Fungal infections in hematopoietic stem-cell transplant patients: a review of epidemiology, diagnosis, and management

The advent of bone marrow transplant has opened doors to a different approach and offered a new treatment modality for various hematopoietic stem-cell-related disorders. Since the first bone marrow transplant in 1957, there has been significant progress in managing patients who undergo bone marrow transplants. Plasma-cell disorders, lymphoproliferative disorders, and myelodysplastic syndrome are the most common indications for hematopoietic stem-cell transplant. Despite the advances, invasive fungal infections remain a significant cause of morbidity and mortality in this high-risk population. The overall incidence of invasive fungal infection in patients with hematopoietic stem-cell transplant is around 4%, but the mortality in patients with allogeneic stem-cell transplant is as high as 13% in one study. Type of stem-cell transplant, conditioning regimen, and development of graft-versus-host disease are some of the risk factors that impact the risk and outcomes in patients with invasive fungal infections. Aspergillus and candida remain the two most common organisms causing invasive fungal infections. Molecular diagnostic methods have replaced some traditional methods due to their simplicity of use and rapid turnaround time. Primary prophylaxis has undoubtedly shown to improve outcomes even though breakthrough infection rates remain high. The directed treatment has seen a significant shift from amphotericin B to itraconazole, voriconazole, and echinocandins, which have shown better efficacy and fewer adverse effects. In this comprehensive review, we aim to detail epidemiology, risk factors, diagnosis, and management, including prophylaxis, empiric and directed management of invasive fungal infections in patients with hematopoietic stem-cell transplant.

Antifungal use in the surgical ICU patient

PURPOSE OF REVIEW

The successful treatment of surgical fungal infections depends of a timely and adequate source control alongside with the use of prompt systemic antifungals. The main challenge of antifungal use in critically ill surgical patients is to find a balance between rational versus indiscriminate use in order to accomplish an antifungal stewardship program.

RECENT FINDINGS

Surgical fungal infections represent an important burden in the daily clinical activity in many ICUs. The efficacy of the available antifungal drugs has not been adequately assessed in randomized controlled trials with surgical fungal infections in ICU patients. Most clinical experience is limited to case reports or uncontrolled case series. Due to the lack of adequate scientific evidence to assess the role of the different antifungals in surgical ICU patients, it is usually suggested to follow the recommendations for invasive candidiasis and candidemia.

SUMMARY

Antifungal use in the surgical patients admitted to an ICU is a complex matter and there are several elements to consider like the presence of septic shock and multiorgan failure, local epidemiology and antifungal resistance, among others. The proper use of antifungals alongside early recognition and prompt source control, are critical factors for improved outcomes.

Fungicidal activity and PK/PD of caspofungin as tools to guide antifungal therapy in a fluconazole-resistant C. parapsilosis candidemia

Candida parapsilosis may be responsible for bloodstream infections (BSI) and it is characterised by an increased incidence of fluconazole resistance. A 75-year old woman with severe comorbidities received the insertion of a peripherally inserted central venous catheter. Fluconazole did not prevent a C. parapsilosis BSI hence caspofungin was started after a nephrotoxic first-line treatment with amphotericin B. The ratio of peak plasma concentration over the minimum inhibitory concentration (C_max/MIC) was adopted to maximise efficacy of caspofungin. MIC and plasma C_max values were obtained by broth microdilution and LC-MS, respectively. Interestingly, daily doses of 1 mg/kg (total daily dose, 50 mg) allowed the achievement of C_max/MIC values > 10. The optimised regimen was safe and effective, leading to negative blood culture at day 8. The patient was discharged home at day 21. Therefore, individualised dosing regimens of caspofungin may be effective and safe even in the case of C. parapsilosis BSI.

Azole-resistant Candida albicans prosthetic joint infection treated with prolonged administration of anidulafungin and two-stage exchange with implant of a mega-prosthesis

Fungal prosthetic joint infection (PJI) is a rare but severe complication of artroplasty. We report a case of PJI due to azole-resistant Candida albicans successfully treated with combination of prolonged administration of anidulafungin and two-stage joint exchange with insertion of a mega-prosthesis.

[Echinocandins: Applied pharmacology]

The echinocandins share pharmacodynamic properties, although there are some interesting differences in their pharmacokinetic behaviour in the clinical practice. They are not absorbed by the oral route. They have a somewhat special distribution in the organism, as some of them can reach high intracellular concentrations while, with some others, the concentration is reduced. They are highly bound to plasma proteins, thus it is recommended to administer a loading dose for anidulafungin and caspofungin, although this procedure is not yet clear with micafungin. Echinocandins are excreted via a non-microsomal metabolism, so the urinary concentration is very low. Some carrier proteins that take part in the biliary clearance process are probably involved in the interactions described with caspofungin and micafungin. These two drugs must be used with caution in patients with severely impaired hepatic function, while all of them can be used without special precautions when there is renal impairment or the patient requires renal replacement therapy.

Antifungal drug resistance in Candida species

Invasive Candida infections are well established infectious entities of immunocompromised or critically ill patients and are characterised by high morbidity and mortality. Owing to the common eukaryotic structure of fungi and humans, a limited number of antifungal drugs is available for therapeutic purposes. In this unsatisfactory scenario, the emergence of drug resistance represents an important health problem. Failure of antifungal treatment can be related to host factors, to the pharmacokinetic and pharmacodynamic parameters of the drug, or to morphological, reproductive modalities and biofilm production of the fungus itself. Innate or acquired antifungal resistance derives from the presence or onset of molecular mechanisms related to the toxic activity of the drug itself. The resulting resistance can thus be extended to different molecules of the same class according to a greater or lesser affinity of the molecules for the target. In addition, non-specific cellular mechanisms of extrusion of toxic substances, such as overexpression of efflux pumps, can play a role involving different antifungal classes. Here we briefly review the current antifungal susceptibility testing methods and their usefulness as predictors of antifungal resistance in Candida spp., focusing on assessment of the involved molecular mechanisms.

Pharmacokinetics of anidulafungin in two critically ill patients with septic shock undergoing CVVH

Candidemia is associated with high mortality rate especially in critically ill (ICU) patients with septic shock and echinocandins such as anidulafungin are recommended as first-line treatment. Available pharmacokinetic studies of anidulafungin in healthy volunteers and in patients with renal or hepatic impairment showed that no dose adjustment is needed even in patients receiving standard intermittent haemodialysis. However, few data are available with continuous veno-venous haemofiltration (CVVH). In this study, the pharmacokinetic of anidulafungin was studied in two ICU patients with candidemia and septic shock undergoing CVVH. Both patients had satisfactory parameters of C(max) (9.04 and 5.68 mg/l, respectively), area under the curve (AUC) (95.18 and 67.48 mg/l h) and C(min) (2.61 and 1.43 mg/l). AUC/MIC ratio and C(max)/MIC values were: 11887 and 8435; 1130.25 and 710, for patients 1 and 2, respectively. Our data confirm that in patients with septic shock anidulafungin presents only mild pharmacokinetic changes compared to data reported during CVVH alone.

Antifungal efficacy of some natural phenolic compounds against significant pathogenic and toxinogenic filamentous fungi

In terms of food safety, species of the Fusarium, Aspergillus and Penicillium genera are considered the most significant because they produce the great majority of known mycotoxins. Developing resistance against commonly used fungicides have become a critical problem in area such as agriculture, the storage and production of food and even in human medicines. The need for research and development of new alternative antifungal treatment based on natural antifungal substances is obvious. Here, the antifungal efficacy of 21 phenolic components of essential oils and plant substances were tested against these filamentous fungi with respect to their different molecular structures. Minimum inhibitory concentration values MIC₅₀ and MIC₁₀₀ were successfully estimated for 15 substances by means of probit analysis. Thymol and carvacrol were evaluated as the most effective. The MIC₅₀ values for thymol ranged from 30 to 52 μg mL(-1). The MIC₁₀₀ values for thymol ranged from 76 to 255 μg mL(-1), respectively. For carvacrol, the MIC₅₀ values ranged from 37 to 76 μg mL(-1), and the MIC100 ranged from 131 to 262 μg mL(-1). The results also revealed differences in the efficacy of phenols depending on molecular structures and different inter-species sensitivity.

Promising antifungal effect of some Euro-Asiatic plants against dangerous pathogenic and toxinogenic fungi

BACKGROUND

Increasing evidence of fungicide-resistant toxinogenic and pathogenic fungal species is obvious. Looking for new possibilities of antifungal treatment or sources of antifungal substances is a major problem. Some medicinal plants exert strong antifungal properties and could be conveniently used as a promising alternative source for presently problematic antifungal treatment in many areas with respect to their natural origin. Methanol extracts of 46 medicinal plants from the Eurasian area were used in a screening assay for antifungal activity in this study. The growth inhibitory effect was tested against six significant pathogenic and toxinogenic fungal species: Fusarium oxysporum, F. verticillioides, Penicillium expansum, P. brevicompactum, Aspergillus flavus and A. fumigatus.

RESULTS

For 14 plant species, the possibility of using them as natural fungicides was indicated. The extract from Grindelia camporum showed significant activity against all target fungal species. The most sensitive target fungus was the toxinogenic and human pathogenic species A. fumigatus.

CONCLUSION

This study has identified 14 extracts of medicinal plants with a potential use as an antifungal treatment in various areas. One of them showed promising efficiency against all selected significant pathogenic and toxinogenic fungal species.

Conclusions. Anidulafungin is a new echinocandin developed for more effective treatment of serious systemic fungal infections

Anidulafungin is a new echinocandin developed for more effective treatment of serious systemic fungal infections. Anidulafungin is a well tolerated echinocandin with a favorable pharmacokinetic profile; in particular, its lack of hepatic metabolism and renal excretion enables drug administration without dosage adjustment to subjects with any degree of impaired hepatic or renal function. This simplifies dosing, with a requirement for only once-daily administration and a lack of drug-drug interactions in patients who require multiple medications.