge, these are the first reports of bloodstream infections by Trichosporon inkin in patients with pemphigus.

OBSERVATIONS

Trichosporon inkin, a novel organism causing bloodstream infection, was detected in 2 patients with pemphigus. An elderly man with pemphigus foliaceus died despite treatment with liposomal amphotericin B, 3 mg/kg/d, and a young girl with pemphigus vulgaris responded to treatment with voriconazole, 8 mg/kg/d, for 24 days. One of the T inkin isolates had a minimal inhibitory concentration of 2 mg/L against amphotericin B, suggesting resistance to the drug.

CONCLUSIONS AND RELEVANCE

Delayed suspicion of invasive infection by T inkin may result in a poor outcome in patients with severe forms of pemphigus. This opportunistic infection is highly refractory to conventional potent antifungal treatment.

Usefulness of matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry for identifying clinical Trichosporon isolates

Trichosporon spp. have recently emerged as significant human pathogens. Identification of these species is important, both for epidemiological purposes and for therapeutic management, but conventional identification based on biochemical traits is hindered by the lack of updates to the species databases provided by the different commercial systems. In this study, 93 strains, or isolates, belonging to 16 Trichosporon species were subjected to both molecular identification using IGS1 gene sequencing and matrix-assisted laser desorption ionisation-time-of-flight (MALDI-TOF) analysis. Our results confirmed the limits of biochemical systems for identifying Trichosporon species, because only 27 (36%) of the isolates were correctly identified using them. Different protein extraction procedures were evaluated, revealing that incubation for 30 min with 70% formic acid yields the spectra with the highest scores. Among the six different reference spectra databases that were tested, a specific one composed of 18 reference strains plus seven clinical isolates allowed the correct identification of 67 of the 68 clinical isolates (98.5%). Although until recently it has been less widely applied to the basidiomycetous fungi, MALDI-TOF appears to be a valuable tool for identifying clinical Trichosporon isolates at the species level.

Invasive Trichosporon infection in solid organ transplant patients: a report of two cases identified using IGS1 ribosomal DNA sequencing and a review of the literature

Trichosporon species are rare etiologic agents of invasive fungal infection in solid organ transplant (SOT) recipients. We report 2 well-documented cases of Trichosporon inkin invasive infection in SOT patients. We also conducted a detailed literature review of Trichosporon species infections in this susceptible population. We gathered a total of 13 cases of Trichosporon species infections. Any type of organ transplantation can be complicated by Trichosporon infection. Bloodstream infections and disseminated infections were the most common clinical presentations. Liver recipients with bloodstream or disseminated infections had poor prognoses. Although the most common species was formerly called Trichosporon beigelii, this species name should no longer be used because of the changes in the taxonomy of this genus resulting from the advent of molecular approaches, which were also used to identify the strains isolated from our patients. Antifungal susceptibility testing highlights the possibility of multidrug resistance. Indeed, Trichosporon has to be considered in cases of breakthrough infection or treatment failure under echinocandins or amphotericin therapy. Voriconazole seems to be the best treatment option.

Multilocus sequence typing of Candida tropicalis shows the presence of different clonal clusters and fluconazole susceptibility profiles in sequential isolates from candidemia patients in Sao Paulo, Brazil

The profiles of 61 Candida tropicalis isolates from 43 patients (28 adults and 15 children) diagnosed with candidemia at two teaching hospitals in São Paulo, Brazil, were characterized by multilocus sequence typing (MLST). For the 14 patients who had bloodstream infections, 32 isolates were serially collected from their blood and/or catheters. Thirty-nine diploid sequence types (DSTs) were differentiated. According to the C. tropicalis MLST database (http://pubmlst.org/ctropicalis/), 36 DSTs and 23 genotypes identified from the 61 isolates had not previously been described. This report represents the first study to characterize sequential isolates of C. tropicalis from candidemia cases in South America. Microvariation in a single gene was found in the sequential isolates from 7 patients. The main polymorphisms occurred in the alleles of the XYR1 gene, specifically at nucleotide positions 215, 242, and 344. Macrovariation in six gene fragments was detected in the isolates from 3 patients. eBURST analysis added two new groups to this study (groups 6 and 18). Additionally, susceptibility tests indicate that 3 isolates were resistant to fluconazole. No correlation was found between the DSTs and susceptibility to fluconazole and/or selective antifungal pressure. Two patients were sequentially infected with resistant and susceptible strains. MLST is an important tool for studying the genetic diversity of multiple/sequential isolates of patients with candidemia, allowing the comparison of our data with those from other regions of the world, as well as allowing an analysis of the genetic relationship among several clones in sequential isolates from the same or different candidemia patient sites (blood or catheter).

Candidemia epidemiology and susceptibility profile in the largest Brazilian teaching hospital complex

INTRODUCTION

Although the spectrum of fungi causing bloodstream fungal infections continues to expand, Candida spp. remains responsible for the majority of these cases.

OBJECTIVE

The purpose of this study was to characterize the candidemia epidemiology, species distribution and antifungal susceptibility patterns at a Brazilian tertiary teaching public hospital with 2,500 beds.

METHODS

Records from the microbiology laboratory were used to identify patients with positive blood cultures during 2006. The in vitro activity of amphotericin B, caspofungin, itraconazole, fluconazole, voricanozole, and posaconazole were determined using the Etest method.

RESULTS

One hundred and thirty-six cases of candidemia were identified and 100 strains were available for antifungal susceptibility testing. The overall incidence of candidemia was 1.87 cases/1.000 admissions and 0.27 cases/1.000 patient-days. Among the patients, 58.1% were male, and the median age was 40 years old. C. albicans was the most common species (52.2%), followed by C. parapsilosis (22.1%), C. tropicalis (14.8%), and C. glabrata (6.6%). All strains were susceptible to amphotericin B with a MIC90 of 0.5 µg/mL. Overall susceptibility for voriconozole, fluconazole, and caspofungin was > 97% with a MIC90 of 0.064, 4.0 and 1.0 µg/mL, respectively. For itraconazole the susceptibility rate was 81% with a MIC90 of 0.5 µg/mL. Posaconazole also demonstrated good in vitro activity with a MIC90 of 0.25 µg/mL.

CONCLUSION

This is the first antifungal susceptibility report in our institution.

Fusariose em paciente imunocomprometido: sucesso terapêutico com voriconazol

A infecção por Fusarium solani é afecção fúngica potencialmente grave em pacientes imunocomprometidos, sobretudo naqueles portadores de neoplasias hematológicas. A mortalidade é alta,sendo limitadas as opções terapêuticas devido às condições da imunidade do doente e à relativa resistência do fungo aos antifúngicos utilizados de rotina. O voriconazol tem-se mostrado boa alternativa terapêutica em pacientes neutropênicos que apresentam fusariose refratária ou pouco responsiva à anfotericina B. Neste artigo relata-se caso de fusariose em doente imunocomprometido tratado com sucesso com voriconazol.