Comparison of the virulence of Scedosporium prolificans strains from different origins in a murine model

Diagnosis of pulmonary Scedosporium apiospermum infection from bronchoalveolar lavage fluid by metagenomic next-generation sequencing in an immunocompetent female patient with normal lung structure: a case report and literature review

BACKGROUND

Scedosporium apiospermum (S. apiospermum) belongs to the asexual form of Pseudallescheria boydii and is widely distributed in various environments. S. apiospermum is the most common cause of pulmonary infection; however, invasive diseases are usually limited to patients with immunodeficiency.

CASE PRESENTATION

A 54-year-old Chinese non-smoker female patient with normal lung structure and function was diagnosed with pulmonary S. apiospermum infection by metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid (BALF). The patient was admitted to the hospital after experiencing intermittent right chest pain for 8 months. Chest computed tomography revealed a thick-walled cavity in the upper lobe of the right lung with mild soft tissue enhancement. S. apiospermum was detected by the mNGS of BALF, and DNA sequencing reads were 426. Following treatment with voriconazole (300 mg q12h d1; 200 mg q12h d2-d20), there was no improvement in chest imaging, and a thoracoscopic right upper lobectomy was performed. Postoperative pathological results observed silver staining and PAS-positive oval spores in the alveolar septum, bronchiolar wall, and alveolar cavity, and fungal infection was considered. The patient's symptoms improved; the patient continued voriconazole for 2 months after surgery. No signs of radiological progression or recurrence were observed at the 10-month postoperative follow-up.

CONCLUSION

This case report indicates that S. apiospermum infection can occur in immunocompetent individuals and that the mNGS of BALF can assist in its diagnosis and treatment. Additionally, the combined therapy of antifungal drugs and surgery exhibits a potent effect on the disease.

Scedosporiosis/lomentosporiosis observational study (SOS): Clinical significance of Scedosporium species identification

Scedosporiosis/lomentosporiosis is a devastating emerging fungal infection. Our objective was to describe the clinical pattern and to analyze whether taxonomic grouping of the species involved was supported by differences in terms of clinical presentations or outcomes. We retrospectively studied cases of invasive scedosporiosis in France from 2005 through 2017 based on isolates characterized by polyphasic approach. We recorded 90 cases, mainly related to Scedosporium apiospermum (n = 48), S. boydii/S. ellipsoideum (n = 20), and Lomentospora prolificans (n = 14). One-third of infections were disseminated, with unexpectedly high rates of cerebral (41%) and cardiovascular (31%) involvement. In light of recent Scedosporium taxonomic revisions, we aimed to study the clinical significance of Scedosporium species identification and report for the first time contrasting clinical presentations between infections caused S. apiospermum, which were associated with malignancies and cutaneous involvement in disseminated infections, and infections caused by S. boydii, which were associated with solid organ transplantation, cerebral infections, fungemia, and early death. The clinical presentation of L. prolificans also differed from that of other species, involving more neutropenic patients, breakthrough infections, fungemia, and disseminated infections. Neutropenia, dissemination, and lack of antifungal prescription were all associated with 3-month mortality. Our data support the distinction between S. apiospermum and S. boydii and between L. prolificans and Scedosporium sp. Our results also underline the importance of the workup to assess dissemination, including cardiovascular system and brain.

Study of Humoral Responses against Lomentospora/Scedosporium spp. and Aspergillus fumigatus to Identify L. prolificans Antigens of Interest for Diagnosis and Treatment

The high mortality rates of Lomentospora prolificans infections are due, above all, to the tendency of the fungus to infect weakened hosts, late diagnosis and a lack of effective therapeutic treatments. To identify proteins of significance for diagnosis, therapy or prophylaxis, immunoproteomics-based studies are especially important. Consequently, in this study murine disseminated infections were carried out using L. prolificans, Scedosporium aurantiacum, Scedosporium boydii and Aspergillus fumigatus, and their sera used to identify the most immunoreactive proteins of L. prolificans total extract and secreted proteins. The results showed that L. prolificans was the most virulent species and its infections were characterized by a high fungal load in several organs, including the brain. The proteomics study showed a high cross-reactivity between Scedosporium/Lomentospora species, but not with A. fumigatus. Among the antigens identified were, proteasomal ubiquitin receptor, carboxypeptidase, Vps28, HAD-like hydrolase, GH16, cerato-platanin and a protein of unknown function that showed no or low homology with humans. Finally, Hsp70 deserves a special mention as it was the main antigen recognized by Scedosporium/Lomentospora species in both secretome and total extract. In conclusion, this study identifies antigens of L. prolificans that can be considered as potential candidates for use in diagnosis and as therapeutic targets and the production of vaccines.

Scedosporium and Lomentospora: an updated overview of underrated opportunists

Species of Scedosporium and Lomentospora are considered as emerging opportunists, affecting immunosuppressed and otherwise debilitated patients, although classically they are known from causing trauma-associated infections in healthy individuals. Clinical manifestations range from local infection to pulmonary colonization and severe invasive disease, in which mortality rates may be over 80%. These unacceptably high rates are due to the clinical status of patients, diagnostic difficulties, and to intrinsic antifungal resistance of these fungi. In consequence, several consortia have been founded to increase research efforts on these orphan fungi. The current review presents recent findings and summarizes the most relevant points, including the Scedosporium/Lomentospora taxonomy, environmental distribution, epidemiology, pathology, virulence factors, immunology, diagnostic methods, and therapeutic strategies.

Voriconazole MICs are predictive for the outcome of experimental disseminated scedosporiosis

Background

Scedosporiosis is associated with a mortality rate of up to 90% in patients suffering from disseminated infections. Recommended first-line treatment is voriconazole, but epidemiological cut-off values and clinical breakpoints have not been determined.

Objectives

To correlate voriconazole treatment response in mice suffering from disseminated scedosporiosis with MIC values determined using CLSI broth microdilution, Etest (bioMérieux) and disc diffusion.

Methods

Voriconazole MICs for 31 Scedosporium apiospermum strains were determined using CLSI broth microdilution, Etest and disc diffusion. Groups of mice were challenged intravenously with 1 out of 16 S. apiospermum strains (voriconazole CLSI broth microdilution MIC range: 0.125-8.0 mg/L) and treated with 40 mg/kg voriconazole orally by gavage once daily. Efficacy of voriconazole was evaluated by a statistically significant ( P  <   0.05) reduction in fungal burden in brain.

Results

A categorical agreement of 90.4% was reached for CLSI broth microdilution and disc diffusion and of 93.6% for CLSI broth microdilution and Etest. Correlation of CLSI MICs and in vivo outcome was good, as mice challenged with strains with an MIC ≤2 mg/L responded to voriconazole therapy in 92.3% and those challenged with strains with an MIC ≥4 mg/L responded to voriconazole therapy in 33.3%.

Conclusions

CLSI broth microdilution and Etest deliver comparable results that enable a prediction of in vivo outcome. Our results suggest that voriconazole is able to reduce fungal burden in the brain of 92.3% of all mice challenged with strains with voriconazole CLSI MICs ≤2 mg/L, while mice challenged with strains with CLSI MICs ≥4 mg/L showed limited response to voriconazole treatment.

Comparative Pathogenicity of Lomentospora prolificans (Scedosporium prolificans) Isolates from Mexican Patients

We identified 11 Lomentospora prolificans isolates recovered from Mexican patients using phenotypic and molecular characteristics. The identification of isolates was assessed by internal transcribed spacer (ITS rDNA) sequencing. In vitro susceptibility to amphotericin B, fluconazole, voriconazole, posaconazole, caspofungin, anidulafungin and micafungin was determined according to Clinical and Laboratory Standards Institute (CLSI) procedures. Three isolates (07-2239, 11-2242 and 04-2673) were used to induce systemic infection in immunocompetent ICR mice. Survival and tissue burden studies were used as markers of pathogenicity. All of the strains were resistant to every antifungal tested with MIC's for AmB (8->8 µg/ml), VRC (16->16 µg/ml), PSC (16->16 µg/ml), FLC (64->64 µg/ml) and echinocandins with MICs ≥8 µg/ml. One hundred, ninety and sixty percent of the infected mice with the strains 07-2239, 11-2242 and 04-2673 died during the study, respectively. Regarding tissue burden, the highest fungal load of the infected mice was detected in brain followed by spleen and kidney, regardless of the strain.

Does a triple combination have better activity than double combinations against multiresistant fungi? Experimental in vitro evaluation

In this study, the in vitro interactions of amphotericin B (AmB), voriconazole (VRC) and anidulafungin (AFG) in double and triple combinations against four species of multiresistant fungi (Fusarium solani, Lomentospora prolificans, Scopulariopsis brevicaulis and Scopulariopsis brumptii) were evaluated. In general, AmB combined with AFG was the most synergistic, especially against F. solani (7/8; 87.5%) when low concentrations of AmB were used, i.e. 0.125-0.5 µg/mL. The least active combination was AmB + VRC, with the lowest percentage of synergy against S. brevicaulis (2/11; 18.2%) and, in general, high concentrations of both antifungals were needed to achieve synergy. The triple combination was also highly synergistic against F. solani and S. brevicaulis, especially when the lowest concentrations of AmB were used, suggesting that use of combined therapies would reduce the toxicity of therapy. The triple combination was more effective than the double combinations in some cases, but not against all strains, suggesting that administration of three drugs is not always useful in the treatment of infections due to multiresistant fungi.

Secretion of Proteases by an Opportunistic Fungal Pathogen Scedosporium aurantiacum

Scedosporium aurantiacum is an opportunistic filamentous fungus increasingly isolated from the sputum of cystic fibrosis patients, and is especially prevalent in Australia. At the moment, very little is known about the infection mechanism of this fungus. Secreted proteases have been shown to contribute to fungal virulence in several studies with other fungi. Here we have compared the profiles of proteases secreted by a clinical isolate Scedosporium aurantiacum (WM 06.482) and an environmental strain (WM 10.136) grown on a synthetic cystic fibrosis sputum medium supplemented with casein or mucin. Protease activity was assessed using class-specific substrates and inhibitors. Subtilisin-like and trypsin-like serine protease activity was detected in all cultures. The greatest difference in the secretion of proteases between the two strains occurred in mucin-supplemented medium, where the activities of the elastase-like, trypsin-like and aspartic proteases were, overall, 2.5–75 fold higher in the clinical strain compared to the environmental strain. Proteases secreted by the two strains in the mucin-supplemented medium were further analyzed by mass spectrometry. Six homologs of fungal proteases were identified from the clinical strain and five from the environmental strain. Of these, three were common for both strains including a subtilisin peptidase, a putative leucine aminopeptidase and a PA-SaNapH-like protease. Trypsin-like protease was identified by mass spectrometry only in the clinical isolate even though trypsin-like activity was present in all cultures. In contrast, high elastase-like activity was measured in the culture supernatant of the clinical strain but could not be identified by mass spectrometry searching against other fungi in the NCBI database. Future availability of an annotated genome will help finalise identification of the S. aurantiacum proteases.

Immunoproteomics-Based Analysis of the Immunocompetent Serological Response to Lomentospora prolificans

The filamentous fungus Lomentospora prolificans is an emerging pathogen causing severe infections mainly among the immunocompromised population. These diseases course with high mortality rates due to great virulence of the fungus, its inherent resistance to available antifungals, and absence of specific diagnostic tools. Despite being widespread in humanized environments, L. prolificans rarely causes infections in immunocompetent individuals likely due to their developed protective immune response. In this study, conidial and hyphal immunomes against healthy human serum IgG were analyzed, identifying immunodominant antigens and establishing their prevalence among the immunocompetent population. Thirteen protein spots from each morph were detected as reactive against at least 70% of serum samples, and identified by liquid chromatography tandem mass spectrometry (LC-MS/MS). Hence, the most seroprevalent antigens were WD40 repeat 2 protein, malate dehydrogenase, and DHN1, in conidia, and heat shock protein (Hsp) 70, Hsp90, ATP synthase β subunit, and glyceraldehyde-3-phosphate dehydrogenase, in hyphae. More interestingly, the presence of some of these seroprevalent antigens was determined on the cell surface, as Hsp70, enolase, or Hsp90. Thus, we have identified a diverse set of antigenic proteins, both in the entire proteome and cell surface subproteome, which may be used as targets to develop innovative therapeutic or diagnostic tools.

Identifying the emerging human pathogen Scedosporium prolificans by using a species-specific monoclonal antibody that binds to the melanin biosynthetic enzyme tetrahydroxynaphthalene reductase

The dematiaceous (melanized) fungus Scedosporium prolificans is an emerging and frequently fatal pathogen of immunocompromised humans and which, along with the closely related fungi Pseudallescheria boydii, Scedosporium apiospermum and S. aurantiacum in the Pseudallescheria-Scedosporium complex, is a contributing aetiology to tsunami lung and central nervous system infections in near-drowning victims who have aspirated water laden with spores. At present, the natural habitat of the fungus is largely unknown, and accurate detection methods are needed to identify environmental reservoirs of infectious propagules. In this study, we report the development of a monoclonal antibody (mAb) (CA4) specific to S. prolificans, which does not cross-react with closely related fungi in the Pseudallescheria-Scedosporium complex or with a wide range of mould and yeast species pathogenic to humans. Using genome sequencing of a soil isolate and targeted gene disruption of the CA4 antigen-encoding gene, we show that mAb CA4 binds to the melanin-biosynthetic enzyme tetrahydroxynaphthalene reductase. Enzyme-deficient mutants produce orange-brown or green-brown spore suspensions compared with the black spore suspension of the wild-type strain. Using mAb CA4 and a mAb (HG12) specific to the related fungi P. boydii, P. apiosperma, S. apiospermum and S. aurantiacum, we demonstrate how the mAbs can be used in combination with a semiselective isolation procedure to track these opportunistic pathogens in environmental samples containing mixed populations of human pathogenic fungi. Specificity of mAb CA4 was confirmed by sequencing of the internally transcribed spacer 1 (ITS1)-5.8S-ITS2 rRNA-encoding regions of fungi isolated from estuarine muds.

ScedosporiumSpecies Infections and Treatments

Scedosporium species are now increasingly isolated from immunocompromised and immunocompetent patients. Unfortunately, Scedosporium species infections are generally resistant to amphotericin B, and S. prolificans strains are particularly resistant to presently-available antifungal agents. Here we review the microbiology, expanding epidemiology, numerous clinical presentations, and diagnostic tools available for Scedosporium species infections. Finally, we detail the available in vitro, animal model, and clinical data on the treatment of Scedosporium species infections with special emphasis on the role of newer antifungal therapies for these recalcitrant infections.

Infection and colonisation due to Scedosporium in Northern Spain. An in vitro antifungal susceptibility and molecular epidemiology study of 60 isolates

Since the latest taxonomical changes in the genus Scedosporium by Gilgado et al. in 2010, no species-specific studies on epidemiology and antifungal susceptibility patterns (AFSP) have so far been published. This study aimed to provide qualitative epidemiological data of Scedosporium spp. isolated from cystic fibrosis (CF) patients and immunocompromised patients from Northern Spain. Isolates were identified by using amplified fragment length polymorphism (AFLP), and species-specific AFSP were generated for all currently available antifungal compounds. AFLP was a useful tool for identification to species-level and for the discrimination of inter- and intra-patient isolates. Scedosporium prolificans represents the most prevalent species in the respiratory tract of CF patients and immunocompromised patients in Northern-Spain, followed by Pseudallescheria boydii, P. apiosperma, and P. ellipsoidea. CF patients were exclusively colonised with either P. boydii or S. prolificans. Patients were colonised over years exclusively with isolates affiliated to one species, but some patients were colonised with multiple strains with different AFSP. The sum of those co-colonising strains in one patient, may appear in vitro and in vivo as a multi-resistant S. prolificans isolate, as strains are morphologically identical and might therefore be regarded as only one strain. A majority of Scedosporium strains (with exception of S. prolificans) were found susceptible for voriconazole and micafungin.

Discrimination of Scedosporium prolificans against Pseudallescheria boydii and Scedosporium apiospermum by semiautomated repetitive sequence-based PCR

The laboratory identification of Pseudallescheria and Scedosporium isolates at the species level is important for clinical and epidemiological purposes. This study used semiautomated repetitive sequence-based polymerase chain reaction (rep-PCR) to identify Pseudallescheria/Scedosporium. Reference strains of Pseudallescheria boydii (n = 12), Scedosporium prolificans (n = 8), Scedosporium apiospermum (n = 9), and clinical/environmental isolates (P. boydii, 7; S. prolificans, 7; S. apiospermum, 7) were analyzed by rep-PCR. All clinical isolates were identified by morphological and phenotypic characteristics and by sequence analysis. Species identification of reference strains was based on the results of available databases. Rep-PCR studies were also conducted with various molds to differentiate Pseudallescheria/Scedosporium spp. from other commonly encountered filamentous fungi. All tested Pseudallescheria/Scedosporium isolates were distinguishable from the other filamentous fungi. All Scedosporium prolificans strains clustered within the cutoff of 85%, and species identification by rep-PCR showed an agreement of 100% with sequence analysis. However, several isolates of P. boydii and S. apiospermum did not cluster within the 85% cutoff with the same species by rep-PCR. Although the identification of P. boydii and S. apiospermum was not correct, the semiautomated rep-PCR system is a promising tool for the identification of S. prolificans isolates.

Different virulence of the species of the Pseudallescheria boydii complex

Pseudallescheria boydii sensu lato is a complex of species involved in severe human infections. We have evaluated, using a murine model, the virulence of 2 strains of each of the most representative species of the complex, i.e., P. boydii sensu stricto, P. minutispora, Scedosporium apiospermum, S. aurantiacum and S. dehoogii. We used two different inocula, i.e., 5 x 10(4) conidia/ml (for immunosuppressed animals) and 1 x 10(6) conidia/ml (for immunocompetent animals), which were administered intravenously. Scedosporium aurantiacum and S. dehoogii were the most virulent species, causing the death of 80% and 70% of the immunocompetent mice, respectively. The remaining species only killed 0-20% of the animals.

Infections caused by Scedosporium spp

Scedosporium spp. are increasingly recognized as causes of resistant life-threatening infections in immunocompromised patients. Scedosporium spp. also cause a wide spectrum of conditions, including mycetoma, saprobic involvement and colonization of the airways, sinopulmonary infections, extrapulmonary localized infections, and disseminated infections. Invasive scedosporium infections are also associated with central nervous infection following near-drowning accidents. The most common sites of infection are the lungs, sinuses, bones, joints, eyes, and brain. Scedosporium apiospermum and Scedosporium prolificans are the two principal medically important species of this genus. Pseudallescheria boydii, the teleomorph of S. apiospermum, is recognized by the presence of cleistothecia. Recent advances in molecular taxonomy have advanced the understanding of the genus Scedosporium and have demonstrated a wider range of species than heretofore recognized. Studies of the pathogenesis of and immune response to Scedosporium spp. underscore the importance of innate host defenses in protection against these organisms. Microbiological diagnosis of Scedosporium spp. currently depends upon culture and morphological characterization. Molecular tools for clinical microbiological detection of Scedosporium spp. are currently investigational. Infections caused by S. apiospermum and P. boydii in patients and animals may respond to antifungal triazoles. By comparison, infections caused by S. prolificans seldom respond to medical therapy alone. Surgery and reversal of immunosuppression may be the only effective therapeutic options for infections caused by S. prolificans.

Infection with Scedosporium apiospermum and S. prolificans, Australia

S. prolificans has become a major pathogen in immunocompromised patients.

Scedosporium apiospermum and S. prolificans are fungi of increasing clinical importance, particularly in persons with underlying diseases. We reviewed the records of 59 patients in Australia from whom Scedosporium spp. were isolated from June 30, 1997, through December 31, 2003. S. apiospermum was isolated predominantly from the respiratory tracts of 28 of 31 patients with underlying lung diseases and resulted in 2 infections and 1 death. The annual number of S. apiospermum isolates remained constant. S. prolificans was isolated from 28 patients only after November 1999. Eight patients with acute myeloid leukemia or hematopoietic stem cell transplants had invasive infection; 4 had fungemia and 6 died from infection. S. prolificans caused locally invasive infection in 2 immunocompetent patients and was found in the respiratory tract of 18 patients with underlying respiratory disease but did not cause fungemia or deaths in these patients. Scedosporium spp. showed distinct clinical and epidemiologic features.

Animal models: an important tool in mycology

Animal models of fungal infections are, and will remain, a key tool in the advancement of the medical mycology. Many different types of animal models of fungal infection have been developed, with murine models the most frequently used, for studies of pathogenesis, virulence, immunology, diagnosis, and therapy. The ability to control numerous variables in performing the model allows us to mimic human disease states and quantitatively monitor the course of the disease. However, no single model can answer all questions and different animal species or different routes of infection can show somewhat different results. Thus, the choice of which animal model to use must be made carefully, addressing issues of the type of human disease to mimic, the parameters to follow and collection of the appropriate data to answer those questions being asked. This review addresses a variety of uses for animal models in medical mycology. It focuses on the most clinically important diseases affecting humans and cites various examples of the different types of studies that have been performed. Overall, animal models of fungal infection will continue to be valuable tools in addressing questions concerning fungal infections and contribute to our deeper understanding of how these infections occur, progress and can be controlled and eliminated.

Scedosporium apiospermum: changing clinical spectrum of a therapy-refractory opportunist*

Current knowledge on the opportunist Scedosporium apiospermum (teleomorph: Pseudallescheria boydii), generated over a period of more than 120 years, is reviewed. The natural environmental habitat of the fungus is unknown; nutrient-rich, brackish waters like river estuaria have been suggested. The fungus is strongly promoted by agricultural and particularly by industrial pollution.

Molecular phylogeny of the Pseudallescheria boydii species complex: proposal of two new species

Pseudallescheria boydii (anamorph Scedosporium apiospermum) is the species responsible for human scedosporiosis, a fungal infection with a high mortality rate and which is difficult to treat. Recently, it has been demonstrated that high genetic variation exists within this species. We have performed a morphological and molecular study involving numerous strains of clinical or environmental origins and from different countries. The analysis of partial sequences of the beta-tubulin (two loci) and calmodulin genes and the internal transcribed spacer region of the rRNA gene has demonstrated that P. boydii is a species complex. The combined analysis of the sequences of the four loci of 60 strains has showed the presence of 44 haplotypes in the in group. Three species morphologically related to P. boydii sensu stricto, i.e., Pseudallescheria angusta, Pseudallescheria ellipsoidea, and Pseudallescheria fusoidea, which had previously been considered synonyms, could be differentiated genetically from P. boydii in our study. It is relevant that two of the three strains now included in P. ellipsoidea have caused invasive infections. The species Pseudallescheria minutispora and Scedosporium aurantiacum are clearly phylogenetically separated from the other species studied and are here proposed as new. Morphological features support this proposal. All the strains included in S. aurantiacum species have a clinical origin, while those included in P. minutispora are environmental. Further studies are needed to demonstrate whether all the species included in the P. boydii complex have different clinical spectra and antifungal susceptibility.

Efficacy of voriconazole in treatment of systemic scedosporiosis in neutropenic mice

We have evaluated the efficacy of voriconazole (VRC) in a murine model of systemic infection by Scedosporium apiospermum. The survival of mice treated with VRC at 5, 20, or 40 mg/kg/day was greater than that of the control group (P< or =0.0009). VRC reduced the tissue burden in the spleen and brain (P<0.001 in both organs) in comparison with that of the control group.

Scedosporium prolificans osteomyelitis in an immunocompetent child treated with voriconazole and caspofungin, as well as locally applied polyhexamethylene biguanide

Scedosporium species are increasingly isolated from immunocompromised and immunocompetent patients. Unfortunately, Scedosporium infections are generally resistant to amphotericin B, and Scedosporium prolificans strains are particularly resistant to the antifungal agents now in use. We report here on an immunocompetent child with S. prolificans-associated osteomyelitis successfully treated with debridement, local irrigation with polyhexamethylene biguanide, and the systemic administration of voriconazole and caspofungin despite poor in vitro activity of voriconazole alone against the isolate. We also review the treatments and outcomes of 28 reported cases of osteomyelitis or septic arthritis caused by Scedosporium species in immunocompetent patients.

Efficacy of albaconazole (UR-9825) in treatment of disseminated Scedosporium prolificans infection in rabbits

There are no effective therapeutics for treating invasive Scedosporium prolificans infections. Doses of 15, 25, and 50 mg/kg of body weight/day for the new triazole albaconazole (ABC) were evaluated in an immunocompetent rabbit model of systemic infection with this mold. Treatments were begun 1 day after challenge and given for 10 days. ABC at any dose was more effective than amphotericin B (AMB) at 0.8 mg/kg/day at clearing S. prolificans from tissue (P < 0.007). The percentages of survival at 25 mg of ABC/kg/day were similar to those obtained with AMB. Rabbits showed 100% survival when they were treated with 50 mg of ABC per kg (P < 0.0001 versus control group), and only this dosage was able to reduce tissue burden significantly in the five organs studied, i.e., spleen, kidneys, liver, lungs, and brain.