Brief Report
23 May 2016

Role of Antifungal Susceptibility Testing in Non-Aspergillus Invasive Mold Infections

ABSTRACT

No clinical breakpoints are available to delineate antifungal drug efficacy in non-Aspergillus invasive mold infections (NAIMIs). In this analysis of 39 NAIMI episodes, the MIC of the first-line antifungal drug was the most important predictor of therapeutic response. For amphotericin B, an MIC of ≤0.5 μg/ml was significantly associated with better 6-week outcomes.

TEXT

Molds other than Aspergillus spp. account for an increasing proportion of invasive fungal infections in the expanding population of immunosuppressed patients (1). Mucorales, Fusarium spp., and Scedosporium spp. are the most frequently seen non-Aspergillus mold pathogens and are associated with a high mortality rate, while Paecilomyces spp. and Scopulariopsis spp. are emerging opportunistic pathogens (15). Antifungal agents often have variable activity against these organisms, many of which are notoriously resistant to multiple antifungal drug classes. The utility of in vitro susceptibility testing in this setting is controversial, as clinical breakpoints are lacking and the correlation between drug MICs and outcomes has, to our knowledge, never been demonstrated. The aim of this study was to investigate factors influencing the outcome of non-Aspergillus invasive mold infections (NAIMIs) with a focus on the association between MICs and response to therapy.
Retrospective analysis of patient medical records where a non-Aspergillus mold was isolated from a clinical specimen between 2009 and 2013 at Duke University (Durham, NC, USA) led to the identification of 39 proven or probable NAIMI cases, according to European Organization for Research and Treatment of Cancer and Mycoses Study Group (EORTC-MSG) definitions (6). Antifungal susceptibility testing (amphotericin B, voriconazole, posaconazole, micafungin) of these samples was performed according to the Clinical and Laboratory Standards Institute (CLSI) M38-A2 procedure (7). The odds ratio (OR) and 95% confidence interval (CI) for predictors of the 6-week response were reported. Fisher's exact test was used for the comparison of categorical variables. This study was approved by the institutional review board of Duke University.
Data regarding underlying conditions, fungal species, first-line antifungal drugs, MICs, surgical procedures, and outcomes of all 39 cases are listed in Table S1 in the supplemental material. Twenty-two patients (56%) had hematological malignancies, 13 patients (33%) were solid-organ transplant recipients, and 3 patients (8%) had diabetes mellitus as the only risk factor for mucormycosis (Table 1). The remaining patient underwent allogeneic bone marrow transplantation for pansclerotic morphea. Mucorales and Fusarium spp. accounted for 49% and 31% of cases, respectively. Scedosporium apiospermum, Scedosporium prolificans, Purpureocillium lilacinum (formerly Paecilomyces lilacinus), Paecilomyces variotii, and Scopulariopsis spp. were isolated in the remaining cases. Mortality at week 4 was 46%, and response to therapy, defined as a complete or partial recovery at week 6 according to EORTC-MSG definitions (8), was 31%. Multiple antifungal drugs were administered during the course of infection, and the analysis was restricted to the drugs used as first-line treatment (i.e., first antifungal drug administered as empirical or targeted therapy and maintained for at least 72 h). Overall, lower MIC values of the first-line antifungal drugs were associated with better success rates, with 86% response at week 6 for an MIC of ≤0.5 μg/ml, 25% for an MIC of 1 to 4 μg/ml, 20% for an MIC of >4 μg/ml, and 0% in the absence of antifungal therapy. In univariate analysis, having received a first-line antifungal drug for which the MIC was ≤0.5 μg/ml was the strongest predictor of therapeutic response (OR, 26.0; 95% CI, 2.62 to 258.20; P = 0.005), followed by infection limited to a single site (OR, 7.27; 95% CI, 1.33 to 39.9; P = 0.02) and having received surgical intervention (OR, 6.0; 95% CI, 1.30 to 27.77; P = 0.02); while underlying disease, neutropenia, and type of fungal pathogen did not have a significant impact on therapeutic responses (Table 2).
TABLE 1
TABLE 1 Characteristics of patients and non-Aspergillus invasive mold infections
CharacteristicNo. (%) of patients
Patients (n = 39) 
    Male24 (62)
    Age (median yr [range])59 (5–76)
    Underlying condition 
        Hematologic malignancy22 (56)
        Allogeneic hematopoietic stem cell transplantation12 (31)
        Solid-organ transplantation13 (33)
        Immunosuppressive therapy23 (59)
        Neutropenia16 (41)
        Diabetes mellitus19 (49)
Infection 
    Proven/probable32 (82)/7 (18)
    Fungal pathogen 
        Mucoralesa19 (49)
        Fusarium spp.12 (31)
        Otherb8 (20)
    Primary site of infection 
        Lung23 (59)
        Skin/Soft tissue9 (23)
        Sinus6 (15)
        Intra-abdominal1 (3)
        Multiple sites21 (54)
    First-line antifungal therapy 
        Amphotericin B10 (26)
        Voriconazole17 (44)
        Posaconazole1 (3)
        Micafungin8 (21)
        No therapy3 (8)
    Outcome 
        Response to therapy (week 6)12 (31)
        Mortality (week 4)18 (46)
a
Rhizopus spp. (n = 10), Cunninghamella spp. (n = 4), Mucor spp. (n = 3), Lichtheimia spp. (n = 2).
b
Scedosporium apiospermum (n = 3), Scedosporium prolificans (n = 1), Purpureocillium lilacinum (n = 2), Paecilomyces variotii (n = 1), Scopulariopsis spp. (n = 1).
TABLE 2
TABLE 2 Predictors of response to therapy at week 6
PredictorOR (95% CI)bP value
Underlying condition  
    Neutropenia0.36 (0.08–1.62)0.18
    Hematologic malignancy0.69 (0.18–2.70)0.6
    Solid-organ transplantation1.70 (0.41–6.98)0.5
Type of infection  
    Mucormycosis2.91 (0.70–12.09)0.2
    Fusariosis0. 34 (0.06–1.87)0.14
    Localized infectiona7.27 (1.33–39.9)0.02
Management  
    Surgery6 (1.30–27.77)0.02
    First-line antifungal drug with MIC of ≤0.5 μg/ml26 (2.62–258.20)0.005
a
Invasive fungal infection limited to a single organ.
b
OR, odds ratio; 95% CI, 95% confidence interval.
We performed subanalyses for individual drugs and pathogens. Amphotericin B was the first-line treatment in 10 cases (8/10 mucormycosis) and was associated with a significantly better 6-week response when the pathogen MIC was ≤0.5 μg/ml versus >0.5 μg/ml (83% versus 0%; P = 0.05) (Table 3). For patients with mucormycosis, there was a trend toward higher response rates for those having received amphotericin B versus another drug as initial therapy (63% versus 18% response at week 6; P = 0.07). Voriconazole was the first-line treatment of fusariosis in 67% of cases despite consistently high MICs (≥16 μg/ml) and was associated with failure in all cases but one (87.5%).
TABLE 3
TABLE 3 Response to amphotericin B therapy at week 6 for various MIC cutoffs
MIC cutoff (μg/ml)Response rate (no. [%]) (n = 10a)P value
MIC ≤ cutoffMIC > cutoff
0.252/2 (100)3/8 (38)0.40
0.55/6 (83)0/4 (0)0.05
15/7 (71)0/3 (0)0.17
25/7 (71)0/3 (0)0.17
45/8 (63)0/2 (0)0.44
a
Rhizopus spp. (n = 6), Mucor spp. (n = 1), Cunninghamella spp. (n = 1), Scedosporium apiospermum (n = 1), Purpureocillium lilacinum (n = 1).
Our data show that NAIMIs are still associated with unacceptably high mortality rates. Unexpectedly, we found the MIC value of the first-line antifungal drug to be the most important factor in predicting response to therapy, an association that was not demonstrated previously (912). It should be emphasized that prior studies assessing predictors of NAIMI focused on overall mortality as an outcome, whereas we specifically assessed response to therapy based on clinical and radiological signs according to EORTC-MSG definitions (8).
The limited data set does not allow for the determination of clinical breakpoints for individual mold-antifungal drug combinations, but our findings suggests that a cutoff of 0.5 μg/ml for amphotericin B among non-Aspergillus molds (especially Mucorales) is associated with better outcomes. Amphotericin B MIC values of Mucorales may vary widely (0.125 to 4 μg/ml in this study), and there appears to be a role for antifungal susceptibility testing to guide antifungal therapy in this setting. While all patients in our series received standard amphotericin B dosing of 3 to 5 mg/kg, higher doses (i.e., 10 mg/kg), as suggested by some experts and despite potentially more adverse events (13, 14), may be appropriate for cases involving Mucorales with higher MICs, as these infections were associated with poor outcomes using standard dosing.
The role of antifungal susceptibility testing for Fusarium spp. and other rare mold species (e.g., Scedosporium spp., Paecilomyces spp., and Scopulariopsis spp.) remains unclear. Most experts have highlighted the lack of correlation between MICs and outcomes for Fusarium spp. and recommended voriconazole as first-line therapy regardless of the MIC values (10, 15, 16). However, in our series, most cases of fusariosis were treated with voriconazole, for which MICs were consistently very high (≥16 μg/ml), and outcomes were very poor. None of the patients with fusariosis received initial therapy with amphotericin B, the only drug displaying relevant in vitro activity against these Fusarium isolates (MICs, 1 to 4 μg/ml).
Neither CLSI nor the European Committee on Antimicrobial Susceptibility Testing (EUCAST) has defined clinical breakpoints for non-Aspergillus molds because of the lack of data correlating MIC values and outcomes. As NAIMIs are relatively rare diseases often with a lack of microbiological documentation, it will be difficult to obtain a sufficiently large data set to address this question in the future. Moreover, multiple confounding factors, such as the degree of immunosuppression or the type and severity of infection, may affect the response to therapy. Although our data have several limitations (retrospective design, limited number of cases), this series of 39 microbiologically documented NAIMI episodes (of which 82% were proven) highlights the crucial role of appropriate initial antifungal therapy in this severe disease. Moreover, it suggests a correlation between lower MICs, particularly for amphotericin B, and better response to therapy and a role for antifungal susceptibility testing of non-Aspergillus molds.

ACKNOWLEDGMENTS

These results were presented at the 7th Trends in Medical Mycology, Lisbon, Portugal, 9 to 12 October 2015, poster 322.
This research received no specific grant from any funding agency.

Supplemental Material

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REFERENCES

1.
Richardson M, Lass-Florl C. 2008. Changing epidemiology of systemic fungal infections. Clin Microbiol Infect 14(Suppl 4):S5–S24.
2.
Doligalski CT, Benedict K, Cleveland AA, Park B, Derado G, Pappas PG, Baddley JW, Zaas DW, Harris MT, Alexander BD. 2014. Epidemiology of invasive mold infections in lung transplant recipients. Am J Transplant 14:1328–1333.
3.
Iwen PC, Schutte SD, Florescu DF, Noel-Hurst RK, Sigler L. 2012. Invasive Scopulariopsis brevicaulis infection in an immunocompromised patient and review of prior cases caused by Scopulariopsis and Microascus species. Med Mycol 50:561–569.
4.
Kontoyiannis DP, Marr KA, Park BJ, Alexander BD, Anaissie EJ, Walsh TJ, Ito J, Andes DR, Baddley JW, Brown JM, Brumble LM, Freifeld AG, Hadley S, Herwaldt LA, Kauffman CA, Knapp K, Lyon GM, Morrison VA, Papanicolaou G, Patterson TF, Perl TM, Schuster MG, Walker R, Wannemuehler KA, Wingard JR, Chiller TM, Pappas PG. 2010. Prospective surveillance for invasive fungal infections in hematopoietic stem cell transplant recipients, 2001-2006: overview of the Transplant-Associated Infection Surveillance Network (TRANSNET) database. Clin Infect Dis 50:1091–1100.
5.
Pastor FJ, Guarro J. 2006. Clinical manifestations, treatment and outcome of Paecilomyces lilacinus infections. Clin Microbiol Infect 12:948–960.
6.
De Pauw B, Walsh TJ, Donnelly JP, Stevens DA, Edwards JE, Calandra T, Pappas PG, Maertens J, Lortholary O, Kauffman CA, Denning DW, Patterson TF, Maschmeyer G, Bille J, Dismukes WE, Herbrecht R, Hope WW, Kibbler CC, Kullberg BJ, Marr KA, Munoz P, Odds FC, Perfect JR, Restrepo A, Ruhnke M, Segal BH, Sobel JD, Sorrell TC, Viscoli C, Wingard JR, Zaoutis T, Bennett JE. 2008. Revised definitions of invasive fungal disease from the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) consensus group. Clin Infect Dis 46:1813–1821.
7.
Clinical and Laboratory Standards Institute (CLSI). 2008. Reference method for broth dilution antifungal susceptibility testing of filamentous fungi—2nd ed. CLSI M38-A2. Clinical and Laboratory Standards Institute, Wayne, PA.
8.
Segal BH, Herbrecht R, Stevens DA, Ostrosky-Zeichner L, Sobel J, Viscoli C, Walsh TJ, Maertens J, Patterson TF, Perfect JR, Dupont B, Wingard JR, Calandra T, Kauffman CA, Graybill JR, Baden LR, Pappas PG, Bennett JE, Kontoyiannis DP, Cordonnier C, Viviani MA, Bille J, Almyroudis NG, Wheat LJ, Graninger W, Bow EJ, Holland SM, Kullberg BJ, Dismukes WE, De Pauw BE. 2008. Defining responses to therapy and study outcomes in clinical trials of invasive fungal diseases: Mycoses Study Group and European Organization for Research and Treatment of Cancer consensus criteria. Clin Infect Dis 47:674–683.
9.
Lanternier F, Dannaoui E, Morizot G, Elie C, Garcia-Hermoso D, Huerre M, Bitar D, Dromer F, Lortholary O. 2012. A global analysis of mucormycosis in France: the RetroZygo study (2005-2007). Clin Infect Dis 54(Suppl 1):S35–S43.
10.
Nucci M, Marr KA, Vehreschild MJ, de Souza CA, Velasco E, Cappellano P, Carlesse F, Queiroz-Telles F, Sheppard DC, Kindo A, Cesaro S, Hamerschlak N, Solza C, Heinz WJ, Schaller M, Atalla A, Arikan-Akdagli S, Bertz H, Galvao Castro C, Jr, Herbrecht R, Hoenigl M, Harter G, Hermansen NE, Josting A, Pagano L, Salles MJ, Mossad SB, Ogunc D, Pasqualotto AC, Araujo V, Troke PF, Lortholary O, Cornely OA, Anaissie E. 2014. Improvement in the outcome of invasive fusariosis in the last decade. Clin Microbiol Infect 20:580–585.
11.
Slavin M, van Hal S, Sorrell TC, Lee A, Marriott DJ, Daveson K, Kennedy K, Hajkowicz K, Halliday C, Athan E, Bak N, Cheong E, Heath CH, Orla Morrissey C, Kidd S, Beresford R, Blyth C, Korman TM, Owen Robinson J, Meyer W, Chen SC, Australia and New Zealand Mycoses Interest Group. 2015. Invasive infections due to filamentous fungi other than Aspergillus: epidemiology and determinants of mortality. Clin Microbiol Infect 21:490.e1-490.e10.
12.
Spellberg B, Kontoyiannis DP, Fredricks D, Morris MI, Perfect JR, Chin-Hong PV, Ibrahim AS, Brass EP. 2012. Risk factors for mortality in patients with mucormycosis. Med Mycol 50:611–618.
13.
Cornely OA, Arikan-Akdagli S, Dannaoui E, Groll AH, Lagrou K, Chakrabarti A, Lanternier F, Pagano L, Skiada A, Akova M, Arendrup MC, Boekhout T, Chowdhary A, Cuenca-Estrella M, Freiberger T, Guinea J, Guarro J, de Hoog S, Hope W, Johnson E, Kathuria S, Lackner M, Lass-Florl C, Lortholary O, Meis JF, Meletiadis J, Munoz P, Richardson M, Roilides E, Tortorano AM, Ullmann AJ, van Diepeningen A, Verweij P, Petrikkos G. 2014. ESCMID and ECMM joint clinical guidelines for the diagnosis and management of mucormycosis 2013. Clin Microbiol Infect 20(Suppl 3):S5–S26.
14.
Tacke D, Koehler P, Markiefka B, Cornely OA. 2014. Our 2014 approach to mucormycosis. Mycoses 57:519–524.
15.
Lortholary O, Obenga G, Biswas P, Caillot D, Chachaty E, Bienvenu AL, Cornet M, Greene J, Herbrecht R, Lacroix C, Grenouillet F, Raad I, Sitbon K, Troke P. 2010. International retrospective analysis of 73 cases of invasive fusariosis treated with voriconazole. Antimicrob Agents Chemother 54:4446–4450.
16.
Tortorano AM, Richardson M, Roilides E, van Diepeningen A, Caira M, Munoz P, Johnson E, Meletiadis J, Pana ZD, Lackner M, Verweij P, Freiberger T, Cornely OA, Arikan-Akdagli S, Dannaoui E, Groll AH, Lagrou K, Chakrabarti A, Lanternier F, Pagano L, Skiada A, Akova M, Arendrup MC, Boekhout T, Chowdhary A, Cuenca-Estrella M, Guinea J, Guarro J, de Hoog S, Hope W, Kathuria S, Lortholary O, Meis JF, Ullmann AJ, Petrikkos G, Lass-Florl C. 2014. ESCMID and ECMM joint guidelines on diagnosis and management of hyalohyphomycosis: Fusarium spp., Scedosporium spp. and others. Clin Microbiol Infect 20(Suppl 3):S27–S46.

Information & Contributors

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Published In

cover image Journal of Clinical Microbiology
Journal of Clinical Microbiology
Volume 54Number 6June 2016
Pages: 1638 - 1640
Editor: A. J. McAdam
PubMed: 27008871

History

Received: 11 February 2016
Returned for modification: 26 February 2016
Accepted: 15 March 2016
Published online: 23 May 2016

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Authors

Frédéric Lamoth
Division of Infectious Diseases and International Health, Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
Clinical Microbiology Laboratory, Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
Infectious Diseases Service, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland
Institute of Microbiology, Lausanne University Hospital, Lausanne, Switzerland
Lauro Damonti
Infectious Diseases Service, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland
Barbara D. Alexander
Division of Infectious Diseases and International Health, Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
Clinical Microbiology Laboratory, Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA

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A. J. McAdam
Editor

Notes

Address correspondence to Frédéric Lamoth, [email protected].

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