Since 2016, New York hospitals and health care facilities have faced an unprecedented outbreak of the pathogenic yeast Candida auris. We tested over 1,000 C. auris isolates from affected facilities and found high resistance to fluconazole (MIC > 256 mg/liter) and variable resistance to other antifungal drugs. Therefore, we tested if two-drug combinations are effective in vitro against multidrug-resistant C. auris.
KEYWORDS: Candida auris, antifungal combination, multidrug resistance
ABSTRACT
Since 2016, New York hospitals and health care facilities have faced an unprecedented outbreak of the pathogenic yeast Candida auris. We tested over 1,000 C. auris isolates from affected facilities and found high resistance to fluconazole (MIC > 256 mg/liter) and variable resistance to other antifungal drugs. Therefore, we tested if two-drug combinations are effective in vitro against multidrug-resistant C. auris. Broth microdilution antifungal combination plates were custom manufactured by TREK Diagnostic System. We used 100% inhibition endpoints for the drug combination as reported earlier for the intra- and interlaboratory agreements against Candida species. The results were derived from 12,960 readings, for 15 C. auris isolates tested against 864 two-drug antifungal combinations for nine antifungal drugs. Flucytosine (5FC) at 1.0 mg/liter potentiated the most combinations. For nine C. auris isolates resistant to amphotericin B (AMB; MIC ≥ 2.0 mg/liter), AMB-5FC (0.25/1.0 mg/liter) yielded 100% inhibition. Six C. auris isolates resistant to three echinocandins (anidulafungin [AFG], MIC ≥ 4.0 mg/liter; caspofungin [CAS], MIC ≥ 2.0 mg/liter; and micafungin [MFG], MIC ≥ 4.0 mg/liter) were 100% inhibited by AFG-5FC and CAS-5FC (0.0078/1 mg/liter) and MFG-5FC (0.12/1 mg/liter). None of the combinations were effective for C. auris 18-1 and 18-13 (fluconazole [FLC] > 256 mg/liter, 5FC > 32 mg/liter) except MFG-5FC (0.1/0.06 mg/liter). Thirteen isolates with a high voriconazole (VRC) MIC (>2 mg/liter) were 100% inhibited by the VRC-5FC (0.015/1 mg/liter). The simplified two-drug combination susceptibility test format would permit laboratories to provide clinicians and public health experts with additional data to manage multidrug-resistant C. auris.
INTRODUCTION
Candida auris is an emerging multidrug-resistant yeast, causing invasive health care-associated infection with high mortality worldwide (1). It was described in 2009 as a new yeast species from the ear discharge of a Japanese patient (2). In the ensuing years, many reports of multidrug-resistant C. auris infections came from South Asia, South Africa, and South America and from travel-related cases from other parts of the world (3–6). A large, localized uninterrupted C. auris outbreak in U.S. health care facilities continues to afflict the New York metro areas (2013 to 2019); C. auris caused 23 deaths among the first 51 clinical case patients in New York (7). In response, the New York State Department of Health (NYSDOH) laboratory scientists and epidemiologists developed a new rapid test and enhanced protocols for the unprecedented surveillance and testing for C. auris (8). To date, over 20,000 clinical samples from 194 facilities were processed in the NYSDOH laboratory. The CLSI broth microdilution method (BMD) was used to test nearly 1,000 C. auris isolates. The results were interpreted according to CDC guidelines in the absence of susceptibility breakpoints for C. auris. They revealed high resistance to fluconazole (MIC ≥ 256 mg/liter) and variable resistance to other antifungal drugs (9). Therefore, we investigated the efficacy of two-drug combinations against a representative set of fifteen drug-resistant C. auris strains.
RESULTS
Among the test group, C. auris 16-1 was susceptible to all antifungals tested, while the remaining 14 isolates showed resistance to fluconazole (FLC; MIC >256 mg/liter) and other drugs as per CDC interpretation (Table 1). Candida auris 16-1 belongs to very minor East Asia clade II in the New York outbreak, as detailed in a recent study (9). The combination test results were derived from 12,960 MIC readings, for 15 C. auris isolates tested against 864 two-drug antifungal combinations for nine antifungal drugs. Flucytosine (5FC) at 1.0 mg/liter potentiated the most successful combinations with other drugs (Table 2). For nine C. auris isolates resistant to amphotericin B (AMB; MIC ≥ 2.0 mg/liter), AMB-5FC (0.25/1.0 mg/liter) yielded 100% inhibition (Table 2). Six C. auris isolates resistant to three echinocandins (anidulafungin [AFG], MIC ≥ 4.0 mg/liter; caspofungin [CAS], MIC ≥ 2.0 mg/liter; and micafungin [MFG], MIC ≥ 4.0 mg/liter), were 100% inhibited by AFG-5FC and CAS-5FC (0.0078/1 mg/liter) and MFG-5FC (0.12/1 mg/liter) combinations. None of the combinations were effective for C. auris 18-1 and 18-13 (FLC > 256 mg/liter, 5FC > 32 mg/liter) except MFG-5FC (0.1/0.06 mg/liter). Thirteen isolates with a high voriconazole (VRC) MIC (>2 mg/liter) were 100% inhibited by the VRC-5FC (0.015/1 mg/liter) combination (Table 2). File S2 in the supplemental material contains notable results for two-drug combinations other than 5FC; none were considered effective. Minimum fungicidal concentrations (MFCs) were obtained only for a few C. auris isolates (see File S3).
TABLE 1.
Conventional antifungal test results for Candida auris isolates
| C. auris | Source | MIC (mg/liter [interpretation])a |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| FLC | VRC | ITC | ISA | POS | AFG | CAS | MFG | AMBb | 5FCb | ||
| 16-1 | Ear | 8 (S) | 0.25 (S) | 0.5 (S) | 0.25 (S) | 0.25 (S) | 0.12 (S) | 0.12 (S) | 0.12 (S) | 0.5 (S) | 0.5 (S) |
| 17-12 | Urine | 32 (S) | 0.5 (S) | 0.06 (S) | 0.015 (S) | 0.03 (S) | 8 (R) | 8 (R) | 8 (R) | 1 (S) | 0.032 (S) |
| 18-14 | NAc | >256 (R) | 1 (S) | 0.25 (S) | 0.5 (S) | 0.03 (S) | 0.06 (S) | 0.015 (S) | 0.06 (S) | 1 (S) | 0.047 (S) |
| 18-15 | Blood | >256 (R) | 1 (S) | 0.25 (S) | 0.5 (S) | 0.03 (S) | 0.12 (S) | 0.03 (S) | 0.06 (S) | 1.5 (S) | 0.064 (S) |
| 17-1 | Blood | >256 (R) | 2 (S) | 0.5 (S) | 0.5 (S) | 0.25 (S) | 4 (R) | 4 (R) | 4 (R) | 1 (S) | 0.094 (S) |
| 17-13 | Urine | >256 (R) | 1 (S) | 0.25 (S) | 0.5 (S) | 0.03 (S) | 0.06 (S) | 0.03 (S) | 0.06 (S) | 3 (R) | 0.032 (S) |
| 17-14 | Groin swab | >256 (R) | 2 (S) | 0.5 (S) | 0.5 (S) | 0.12 (S) | 4 (R) | 2 (R) | 4 (R) | 0.75 (S) | 0.032 (S) |
| 17-15 | Skin rash swab | >256 (R) | 2 (S) | 0.5 (S) | 0.5 (S) | 0.25 (S) | 4 (R) | 2 (R) | 4 (R) | 0.75 (S) | 0.032 (S) |
| 17-16 | Urine | >256 (R) | 2 (S) | 0.5 (S) | 0.5 (S) | 0.12 (S) | 4 (R) | 2 (R) | 4 (R) | 1 (S) | 0.023 (S) |
| 17-17 | Nares swab | >256 (R) | 4 (R) | 0.5 (S) | 0.5 (S) | 0.06 (S) | 0.25 (S) | 0.03 (S) | 0.06 (S) | 3 (R) | 0.064 (S) |
| 17-18 | Nares swab | >256 (R) | 2 (S) | 0.5 (S) | 1 (S) | 0.12 (S) | 0.25 (S) | 0.06 (S) | 0.06 (S) | 3 (R) | 0.064 (S) |
| 18-1 | Wound swab | 128 (R) | 0.5 (S) | 0.12 (S) | 0.12 (S) | 0.03 (S) | 0.25 (S) | 0.03 (S) | 0.12 (S) | 1 (S) | >32 (R) |
| 18-2 | Ascites fluid | >256 (R) | 2 (S) | 1 (R) | 1 (S) | 0.25 (S) | 8 (R) | 2 (R) | 4 (R) | 1.5 (S) | 0.064 (S) |
| 18-5 | Urine | >256 (R) | 2 (S) | 0.25 (S) | 0.5 (S) | 0.06 (S) | 0.12 (S) | 0.03 (S) | 0.12 (S) | 2 (R) | 0.094 (S) |
| 18-13 | Rectal swab | 256 (R) | 0.5 (S) | 0.12 (S) | 0.12 (S) | 0.03 (S) | 0.12 (S) | 0.03 (S) | 0.12 (S) | 1 (S) | >32 (R) |
CLSI broth microdilution method, 50% inhibition endpoint. CDC susceptibility breakpoints were used for interpretation: S, susceptible; R, resistant.
Etest, AMB (100% inhibition), 5FC (90% inhibition).
NA, not available.
TABLE 2.
Candida auris antifungal combination testing of various drugs in combination with 5FCa
| Drug(s) | MIC (mg/liter) for Candida auris strain: |
||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 17-1 | 17-12 | 17-13 | 17-14 | 17-15 | 17-16 | 17-17 | 17-18 | 18-1 | 18-2 | 18-5 | 18-13 | 18-14 | 18-15 | 16-1 | |
| AMB | 1 | 2 | >2 | 1 | >2 | >2 | 1 | >2 | 1 | 2 | 2 | 0.5 | >2 | 2 | 0.5 |
| 5FC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | >32 | 1 | 1 | >32 | 1 | 1 | 1 |
| AMB-5FC | 0.2/1 | 0.25/1 | 0.25/1 | 0.25/1 | 0.25/1 | 0.25/1 | 0.015/1 | 0.25/1 | NA | 0.015/1 | 0.25/1 | NAb | 0.12/1 | 0.12/1 | 0.25/1 |
| AFG | >4 | >4 | 2 | >4 | >4 | >4 | 0.5 | 2 | 0.5 | >4 | 4 | 0.5 | 2 | 4 | 0.12 |
| 5FC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | >32 | 1 | 1 | >32 | 1 | 1 | 1 |
| AFG-5FC | 0.0078/1 | 0.0078/1 | 0.12/1 | 0.0078/1 | 0.015/2 | 0.0078/1 | 0.12/1 | 0.5/0.25 | NA | 0.0078/1 | 0.12/1 | 0.5/0.25 | 0.12/1 | 0.12/1 | 0.12/1 |
| CAS | >4 | >4 | >4 | >4 | >4 | >4 | >4 | >4 | >4 | >4 | >4 | >4 | >4 | >4 | 0.12 |
| 5FC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | >32 | 1 | 1 | >32 | 1 | 1 | 1 |
| CAS-5FC | 0.0078/1 | 0.0078/1 | 0.12/1 | 0.0078/1 | 0.015/2 | 0.0078/1 | 0.5/0.25 | 0.12/1 | NA | 0.0078/1 | 0.25/2 | NA | 0.12/1 | 0.12/1 | 0.12/1 |
| MFG | >4 | >4 | 0.25 | >4 | >4 | >4 | 0.12 | 0.25 | 0.25 | >4 | 0.25 | 0.25 | 1 | 0.25 | 0.12 |
| 5FC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | >32 | 1 | 1 | >32 | 1 | 1 | 1 |
| MFG-5FC | 0.12/1 | 0.06/0.5 | 0.12/1 | 0.12/1 | 0.12/1 | 0.12/1 | 0.12/1 | 0.25/0.12 | 0.1/0.06 | 0.12/1 | 0.12/1 | 0.1/0.06 | 0.12/1 | 0.12/1 | 0.12/1 |
| POS | 0.5 | 0.12 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.12 | 1 | >1 | 1 | 1 | 0.25 |
| 5FC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | >32 | 1 | 1 | >32 | 1 | 1 | 1 |
| POS-5FC | 0.0078/1 | 0.06/0.12 | NA | 0.0078/1 | 0.12/1 | 0.12/1 | 0.0078/1 | 0.0078/1 | 0.12/1 | 0.0078/1 | 0.12/1 | 0.5/1 | 0.0078/1 | 0.25/2 | 0.12/1 |
| ISA | >2 | 0.12 | >2 | >2 | >2 | >2 | >2 | >2 | 1 | >2 | 2 | >2 | >2 | >2 | 0.06 |
| 5FC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | >32 | 1 | 1 | >32 | 1 | 1 | 1 |
| ISA-5FC | 0.0078/1 | 0.12/1 | 0.12/1 | 0.06/1 | 0.12/1 | 0.0078/1 | 0.0078/1 | 0.0078/1 | 1/1 | 0.0078/1 | 0.12/1 | NA | 0.0078/1 | 0.25/2 | 0.12/1 |
| ITC | >1 | 0.06 | 0.5 | 0.5 | 0.5 | 0.5 | >1 | >1 | >1 | 0.5 | 1 | >1 | >1 | >1 | 0.5 |
| 5FC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | >32 | 1 | 1 | >32 | 1 | 1 | 1 |
| ITC-5FC | 0.03/1 | 0.03/1 | 0.06/1 | 0.003/1 | 0.06/1 | 0.003/1 | 0.003/1 | 0.06/1 | 0.5/1 | 0.003/1 | 0.06/1 | 0.5/1 | 0.003/1 | 0.12/2 | 0.03/0.5 |
| VRC | >2 | 1 | >2 | >2 | >2 | >2 | >2 | >2 | >2 | >2 | >2 | >2 | >2 | >2 | 0.12 |
| 5FC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | >32 | 1 | 1 | >32 | 1 | 1 | 1 |
| VRC-5FC | 0.015/1 | 0.12/0.5 | 0.25/1 | 0.015/1 | 0.25/1 | 0.015/1 | 0.015/1 | 0.015/1 | 1/1 | 0.015/1 | 0.25/1 | NA | 0.015/1 | 0.5/2 | 0.25/1 |
The details of test methods and 100% inhibition endpoints are provided in Materials and Methods.
NA, not available.
DISCUSSION
The clinical and public health microbiology community is on high alert because of the alarming rise in the incidence and spread of drug-resistant C. auris globally (10). An effective therapeutic intervention is indicated for invasive C. auris infections associated with high mortality (7, 11). The results from the present study fill a gap in the published literature, as there is no report on the efficacy of antifungal combinations against C. auris from the New York outbreak. These findings suggested that C. auris strains with various resistance patterns were susceptible to low dose combinations of existing drugs. A few effective combinations of antifungals exerted fungicidal activities, which was an additional indicator of the drug combination efficacy. The earlier multilaboratory evaluation showed that 100% inhibition endpoints provide a reliable method for antifungal combination testing vis-a-vis the ∑FIC (summation of fractional inhibitory concentration) index (12). We further optimized the method by using fixed drug concentrations instead of the checkerboard dilutions, as described by other authors in earlier publications (13, 14). As almost all NY isolates belonged to the South Asian clade I, it remains to be determined by other investigators if the resistant C. auris strains from South Africa and South America clades respond similarly to the antifungal combinations. The findings of the present study need further evaluation by pharmacokinetic/pharmacodynamic studies and testing in animal models to assess their clinical relevance (15, 16). In conclusion, a limited set of two-drug combinations of antifungals were efficacious in vitro against multidrug-resistant C. auris isolates. The simplified two-drug combination susceptibility test format would permit laboratories to provide clinicians and public health experts with additional data to manage multidrug-resistant C. auris.
MATERIALS AND METHODS
Isolates and conventional antifungal testing.
C. auris isolates were initially processed on Sabouraud dextrose agar at 30°C, and single colonies were used to confirm identity on Sabouraud dulcitol agar at 40°C, and with matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF-MS) and internal transcribed spacer (ITS)-D1/D2 sequencing (7, 9). The isolates were stored at −80°C in 20% sterile glycerol. CLSI broth microdilution and Etest (bioMérieux, USA) were used for antifungal susceptibility testing routinely. We followed CLSI endpoint readings (50% inhibition for most drugs) except for amphotericin B and 5-flucytosine (100% and 90% inhibition, respectively, according to the product insert for Etest [bioMérieux USA]). An advisory from the Centers for Disease Control and Prevention was used for C. auris antifungal susceptibility test result interpretation (https://www.cdc.gov/fungal/candida-auris/c-auris-antifungal.html). CDC recommends the following susceptibility breakpoints: fluconazole (FLC), ≥32 mg/liter; amphotericin B (AMB), ≥2 mg/liter; anidulafungin (AFG), ≥4 mg/liter; caspofungin (CAS), ≥2 mg/liter; micafungin (MFG), ≥4 mg/liter. Voriconazole (VRC) and other triazoles were assessed using the FLC susceptibility value. Antifungal names were abbreviated according to Antimicrobial Agents and Chemotherapy recommendations.
Antifungal combination testing.
Nine drugs were selected for the combination testing: AMB, AFG, CAS, MFG, flucytosine (5FC), isavuconazole (ISA), posaconazole (POS), VRC, and itraconazole (ITC). FLC was not tested in any combination because of the widespread resistance in our isolate collection. Broadly, we followed the method described earlier from a multilaboratory evaluation of antifungal combination testing (12). In the present study, two fixed concentrations of each drug were tested. The antifungal drug values in the combination were selected after considering reported maximum concentration of drug in serum (Cmax) from the FDA drug approvals and databases site (https://www.fda.gov/drugs/development-approval-process-drugs/drug-approvals-and-databases) and concentrations considered resistant for C. auris (https://www.cdc.gov/fungal/candida-auris/c-auris-antifungal.html). The drug combinations were dispensed in a total volume of 100 μl. The 96-well microtiter plates were custom manufactured and tested for sterility by TREK Diagnostic System, part of Thermo Fisher Scientific (Oakwood Village, OH, USA). They were transferred under ice packs to our site and stored at −80°C until used. The schematic of plate design is provided in File S1 in the supplemental material. We also prepared 2-fold dilutions of each drug combination by adding 100 μl sterile RPMI 1640 to the initial well and transferring 100 μl of the 200-μl mix into a microwell of a new 96-well microtiter plate. This dilution scheme provided one-half, one-fourth, one-eighth, 1/16th, and 1/32nd concentrations of each drug in the initial well. The inoculation, incubation, 100% inhibition endpoint reading, and use of Candida krusei ATCC 6258 as the quality control strain were as published earlier from a multilaboratory evaluation of antifungal combination testing (12, 17). Briefly, C. auris cultures were streaked on Sabouraud dextrose agar and incubated for 24 h at 35°C. Cells were suspended in sterile water to an absorbance (A530) of 0.08 to 0.1 as measured with a Mettler Toledo UV5 bio spectrophotometer; 20 μl of the cell suspension was added to 11 ml of RPMI 1640 broth tube. One-hundred microliters of the suspension in RPMI 1640 was added to each well of the 96-well microtiter plate with the single drugs and drug combinations. The plates were incubated at 35°C for 48 h, and 100% inhibition reading was obtained with an illuminated convex mirror plate reader (12). A two-drug combination was considered effective if a two-dilution or more reduction was seen relative to the values obtained with single drugs, except for 5FC. Twenty microliters of the drug-fungal suspension from each well were transferred to a fresh 96-well microtiter plate that contained 180 μl of sterile RPMI 1640 per well to set up the sterility testing. We incubated the sterility plates at 35°C for 48 h and determined the minimum fungicidal concentration (MFC) from each well with no visible growth (18, 19). In preliminary experiments, a good correlation was observed between MFC values obtained from microbroth plates and Sabouraud dextrose agar (details not shown).
Supplementary Material
ACKNOWLEDGMENTS
We thank the members of the New York State Healthcare Epidemiology and Infection Control Program, Candida auris Investigation Workgroup, and the staff members from various hospitals and long-term care facilities for help with surveillance samples. We also thank two anonymous reviewers for their helpful comments for the improvement of the original manuscript.
This publication was supported in part by Cooperative Agreement number NU50CK000516, funded by the Centers for Disease Control and Prevention. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention or the Department of Health and Human Services.
B. O’Brien performed the experiments and tabulated and analyzed the data, S. Chaturvedi supervised single drug testing and interpretation, helped to interpret combination testing, and critiqued the draft manuscript, and V. Chaturvedi conceived and designed the study, interpreted data, and wrote the manuscript.
Footnotes
Supplemental material is available online only.
REFERENCES
- 1.Lockhart SR, Etienne KA, Vallabhaneni S, Farooqi J, Chowdhary A, Govender NP, Colombo AL, Calvo B, Cuomo CA, Desjardins CA, Berkow EL, Castanheira M, Magobo RE, Jabeen K, Asghar RJ, Meis JF, Jackson B, Chiller T, Litvintseva AP. 2017. Simultaneous emergence of multidrug-resistant Candida auris on 3 continents confirmed by whole-genome sequencing and epidemiological analyses. Clin Infect Dis 64:134–140. doi: 10.1093/cid/ciw691. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Satoh K, Makimura K, Hasumi Y, Nishiyama Y, Uchida K, Yamaguchi H. 2009. Candida auris sp. nov., a novel ascomycetous yeast isolated from the external ear canal of an inpatient in a Japanese hospital. Microbiol Immunol 53:41–44. doi: 10.1111/j.1348-0421.2008.00083.x. [DOI] [PubMed] [Google Scholar]
- 3.Vallabhaneni S, Kallen A, Tsay S, Chow N, Welsh R, Kerins J, Kemble SK, Pacilli M, Black SR, Landon E, Ridgway J, Palmore TN, Zelzany A, Adams EH, Quinn M, Chaturvedi S, Greenko J, Fernandez R, Southwick K, Furuya EY, Calfee DP, Hamula C, Patel G, Barrett P, Lafaro P, Berkow EL, Moulton-Meissner H, Noble-Wang J, Fagan RP, Jackson BR, Lockhart SR, Litvintseva AP, Chiller TM. 2017. Investigation of the first seven reported cases of Candida auris, a globally emerging invasive, multidrug-resistant fungus-United States, May 2013-August 2016. Am J Transplant 17:296–299. doi: 10.1111/ajt.14121. [DOI] [PubMed] [Google Scholar]
- 4.Govender NP, Magobo RE, Mpembe R, Mhlanga M, Matlapeng P, Corcoran C, Govind C, Lowman W, Senekal M, Thomas J. 2018. Candida auris in South Africa, 2012–2016. Emerg Infect Dis 24:2036–2040. doi: 10.3201/eid2411.180368. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Chowdhary A, Anil Kumar V, Sharma C, Prakash A, Agarwal K, Babu R, Dinesh KR, Karim S, Singh SK, Hagen F, Meis JF. 2014. Multidrug-resistant endemic clonal strain of Candida auris in India. Eur J Clin Microbiol Infect Dis 33:919–926. doi: 10.1007/s10096-013-2027-1. [DOI] [PubMed] [Google Scholar]
- 6.Calvo B, Melo ASA, Perozo-Mena A, Hernandez M, Francisco EC, Hagen F, Meis JF, Colombo AL. 2016. First report of Candida auris in America: clinical and microbiological aspects of 18 episodes of candidemia. J Infect 73:369–374. doi: 10.1016/j.jinf.2016.07.008. [DOI] [PubMed] [Google Scholar]
- 7.Adams E, Quinn M, Tsay S, Poirot E, Chaturvedi S, Southwick K, Greenko J, Fernandez R, Kallen A, Vallabhaneni S, Haley V, Hutton B, Blog D, Lutterloh E, Zucker H, Candida auris Investigation Workgroup . 2018. Candida auris in healthcare facilities, New York, USA, 2013–2017. Emerg Infect Dis 24:1816–1824. doi: 10.3201/eid2410.180649. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Leach L, Zhu Y, Chaturvedi S. 2018. Development and validation of a real-time PCR assay for rapid detection of Candida auris from surveillance samples. J Clin Microbiol 56:e01223-17. doi: 10.1128/JCM.01223-17. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Zhu Y, O’Brien B, Leach L, Clark A, Bates M, Adams E, Ostrowsky B, Quinn M, Dufort E, Southwick K, Erazo R, Haley VB, Bucher C, Chaturvedi V, Limberger RJ, Blog D, Lutterloh E, Chaturvedi S. 2019. Laboratory analysis of an outbreak of Candida auris in New York from 2016 to 2018-impact and lessons learned. J Clin Microbiol doi: 10.1128/JCM.01503-19. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Tsay S, Kallen A, Jackson BR, Chiller TM, Vallabhaneni S. 2018. Approach to the investigation and management of patients with Candida auris, an emerging multidrug-resistant yeast. Clin Infect Dis 66:306–311. doi: 10.1093/cid/cix744. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Ruiz-Gaitán A, Moret AM, Tasias-Pitarch M, Aleixandre-López AI, Martínez-Morel H, Calabuig E, Salavert-Lletí M, Ramírez P, López-Hontangas JL, Hagen F, Meis JF, Mollar-Maseres J, Pemán J. 2018. An outbreak due to Candida auris with prolonged colonisation and candidaemia in a tertiary care European hospital. Mycoses 61:498–505. doi: 10.1111/myc.12781. [DOI] [PubMed] [Google Scholar]
- 12.Ren P, Luo M, Lin S, Ghannoum MA, Isham N, Diekema DJ, Pfaller MA, Messer S, Lockhart SR, Iqbal N, Chaturvedi V. 2015. Multilaboratory testing of antifungal drug combinations against Candida species and Aspergillus fumigatus: utility of 100 percent inhibition as the endpoint. Antimicrob Agents Chemother 59:1759–1766. doi: 10.1128/AAC.04545-14. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Pfaller MA, Barry AL, Fuchs PC, Gerlach EH, Hardy DJ, McLaughlin JC. 1993. Comparison of fixed concentration and fixed ratio options for dilution susceptibility testing of Gram-negative bacilli to ampicillin and ampicillin/sulbactam. Eur J Clin Microbiol Infect Dis 12:356–362. doi: 10.1007/bf01964434. [DOI] [PubMed] [Google Scholar]
- 14.Bradford PA, Huband MD, Stone GG. 2018. A systematic approach to the selection of the appropriate avibactam concentration for use with ceftazidime in broth microdilution susceptibility testing. Antimicrob Agents Chemother 62:e00223-18. doi: 10.1128/AAC.00223-18. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Lepak AJ, Andes DR. 2014. Antifungal pharmacokinetics and pharmacodynamics. Cold Spring Harb Perspect Med 5:a019653. doi: 10.1101/cshperspect.a019653. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Hager CL, Larkin EL, Long L, Zohra Abidi F, Shaw KJ, Ghannoum MA. 2018. In vitro and in vivo evaluation of the antifungal activity of APX001A/APX001 against Candida auris. Antimicrob Agents Chemother 62:e02319-17. doi: 10.1128/AAC.02319-17. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Chaturvedi V, Ramani R, Ghannoum MA, Killian SB, Holliday N, Knapp C, Ostrosky-Zeichner L, Messer SA, Pfaller MA, Iqbal NJ, Arthington-Skaggs BA, Vazquez JA, Sein T, Rex JH, Walsh TJ. 2008. Multilaboratory testing of antifungal combinations against a quality control isolate of Candida krusei. Antimicrob Agents Chemother 52:1500–1502. doi: 10.1128/AAC.00574-07. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Ramani R, Chaturvedi V. 2007. Antifungal susceptibility profiles of Coccidioides immitis and Coccidioides posadasii from endemic and non-endemic areas. Mycopathologia 163:315–319. doi: 10.1007/s11046-007-9018-7. [DOI] [PubMed] [Google Scholar]
- 19.Espinel-Ingroff A, Fothergill A, Peter J, Rinaldi MG, Walsh TJ. 2002. Testing conditions for determination of minimum fungicidal concentrations of new and established antifungal agents for Aspergillus spp.: NCCLS collaborative study. J Clin Microbiol 40:3204–3208. doi: 10.1128/jcm.40.9.3204-3208.2002. [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.