Aspergillus-specific and mucorales-specific PCR testing in bronchoalveolar lavage fluid for the diagnosis of invasive pulmonary mould infection

Elisabeth Wehrle

Abstract: 

Background: Invasive pulmonary mould infections (IMI) mainly caused by Aspergillus species (spp.)
and Mucorales spp. are associated with significant morbidity and mortality in patients with underlying
haematological malignancies and undergoing haematopoietic stem cell transplantation (HSCT). This is
among others due to the difficulty of early and accurate diagnosis. Although galactomannan (GM)
index has facilitated diagnosis in high-risk populations, it does not identify the causative species and
misses Mucorales. We therefore evaluated the diagnostic performance of an in-house Aspergillus
species-specific and Mucorales species-specific PCR in bronchoalveolar lavages (BAL) in patients
with presumed IMI.
Material/methods: Aspergillus spp. PCR and Mucorales spp. PCR were conducted in 90 BAL fluid
samples from haematological patients with presumed IMI at a tertiary care center in Switzerland
between 2011 and 2014. PCR for Mucorales spp. consists of 2 real-time PCR assays, which amplify
parts of the 18s and 28s RNA gene, while the Aspergillus spp. real-time PCR amplifies the internal
transcriber spacer 1 (ITS1). BAL fluid GM index level of ≥0.5, culture, histology and GM serum index
level of ≥0.5 were used as the gold standard for diagnosis of IMI. IMI was classified as possible,
probable and proven IMI according to the European Organisation for Research and Treatment of
Cancer/Invasive Fungal Infections Cooperative Group (EORTC/MSG) definition.
Results: Ninety BAL samples from 67 patients were investigated. Most patients had undergone
allogeneic HSCT (n= 51, 57%), had a recent history of neutropenia (n= 30, 33%) and/or were treated
with steroids (n= 33, 37%). IMI was classified as proven in six (6.7%), as probable in 41 (46%), and as
possible in 43 (48%) cases according to the EORTC definition. In total, 14 (16%) of 90 BAL fluid
samples were PCR positive. Aspergillus fumigatus was detected in 11 (79%) and Mucorales spp. in 3
(21%) BAL samples. Thirteen (28%) of 47 probable/proven BAL episodes and 1 (2%) of the 43
possible BAL episodes were PCR positive. This resulted in sensitivity, specificity, and positive and
negative predictive values (PPV; NPV) of 27.7%, 97.7%, 92.9%, and 55.3%, respectively. GM from
BAL alone provided a sensitivity of 76.6%, specificity of 100%, PPV of 100%, and NPV of 79.6%,
respectively. Both PCR methods combined with GM BAL (n=90 (100%)) resulted in a sensitivity of
78.7%, specificity of 97.7%, PPV of 97.4%, and NPV of 80.8%. Uni- and multivariable analyses will be
performed to identify factors influencing the performance of these PCRs.
Conclusions: Aspergillus and Mucorales PCR from BAL fluid might be useful for identifying the mould
species, and together with BAL GM might facilitate diagnosis of IMI.

2016

abstract No: 

#3490

Full conference title: 

26th European Congress of Clinical Microbiology and Infectious Diseases
    • ECCMID 26th (2016)