Pattern of Antifungal Susceptibility in Pathogenic Molds by Microdilution Method at a Tertiary Care Hospital

Author(s):

Maria Khan*, Aamer Ikram, Gohar Zaman, Adeel Gardezi and Farida Khurram Lalani

Fungal infections are increasingly being recognized especially in immunocompromised patients. Susceptibility of molds varies from species to species and timely generated reports can aid clinicians in the appropriate therapeutic decision. The study was conducted to determine the pattern of pathogenic molds in our tertiary care set-ups and the existing susceptibility by the standard broth microdilution method. The study was conducted in Armed Forces Institute of Pathology, Rawalpindi from January through December, 2016. Isolated fungal molds were tested against antifungal drugs by broth microdilution method; amphotericin B, fluconazole and voriconazole. A total of 110 isolates were tested by broth dilution antifungal susceptibility testing of filamentous fungi approved by the Clinical and Laboratory Standards Institute M38-A2 document. Mean age was 43 years and gender 79 (71.8%) patients were male and 31 (28.2%) patients were female. A total of 110 isolates (Aspergillus spp., n=45; Alternaria spp., n=40; and Cladosporium spp. n=25) were tested by broth dilution antifungal susceptibility testing of filamentous fungi. Amphotericin B was susceptible (MIC ≤1 μg/ml) in 37 (82.2%) of patients with Aspergillus fumigatus, 35 (87.5%) of patients with Alternaria alternata and (19) 76% of patients with Cladosporium sphaerospermum. While Amphotericin B was resistant (MIC ≥ 4 μg/ml) in (6) 13.4% of patients with Aspergillus fumigatus, (1) 2.5% in patient with Alternaria alternata and (2) 8% of in patients with Cladosporium sphaerospermum.

Susceptibility of mold in Fluconazole (MIC ≤ 8 μg/ml) was analyzed in which none of patients with Aspergillus fumigatus were sensitive, (1) 2.5% of patient with Alternaria alternata and none of patients with Cladosporium sphaerospermum. While Fluconazole was resistant (MIC ≥64 μg/ ml) in (43) 95.6% of patients with Aspergillus fumigatus, (35) 87.5% of patients with alternaria and (21) 84% of patients with Cladosporium sphaerospermum.

Voriconazole was susceptible (MIC ≤0.125 μg/ml) in (38) 84.5% of patients with Aspergillus fumigatus, (33) 82.5% of patients with Alternaria alternata and (21) 84% of patients with Cladosporium sphaerospermum.

The isolated molds exhibited variable susceptibilities to antifungals. The increasing number of invasive mold infections, coupled with documented resistance to antifungal agents, has potentiated the need for having standardized methods for determining the in vitro susceptibilities of both new and established antifungal agents against clinical isolates of filamentous fungi.