By Stan Deresinski, MD, FACP, FIDSA

Clinical Professor of Medicine, Stanford University

SYNOPSIS: Candidemia, a common bloodstream infection in the United States, is associated with high mortality. There is concern about increasing resistance to antifungals.

SOURCE: Tsay SV, Mu Y, Williams S, et al. Burden of candidemia in the United States, 2017. Clin Infect Dis 2020;71:e449-e453.

The Centers for Disease Control and Prevention (CDC) examined cases of Candida bloodstream infections using surveillance data for the year 2017 from the Emerging Infections Program (EIP) conducted in 45 counties with a total population of 17 million in nine states. The states represented were California, Colorado, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee. This program identified 1,226 cases of candidemia in 1,140 patients (taking into account recurrent episodes). Individuals > 65 years of age accounted for 41.5% of cases and had, by far, the highest incidence rate (20.1 per 100,000 persons). Blacks also were overrepresented, accounting of 31.6% of cases, with a rate of 12.3 per 100,000. All-cause in-hospital mortality was 25% (31% in those 65 years of age) and was 15% within seven days of the onset of candidemia.

Of 1,122 isolates analyzed at CDC, Candida albicans accounted for 38% and Candida glabrata for 30%, followed by Candida parapsilosis (14%) and Candida tropicalis (7%). Overall, 6% of Candida isolates were resistant to fluconazole, with variability by species: 0.5% in C. albicans, 7% in C. glabrata, and 9% in C. parapsilosis. Only 2% (mostly C. glabrata) were resistant to an echinocandin.

Based on these data, the authors estimated that 22,600 cases of candidemia occurred in the United States in 2017, with an incidence of 7.0 per 100,000 persons, with almost one-half of the cases occurring in individuals > 65 years of age and almost one-fourth occurring in Blacks. The geographic rates of candidemia ranged from a low of 5.9 cases per 100,000 in Pacific states to 7.7 and 7.9 per 100,000 in the South Atlantic and East South Central states, respectively.

COMMENTARY

These data point out the large burden of candidemia in the United States. It should be recognized that blood cultures are estimated to be positive in only approximately one-half of patients with invasive candidiasis.

The reason for the higher rates of candidema in South Atlantic and East South Central states may be related to the injection drug use epidemic as well as the excessive use of antibacterials in those states. The overall rates of resistance to fluconazole and to echinocandins were relatively low, but, as pointed out by the authors, varied greatly among institutions. At Stanford in 2017, fluconazole resistance was identified in 3% of C. albicans, 14% of C. glabrata, 15% of C. tropicalis, and 0% of C. parapsilosis. The last is quite different from the 9% recorded in the CDC study. The only resistance to an echinocandin (caspofungin) noted among these four species at Stanford was a 7% incidence of resistance of C. glabrata to caspofungin. Given the changing demographics of the country, the incidence of candidemia (and other forms of invasive candidiasis) is likely to increase, as is the incidence of antifungal resistance, including to echinocandins.

Among Candida resistant to antifungals there is, of course, great concern regarding multidrug-resistant Candida auris. This organism first appeared in the United States in the middle of 2015 and, by early 2019, had been identified as the cause of > 300 bloodstream infections. It can be anticipated that this number is increasing.