We examined the susceptibilities to fluconazole of 642 bloodstream infection (BSI) isolates of Candida glabrata and grouped the isolates by patient age and geographic location within the United States. Susceptibility of C. glabrata to fluconazole was lowest in the northeast region (46%) and was highest in the west (76%). The frequencies of isolation and of fluconazole resistance among C. glabrata BSI isolates were higher in the present study (years 2001 to 2007) than in a previous study conducted from 1992 to 2001. Whereas the frequency of C. glabrata increased with patient age, the rate of fluconazole resistance declined. The oldest age group (>80 years) had the highest proportion of BSI isolates that were C. glabrata (32%) and the lowest rate of fluconazole resistance (5%).Candidemia is without question the most important of the invasive mycoses (6,33,35,61,65,68,78,86,88). Treatment of candidemia over the past 20 years has been enhanced considerably by the introduction of fluconazole in 1990 (7, 10, 15, 28, 29, 31, 40, 56-58, 61, 86, 90). Because of its widespread usage, concern about the development of fluconazole resistance among Candida spp. abounds (2,6,14,32,47,53,55,56,59,60,62,80,86). Despite these concerns, fluconazole resistance is relatively uncommon among most species of Candida causing bloodstream infections (BSI) (5,6,22,24,33,42,54,56,65,68,71,86). The exception to this statement is Candida glabrata, of which more than 10% of BSI isolates may be highly resistant (MIC Ն 64 g/ml) to fluconazole (6, 9, 15, 23, 30, 32, 36, 63-65, 71, 87, 91). Suboptimal fluconazole dosing practices (low dose [Ͻ400 mg/day] and poor indications) may lead to an increased frequency of isolation of C. glabrata as an etiological agent of candidemia in hospitalized patients (6,17,29,32,35,41,47,55,60,68,85) and to increased fluconazole (and other azole) resistance secondary to induction of CDR efflux pumps (2,11,13,16,43,47,50,55,69,77,83,84) and may adversely affect the survival of treated patients (7,10,29,40,59,90). Among the various Candida species, C. glabrata alone has increased as a cause of BSI in U.S. intensive care units since 1993 (89). Within the United States, the proportion of fungemias due to C. glabrata has been shown to vary from 11% to 37% across the different regions (west, midwest, northeast, and south) of the country (63, 65) and from Ͻ10% to Ͼ30% within single institutions over the course of several years (9, 48). It has been shown that the prevalence of C. glabrata as a cause of BSI is potentially related to many disparate factors in addition to fluconazole exposure, including geographic characteristics (3, 6, 63-65, 71, 88), patient age (5,6,25,35,41,42,48,63,82,92), and other characteristics of the patient population studied (1, 32, 35, 51). Because C. glabrata is relatively resistant to fluconazole, the frequency with which it causes BSI has important implications for therapy (21,29,32,40,41,45,56,57,59,80,81,86,90).Previously, we examined the susceptibilities to fluconazole of 559 BSI isolates ...