Mycological and Molecular Analysis of Soil Keratinophilic Fungi Isolated in Summer Beaches of the Korean South Coast

Park, Joonsoo; Kim, Inyong; Kim, Youngil; Bang, Yong Jun; Jun, Jae Bok; Choi, Jong Soo

Abstract

BACKGROUND
Some species of soil keratinophilic fungi (KPF) are known to be pathogens that may lead to cutaneous infection. People exposed to these species through direct contact with soil on beaches can contract KPF infection. However, there is little literature regarding pathogenic KPF isolated from beaches during summer time.
OBJECTIVE
This study aims to evaluate the distribution of soil KPF isolated from beaches in Korea during summer.
METHODS
One hundred eighty soil samples from six beaches in the southern coastline of Korea under three different climatic conditions were collected. The KPF species were isolated using the hair-baiting technique. Then, molecular identification was performed by sequencing the ribosomal RNA (rRNA) internal transcribed spacer (ITS) region to investigate the exact species of the isolated fungi.
RESULTS
Among the one hundred eighty soil samples, twenty-nine strains (16.1%) of KPF were recovered. The isolation rate of KPF among the beaches varied from 0 to 34.5%. KPF was most frequently isolated in shaded dry areas (30%), followed by sunny dry areas (18.3%), and sunny wet areas (0%). Molecular identification of the fungi using rRNA ITS analysis helped in their classification. Microsporum gypseum/Arthroderma incurvatum (69.0%), Microsporum gypseum/Arthroderma gypseum (3.4%), Trichophyton ajelloi/Arthroderma uncinatum (13.8%), Microsporum cookei/Arthroderma cajetani (10.3%), and Chrysosporium indicum/Aphanoascus terreus (3.4%) were identified. Single nucleotide polymorphism (SNP) was observed at position 180 of the rRNA ITS2 in the 20 strains of Microsporum gypseum/Arthroderma incurvatum, and the species was divided into Types 1 (14 strains) and 2 (6 strains) depending on the base present at the SNP position. The geographic distribution of these two types differed.
CONCLUSION
Our results show that the beach is a possible source of keratinophilic fungal infection in humans. People should be aware of pathogenic fungi on the soil of beaches during summer and take measures to prevent possible superficial fungal infections.