Abstract Objectives To identify the frequency of micafungin resistance among clinically significant isolates of Candida stored at our institution from 2005 to 2015. Chart review of patients with resistant isolates then informed the clinical setting and outcomes associated with these infections. Methods Clinical Candida isolates had been stored at −80°C in Brucella broth with 20% glycerol from 2005. Isolates were tested using broth microdilution to determine micafungin MICs. All Candida glabrata isolates and all isolates demonstrating decreased susceptibility to micafungin were screened for FKS mutations using a Luminex assay. Results In total, 3876 Candida isolates were tested for micafungin resistance, including 832 C. glabrata isolates. Of those, 33 isolates from 31 patients were found to have either decreased susceptibility to micafungin and/or an FKS mutation. C. glabrata accounted for the majority of these isolates. While bloodstream infections were found to have a very high mortality rate, isolates from other sites were uncommonly associated with 30-day mortality. Overall resistance rates were very low. Conclusions Echinocandin resistance in C. glabrata has been increasingly reported but rates at our institution remain very low. We hypothesize that a focus on antifungal stewardship may have led to these observations. Knowledge of local resistance patterns is key to appropriate empirical treatment strategies. Introduction Candidaemia and non-candidaemic invasive candidiasis are important causes of nosocomial infections in the USA.1 In addition to being associated with excessive mortality, an area of particular concern is the emergence of antifungal-resistant Candida isolates, especially those that are resistant to multiple agents, including the antifungal azoles and the echinocandins.2–5 These MDR Candida strains represent a major challenge to effective management of this common healthcare-associated infection. Echinocandin resistance has been reported from several individual sites and large surveys of candidaemia. Single-centre studies are showing some concern regarding an increasing frequency of echinocandin resistance occurring as well as a trend towards worse outcomes in those patients with bloodstream infections due to echinocandin-resistant Candida.2–7 There are far fewer data regarding outcomes associated with non-candidaemic invasive candidiasis, although anecdotal reports suggest poorer outcomes in the setting of intra-abdominal disease.8,9 Rates of echinocandin resistance range from 1% to 13% in published reports. Resistance is usually mediated via point mutations in the genes encoding the FKS1 and FKS2 subunits of the glucan synthase protein.10,11 Phenotypic resistance, as measured by MIC, and genetic mutations generally occur concurrently but not always. Discordant azole resistance and echinocandin resistance are reported frequently among Candida glabrata isolates, but resistance and genetic mutations have been reported across multiple, clinically relevant species. With rates of azole resistance among C. glabrata isolates approaching 20%–30% in some surveys, there is a greater likelihood of dual resistance to both azoles and echinocandins. Based on the aggregate results of large prospective randomized trials, echinocandins are considered first-line therapy for most cases of candidaemia and are generally recommended for empirical treatment of suspected invasive candidiasis.12,13 Unfortunately, there are no prospective data on the optimal management of echinocandin-resistant Candida infections and the emergence of these organisms presents a unique and difficult challenge to clinicians managing these infections. Here, we screened for phenotypic and genotypic resistance to micafungin in 3876 clinically significant Candida isolates collected over 11 years from a single institution and describe the outcomes of patients with echinocandin-resistant isolates following treatment. Materials and methods Clinical isolates of Candida spp. had been stored at −80°C in Brucella broth with 20% glycerol at the University of Alabama at Birmingham from 2005 to 2015. These isolates were recently tested using broth microdilution (CLSI M27-A3 and CLSI M27-S4) to determine MICs of micafungin.14,15 Micafungin resistance testing was not being performed as part of clinical routine during the study period; all testing described here was performed retrospectively. As such, this information was not available to treating physicians at that time. Additionally, all C. glabrata isolates and other isolates with decreased susceptibility were submitted to the CDC for genetic sequencing of FKS1 and FKS2. We reviewed the charts of all patients with a positive culture for C. glabrata with decreased susceptibility to micafungin and/or a mutation in an FKS gene. C. glabrata isolates were initially screened for the presence of FKS mutations in hotspot 1 of the FKS1 and FKS2 genes using a Luminex assay, as previously described.16 For any isolate that was determined to be non-WT by the Luminex assay, the hotspot 1 region of the FKS1 and FKS2 genes were sequenced to confirm the mutation.11 Because previous surveillance revealed an exceedingly low level of hotspot 2 mutations in C. glabrata, the hotspot 2 regions of FKS1 and FKS2 were not sequenced.11 Results We identified and tested 3876 Candida isolates collected from 2005 to 2015. The most common species seen were: 1921 Candida albicans, 832 C. glabrata, 508 Candida parapsilosis, 405 Candida tropicalis, 88 Candida krusei, 43 Candida guilliermondii and 20 Candida lusitaniae. There were 33 isolates that demonstrated decreased susceptibility to micafungin and/or had an FKS mutation. The isolates were collected from 31 unique patients. There were 15 isolates from the blood, 10 isolates from abdominal fluid, 5 isolates from urine, 2 isolates from lungs and 1 isolate from an intravascular catheter tip. Two patients had concurrent isolates from both blood and abdominal fluid. The first resistant isolate was identified in 2007. The overall trend for candidaemia rates can be seen in Figure 1. Among the 15 blood isolates, 12 were identified as C. glabrata, 2 as C. tropicalis and 1 as C. lusitaniae. Among the candidaemia patients, there were 9 deaths (60%) at 30 days from the time of blood culture collection. Five of the isolates (33%) demonstrated an MIC in the susceptible range but had an FKS mutation. Two isolates had an intermediate MIC with one of those having an FKS mutation. The remaining eight isolates (53%) had resistant MICs ranging from 0.25 to >16 mg/L with only two having an FKS mutation. Treatment information was available for 13 patients. Of those, 12 received micafungin and only one received fluconazole. Figure 1. View largeDownload slide Candida bloodstream infections over time. BSI, bloodstream infection. Figure 1. View largeDownload slide Candida bloodstream infections over time. BSI, bloodstream infection. The median age of patients with a resistant isolate was 43 (range = 22–84). Most patients were white (60%) and female (60%), and most were receiving total parenteral nutrition, had been on broad-spectrum parenteral antibacterial agents and had received an echinocandin in the preceding 3 months. Further details of this group can be seen in Table 1. Table 1. Characteristics of patients with echinocandin-resistant bloodstream infection Male, n (%) 6 (40) Age (years), median 43 Race, n (%) white 9 (60) black 5 (33.3) other 1 (6.7) Comorbidities, n (%) diabetes mellitus 6 (40) dialysis 2 (13.3) cirrhosis 1 (6.7) major surgery 3 (20) malignancy 4 (26.7) immunosuppression 3 (20) total parenteral nutrition 9 (60) intravenous antibiotics 12 (80) previous echinocandin (prior 3 months) 5 (33.3) ICU 8 (53.3) central venous line 13 (86.7) mechanical ventilation 7 (46.7) concurrent bacteraemia 7 (46.7) prior candidaemia 6 (40) polycandidaemia 4 (26.7) Male, n (%) 6 (40) Age (years), median 43 Race, n (%) white 9 (60) black 5 (33.3) other 1 (6.7) Comorbidities, n (%) diabetes mellitus 6 (40) dialysis 2 (13.3) cirrhosis 1 (6.7) major surgery 3 (20) malignancy 4 (26.7) immunosuppression 3 (20) total parenteral nutrition 9 (60) intravenous antibiotics 12 (80) previous echinocandin (prior 3 months) 5 (33.3) ICU 8 (53.3) central venous line 13 (86.7) mechanical ventilation 7 (46.7) concurrent bacteraemia 7 (46.7) prior candidaemia 6 (40) polycandidaemia 4 (26.7) Table 1. Characteristics of patients with echinocandin-resistant bloodstream infection Male, n (%) 6 (40) Age (years), median 43 Race, n (%) white 9 (60) black 5 (33.3) other 1 (6.7) Comorbidities, n (%) diabetes mellitus 6 (40) dialysis 2 (13.3) cirrhosis 1 (6.7) major surgery 3 (20) malignancy 4 (26.7) immunosuppression 3 (20) total parenteral nutrition 9 (60) intravenous antibiotics 12 (80) previous echinocandin (prior 3 months) 5 (33.3) ICU 8 (53.3) central venous line 13 (86.7) mechanical ventilation 7 (46.7) concurrent bacteraemia 7 (46.7) prior candidaemia 6 (40) polycandidaemia 4 (26.7) Male, n (%) 6 (40) Age (years), median 43 Race, n (%) white 9 (60) black 5 (33.3) other 1 (6.7) Comorbidities, n (%) diabetes mellitus 6 (40) dialysis 2 (13.3) cirrhosis 1 (6.7) major surgery 3 (20) malignancy 4 (26.7) immunosuppression 3 (20) total parenteral nutrition 9 (60) intravenous antibiotics 12 (80) previous echinocandin (prior 3 months) 5 (33.3) ICU 8 (53.3) central venous line 13 (86.7) mechanical ventilation 7 (46.7) concurrent bacteraemia 7 (46.7) prior candidaemia 6 (40) polycandidaemia 4 (26.7) Sixteen resistant isolates were from sources other than blood. Two of these isolates were from a pulmonary/airway source and were deemed insignificant and not examined in conjunction with clinical outcome. The remaining resistant isolates included eight from the abdomen, five from urine and one from an intravascular catheter tip. Among these non-blood isolates, there were 12 C. glabrata, 1 C. krusei and 1 C. tropicalis. There were 3 (21%) deaths among the 14 patients, all of which occurred in patients with abdominal isolates. Eleven (79%) patients were treated with an antifungal and managed as having a true Candida infection. Three patients (one each with abdominal, urine and catheter tip isolates) were not treated with an antifungal. Of those who were treated, seven patients received micafungin, two patients received fluconazole, one patient received amphotericin B and one patient received voriconazole. Five of these isolates demonstrated discordant findings between MICs of micafungin and FKS results. The remaining nine isolates demonstrated resistant MIC values and FKS mutations. Among patients with intra-abdominal candidiasis, four had suffered complications of pancreatitis and three had an enteric fistula. All five patients with urinary isolates were kidney transplant recipients. Trends over time for candidaemia and echinocandin-resistant infections at our institution can be seen in Figure 1. During the course of the study period, we observed a trend towards decreased numbers of cases of candidaemia annually. Infections involving micafungin-resistant Candida isolates have remained low throughout the study period. Overall, micafungin resistance was seen in 1.2% of all candidaemia isolates during the years 2008 to 2015, the highest year being 2014 with 4.7% echinocandin-resistant isolates. Discussion Antifungal resistance in Candida infections, especially resistance to echinocandins, is an increasing concern. Based on reports of echinocandin resistance in C. glabrata, coupled with the emergence of Candida auris, it is becoming increasingly important to understand local resistance patterns. As part of developing this background information at our institution, we found uncommon and sporadic resistance without a clear upward trend. Prior therapy with an echinocandin is the primary reported risk factor for developing a candidaemia with an echinocandin-resistant strain of Candida.2,5 However, a large multicentre study designed to better understand the impact of antifungal resistance on outcomes is a critical need. Moreover, there are few published data on the outcomes of non-candidaemic invasive candidiasis due to echinocandin-resistant organisms. Further studies are also required in this syndrome to more fully understand its frequency and impact on clinical and mycological outcomes. Increasing antifungal resistance has been demonstrated at multiple institutions similar to ours and it is unclear why we did not observe a similar trend. The consistent risk factor across different institutional studies for developing resistance has been prior echinocandin exposure.2,3,5 Given the current IDSA guidelines recommending echinocandins for empirical therapy in candidaemia and invasive candidiaisis, a high level of empiric echinocandin usage in the at-risk population will likely lead to increased resistance. The common cited risk factors for invasive candidiasis (broad-spectrum antibiotic usage, renal dialysis, intensive care, total parenteral nutrition etc.) are all present in abundance at our institution.17 Factors that may have played a role in limiting the development of echinocandin resistance at our institution include a very proactive and aggressive antimicrobial (including antifungal) stewardship programme that discourages excessive and prolonged empirical echinocandin use and exposure, routine availability of echinocandin susceptibility testing, and effective infection prevention measures. We cannot exclude that we may have missed a minor mutation in hotspot 2 that either failed to raise the MIC value or appeared in one of our isolates with elevated MIC values but without a hotspot 1 mutation. However, a prior study that sequenced this region in 77 isolates with decreased susceptibility did not detect a single hotspot 2 mutation.11 In summary, we present data from a large referral regional medical centre, traditionally with a high rate of candidaemia, and have demonstrated not only a declining incidence of candidaemia from 2005 to 2015, similar to that recently reported in Atlanta and Baltimore,18 but also a low and stable rate of echinocandin resistance in this same group of over 3800 isolates, including C. glabrata. The declining incidence of candidaemia is certainly multifactorial, but we hypothesize that our very low frequency of echinocandin resistance may reflect, in part, an aggressive approach to antimicrobial stewardship (including antifungals) based on emphasizing de-escalation of echinocandin therapy, when appropriate, and limiting the duration of empirical echinocandin use. We are unaware of data from similar institutions with higher rates of echinocandin resistance to allow for this comparison. We suggest that our data support limiting echinocandin exposure as an important intervention towards reducing echinocandin resistance in Candida species. Funding This work was supported by an investigator-initiated grant (P. G. P.) from Astellas Pharma US, Inc. Transparency declarations P. G. P.: grants from Merck, Astellas, Gilead, Scynexis, Cidara, Amplyx and IMMY, and scientific advisor for Gilead, Scynexis, Amplyx and Cidara. All other authors: none to declare. References 1 Magill SS , Edwards JR , Bamberg W et al. Multistate point-prevalence survey of health care-associated infections . N Engl J Med 2014 ; 370 : 1198 – 208 . Google Scholar CrossRef Search ADS PubMed 2 Alexander BD , Johnson MD , Pfeiffer CD et al. Increasing echinocandin resistance in Candida glabrata: clinical failure correlates with presence of FKS mutations and elevated minimum inhibitory concentrations . Clin Infect Dis 2013 ; 56 : 1724 – 32 . Google Scholar CrossRef Search ADS PubMed 3 Beyda ND , John J , Kilic A et al. FKS mutant Candida glabrata: risk factors and outcomes in patients with candidemia . Clin Infect Dis 2014 ; 59 : 819 – 25 . Google Scholar CrossRef Search ADS PubMed 4 Pfaller MA , Castanheira M , Lockhart SR et al. Frequency of decreased susceptibility and resistance to echinocandins among fluconazole-resistant bloodstream isolates of Candida glabrata . J Clin Microbiol 2012 ; 50 : 1199 – 203 . Google Scholar CrossRef Search ADS PubMed 5 Vallabhaneni S , Cleveland AA , Farley MM et al. Epidemiology and risk factors for echinocandin nonsusceptible Candida glabrata bloodstream infections: data from a large multisite population-based candidemia surveillance program, 2008-2014 . Open Forum Infect Dis 2015 ; 2 : ofv163 . Google Scholar CrossRef Search ADS PubMed 6 Fekkar A , Dannaoui E , Meyer I et al. Emergence of echinocandin-resistant Candida spp. in a hospital setting: a consequence of 10 years of increasing use of antifungal therapy? Eur J Clin Microbiol Infect Dis 2014 ; 33 : 1489 – 96 . Google Scholar CrossRef Search ADS PubMed 7 Shields RK , Nguyen MH , Press EG et al. The presence of an FKS mutation rather than MIC is an independent risk factor for failure of echinocandin therapy among patients with invasive candidiasis due to Candida glabrata . Antimicrob Agents Chemother 2012 ; 56 : 4862 – 9 . Google Scholar CrossRef Search ADS PubMed 8 Cheng S , Clancy CJ , Hartman DJ et al. Candida glabrata intra-abdominal candidiasis is characterized by persistence within the peritoneal cavity and abscesses . Infect Immun 2014 ; 82 : 3015 – 22 . Google Scholar CrossRef Search ADS PubMed 9 Shields RK , Nguyen MH , Press EG et al. Abdominal candidiasis is a hidden reservoir of echinocandin resistance . Antimicrob Agents Chemother 2014 ; 58 : 7601 – 5 . Google Scholar CrossRef Search ADS PubMed 10 Pfaller MA , Diekema DJ , Andes D et al. Clinical breakpoints for the echinocandins and Candida revisited: integration of molecular, clinical, and microbiological data to arrive at species-specific interpretive criteria . Drug Resist Updat 2011 ; 14 : 164 – 76 . Google Scholar CrossRef Search ADS PubMed 11 Pham CD , Iqbal N , Bolden CB et al. Role of FKS mutations in Candida glabrata: MIC values, echinocandin resistance, and multidrug resistance . Antimicrob Agents Chemother 2014 ; 58 : 4690 – 6 . Google Scholar CrossRef Search ADS PubMed 12 Cornely OA , Bassetti M , Calandra T et al. ESCMID* guideline for the diagnosis and management of Candida diseases 2012: non-neutropenic adult patients . Clin Microbiol Infect 2012 ; 18 Suppl 7: 19 – 37 . Google Scholar CrossRef Search ADS PubMed 13 Pappas PG , Kauffman CA , Andes DR et al. Clinical practice guideline for the management of candidiasis: 2016 update by the Infectious Diseases Society of America . Clin Infect Dis 2016 ; 62 : e1 – 50 . Google Scholar CrossRef Search ADS PubMed 14 Clinical and Laboratory Standards Institute . Reference Method for Broth Dilution Antifungal Susceptibility Testing of Yeasts—Third Edition: Approved Standard M27-A3 . CLSI , Wayne, PA, USA , 2008 . 15 Clinical and Laboratory Standards Institute . Reference Method for Broth Dilution Antifungal Susceptibility Testing of Yeasts: Fourth Informational Supplement M27-S4 . CLSI , Wayne, PA, USA , 2012 . 16 Pham CD , Bolden CB , Kuykendall RJ et al. Development of a Luminex-based multiplex assay for detection of mutations conferring resistance to echinocandins in Candida glabrata . J Clin Microbiol 2014 ; 52 : 790 – 5 . Google Scholar CrossRef Search ADS PubMed 17 McCarty TP , Pappas PG. Invasive candidiasis . Infect Dis Clin North Am 2016 ; 30 : 103 – 24 . Google Scholar CrossRef Search ADS PubMed 18 Cleveland AA , Harrison LH , Farley MM et al. Declining incidence of candidemia and the shifting epidemiology of Candida resistance in two US metropolitan areas, 2008-2013: results from population-based surveillance . PLoS One 2015 ; 10 : e0120452 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: email@example.com. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)
Journal of Antimicrobial Chemotherapy – Oxford University Press
Published: Feb 28, 2018
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