Prevalent Drug Resistance Among Oral Yeasts from Asymptomatic Patients in Hainan, China

The oral cavity is a significant niche of the human microbiome and a gateway for the microbiota in many other human body sites. As a result, understanding the oral microbiota has broad implications for the prevention and management of human infectious diseases. Opportunistic yeast infections are among the most prevalent fungal infections of humans, and most opportunistic yeast pathogens are common residents of the oral mucosa. However, relatively little is known about the drug susceptibility profiles of oral yeasts. Here, we report the species distribution and patterns of antifungal susceptibility profiles among 313 yeasts isolated from the oral cavities of 301 asymptomatic hospitalized patients in Hainan Province in southern China. These yeasts were tested for their susceptibilities to the following five drugs: amphotericin B, fluconazole, itraconazole, ketoconazole, and fluorocytosine. Since none of the sampled hosts had taken any antifungal drugs at least 3 months before samples were taken, we hypothesized that little or no drug resistance should be observed. Contrary to our expectations, our analyses identified that 29 % (91/313) of the isolates were resistant to at least one drug and 14.3 % (45/313) were resistant to two or more of the five common drugs. The potential sources of the observed resistance were discussed.