Demographic Characteristics and Crude Incidence Rates
From January 1, 2017, to December 31, 2020, 392 incident cases of candidemia were identified in residents of Alameda County (Figure 1). The median age of the patients was 61.4 years (interquartile range, 52-74 years). Almost half (47%) of the patients were ≥ 65 years old. Seven (1.8%) of the patients were <18 years of age and they made up the smallest fraction of the study population (Table 1). There were more males than females in the population (229 vs 163), representing 58.4% vs 41.6% respectively. Most of the patients were white (132, 33.7%), followed by Black or African American (100, 25.5%).
The crude incidence averaged over four years was 5.9 per 100,000 population, with a range of 5- 6.5 cases/100,000 population. Demographic data by age group and sex for 2020 for Alameda County was not yet available on the US Census Bureau website; hence we could not calculate the age and sex-specific rates for 2020.
The crude annual incidence of candidemia, averaged over three years (2017-2019) varied by age group. Participants in the ≥65-year age group had the highest crude incidence (19.7 per 100,000 population), while those in the <18 year age group had the lowest annual incidence at 0.6 per 100,000 population (Figure 2). The mean crude incidence of candidemia among males over the three-year period from 2017 to 2020 was 6.8 per 100,000 population, which was higher than that for females, 4.8 per 100,000 population. The incidence in Blacks/African Americans averaged 14.8 per 100,000 over the four-year study period (range: 21.9-9), while for non-blacks, it averaged 4.9 per 100,000 population (range 4.2-5.1). (Figure 3).
Candida species distribution
Candida glabrata was the most common species, causing candidemia in 149 cases (38.0%). It was followed by Candida albicans in 130 cases (33.2%). Though Candida glabrata predominated, the difference in the absolute counts between Candida albicans and Candida glabrata was not significant (p = 0.32, CI -15.46-5.97). The other species causing candidemia were Candida parapsilosis, 45 cases (11.5%), Candida tropicalis, 25 cases (6.4%), Candida dubliniensis, 8 cases (2.0%), and Candida lusitaniae, 8 cases (2.0%). Mixed Candida species infections were present in 13 patients (3.3%). Other species of Candida accounted for 27 candidemia cases (6.9%) (Figure 4).
Underlying Conditions and Risk Factors for Candidemia
Most of the patients with candidemia had at least one underlying condition. The most common risk factor present in the candidemia patients was the presence of a central venous catheter. Almost two-thirds (64.3%) of the participants had a central venous catheter in place two days before the positive culture (Table 2), while almost half (47.7%) of the patients had been hospitalized in the 90 days before the date of the positive culture. Almost half, (45.9%), of the patients had been present in the ICU during the 14 days before the positive culture.
Overall, 158 patients (40.3%) had diabetes mellitus, which was the most common underlying medical condition in the study participants. Most of the cases 311(79.3%) had received systemic antibiotics in the two weeks preceding the positive candida culture, while just over one fourth of the cases, 104(26.5%), had received systemic antifungal medications during the 14 days before the positive culture. Previous candidemia had occurred in just 10 (2.6%) of the incident cases. A few of the cases, 3(0.8%), were in pregnant women (Table 2).
Outcome
The case fatality ratio (CFR) 30 days after a positive culture was 36%. This CFR also varied by age group; the CFR was 0.7% in the <18 age group, 6.4% in the 18-44 year age group, 34.8% in the 45-64 year age group and 56.7% in the ≥65 years age group. This increase in mortality with increasing age category was significant (p = 9.78 x10-5).
Case fatality ratios however did not differ significantly by race. Comparing Blacks with non-blacks, 36 of 101 black participants died (35.6%), and 105 of 291 (36.1%) of non-blacks died (p = 1). In addition, the CFR did not vary by sex. Approximately one-third of the male patients, 84/229 (36.7%) died, as did a similar proportion of female patients, 57/163 (35.0%) (p = 0.81).
Predictors of Mortality
Bivariate regression models showed several risk factors for mortality among patients with candidemia including age ≥ 65 years, total parenteral nutrition, chronic liver disease, prior systemic antibiotic therapy, cirrhosis of the liver, and prior ICU admission before culture being significant predictors of mortality (Figure 5). However, on multivariate analysis, just age ≥ 65 years (RR 2.01, CI 1.51 - 2.68, p<0.001), prior receipt of systemic antibiotic therapy, (RR 1.84, CI 1.06 - 3.17, p =0.029), cirrhosis of the liver (RR 1.82, CI 1.36 - 2.43, p<0.001), and prior admission to the ICU before culture (RR1.66, CI 1.28 - 2.14, p<0.001) remained significant predictors of mortality. (Table 3). Mortality did not differ by Candida species (X2 = 12, p = 0.09).