In Vitro Susceptibility of Invasive Isolates of Candida spp. to Anidulafungin, Caspofungin, and Micafungin: Six Years of Global Surveillance

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1 JOURNAL OF CLINICAL MICROBIOLOGY, Jan. 2008, p Vol. 46, No /08/$ doi: /jcm Copyright 2008, American Society for Microbiology. All Rights Reserved. In Vitro Susceptibility of Invasive Isolates of Candida spp. to Anidulafungin, Caspofungin, and Micafungin: Six Years of Global Surveillance M. A. Pfaller, 1 * L. Boyken, 1 R. J. Hollis, 1 J. Kroeger, 1 S. A. Messer, 1 S. Tendolkar, 1 and D. J. Diekema 1,2 Departments of Pathology 1 and Medicine, 2 Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa Received 24 September 2007/Returned for modification 7 November 2007/Accepted 12 November 2007 The echinocandins are being used increasingly as therapy for invasive candidiasis. Prospective sentinel surveillance for the emergence of in vitro resistance to the echinocandins among invasive Candida sp. isolates is indicated. We determined the in vitro activities of anidulafungin, caspofungin, and micafungin against 5,346 invasive (bloodstream or sterile-site) isolates of Candida spp. collected from over 90 medical centers worldwide from 1 January 2001 to 31 December We performed susceptibility testing according to the CLSI M27-A2 method and used RPMI 1640 broth, 24-h incubation, and a prominent inhibition endpoint for determination of the MICs. Of 5,346 invasive Candida sp. isolates, species distribution was 54% C. albicans, 14% C. parapsilosis, 14% C. glabrata, 12% C. tropicalis, 3% C. krusei, 1% C. guilliermondii, and 2% other Candida spp. Overall, all three echinocandins were very active against Candida: anidulafungin (MIC 50, 0.06 g/ml; MIC 90,2 g/ml), caspofungin (MIC 50, 0.03 g/ml; MIC 90, 0.25 g/ml), micafungin (MIC 50, g/ml; MIC 90,1 g/ml). More than 99% of isolates were inhibited by <2 g/ml of all three s. Results by species (expressed as the percentages of isolates inhibited by <2 g/ml of anidulafungin, caspofungin, and micafungin, respectively) were as follows: for C. albicans, 99.6%, 100%, and 100%; for C. parapsilosis, 92.5%, 99.9%, and 100%; for C. glabrata, 99.9%, 99.9%, and 100%; for C. tropicalis, 100%, 99.8%, and 100%; for C. krusei, 100%, 100%, and 100%; and for C. guilliermondii, 90.2%, 95.1%, and 100%. There was no significant change in the activities of the three echinocandins over the 6-year study period and no difference in activity by geographic region. All three echinocandins have excellent in vitro activities against invasive strains of Candida isolated from centers worldwide. Our prospective sentinel surveillance reveals no evidence of emerging echinocandin resistance among invasive clinical isolates of Candida spp. * Corresponding author. Mailing address: Medical Microbiology Division, C606 GH, Department of Pathology, University of Iowa College of Medicine, Iowa City, IA Phone: (319) Fax: (319) michael-pfaller@uiowa.edu. Published ahead of print on 21 November The echinocandin class of antifungal s acts by inhibition of the synthesis of 1,3- -D-glucan in the fungal cell wall (31, 41). All three available echinocandins anidulafungin (Pfizer), caspofungin (Merck), and micafungin (Astellas) possess fungicidal activity against most species of Candida, including those resistant to polyenes (23) and to azoles (1, 3, 4, 7, 11, 18, 25, 26, 34 36, 41, 43). Caspofungin and anidulafungin have been approved by the U.S. Food and Drug Administration (FDA; years 2002 and 2006, respectively) for the treatment of invasive candidiasis, including candidemia (20, 40), and micafungin has been approved for the treatment of esophageal candidiasis (year 2005) (5). Although FDA approval of this drug for the treatment of candidemia is pending, micafungin has been shown to be safe and efficacious in the treatment of candidemia in recently published open-label (1, 26) and randomized (16, 28) clinical trials. These s all provide excellent clinical efficacy coupled with low toxicity for the treatment of serious candidal infections. Collaborative studies conducted by the Clinical and Laboratory Standards Institute (CLSI) Subcommittee have resulted in the development of a standardized broth microdilution (BMD) method for determining echinocandin MICs for Candida spp. (24). The method employs RPMI 1640 broth medium, incubation at 35 C for 24 h, and a MIC endpoint criterion of prominent reduction in growth ( 50% inhibition relative to control growth). The CLSI method provides reproducible MIC results with good separation of the wildtype MIC distribution from isolates with mutations in the FKS1 gene, for which reduced susceptibility to echinocandins has been demonstrated (24, 31, 33). The availability of this standardized method has facilitated the performance of largescale surveillance studies that have documented the potency and spectrum of echinocandin drugs against clinical isolates of Candida spp. (7, 25, 34 36). Recently, the CLSI Subcommittee has taken into consideration the MIC distributions generated by the in vitro surveys, the mechanisms of action and of resistance known for the echinocandins, the pharmacokinetic and pharmacodynamic data available, and the clinical efficacy of each as it relates to the MIC for the infecting strain to arrive at a consensus MIC breakpoint for a susceptibility of 2 g/ml for Candida spp. to all three echinocandins (minutes of the June 2007 meeting of the CLSI Subcommittee; data not shown). This breakpoint encompasses more than 99% of all Candida isolates against each and reliably discriminates the susceptible wild-type strains from those with target site mutations (31, 38). As patient exposure to echinocandins broadens, the number of infecting strains with reduced susceptibility may increase Downloaded from on January 1, 2019 by guest 150

2 VOL. 46, 2008 CANDIDA SUSCEPTIBILITY TO THE ECHINOCANDINS 151 (31). Indeed, data from in vitro surveys document the presence of rare strains of otherwise highly susceptible species that exhibit unusually high MICs for one or more echinocandins (7, 34 36). Furthermore, they highlight the presence of less-susceptible species, such as C. parapsilosis and C. guilliermondii, the MICs for which may be 10- to 100-fold higher than those observed for C. albicans, C. glabrata, and C. tropicalis (2, 25, 38). Notably, sporadic treatment failures consistent with clinical resistance have been documented in association with socalled high-mic isolates (i.e., MIC 2 g/ml) (8, 10, 12, 14, 17, 19, 21, 30, 39). In each case, the MIC of the echinocandin used in treatment was shown to increase progressively during the course of therapy, and where investigated, a mutation in FKS1 was demonstrated in the high-mic isolate (12, 17, 19). In most (but not all) instances, resistance to all three echinocandins was demonstrated, consistent with known mechanisms of action and resistance to echinocandins in Candida (31). These observations underscore the importance of antifungal susceptibility testing of echinocandins in detecting unusual resistance profiles as these s are used more broadly worldwide. In the present study, we provide a unique head-to-head comparison of all three clinically available echinocandins by using CLSI reference BMD for a global collection of 5,346 bloodstream infection (BSI) isolates of Candida spp. We examine geographic trends in both species distribution and echinocandin activity and discuss issues of cross-resistance to the three s. MATERIALS AND METHODS Organisms. A total of 5,346 clinical isolates obtained internationally from 91 medical centers from 2001 to 2006 were. The collection included 2,869 strains of Candida albicans, 759 of Candida parapsilosis, 747 of Candida glabrata, 625 of Candida tropicalis, 136 of Candida krusei, 61 of Candida guilliermondii, 58 of Candida lusitaniae, 37 of Candida kefyr, 24 of Candida famata, 11 of Candida pelliculosa,8ofcandida lipolytica,6ofcandida dubliniensis,2ofcandida rugosa, 2ofCandida zeylanoides,and1ofcandida intermedia. All isolates were obtained from blood or other normally sterile sites and represented individual infectious episodes. The isolates were collected at individual study sites and were sent to the University of Iowa (Iowa City) for identification and susceptibility testing as described previously (33 36). The isolates were identified by standard methods (9) and stored as water suspensions until used in the study. Prior to testing, each isolate was passaged at least twice onto potato dextrose agar (Remel) and CHROMagar Candida (Becton Dickinson and Company, Sparks, MD) to ensure purity and viability. s. Reference powders of anidulafungin, caspofungin, and micafungin were obtained from their respective manufacturers. Stock solutions were prepared in water (caspofungin and micafungin) or dimethyl sulfoxide (anidulafungin), and serial twofold dilutions in RPMI 1640 medium (Sigma, St. Louis, MO) buffered to ph 7.0 with M MOPS (morpholinepropanesulfonic acid) buffer (Sigma) were made. susceptibility testing. BMD testing was performed in accordance with the guidelines in CLSI document M27-A2 (22) by using RPMI 1640 medium, an inoculum of to cells/ml, and incubation at 35 C. MICs were determined visually, after 24 h of incubation, as the lowest concentration of drug that caused a significant diminution ( 50% inhibition) of growth below control levels (18, 33 36). Quality control. Quality control was performed by testing CLSI-recommended strains C. krusei ATCC 6258 and C. parapsilosis ATCC (22). RESULTS AND DISCUSSION Candida species TABLE 1. Species distribution of Candida isolates by geographic region APAC (n 958) LAM (n 1,112) % of isolates a EU (n 1,787) NAM (n 1,489) Total (n 5,346) C. albicans C. parapsilosis C. glabrata C. tropicalis C. krusei C. guilliermondii C. lusitaniae C. kefyr C. famata Candida spp. b a Regions: APAC, Asia-Pacific (16 study sites); LAM, Latin America (15 study sites); EU, Europe (32 study sites); NAM, North America (28 study sites). For each region, the number of isolates (n) is given in parentheses. b Includes C. pelliculosa (11 isolates), C. lipolytica (8 isolates), C. dubliniensis (6 isolates), C. rugosa (2 isolates), C. zeylanoides (2 isolates), and C. intermedia (1 isolate). Table 1 demonstrates the species distribution of Candida BSI isolates according to the geographic region of origin. A total of 5,346 isolates were obtained from 91 different medical centers in the Asia-Pacific region (16 sites), Latin America (15 sites), Europe (32 sites), and North America (28 sites). Consistent with previous reports (32, 35 38), the distributions of Candida species isolated from blood and other sterile sites differed considerably across the different regions. C. albicans constituted well over 50% of BSI isolates in Europe (58.42%) and the Asian-Pacific region (57.1%), whereas only 47.9% of isolates from Latin America and 50% of isolates from North America were C. albicans. Likewise, C. parapsilosis and C. tropicalis were prominent in the Asian- Pacific and Latin American regions but less so in both Europe and North America. Whereas C. glabrata was the most common species after C. albicans in both North America and Europe, it was distinctly less common than both C. parapsilosis and C. tropicalis in Latin America and the Asian-Pacific region. Finally, C. krusei was considerably more common in Europe than in the other three regions, whereas the same was true for C. guilliermondii in Latin America. These two species are especially notable for their propensity toward multidrug resistance compared to other more common species of Candida (37; M. A. Pfaller, D. J. Diekema, D. L. Gibbs, V. A. Newell, J. F. Meis, I. M. Gould, W. Fu, A. L. Colombo, E. Rodriguez-Noriega, and the Global Surveillance Group, submitted for publication). Table 2 summarizes that in vitro susceptibility of 5,346 isolates of Candida spp. to anidulafungin, micafungin, and caspofungin when in RPMI 1640 medium with 24-h incubation and the prominent reduction endpoint criteria. First of all, it should be noted that all three echinocandins demonstrate excellent potency and spectrum with 98.8 to 100% of all isolates susceptible at the MIC breakpoint of 2 g/ml. The degrees of susceptibility of isolates to all three echinocandins did not change over the duration of the study (data not shown). A MIC of 4 g/ml for any echinocandin was observed for only six (0.1%) of the 5,346 isolates : three isolates of C. guilliermondii (caspofungin MIC, 8 g/ml), and one isolate each of C. glabrata (caspofungin MIC, 8 g/ml), C. tropicalis (caspofungin MIC, 8 g/ml), and C. rugosa (anidulafungin MIC, 8 g/ml). As noted previously (33 36), the MIC distribution for each of the echinocandins defined two broad groups among the nine major species (Tables 1 and 3). C. albicans, C. glabrata, C. tropicalis, C. krusei, and C. kefyr were all highly susceptible

3 152 PFALLER ET AL. J. CLIN. MICROBIOL. TABLE 2. In vitro susceptibilities of 5,346 clinical isolates of Candida spp. to anidulafungin, caspofungin, and micafungin Organism No. of isolates Cumulative % of isolates susceptible at a MIC ( g/ml) of a : C. albicans 2,869 Anidulafungin Caspofungin Micafungin C. parapsilosis 759 Anidulafungin Caspofungin Micafungin C. glabrata 747 Anidulafungin Caspofungin Micafungin C. tropicalis 625 Anidulafungin Caspofungin Micafungin C. krusei 136 Anidulafungin Caspofungin Micafungin C. guilliermondii 61 Anidulafungin Caspofungin Micafungin C. lusitaniae 58 Anidulafungin Caspofungin Micafungin C. kefyr 37 Anidulafungin Caspofungin Micafungin C. famata 24 Anidulafungin Caspofungin Micafungin Candida spp. 30 Anidulafungin Caspofungin Micafungin Total 5,346 Anidulafungin Caspofungin Micafungin a Values corresponding to MICs at which at least 90% of isolates are inhibited are listed in bold type. to each of the echinocandins (modal MIC, to 0.06 g/ml; MIC 90, to 0.25 g/ml), whereas C. parapsilosis (modal MIC, 0.25 to 1 g/ml; MIC 90,1to2 g/ml), C. guilliermondii (modal MIC, 0.5 to 1 g/ml; MIC 90,1to2 g/ml), C. lusitaniae (modal MIC, 0.12 to 0.5 g/ml; MIC 90, 0.25 to 0.5 g/ml), and C. famata (modal MIC, 0.25 to 0.5 g/ml; MIC 90,1to2 g/ml) were significantly less susceptible to all three s. These differences may be due to differences in the sensitivities of the glucan synthesis enzyme complex to echinocandin inhibition (6, 15, 29, 31). Importantly, 90 to 100% of the isolates of the last four species listed are classified as susceptible to all three echinocandins based on the 2- g/ml breakpoint. Although the reduced susceptibilities of species such as C. parapsilosis and C. guilliermondii relative to those of C. albicans, C. glabrata, and C. tropicalis have not proven to influence outcomes in the various clinical trials (13, 16, 20, 26, 40), reduced susceptibility may come into play when infections with these species involve the eye or central nervous system, where adequate free drug levels cannot be readily obtained (30, 39). The echinocandin susceptibilities of isolates stratified by geographic region and by species are shown in Table 3. Despite the differences in species distribution noted previously, the same overall and species-specific activities were observed for each echinocandin in each of the four regions. One important observation that can be made from this large data set is that although rare, isolates of C. albicans for which anidulafungin MICs were 2 g/ml were detected in all four geographic regions (Table 3). Although such isolates would still be considered to be susceptible based on the newly described CLSI breakpoints, they must be recognized as distinctly unusual, given that the modal MIC for this species is 0.03 g/ml (Table 3). Notably, of the 12 isolates of C. albicans with this high-mic anidulafungin phenotype, all were found to have micafungin MICs of 0.5 to 1 g/ml (modal MIC of micafungin for C. albicans is g/ml) and caspofungin MICs of 0.12 to 0.25 g/ml (modal MIC of caspofungin for C. albicans is 0.03 g/ml). Although susceptible, these isolates are clearly outside of the normal wild-type distribution of echinocandin MICs for C. albicans. Isolates with this abnormal phenotype warrant further study, and although they may respond clinically to echinocandin treatment, they could pose problems under conditions of decreased drug penetration. An analogous situation can be seen with C. tropicalis, of which three isolates for which anidulafungin MICs of 2 g/ml (modal MIC of anidulafungin for C. tropicalis is 0.03 g/ml) were detected (Table 3). The caspofungin MICs for these isolates were 0.25, 1, and 16 g/ml (modal MIC of caspofungin for C. tropicalis is 0.03 g/ml), and the micafungin MICs were

4 VOL. 46, 2008 CANDIDA SUSCEPTIBILITY TO THE ECHINOCANDINS 153 TABLE 3. Variation in echinocandin MIC profiles by geographic region Region(s) and species No. of isolates No. of isolates for which the MIC ( g/ml) was: Asia-Pacific C. albicans 547 Anidulafungin Caspofungin Micafungin C. parapsilosis 153 Anidulafungin Caspofungin Micafungin C. glabrata 81 Anidulafungin Caspofungin Micafungin C. tropicalis 136 Anidulafungin Caspofungin Micafungin C. krusei 9 Anidulafungin 4 5 Caspofungin 7 2 Micafungin C. guilliermondii 7 Anidulafungin Caspofungin Micafungin C. lusitaniae 6 Anidulafungin Caspofungin 3 3 Micafungin C. kefyr 1 Anidulafungin 1 Caspofungin 1 Micafungin 1 C. famata 8 Anidulafungin Caspofungin Micafungin Latin America C. albicans 533 Anidulafungin Caspofungin Micafungin C. parapsilosis 207 Anidulafungin Caspofungin Micafungin C. glabrata 63 Anidulafungin Caspofungin Micafungin C. tropicalis 222 Anidulafungin Caspofungin Micafungin C. krusei 18 Anidulafungin Caspofungin Micafungin C. guilliermondii 40 Anidulafungin Caspofungin Micafungin C. lusitaniae 7 Anidulafungin 3 4 Caspofungin Micafungin 5 2 C. kefyr 7 Anidulafungin Caspofungin 7 Micafungin 4 3 C. famata 8 Anidulafungin Caspofungin Micafungin Europe C. albicans 1,044 Anidulafungin Caspofungin Micafungin C. parapsilosis 190 Anidulafungin Caspofungin Micafungin C. glabrata 249 Anidulafungin Continued on following page

5 154 PFALLER ET AL. J. CLIN. MICROBIOL. TABLE 3 Continued Region(s) and species No. of isolates No. of isolates for which the MIC ( g/ml) was: Caspofungin Micafungin C. tropicalis 153 Anidulafungin Caspofungin Micafungin C. krusei 87 Anidulafungin Caspofungin Micafungin C. guilliermondii 9 Anidulafungin Caspofungin Micafungin C. lusitaniae 23 Anidulafungin Caspofungin Micafungin C. kefyr 22 Anidulafungin Caspofungin Micafungin 6 16 C. famata 4 Anidulafungin Caspofungin Micafungin North America C. albicans 745 Anidulafungin Caspofungin Micafungin C. parapsilosis 209 Anidulafungin Caspofungin Micafungin C. glabrata 354 Anidulafungin Caspofungin Micafungin C. tropicalis 114 Anidulafungin Caspofungin Micafungin C. krusei 22 Anidulafungin Caspofungin Micafungin C. guilliermondii 5 Anidulafungin 3 2 Caspofungin Micafungin C. lusitaniae 22 Anidulafungin Caspofungin Micafungin C. kefyr 7 Anidulafungin Caspofungin 3 4 Micafungin C. famata 4 Anidulafungin Caspofungin Micafungin ,1, and 1 g/ml (modal MIC of micafungin for C. tropicalis is to 0.03 g/ml). Again, these three strains exhibit a high-mic phenotype for all three echinocandins relative to the wild-type MIC distribution. Similarly, one isolate of C. glabrata was noted to be nonsusceptible to both caspofungin (MIC 8 g/ml) and anidulafungin (MIC 4 g/ml), with susceptibility to micafungin, having a MIC of 1 g/ml, but this MIC is still high compared to the modal MIC of g/ml. Although C. guilliermondii is well known for its reduced susceptibility to caspofungin (33, 37), MICs for this are generally 1 g/ml with a modal MIC of 0.5 g/ml (Tables 2 and 3). In the present study, we detected three isolates, all from Latin America, for which the caspofungin MICs were 8 g/ml (Table 3). Similar to that described for high-mic isolates of C. albicans, C. glabrata, and C. tropicalis, these isolates were found to have anidulafungin MICs of 1, 4, and 4 g/ml (modal MIC for anidulafungin and C. guilliermondii is 1 g/ml) and micafungin MICs of 0.5, 1, and 2 g/ml (the modal MIC of micafungin for C. guilliermondii is 0.5 g/ml). Thus, although isolates of Candida with a high-echinocandin-mic phenotype are very rare, they may be detected worldwide, exist among several different species, and generally exhibit MICs outside of the wild-type distribution for all three echinocandins. Notably, we did not detect any isolates of C. parapsilosis that exhibited the multiazole- and multiechinocandin-resistant phenotype described by Moudgal et al. (21) and by Vazquez et al. (42),

6 VOL. 46, 2008 CANDIDA SUSCEPTIBILITY TO THE ECHINOCANDINS 155 suggesting that this phenotype has not spread beyond the initially reported environment. The results of this study clearly demonstrate the comparable and excellent spectrum and potency of all three available echinocandin antifungal s against a large collection of clinically important Candida spp. We have shown that the activities of all three s remain consistent over time and broad geographic regions and that species-specific differences in echinocandin activities against Candida are apparent worldwide. Although slight differences in potency in vitro may be observed among the three echinocandins for a given species of Candida, such differences have been shown to be normalized by the addition of serum to the in vitro test system (27) and do not appear to be significant in vivo (31). In addition to highlighting the presence of species such as C. parapsilosis and C. guilliermondii, which exhibit decreased susceptibilities to all three echinocandins, this large survey provides additional documentation of the presence of rare strains of otherwise highly susceptible species of Candida that exhibit unusually high MICs for, but are not necessarily nonsusceptible (MIC 2 g/ml) to, all three echinocandins. These high-mic strains are sufficiently rare that they have not been encountered with any frequency in clinical trials (13, 16, 20, 26, 40), although several isolates with echinocandin MICs of 2 g/ml have recently been associated with clinical resistance to echinocandin therapy in published case reports (8, 10, 12, 14, 17, 19, 21, 30, 39). Thus far, the rare high-echinocandin-mic phenotypes appear to exhibit a classspecific resistance profile. 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7 156 PFALLER ET AL. J. CLIN. MICROBIOL. Reboli, B. Suh, R. Digumarti, C. Wu, L. L. Kovanda, L. J. Arnold, and D. N. Buell Micafungin versus caspofungin for treatment of candidemia and other forms of invasive candidiasis. Clin. Infect. Dis. 45: Park, S., R. Kelly, J. N. Kahn, J. Robles, M. J. Hsu, E. Register, W. Li, V. Vyas, H. Fan, G. Abruzzo, A. Flattery, C. Gill, G. Chrebet, S. A. Parent, M. Kurtz, H. Teppler, C. M. Douglas, and D. S. Perlin Specific substitutions in the echinocandin target Fks1p account for reduced susceptibility of rare laboratory and clinical Candida sp. isolates. Antimicrob. Agents Chemother. 49: Pelletier, R., I. Alarie, R. Lagace, and T. J. Walsh Emergence of disseminated candidiasis caused by Candida krusei during treatment with caspofungin: case report and review of literature. Med. Mycol. 43: Perlin, D. S Resistance to echinocandin-class antifungal drugs. Drug Resist. Updat. 10: Pfaller, M. A., and D. J. Diekema Twelve years of fluconazole in clinical practice: global trends in species distribution and fluconazole susceptibility of bloodstream isolates of Candida. Clin. Microbiol. Infect. 10(Suppl. 1): Pfaller, M. A., S. A. Messer, L. Boyken, C. Rice, S. Tendolkar, R. J. Hollis, and D. J. Diekema Further standardization of broth microdilution methodology for in vitro susceptibility testing of caspofungin against Candida species by use of an international collection of more than 3,000 clinical isolates. J. Clin. Microbiol. 42: Pfaller, M. A., L. Boyken, R. J. Hollis, S. A. Messer, S. Tendolkar, and D. J. Diekema In vitro activities of anidulafungin against more than 2,500 clinical isolates of Candida spp., including 315 isolates resistant to fluconazole. J. Clin. Microbiol. 43: Pfaller, M. A., L. Boyken, R. J. Hollis, S. A. Messer, S. Tendolkar, and D. J. Diekema In vitro susceptibilities of Candida spp. to caspofungin: four years of global surveillance. J. Clin. Microbiol. 44: Pfaller, M. A., L. Boyken, R. J. Hollis, S. A. Messer, S. Tendolkar, and D. J. Diekema Global surveillance of in vitro activity of micafungin against Candida: a comparison with caspofungin by CLSI-recommended methods. J. Clin. Microbiol. 44: Pfaller, M. A., D. J. Diekema, M. Mendez, C. Kibbler, P. Erzsebet, S. C. Chang, D. L. Gibbs, V. A. Newell, and the Global Surveillance Group Candida guilliermondii, an opportunistic fungal pathogen with decreased susceptibility to fluconazole: geographic and temporal trends from the ARTEMIS DISK Surveillance Program. J. Clin. Microbiol. 44: Pfaller, M. A., and D. J. Diekema Epidemiology of invasive candidiasis: a persistent public health problem. Clin. Microbiol. Rev. 20: Prabhu, R. M., and R. Orenstein Failure of caspofungin to treat brain abscesses secondary to Candida albicans prosthetic valve endocarditis. Clin. Infect. Dis. 39: Reboli, A. C., C. Rotstein, P. G. Pappas, S. W. Chapman, D. H. Kett, D. Kumar, R. Betts, M. Wible, B. P. Goldstein, J. Schranz, D. S. Krause, and T. J. Walsh Anidulafungin versus fluconazole for invasive candidiasis. N. Engl. J. Med. 356: Rogers, T. R., E. M. Johnson, and C. Munro Echinocandin antifungal drug resistance. J. Invasive Fungal Infect. 1: Vazquez, J. A., A. Chen, M. Buhari, J. Chandra, P. Mukhejie, and M. A. Ghannoum Abstr. 8th ASM Conf. Candida Candidiasis, abstr. A Wagner, C., W. Graninger, E. Presterl, and C. Joukhadar The echinocandins: comparison of their pharmacokinetics, pharmacodynamics and clinical applications. Pharmacology 78: Downloaded from on January 1, 2019 by guest

8 JOURNAL OF CLINICAL MICROBIOLOGY, Sept. 2008, p Vol. 46, No /08/$ doi: /jcm AUTHOR S CORRECTION In Vitro Susceptibility of Invasive Isolates of Candida spp. to Anidulafungin, Caspofungin, and Micafungin: Six Years of Global Surveillance M. A. Pfaller, L. Boyken, R. J. Hollis, J. Kroeger, S. A. Messer, S. Tendolkar, and D. J. Diekema Departments of Pathology and Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa Volume 46, no. 1, p , In our recent report describing the in vitro susceptibility of 5,346 Candida spp. to the echinocandins, we noted the excellent activity of the echinocandins and the lack of evidence of emerging echinocandin resistance over 6 years of global surveillance. We also described 12 (out of a total of 2,869) isolates of Candida albicans that demonstrated a high-anidulafungin-mic phenotype, which we defined as an anidulafungin MIC of 2 g/ml. We noted that these isolates, while still susceptible according to the recently approved Clinical and Laboratory Standards Institute (CLSI) breakpoint of 2 g/ml (minutes of the June 2007 meeting of the CLSI Subcommittee), were nonetheless of interest because their echinocandin MICs were distinctly higher than the normal wild-type distribution of echinocandin MICs for C. albicans (page 152, column 2, lines 1 18). While pulling these 12 isolates from our bank for further evaluation, we noted that none of them demonstrated the characteristic green color of C. albicans on CHROMagar Candida (Becton Dickinson and Company, Sparks, MD), yet the Vitek Yeast Biochemical Card (YBC; biomerieux, Inc., Hazelwood, MO) identified each isolate as C. albicans. To further evaluate these isolates, we performed randomly amplified polymorphic DNA (RAPD) analysis (A. Tavanti, A. D. Davidson, N. A. Gow, M. C. Maiden, and F. C. Odds, J. Clin. Microbiol. 43: , 2005). All 12 isolates were confirmed to be C. parapsilosis by RAPD analysis. Further evaluation of these isolates (with the assistance of David Pincus and Nancy Moss in the research and development group at biomerieux, Inc.) revealed that all demonstrated the same atypical pattern for the Vitek YBC database (for C. parapsilosis), specifically for three reactions, those involving alpha methyl-d-glucoside (AMG), melezitose (MLZ), and xylitol (XLT). All 12 isolates were AMG negative, MLZ negative, and XLT positive in our hands. Based upon these three atypical reactions, the YBC algorithm generated C. albicans as the best match for each isolate. These findings were confirmed by sending the isolates to biomerieux, Inc., for testing, which revealed highly variable AMG statuses (with only 3 of the 12 isolates being strongly negative), negative MLZ results for 11 of the 12 isolates, and positive XLT results for all 12 isolates. When with the API 20-C system, 11 of the 12 isolates were correctly identified as C. parapsilosis, and when on the Vitek 2 YST card, all 12 were correctly identified, with 3 of the 12 giving a low discrimination call with C. famata. We regret that we did not detect this species identification error prior to publication. At the time of the initial receipt and characterization of the isolates, all were identified as C. albicans based upon the Vitek YBC result. We are in the process of systematically assessing the error rate of our Vitek YBC system for identification of C. parapsilosis, in particular the rare misidentification of C. parapsilosis as C. albicans. Preliminary findings suggest that this is an uncommon event, occurring for fewer than 2% of all C. parapsilosis isolates on the YBC (data not shown). In each case of misidentification we have detected thus far, the CHROMagar appearance of the organism is not consistent with that of C. albicans. We no longer accept a Vitek YBC result of C. albicans for an isolate without a characteristic CHROMagar appearance. In addition, we confirm the identification of all Candida species isolates with any echinocandin MIC of 1 g/ml by means including the use of molecular methods as required (S. R. Lockhart, S. A. Messer, M. A. Pfaller, and D. J. Diekema, J. Clin. Microbiol., 46: , 2008). The misidentification of the 12 C. parapsilosis isolates does not change any of the aggregate susceptibility data presented in our article, since all of the isolates in question were susceptible to the echinocandins, nor does it alter the MIC 50 and MIC 90 data reported or the conclusions of the study, which were that all three echinocandins have excellent in vitro activity against invasive isolates of Candida from centers worldwide and that our prospective sentinel surveillance reveals no evidence of emerging echinocandin resistance among invasive clinical isolates of Candida. These findings further emphasize the potent in vitro activity of the echinocandins against C. albicans. 3184

9 VOL. 46, 2008 AUTHOR S CORRECTION 3185 Page 151, Table 1: The entries for C. albicans and C. parapsilosis should appear as shown below. Candida species APAC (n 958) LAM (n 1,112) % of isolates a EU (n 1,787) NAM (n 1,489) Total (n 5,346) C. albicans C. parapsilosis Page 152, Table 2: The entries for C. albicans and C. parapsilosis should appear as shown below. Organism No. of isolates Cumulative % of isolates susceptible at a MIC ( g/ml) of: C. albicans 2,857 Anidulafungin a Caspofungin Micafungin C. parapsilosis 771 Anidulafungin Caspofungin Micafungin Pages , Table 3: The entries for C. albicans and C. parapsilosis should appear as shown below. Region(s) and species No. of isolates No. of isolates for which the MIC ( g/ml) was: Asia-Pacific C. albicans 545 Anidulafungin Caspofungin Micafungin C. parapsilosis 155 Anidulafungin Caspofungin Micafungin Latin America C. albicans 531 Anidulafungin Caspofungin Micafungin C. parapsilosis 209 Anidulafungin Caspofungin Micafungin Europe C. albicans 1,040 Anidulafungin Caspofungin Micafungin C. parapsilosis 194 Anidulafungin Caspofungin Micafungin North America C. albicans 741 Anidulafungin Caspofungin Micafungin C. parapsilosis 213 Anidulafungin Caspofungin Micafungin