Aspergillosis by cryptic Aspergillus species: A case series and review of the literature

BACKGROUND

The cryptic Aspegillus species are rare, these microorganisms are usually more resistant to common antifungal therapies. Therefore, a correct identification is important when evaluating the impact of such species in aspergillosis.

AIMS

We aimed to describe the frequency, clinical and microbiological characteristics, and the outcomes of those cases of aspergillosis caused by cryptic species in a tertiary hospital.

METHODS

We retrospectively identified all microbiologically documented cases of aspergillosis between January 2013 and December 2018. Definitive species identification of clinically significant isolates was achieved via sequencing methods. The polymerase chain reaction (PCR) products were sequenced, and the results obtained were compared to sequences deposited in GenBank. Antifungal susceptibility testing was performed using the Sensititre® YeastOne® panel.

RESULTS

A total of 679 Aspergillus isolates were recovered from 489 patients, of which 109 were clinically relevant. Ten (9.2%) isolates were identified as cryptic species: Aspergillus arcoverdensis (2), Aspergillus lentulus (2), Aspergillus ellipticus (2), Aspergillus alliaceus (1), Aspergillus nomius (1), Aspergillus tubingensis (1) and Aspergillus montevidensis (1). Most patients already suffered some type of immunosuppression. Half of these patients had required intensive care before the infection showed up, and most of them had a pulmonary infection. Mortality at the 100-day follow-up was 40%. Antifungal susceptibility testing was performed on three of the isolates (A. arcoverdensis, A. tubingensis and A. nomius), which showed high minimum inhibitory concentrations (MIC) for azoles and amphotericin B.

CONCLUSIONS

The frequency of cryptic species in our centre was 9.2%. Most patients had some degree of immunosuppression, and the mortality rate was 40%.

[Relevance of liposomal amphotericin B in the treatment of invasive fungal infections in patients with hematologic malignancies]

Liposomal amphotericin B (L-AmB) has been a key cornerstone for the management of invasive fungal infections (IFI) caused by a wide array of molds and yeasts during the last three decades. Multiple studies performed over this period have generated a large body of evidence on its efficacy and safety, becoming the main antifungal agent in the management of IFI in patients with hematologic malignancies in several not mutually exclusive clinical settings. First, L-AmB is the most commonly used antifungal agent in patients undergoing intensive chemotherapy for acute leukemia and high-risk myelodysplastic syndrome, as well as in hematopoietic stem cell transplant recipients. Additionally, due to the administration of newer targeted therapies (such as monoclonal antibodies or small molecule inhibitors), opportunistic mold infections are increasingly being reported in patients with hematologic malignancies usually considered low-risk for IFI. These agents usually have a high drug-drug interaction potential, being triazoles, commonly used for antifungal prophylaxis, included. Finally, patients developing breakthrough IFI because of either subtherapeutic concentrations of antifungal prophylactic drugs in blood or selection of resistant strains, require broad spectrum antifungal therapy, usually with an antifungal of a different class. In both situations, L-AmB remains as the best option for early antifungal therapy.