Risk factors and clinical outcomes of breakthrough yeast bloodstream infections in patients with hematological malignancies in the era of newer antifungal agents

A review of the epidemiology of invasive fungal infections in Asian patients with hematological malignancies (2011-2021)

The incidence of invasive fungal infection (IFI) is increasing, especially among patients diagnosed with hematological malignancies due to their immunocompromised nature. Other risk factors include advanced age, exposure to immunosuppressants, neutropenia, and catheter use. Some of the most common IFI organisms reported are Candida and Aspergillus species, and other fungal species, including Scedosporium, Trichosporon, Cryptococcus, and Fusarium have also increasingly been reported in the past years. However, the epidemiologic data on IFI among patients with hematological malignancies in Asian countries are lacking. Therefore, we investigated published epidemiologic data on such cases from the past 10 years (2011-2021) and discuss the challenges faced in the diagnosis and management of IFIs in Asia.

Epidemiology of Invasive Candidiasis

Invasive candidiasis (IC) is an increasingly prevalent, costly, and potentially fatal infection brought on by the opportunistic yeast, Candida. Previously, IC has predominantly been caused by C. albicans which is often drug susceptible. There has been a global trend towards decreasing rates of infection secondary to C. albicans and a rise in non-albicans species with a corresponding increase in drug resistance creating treatment challenges. With advances in management of malignancies, there has also been an increase in the population at risk from IC along with a corresponding increase in incidence of breakthrough IC infections. Additionally, the emergence of C. auris creates many challenges in management and prevention due to drug resistance and the organism's ability to transmit rapidly in the healthcare setting. While the development of novel antifungals is encouraging for future management, understanding the changing epidemiology of IC is a vital step in future management and prevention.

Comparison of amphotericin B lipid complex, deoxycholate amphotericin B, fluconazole, and anidulafungin activity against Candida albicans biofilm isolated from breakthrough candidemia

INTRODUCTION

Biofilm formation causes virulence and resistance in Candida albicans. However, little is known about breakthrough candidemia isolates. We evaluated the antifungal activity of fluconazole, anidulafungin, deoxycholate amphotericin B (dAMB), and amphotericin B lipid complex (ABLC) against biofilms of C. albicans isolated from patients with breakthrough candidemia.

METHODS

The present study used strains of C. albicans isolated from breakthrough and non-breakthrough candidemia patients (control group). The susceptibility of planktonic cells to amphotericin B, anidulafungin, and fluconazole was determined by broth microdilution. Antifungal activity in sessile cells was evaluated using the minimum biofilm eradication concentration (MBEC), metabolic activity was estimated by reducing MTT, and biomass was estimated using crystal violet retention.

RESULTS

The planktonic strains were susceptible to amphotericin B, anidulafungin, and fluconazole, with minimum inhibitory concentrations of 1, ≤0.03, and 2mg/L, respectively. However, fluconazole and anidulafungin did not exert an antifungal effect on biofilms. Additionally, dAMB and ABCL reduced the metabolic activity and biomass. However, eradication was only achieved using 16mg/L dAMB. C. albicans isolates of breakthrough candidemia exhibited strong biofilm production, and the in vitro activity of available therapeutic options was poor.

CONCLUSION

In the present study, only dAMB and ABCL exhibited antibiofilm effects against sessile breakthrough candidemia isolates.

Molecular diagnosis, phylogenetic analysis, and antifungal susceptibility profiles of Candida species isolated from neutropenic oncological patients

BACKGROUND

Neutropenia is the most important cause of life-threatening invasive fungal infections (IFIs). Here, we studied the frequency and antifungal susceptibility profiles of Candida species that colonized or caused infections among neutropenic patients with solid or hematological malignancies.

METHODS

A total of 362 clinical samples were collected from 138 patients. After initial isolation using a mix of mycological methods, isolates were screened using chromogenic culture media. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was applied for molecular identification. Positive or suspected cases were confirmed using the reference method of sequencing. Antifungal susceptibility testing for voriconazole and caspofungin was carried out using the microbroth dilution method. An in-silico assay was applied for phylogenetic analysis.

RESULTS

Thirty-four Candida strains were isolated. C. albicans (47.06%) and C. glabrata (29.41%) were the most frequent strains. Antifungal treatment reduced the chance of Candida colonization by almost 76% in neutropenic patients (OR: 1.759; 95% CI: 1.349 to 2.390; p value: 0.000). An unusual and non-resistant strain, C. lambica, was reported from the bloodstream of a 56-year-old man with hematologic malignancy (HM). Eight isolates were non-susceptible, and one isolate was resistant to voriconazole. Also, four isolates were non-susceptible to caspofungin.

CONCLUSION

We can conclude that there is a cause-and-effect relationship between neutropenia, HM background, and Candida species separated from neutropenic patients, which can lead to possible infections. Further and repetitive studies are recommended using different molecular methods for better prediction and management of fungal infections in neutropenic patients.

Application of metagenomic next-generation sequencing in the diagnosis of pulmonary invasive fungal disease

Background

Metagenomic next-generation sequencing (mNGS) is increasingly being used to detect pathogens directly from clinical specimens. However, the optimal application of mNGS and subsequent result interpretation can be challenging. In addition, studies reporting the use of mNGS for the diagnosis of invasive fungal infections (IFIs) are rare.

Objective

We critically evaluated the performance of mNGS in the diagnosis of pulmonary IFIs, by conducting a multicenter retrospective analysis. The methodological strengths of mNGS were recognized, and diagnostic cutoffs were determined.

Methods

A total of 310 patients with suspected pulmonary IFIs were included in this study. Conventional microbiological tests (CMTs) and mNGS were performed in parallel on the same set of samples. Receiver operating characteristic (ROC) curves were used to evaluate the performance of the logarithm of reads per kilobase per million mapped reads [lg(RPKM)], and read counts were used to predict true-positive pathogens.

Result

The majority of the selected patients (86.5%) were immunocompromised. Twenty species of fungi were detected by mNGS, which was more than was achieved with standard culture methods. Peripheral blood lymphocyte and monocyte counts, as well as serum albumin levels, were significantly negatively correlated with fungal infection. In contrast, C-reactive protein and procalcitonin levels showed a significant positive correlation with fungal infection. ROC curves showed that mNGS [and especially lg(RPKM)] was superior to CMTs in its diagnostic performance. The area under the ROC curve value obtained for lg(RPKM) in the bronchoalveolar lavage fluid of patients with suspected pulmonary IFIs, used to predict true-positive pathogens, was 0.967, and the cutoff value calculated from the Youden index was −5.44.

Conclusions

In this study, we have evaluated the performance of mNGS-specific indicators that can identify pathogens in patients with IFIs more accurately and rapidly than CMTs, which will have important clinical implications.

Systematic Characterization of Epidemiology, Antifungal Susceptibility, Risk Factors and Outcomes of Candidaemia: A Six-Year Chinese Study

Background

Candida bloodstream infection (BSI), the fourth most common nosocomial BSI, is an urgent global health challenge with the tremendous growth in antifungal resistance rate and mortality rate.

Purpose

To establish the epidemiology, species distribution, risk factors, and 30-day mortality of candidaemia among 115 patients in this 6-year surveillance study.

Materials and Methods

We retrospectively analyzed the clinical characteristics, epidemiology, antifungal susceptibility patterns, and risk factors for morbidity and mortality of 115 candidaemia cases diagnosed in one tertiary care hospital from January 2016 through December 2021.

Results

Of the 115 candidaemia cases, the most prevalent species were Candida tropicalis (33.0%), followed by Candida albicans (27.8%), Candida parapsilosis complex (19.1%), and others. The overall incidence was 0.21 cases/1000 admissions. The overall crude resistance rate of Candida spp. against azoles was 20.0% (23/115), while Candida tropicalis showed a significant increase in the resistance rate to azoles (from 1/6, 16.7% in 2017 to 6/10, 60.0% in 2021). Multivariate analyses demonstrated that hematological malignancy and neutropenia were significantly associated with Candida tropicalis BSI than Candida non-tropicalis BSI. Candida albicans BSI had a significantly higher rate of previous surgery than Candida non-albicans BSI. Candida parapsilosis BSI had a significantly higher rate of receiving total parenteral nutrition (TPN). The overall 30-day mortality rate was 27.0% (31/115). The presence of high age-adjusted Charlson comorbidity index (aCCI), neutropenia, and septic shock were factors independently associated with increased 30-day mortality.

Conclusion

Candida tropicalis are emerging as the predominant isolate in candidaemia. Of note, the unexpectedly increased resistance rate to azoles in Candida tropicalis BSI was observed. The aCCI scores, neutropenia, and septic shock were independently associated with 30-day mortality. Prompt, adequate antifungal treatment among high-risk patients may lead to a reduction in mortality.

Advances in prophylaxis and treatment of invasive fungal infections: perspectives on hematologic diseases

Invasive fungal infections (IFIs) are common causes of mortality and morbidity in patients with hematologic diseases. Delayed initiation of antifungal treatment is related to mortality. Aspergillus sp. is the leading cause of IFI followed by Candida sp. Diagnosis is often challenging owing to variable conditions related to underlying diseases. Clinical suspect and prompt management is important. Imaging, biopsy, and non-culture-based tests must be considered together. New diagnostic procedures have been improved, including antigen-based assays and molecular detection of fungal DNA. Among hematologic diseases, patients with acute myeloid leukemia, myelodysplastic syndrome, recipients of hematopoietic stem cell transplantation are at high risk for IFIs. Antifungal prophylaxis is recommended for these high-risk patients. There are continuous attempts to achieve ideal management of IFIs. Scoring system for quality control has been developed with important recommendations of current guidelines. Higher adherence to guidelines is related to decreased mortality in IFIs.

Invasive aspergillosis in relapsed/refractory acute myeloid leukaemia patients: Results from SEIFEM 2016-B survey

BACKGROUND

In patients with relapsed/refractory acute myeloid leukaemia (R/R AML) who received salvage chemotherapy, limited and not updated studies explored the incidence of invasive aspergillosis (IA) and the role of antifungal prophylaxis (AP). The aims of this multicentre retrospective 'SEIFEM 2016-B' study were as follows: (1) to evaluate the current rate and the outcome of proven/probable IA and (2) to assess the efficacy of AP, in a large 'real life' series of patient with R/R AML submitted to salvage chemotherapy.

RESULTS

Of 2250 R/R AML patients, a total of 74 cases of IA (5.1%) were recorded as follows: 10 (0.7%) proven and 64 (4.3%) probable. Information about AP were available in 73/74 (99%) patients. Fifty-eight (79%) breakthrough infections occurred, mainly during AP with posaconazole [25 (43%)]. The patients who received AP during salvage chemotherapy showed a benefit from antifungal therapy (AT) than patients who did not received AP [43 (86%) vs 7 (14%); p < .033]. In a multivariate analysis, AP and absence of severe mucositis had a significant favourable effect on overall response rate.

CONCLUSION

Our data demonstrated that the incidence of IA during the salvage chemotherapy is similar to the past. Nevertheless, the attributable mortality rate (AMR) appears to be lower than that previously reported in R/R AML. Further prospective studies should be performed to confirm our preliminary observation and understand and the why a decreased AMR is reported in this setting of high-risk patients.

Invasive Fungal Disease in Patients with Newly Diagnosed Acute Myeloid Leukemia

This single-center retrospective study of invasive fungal disease (IFD) enrolled 251 adult patients undergoing induction chemotherapy for newly diagnosed acute myeloid leukemia (AML) from 2014–2019. Patients had primary AML (n = 148, 59%); antecedent myelodysplastic syndrome (n = 76, 30%), or secondary AML (n = 27, 11%). Seventy-five patients (30%) received an allogeneic hematopoietic cell transplant within the first year after induction chemotherapy. Proven/probable IFD occurred in 17 patients (7%). Twelve of the 17 (71%) were mold infections, including aspergillosis (n = 6), fusariosis (n = 3), and mucomycosis (n = 3). Eight breakthrough IFD (B-IFD), seven of which were due to molds, occurred in patients taking antifungal prophylaxis. Patients with proven/probable IFD had a significantly greater number of cumulative neutropenic days than those without an IFD, HR = 1.038 (95% CI 1.018–1.059), p = 0.0001. By cause-specific proportional hazards regression, the risk for IFD increased by 3.8% for each day of neutropenia per 100 days of follow up. Relapsed/refractory AML significantly increased the risk for IFD, HR = 7.562 (2.585–22.123), p = 0.0002, and Kaplan-Meier analysis showed significantly higher mortality at 1 year in patients who developed a proven/probable IFD, p = 0.02. IFD remains an important problem among patients with AML despite the use of antifungal prophylaxis, and development of IFD is associated with increased mortality in these patients.

Clinical Characteristics and Outcomes of Breakthrough Candidemia in 71 Hematologic Malignancy Patients and/or Allogeneic Hematopoietic Stem Cell Transplant Recipients: A Single-center Retrospective Study From China, 2011-2018

BACKGROUND

Antifungal prophylaxis may result in breakthrough infections in hematology patients with severe agranulocytosis, with few studies assessing risk factors and clinical outcomes of breakthrough candidemia. We described the distribution of Candida species, assessed risk factors for mortality in such patients, and determined differences in the incidence and mortality of breakthrough candidemia between patients who did or did not receive an allogeneic hematopoietic stem cell transplant.

METHODS

We collected clinical and microbiological data of patients with hematologic malignancies and breakthrough candidemia from a single center. Seven-day and 30-day follow-up outcomes were recorded; the incidence and mortality of breakthrough candidemia between patients who did or did not undergo an allogeneic transplant were compared. Kaplan-Meier survival estimates were used to generate survival curves, and predictors were identified using Cox regression analyses.

RESULTS

Of 71 enrolled patients, 17 received allogeneic transplants. Incidences of breakthrough candidemia were 17 of 2924 (0.58%) and 54 of 12 015 (0.45%) in the transplant and nontransplant groups, respectively (P = .35). The most common isolate was Candida tropicalis, and antifungal agent combinations were the most common first-line treatment. Cumulative mortality rates of patients were 21.1% and 31.0% at days 7 and 30, respectively, and they significantly differed between both groups. Septic shock, central venous catheter removal, and granulocyte recovery were significantly associated with 7-day mortality; the latter 2 remained independent predictors of 30-day mortality.

CONCLUSIONS

Breakthrough candidemia-related mortality was higher in the allogeneic transplant group, although the incidence was not significantly different between the groups. Prompt and adequate antifungal treatment with catheter removal may reduce mortality.

Interaction Between Dendritic Cells and Candida krusei β-Glucan Partially Depends on Dectin-1 and It Promotes High IL-10 Production by T Cells

Host-Candida interaction has been broadly studied during Candida albicans infection, with a progressive shift in focus toward non-albicans Candida species. C. krusei is an emerging multidrug resistant pathogen causing rising morbidity and mortality worldwide. Therefore, understanding the interplay between the host immune system and C. krusei is critically important. Candia cell wall β-glucans play significant roles in the induction of host protective immune responses. However, it remains unclear how C. krusei β-glucan impacts dendritic cell (DC) responses. In this study, we investigated DC maturation and function in response to β-glucans isolated from the cell walls of C. albicans, C. tropicalis, and C. krusei. These three distinct Candida β-glucans had differential effects on expression of the DC marker, CD11c, and on DC maturation. Furthermore, bone-marrow derived DCs (BMDCs) showed enhanced cytokine responses characterized by substantial interleukin (IL)-10 production following C. krusei β-glucan stimulation. BMDCs stimulated with C. krusei β-glucan augmented IL-10 production by T cells in tandem with increased IL-10 production by BMDCs. Inhibition of dectin-1 ligation demonstrated that the interactions between dectin-1 on DCs and cell wall β-glucans varied depending on the Candida species. The effects of C. krusei β-glucan were partially dependent on dectin-1, and this dependence, in part, led to distinct DC responses. Our study provides new insights into immune regulation by C. krusei cell wall components. These data may be of use in the development of new clinical approaches for treatment of patients with C. krusei infection.

Breakthrough invasive fungal infections: Who is at risk?

The epidemiology of invasive fungal infections (IFIs) in immunocompromised individuals has changed over the last few decades, partially due to the increased use of antifungal agents to prevent IFIs. Although this strategy has resulted in an overall reduction in IFIs, a subset of patients develop breakthrough IFIs with substantial morbidity and mortality in this population. Here, we review the most significant risk factors for breakthrough IFIs in haematology patients, solid organ transplant recipients, and patients in the intensive care unit, focusing particularly on host factors, and highlight areas that require future investigation.

Clinical characteristics and implications of mixed candida/bacterial bloodstream infections in patients with hematological diseases

The incidence of mixed candida/bacterial blood infections (BSIs) has been reported to account for 20% of all cases of candidaemia. However, its clinical characteristics and implications in patients with hematological diseases are not clear. We conducted a retrospective case-control study of hematological patients complicated with candidaemia over the past 5-year period to identify the risk factors and clinical implications of mixed candidia/bacterial BSIs (case group) vs. monobacterial candidiasis (control group). Of all 65 enrolled patients with candidaemia, 20 cases (30.8%) met the diagnostic criteria for mixed candida/bacterial BSIs. Candida tropicalis was the most common candida species in all patients. Klebsiella pneumoniae was the most detected bacteria (35%) in case group. Previous hospital stay ≥ 28 days, organic damage during candidaemia, and positive procalcitonin (PCT) test were the risk factors of mixed candida/bacterial BSIs. Cumulative mortality of all patients enrolled was 26.2% at day 30, with significant differences between case and control group. In multivariate analysis, organic damage and granulocyte recovery were the two predictive factors for 30-day mortality. Mixed candida/bacterial BSIs are fatal complications of infection which account for a considerable part of candidaemia; multicenter and large-scale clinical studies are required in the future.

Breakthrough Invasive Fungal Infections in Patients with Acute Myeloid Leukemia

OBJECTIVES

We sought to determine the occurrence, risk factors, effect of antifungal prophylaxis, and outcomes of invasive fungal infections (IFIs) in patients with acute myeloid leukemia (AML).

PATIENTS AND METHODS

We performed a retrospective analysis of all adult patients admitted to the University of Michigan Health System for AML over a 3-year period from 2010 to 2013. We determined comorbidities, hematopoietic cell transplant (HCT) status, antifungal prophylaxis, proven and probable IFI, and outcomes at 12 weeks after initiation of appropriate antifungal therapy.

RESULTS

Of 333 patients in our cohort, 116 of whom had received a HCT, 98 (29%) developed an IFI. Of the 30 (9%) patients who had a proven or probable IFI, 18 had breakthrough infection while on micafungin (n = 5), voriconazole (n = 4), posaconazole (n = 5), or fluconazole (n = 4). Breakthrough IFIs were due to Aspergillus species (n = 11), other molds (n = 4), and Candida species (n = 3). Factors associated with breakthrough IFI were prolonged severe neutropenia (p = .05) and having received tacrolimus (p = .04). Antifungal therapy was successful in 7 of the 18 (39%) patients with breakthrough IFI and 8 of the 12 (67%) patients with non-breakthrough IFI, p = .13. Mortality at 12 weeks was 27%, 5 with breakthrough IFI and 3 with non-breakthrough IFI and was associated with prolonged severe neutropenia, p = .04.

CONCLUSIONS

Patients with AML remain at risk for IFI despite the use of several different antifungal agents for prophylaxis. Mortality remains high in patients with AML who develop IFI.

Breakthrough bloodstream infections in critically ill non-neutropenic patients: higher incidence and better survival than non-breakthrough infections

Introduction. Breakthrough bloodstream infections (BSIs) are rare among non-neutropenic patients.Aim. Our goal was to determine the risk factors associated with development of breakthrough BSIs among critically ill non-neutropenic patients and its role in mortality.Methodology. During a 24-month period (August 2016 to July 2018), all BSIs among non-neutropenic patients hospitalized at the University General Hospital of Patras, Greece, were included. Antimicrobial resistance of isolates was interpreted according to EUCAST guidelines. BSIs were considered as breakthrough when blood cultures yielded a pathogen in a patient who, for at least the previous 72 h, had been receiving at least one antibiotic to which the isolated microorganism was susceptible.Results. Among 217 episodes of BSI, 118 (54.4 %) developed a breakthrough infection. Primary BSIs predominated (101; 46.5 %), followed by catheter-related BSIs (56; 25.8 %). Gram-negative bacteria represented the most common pathogens isolated (157; 72.4 %), followed by Gram-positive bacteria (36; 16.6 %) and fungi (36; 16.6 %). Factors independently associated with the development of breakthrough BSIs were immunosuppressive therapy, obesity (body mass index ≥30 kg m^{- 2}), infection by Gram-positive bacteria, noradrenaline dose during 24 h from BSI onset, prior use of colistin and antifungal treatment. Overall 14-day mortality was 23.0 % (50 patients). Multivariate analysis revealed noradrenaline dose during 24 h from BSI onset as an independent predictor of mortality, while appropriate empiric antimicrobial treatment and breakthrough BSI were identified as predictors of good prognosis.Conclusion. Breakthrough BSIs were common among critically ill non-neutropenic patients and these patients were associated with better survival because they were de facto receiving appropriate antibiotics.

β-1,3-Glucan/CR3/SYK pathway-dependent LC3B-II accumulation enhanced the fungicidal activity in human neutrophils

Since molecular genotyping has been established for the Candida species, studies have found that a single Candida strain (endemic strain) can persist over a long period of time and results in the spread of nosocomial invasive candidiasis without general characteristics of horizontal transmissions. Our previous study also found the existence of endemic strains in a cancer center in Tianjin, China. In the current study, we performed further investigation on endemic and non-endemic Candida albicans strains, with the aim of explaining the higher morbidity of endemic strains. In an in vivo experiment, mice infected with endemic strains showed significantly shorter survival time and higher kidney fungal burdens compared to mice infected with non-endemic strains. In an in vitro experiment, the killing percentage of neutrophils to endemic strains was significantly lower than that to non-endemic strains, which is positively linked to the ratio of LC3B-II/I in neutrophils. An immunofluorescence assay showed more β-1,3-glucan exposure on the cell walls of non-endemic strains compared to endemic strains. After blocking the β-glucan receptor (CR3) or inhibiting downstream kinase (SYK) in neutrophils, the killing percent to C. albicans (regardless of endemic and non-endemic strains) and the ratio of LC3B-II/I of neutrophils were significantly decreased. These data suggested that the killing capability of neutrophils to C. albicans was monitored by β-1,3-glucan via CR3/SYK pathway-dependent LC3B-II accumulation and provided an explanation for the variable killing capability of neutrophils to different strains of C. albicans, which would be beneficial in improving infection control and therapeutic strategies for invasive candidiasis.

Cell wall mannan of Candida krusei mediates dendritic cell apoptosis and orchestrates Th17 polarization via TLR-2/MyD88-dependent pathway

Dendritic cells (DCs) abundantly express diverse receptors to recognize mannans in the outer surface of Candida cell wall, and these interactions dictate the host immune responses that determine disease outcomes. C. krusei prevalence in candidiasis worldwide has increased since this pathogen has developed multidrug resistance. However, little is known how the immune system responds to C. krusei. Particularly, the molecular mechanisms of the interplay between C. krusei mannan and DCs remain to be elucidated. We investigated how C. krusei mannan affected DC responses in comparison to C. albicans, C. tropicalis and C. glabrata mannan. Our results showed that only C. krusei mannan induced massive cytokine responses in DCs, and led to apoptosis. Although C. krusei mannan-activated DCs underwent apoptosis, they were still capable of initiating Th17 response. C. krusei mannan-mediated DC apoptosis was obligated to the TLR2 and MyD88 pathway. These pathways also controlled Th1/Th17 switching possibly by virtue of the production of the polarizing cytokines IL-12 and IL-6 by the C. krusei mannan activated-DCs. Our study suggests that TLR2 and MyD88 pathway in DCs are dominant for C. krusei mannan recognition, which differs from the previous reports showing a crucial role of C-type lectin receptors in Candida mannan sensing.