Invasive fungal infections among organ transplant recipients: results of the Transplant-Associated Infection Surveillance Network (TRANSNET)

Global trends in the distribution of Candida species causing candidemia

Only five species account for 92% of cases of candidemia (Candida albicans, C. glabrata, C. tropicalis, C. parapsilosis, and C. krusei); however, their distribution varies in population-based studies conducted in different geographical areas. C. albicans is the most frequent species, but considerable differences are found between the number of cases caused by C. glabrata and C. parapsilosis. Studies from Northern Europe and the USA reported a high number of cases caused by C. glabrata, whereas studies from Spain and Brazil demonstrated a lower number of cases caused by C. glabrata and a higher number of cases attributed to C. parapsilosis. Globally, the frequency of C. albicans is decreasing, while that of C. glabrata and C. krusei is stable, and C. parapsilosis and C. tropicalis are increasing. Patient characteristics and prior antifungal therapy also have a considerable influence on the distribution and frequency of Candida spp., regardless of the geographical area. C. albicans is more frequent in patients aged up to 18 years, the frequency of C. parapsilosis decreases with age, and C. glabrata is more common in the elderly. Finally, the presence of horizontal transmission of Candida spp. isolates (reported mainly in patients from the adult medical and post-surgical ICU, patients from oncology-haematology units, and neonates) can affect species distribution.

Parainfluenza virus lower respiratory tract disease after hematopoietic cell transplant: viral detection in the lung predicts outcome

BACKGROUND

Parainfluenza virus (PIV) commonly infects patients following hematopoietic cell transplantation (HCT), frequently causing lower respiratory tract disease (LRTD). The definition of LRTD significantly differs among studies evaluating the impact of PIV after HCT.

METHODS

We retrospectively evaluated 544 HCT recipients with laboratory-confirmed PIV and classified LRTD into 3 groups: possible (PIV detection in upper respiratory tract with new pulmonary infiltrates with/without LRTD symptoms), probable (PIV detection in lung with LRTD symptoms without new pulmonary infiltrates), and proven (PIV detection in lung with new pulmonary infiltrates with/without LRTD symptoms).

RESULTS

Probabilities of 90-day survival after LRTD were 87%, 58%, and 45% in possible, probable, and proven cases, respectively. Patients with probable and proven LRTD had significantly worse survival than those with upper respiratory tract infection (probable: hazard ratio [HR], 5.87 [P < .001]; proven: HR, 9.23 [P < .001]), whereas possible LRTD did not (HR, 1.49 [P = .27]). Among proven/probable cases, oxygen requirement at diagnosis, low monocyte counts, and high-dose steroid use (>2 mg/kg/day) were associated with high mortality in multivariable analysis.

CONCLUSIONS

PIV LRTD with viral detection in lungs (proven/probable LRTD) was associated with worse outcomes than was PIV LRTD with viral detection in upper respiratory samples alone (possible LRTD). This new classification should impact clinical trial design and permit comparability of results among centers.

Endemic fungal infections in solid organ and hematopoietic cell transplant recipients enrolled in the Transplant-Associated Infection Surveillance Network (TRANSNET)

BACKGROUND

Invasive fungal infections are a major cause of morbidity and mortality among solid organ transplant (SOT) and hematopoietic cell transplant (HCT) recipients, but few data have been reported on the epidemiology of endemic fungal infections in these populations.

METHODS

Fifteen institutions belonging to the Transplant-Associated Infection Surveillance Network prospectively enrolled SOT and HCT recipients with histoplasmosis, blastomycosis, or coccidioidomycosis occurring between March 2001 and March 2006.

RESULTS

A total of 70 patients (64 SOT recipients and 6 HCT recipients) had infection with an endemic mycosis, including 52 with histoplasmosis, 9 with blastomycosis, and 9 with coccidioidomycosis. The 12-month cumulative incidence rate among SOT recipients for histoplasmosis was 0.102%. Occurrence of infection was bimodal; 28 (40%) infections occurred in the first 6 months post transplantation, and 24 (34%) occurred between 2 and 11 years post transplantation. Three patients were documented to have acquired infection from the donor organ. Seven SOT recipients with histoplasmosis and 3 with coccidioidomycosis died (16%); no HCT recipient died.

CONCLUSIONS

This 5-year multicenter prospective surveillance study found that endemic mycoses occur uncommonly in SOT and HCT recipients, and that the period at risk extends for years after transplantation.

Invasive fungal infections in liver transplant recipients

OBJECTIVES

We sought to assess the incidence of invasive fungal infections and identify the risk factors and outcome of invasive fungal infections in liver transplant recipient.

MATERIALS AND METHODS

A retrospective analysis was made of 408 patients who received a liver transplant between January 1990 to December 2012 at Baskent University in Ankara, Turkey. Only 305 of 408 patients were included. Demographic and clinical findings were reviewed, and these findings were compared between patients with or without invasive fungal infections.

RESULTS

Ten of 408 liver transplant patients (2.5%) developed invasive fungal infections. Aspergillus was the most common cause of invasive fungal infections (n=8), followed by Candida (n=1), and Cryptococcus neoformans (n=1). Pulmonary involvement was dominant in all patients (n=10), and only 1 patient had disseminated fungal infection (cryptococcosis). The mean time from transplant to invasive fungal infection diagnosis was 32 ± 19.2 days. Most patients with invasive fungal infection (9/10) died. Mean survival time between diagnosis of fungal infection and death was 24.2 ± 27.3 days in all 10 patients. Fungal infections occurred significantly more frequently in patients with older transplant age, diabetes mellitus, cytomegalovirus infection, renal insufficiency. In addition, other risk factors included long stays in the surgical intensive care unit, the overall length of stay in hospital, and having preoperative high creatinine level.

CONCLUSIONS

Invasive fungal infections were associated with increased morbidity and mortality among liver transplant recipients, with Aspergillus spp. being the most common pathogen in our series. Because of its high mortality rate, it is important to follow up transplant patients for the development of invasive fungal infections.

Elevated CXCL10 (IP-10) in bronchoalveolar lavage fluid is associated with acute cellular rejection after human lung transplantation

BACKGROUND

CXCL10 (IP-10) is a potent chemoattractant for T cells that has been postulated to play a role in infection and acute cellular rejection (ACR) in animal models. We measured CXCL10 (IP-10) (and other cytokines previously implicated in the pathogenesis of ACR) in the bronchoalveolar lavage (BAL) of lung transplant recipients (LTRs) to determine the association between CXCL10 (IP-10) and ACR in LTRs.

METHODS

In a prospective study of 85 LTRs, expression of cytokines (tumor necrosis factor, interferon-γ, interleukin [IL]-6, IL-8, IL-15, IL-16, IL-17, CXCL10 [IP-10], and MCP-1 [CCL2]) in BAL samples (n=233) from patients with episodes of ACR (n=44), infection ("Infect"; n=25), concomitant "Infect+ACR" (n=10), and "No Infect and No ACR" (n=154) were analyzed.

RESULTS

The levels of both CXCL10 (IP-10) and IL-16 were significantly increased in histologically proven ACR compared with the "No Infect and No ACR" group (CXCL10 [IP-10]: 107.0 vs. 31.9 pg/mL [P=0.001] and IL-16: 472.1 vs. 283.01 pg/mL [P=0.01]). However, in a linear mixed-effects model, significant association was found only between CXCL10 (IP-10) and ACR. A one-log increase of CXCL10 (IP-10) was associated with a 40% higher risk of ACR (odds ratio, 1.4; 95% confidence interval, 1.12-1.84).

CONCLUSION

Higher values of CXCL10 (IP-10) in BAL fluid are associated with ACR in LTRs, suggesting a potential mechanistic role in the pathogenesis of ACR in LTRs. These results suggest that therapeutic strategies to inhibit CXCL10 (IP-10) and or its cognate receptor, CXCR3, warrant investigation to prevent and/or treat ACR in clinical lung transplantation.

Mouse model of invasive fungal infection

The mouse intravenous (IV) challenge model of Candida albicans invasive fungal infection has been widely used to study the importance of the innate immune system in these infections. This chapter describes this well-characterized model, where fungal cells are administered directly into the mouse bloodstream to initiate a systemic infection. The preparation of tissue samples from infected mice to allow evaluation of disease progression and host responses is also described.

Cryptococcal infections: changing epidemiology and implications for therapy

Although the incidence of HIV-associated cryptococcosis has decreased in developed countries since the introduction of antiretroviral therapy, this disease continues to cause significant morbidity and mortality in sub-Saharan Africa among patients with AIDS. Important strides have been made in an attempt to decrease the burden of disease, particularly the development of the lateral flow assay cryptococcal antigen (LFA CrAg) as a diagnostic tool in resource-limited settings, coupled with the introduction of pre-emptive treatment with fluconazole for HIV-positive patients at risk for cryptococcosis with a positive LFA CrAg. Among solid organ transplant recipients, recent prospective studies have identified cryptococcosis as the third most common invasive fungal infection, and progress is being made toward earlier diagnosis and more effective therapy. Finally, the Cryptococcus gattii outbreak in British Columbia, Canada and the US Pacific Northwest is providing important new insights into the emergence of this pathogen in geographic areas previously considered low risk for acquisition of infection. Understanding the similarities and differences among C. gattii and C. neoformans infections will provide critical insights into the behavior of these organisms in the human host. Both pathogens affect immunocompetent and immunosuppressed hosts, causing pulmonary, central nervous system and widely disseminated infections. Treatment recommendations in the future will necessarily take into account the site of infection, clinical severity of the infection, Cryptococcus species, host immune status and economic resources.

Genetic PTX3 deficiency and aspergillosis in stem-cell transplantation

BACKGROUND

The soluble pattern-recognition receptor known as long pentraxin 3 (PTX3) has a nonredundant role in antifungal immunity. The contribution of single-nucleotide polymorphisms (SNPs) in PTX3 to the development of invasive aspergillosis is unknown.

METHODS

We screened an initial cohort of 268 patients undergoing hematopoietic stem-cell transplantation (HSCT) and their donors for PTX3 SNPs modifying the risk of invasive aspergillosis. The analysis was also performed in a multicenter study involving 107 patients with invasive aspergillosis and 223 matched controls. The functional consequences of PTX3 SNPs were investigated in vitro and in lung specimens from transplant recipients.

RESULTS

Receipt of a transplant from a donor with a homozygous haplotype (h2/h2) in PTX3 was associated with an increased risk of infection, in both the discovery study (cumulative incidence, 37% vs. 15%; adjusted hazard ratio, 3.08; P=0.003) and the confirmation study (adjusted odds ratio, 2.78; P=0.03), as well as with defective expression of PTX3. Functionally, PTX3 deficiency in h2/h2 neutrophils, presumably due to messenger RNA instability, led to impaired phagocytosis and clearance of the fungus.

CONCLUSIONS

Genetic deficiency of PTX3 affects the antifungal capacity of neutrophils and may contribute to the risk of invasive aspergillosis in patients treated with HSCT. (Funded by the European Society of Clinical Microbiology and Infectious Diseases and others.).

Invasive Trichosporon infection in solid organ transplant patients: a report of two cases identified using IGS1 ribosomal DNA sequencing and a review of the literature

Trichosporon species are rare etiologic agents of invasive fungal infection in solid organ transplant (SOT) recipients. We report 2 well-documented cases of Trichosporon inkin invasive infection in SOT patients. We also conducted a detailed literature review of Trichosporon species infections in this susceptible population. We gathered a total of 13 cases of Trichosporon species infections. Any type of organ transplantation can be complicated by Trichosporon infection. Bloodstream infections and disseminated infections were the most common clinical presentations. Liver recipients with bloodstream or disseminated infections had poor prognoses. Although the most common species was formerly called Trichosporon beigelii, this species name should no longer be used because of the changes in the taxonomy of this genus resulting from the advent of molecular approaches, which were also used to identify the strains isolated from our patients. Antifungal susceptibility testing highlights the possibility of multidrug resistance. Indeed, Trichosporon has to be considered in cases of breakthrough infection or treatment failure under echinocandins or amphotericin therapy. Voriconazole seems to be the best treatment option.

Nonmammalian model systems to investigate fungal biofilms

Medical advances have resulted in an increase in the number of patients in immunocompromised states, vulnerable to infection, or individuals fitted with medical devices that form niches for microbial infections. These infections are difficult to treat and have significant morbidity and mortality rates. An important factor in the pathogenesis of fungal diseases is the development of biofilm-forming communities, enabling the invasion of host tissues and resistance to antimicrobial compounds. To investigate the genetic requirements for filamentation and seek compounds that inhibit the process, invertebrate hosts are employed as models of in vivo infection. The purpose of our review is to highlight methods that can be utilized to investigate fungal filamentation, an important step in the development of biofilms, in the invertebrate hosts Galleria mellonella, Caenorhabditis elegans, and Drosophila melanogaster.

Invasive candidiasis serological diagnosis in solid organ transplant recipients

Solid organ transplant recipients are at high risk of fungal infections, because of ongoing immunosuppressive treatment. There are three post organ transplant phases: early, intermediate, and late, all of them at risk of Candida infections. Since conventional tests are insufficient, specific secondary diagnostic tests are still being explored. Serological tests are currently the most common choice. The present study was to determine the usefulness of mannan antigen and anti-mannan antibody detection in diagnosing invasive candidiasis in liver or kidney transplant recipients. The levels of mannan and anti-mannan antibodies were assessed with Platelia Candida Ag Plus, and Platelia Candida Ab Plus (Biorad, Marne-la-Coquette, France) commercial tests, according to manufacturer's guidelines. Sixty six serum samples were obtained from 25 patients (9 liver transplant recipients, 7 kidney transplant recipients, and 9 patients prepared for a kidney transplant), 29 serum samples from 15 patients tested positive for mannan antigen. Serum samples were obtained from 14 patients tested positive for anti- mannan antibodies. Fungal antigen detection in blood serum in patients under immunosuppression, especially with neutropenia, suggests that antifungal treatment should be administered. Serological tests, especially mannan and anti-mannan ones, are very useful for confirmation or exclusion of invasive candidiasis in high-risk patients.

Comparison between cytologic examination of fungi in bronchial washings and bronchoalveolar lavage specimens and culture: a review of 100 cases with emphasis on diagnostic pitfalls

INTRODUCTION

Microbiology culture is the "gold standard" for diagnosis of fungal infections; however, culture has a lengthy turnaround time. A more timely assessment is possible with cytology and Gomori-methamine silver (GMS) staining.

MATERIALS AND METHODS

A total of 100 respiratory tract specimens with a positive fungal Gomori-methamine silver stain and corresponding culture were selected. The cytology slides were reviewed for factors contributing to discrepant results. Specimens were classified as 2 types of variances: interpretative and sampling. Concordant diagnoses were also evaluated.

RESULTS

Eighty-two cases had fungal organisms that grew in culture. The remaining 18 cases were composed solely of fungal organisms that did not grow in culture (17 cases with Pneumocystis jirovecii; 1 case with Pityrosporum ovale). These 18 cases were excluded from the variance analysis. Thirty-three of 82 cases (40%) had concordant cytology and microbiology results, whereas 49 cases were discrepant. Variances were both sampling (41 cases) and interpretive (8 cases). Interpretive variances were predominantly Aspergillus species misinterpreted as Candida. Difficulty identifying true septate hyphae was the major contributing factor for misinterpretation.

CONCLUSIONS

Cytologic evaluation of respiratory specimens remains a useful preemptive diagnostic tool in the rapid diagnosis of fungal infection. Cytology samples significantly contribute to the diagnosis of respiratory fungi. However, interpretive variances between Aspergillus and Candida organisms are common. Awareness of the characteristic features that distinguish fungal organisms can further improve the diagnostic utility of cytology.

Eosinophil deficiency compromises lung defense against Aspergillus fumigatus

Exposure to the mold Aspergillus fumigatus may result in allergic bronchopulmonary aspergillosis, chronic necrotizing pulmonary aspergillosis, or invasive aspergillosis (IA), depending on the host's immune status. Neutrophil deficiency is the predominant risk factor for the development of IA, the most life-threatening condition associated with A. fumigatus exposure. Here we demonstrate that in addition to neutrophils, eosinophils are an important contributor to the clearance of A. fumigatus from the lung. Acute A. fumigatus challenge in normal mice induced the recruitment of CD11b+ Siglec F+ Ly-6G(lo) Ly-6C(neg) CCR3+ eosinophils to the lungs, which was accompanied by an increase in lung Epx (eosinophil peroxidase) mRNA levels. Mice deficient in the transcription factor dblGATA1, which exhibit a selective deficiency in eosinophils, demonstrated impaired A. fumigatus clearance and evidence of germinating organisms in the lung. Higher burden correlated with lower mRNA expression of Epx (eosinophil peroxidase) and Prg2 (major basic protein) as well as lower interleukin 1β (IL-1β), IL-6, IL-17A, granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and CXCL1 levels. However, examination of lung inflammatory cell populations failed to demonstrate defects in monocyte/macrophage, dendritic cell, or neutrophil recruitment in dblGATA1-deficient mice, suggesting that the absence of eosinophils in dlbGATA1-deficient mice was the sole cause of impaired lung clearance. We show that eosinophils generated from bone marrow have potent killing activity against A. fumigtaus in vitro, which does not require cell contact and can be recapitulated by eosinophil whole-cell lysates. Collectively, our data support a role for eosinophils in the lung response after A. fumigatus exposure.

Cryptococcal infection in non-HIV immunosuppressed patients - Three case reports in a nephrology setting

Cryptococcal infection has been increasing among immunosuppressed population. We report three cases of Cryptococcus neoformans infection in immunosuppressed patients – two renal transplanted and one with lupus nephritis. Early infection (<3months) was diagnosed in two – an allograft Cryptococcus infection and a central nervous system involvement. The third, a 10-year transplant vintage patient, presented with cryptococcal meningitis. Amphotericin B provided good clinical outcomes. We outline the importance of suspicion for cryptococcal infection in immunosuppressed patients.

Enhancing molecular approaches for diagnosis of fungal infections

Molecular tests can improve the diagnosis of fungal infections. Despite the increasing application for fungal detection, molecular tests are still not accepted as a diagnostic criterion to define invasive fungal diseases. This limitation is largely due to a lack of a standardized method. Method standardization can be achieved by following a consensus protocol developed by a working group, by performing a molecular test in a centralized laboratory or by using a commercial assay that provides a standardized method and quality-controlled reagents. Forming a consortium or a working group consisting of large-scale diagnostic mycology laboratories can accelerate the process of validating and implementing a commercial molecular assay for clinical use through a joint effort between industry partners and clinicians. Development of molecular tests not only for the detection of fungi but also for the identification of antifungal drug resistance directly in blood, bronchoalveolar lavage fluid, cerebrospinal fluid, and formalin-fixed and paraffin-embedded tissues greatly enhances fungal diagnostic capacities. Advances of developing quantitative assays and RNA detection platforms may provide another avenue to further improve fungal diagnostics.

Endemic mycoses in immunocompromised hosts

Endemic mycoses remain a significant cause of morbidity and mortality among immunocompromised patients. As the number of immunosuppressed individuals increases worldwide, the incidence of endemic mycoses is also expected to rise. In immunocompromised patients, endemic mycoses can present in atypical fashion, cause more severe and/or disseminated disease, and result in higher mortality. Despite several noteworthy advances over the past decade, significant challenges remain with regard to the prevention, diagnosis, and therapy of endemic mycoses in immunocompromised hosts. This review highlights important developments related to the epidemiology, diagnosis, treatment, and prevention of commonly encountered endemic mycoses. We also discuss emerging topics, knowledge gaps, and areas of future research.

Clinical and tree hollow populations of human pathogenic yeast in Hamilton, Ontario, Canada are different

Yeast are among the most frequent pathogens in humans. The dominant yeast causing human infections belong to the genus Candida and Candida albicans is the most frequently isolated species. However, several non-C. albicans species are becoming increasingly common in patients worldwide. The relationships between yeast in humans and the natural environments remain poorly understood. Furthermore, it is often difficult to identify or exclude the origins of disease-causing yeast from specific environmental reservoirs. In this study, we compared the yeast isolates from tree hollows and from clinics in Hamilton, Ontario, Canada. Our surveys and analyses showed significant differences in yeast species composition, in their temporal dynamics, and in yeast genotypes between isolates from tree hollows and hospitals. Our results are inconsistent with the hypothesis that yeast from trees constitute a significant source of pathogenic yeast in humans in this region. Similarly, the yeast in humans and clinics do not appear to contribute to yeast in tree hollows.

Infection in cancer and transplantation

The range of opportunist pathogens in cancer and transplant patients continues to increase. New treatment modalities and forms of immunosuppression following transplantation have improved survival from the underlying disease but can lead to prolonged immunosuppression and increased risk of infection. NICE guidelines for the management of neutropenic sepsis are now available but have aroused some controversy, particularly over the recommendation for quinolone prophylaxis in high-risk patient groups.

In addition to neutropenia, long-term defects in cell-mediated immunity are exposing patients to risk of chronic, viral, protozoal and fungal infection. Advances in diagnostic techniques have the potential to improve management and limit unnecessary empirical treatment, allowing a move towards a diagnosis-driven strategy. However, interpreting the clinical validity and utility of some of these assays can be difficult, particularly for low-prevalence infection where the positive predictive value of any diagnostic test is likely to be low and prompt empirical antibacterial therapy is still indicated in neutropenic patients.

Impact of in vivo triazole and echinocandin combination therapy for invasive pulmonary aspergillosis: enhanced efficacy against Cyp51 mutant isolates

Previous studies examining combination therapy for invasive pulmonary aspergillosis (IPA) have revealed conflicting results, including antagonism, indifference, and enhanced effects. The most commonly employed combination for this infection includes a mold-active triazole and echinocandin. Few studies have evaluated combination therapy from a pharmacodynamic (PD) perspective, and even fewer have examined combination therapy against both wild-type and azole-resistant Cyp51 mutant isolates. The current studies aim to fill this gap in knowledge. Four Aspergillus fumigatus isolates were utilized, including a wild-type strain, an Fks1 mutant (posaconazole susceptible and caspofungin resistant), and two Cyp51 mutants (posaconazole resistant). A neutropenic murine model of IPA was used for the treatment studies. The dosing design included monotherapy with posaconazole, monotherapy with caspofungin, and combination therapy with both. Efficacy was determined using quantitative PCR, and results were normalized to known quantities of conidia (conidial equivalents [CE]). The static dose, 1-log kill dose, and associated PD target area under the curve (AUC)/MIC ratio were determined for monotherapy and combination therapy. Monotherapy experiments revealed potent activity for posaconazole, with reductions of 3 to 4 log10 Aspergillus CE/ml with the two "low"-MIC isolates. Posaconazole alone was less effective for the two isolates with higher MICs. Caspofungin monotherapy did not produce a significant decrease in fungal burden for any strain. Combination therapy with the two antifungals did not enhance efficacy for the two posaconazole-susceptible isolates. However, the drug combination produced synergistic activity against both posaconazole-resistant isolates. Specifically, the combination resulted in a 1- to 2-log10 decline in burden that would not have been predicted based on the monotherapy results for each drug. This corresponded to a reduction in the free-drug posaconazole AUC/MIC ratio needed for stasis of up to 17-fold. The data suggest that combination therapy using a triazole and an echinocandin may be a beneficial treatment strategy for triazole-resistant isolates.

Diagnosis and treatment of invasive fungal infections focus on liposomal amphotericin B

Invasive fungal infections (IFIs) are responsible for significant morbidity and mortality, especially in immunocompromised patients and in those requiring admission to an intensive care unit. The epidemiology of IFI is changing, and an increment in non-Aspergillus filamentous fungi and non-Candida albicans species has been observed. The present paper reviews the epidemiology and diagnosis of IFIs. Regarding the treatment of IFIs, it focuses primarily on the role of liposomal amphotericin B in this setting. The main recommendations put forth by expert societies and groups are discussed.

Renal mucormycosis: a rare and potentially lethal complication of kidney transplantation

Renal mucormycosis is a rare and potentially lethal complication of kidney transplantation. We describe two cases of renal mucormycosis following deceased donor kidney transplantation. This is the second report of renal mucormycosis following kidney transplantation in the United States, and the first case of renal mucormycosis infection presumed to be of recipient origin. Case A had an early presentation of mucormycosis isolated to the kidney allograft. He had an unexpected rise in serum creatinine and leukocytosis necessitating allograft biopsy which showed mucormycosis. He underwent transplant nephrectomy on posttransplant day 11, was treated with amphotericin B, and discharged home on posttransplant day 22. Case B had a late presentation of renal mucormycosis, preceded by a cutaneous manifestation. One year after kidney transplantation he had a nonhealing knee ulcer which on biopsy showed cutaneous mucormycosis. Treatment included aggressive debridement and amphotericin B. Allograft biopsy showed mucormycosis, necessitating transplant nephrectomy. He was discharged to a rehabilitation facility and died from noninfectious causes. Review of the published literature of renal mucormycosis cases following kidney transplantation reveals a mortality rate of more than 50%. The key to successful outcome is early recognition, prompt institution of surgical debridement of all infected tissue, and appropriate antifungal therapy.

Respiratory tract infections in the immunocompromised

PURPOSE OF REVIEW

Pulmonary infections are particularly common in the immunosuppressed host. This review discusses emerging threats, newer modalities of diagnostic tests and emerging treatment options, and also highlights the increasing problem of antimicrobial resistance.

RECENT FINDINGS

Nosocomial pneumonia is increasingly due to multidrug-resistant Gram-negative organisms in immunosuppressed patients. Viral pneumonias remain a very significant threat, present atypically and carry a high mortality. Aspergillosis remains the most common fungal infection, and infections due to Mucorales are increasing. Multidrug-resistant tuberculosis is on the increase throughout the world. Mixed infections are common and early bronchoscopy with appropriate microbiological tests, including molecular diagnostics, optimise management and reduce mortality.

CONCLUSION

Pulmonary infection remains the most frequent infectious complication in the immunocompromised host. These complex infections are often mixed, have atypical presentations and can be due to multidrug-resistant organisms. Multidisciplinary involvement in specialist centres with appropriate diagnostics, treatment and infection control improves outcome. There is a desperate need for new antimicrobial agents active against Gram-negative pathogens.

Aspergillus PCR-based investigation of fresh tissue and effusion samples in patients with suspected invasive Aspergillosis enhances diagnostic capabilities

Although it is a severe complication in immunocompromised patients, diagnosing invasive fungal disease (IFD), especially invasive aspergillosis (IA), remains difficult. In certain clinical scenarios, examining tissue samples for identification of the infectious organism becomes important. As culture-based methods rarely yield results, the performance of an Aspergillus-specific nested PCR in fresh tissue or pleural effusion samples was evaluated. Fresh tissue (n = 59) and effusion (n = 47) specimens from 79 immunocompromised patients were subjected to an Aspergillus-specific PCR assay. Twenty-six patients had proven (n = 20) or probable (n = 6) IFD, according to the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) criteria, while the remaining patients were classified as having either possible IFD (n = 30) or no IFD (n = 23). IA was identified as the underlying IFD in 21/26 proven/probable cases. PCR positivity was observed for 18/21 proven/probable and 6 possible IA cases; cases classified as no IA did not show positive signals. Patients with proven IFD (n = 5) with cultures positive for non-Aspergillus molds also had negative Aspergillus PCR results. Aspergillus PCR performance analysis yielded sensitivity and specificity values of 86% (95% confidence interval [CI], 65% to 95%) and 100% (95% CI, 86% to 100%), respectively, thus leading to a diagnostic odds ratio of >200. In this analysis, good diagnostic performance of the PCR assay for detection of IA was observed for tissue samples, while effusion samples showed lower sensitivity rates. PCR testing represents a complementary tool; a positive PCR result strengthens the likelihood of IA, whereas IA seems unlikely in cases with negative results but findings could indicate non-Aspergillus IFD. Thus, PCR testing of these specimens enhances the diagnostic capabilities.

Isavuconazole (BAL4815) pharmacodynamic target determination in an in vivo murine model of invasive pulmonary aspergillosis against wild-type and cyp51 mutant isolates of Aspergillus fumigatus

Invasive pulmonary aspergillosis (IPA) continues to rise in concert with increasing numbers of immune suppression techniques to treat other medical conditions and transplantation. Despite these advances, morbidity and mortality rates remain unacceptably high. One strategy used to optimize outcomes is antifungal pharmacodynamic (PD) examination. We explored the pharmacodynamics of a new triazole in development, isavuconazole, in a murine neutropenic IPA model. Ten A. fumigatus isolates were used, including four wild-type isolates and six cyp51 mutants. The MIC range was 0.125 to 8 mg/liter. Following infection, groups of mice were treated orally with the prodrug (BAL8557) at 40 to 640 mg/kg/12 h for 7 days. Efficacy was determined by quantitative PCR of lung homogenates. At the start of therapy, mice had 4.97 log10 conidial equivalents (CE)/ml of lung homogenate, and this increased to 6.82 log10 CE/ml of lung homogenate in untreated animals. The infection model was uniformly lethal in untreated control mice. The PD target endpoints examined included the static-dose AUC/MIC ratio and the 1-log10 killing AUC/MIC ratio. A stasis endpoint was achieved for all isolates with an MIC of ≤1 mg/liter and 1-log10 killing in all isolates with an MIC of ≤0.5 mg/liter, regardless of the presence or absence of the cyp51 mutation. The static-dose range was 65 to 617 mg/kg/12 h. The corresponding median free-drug AUC/MIC ratio was near 5. The 1-log10 killing dose range was 147 to 455 mg/kg/12 h, and the corresponding median free-drug AUC/MIC ratio was 11.1. These values are similar to those previously reported for other triazoles.

Transcriptional activation of heat shock protein 90 mediated via a proximal promoter region as trigger of caspofungin resistance in Aspergillus fumigatus

Invasive aspergillosis is a deadly infection for which new antifungal therapies are needed. Heat shock protein 90 (Hsp90) is an essential chaperone in Aspergillus fumigatus representing an attractive antifungal target. Using a thiamine-repressible promoter (pthiA), we showed that genetic repression of Hsp90 significantly reduced virulence in a murine model of invasive aspergillosis. Moreover, substituting the A. fumigatus hsp90 promoter with 2 artificial promoters (potef, pthiA) and the Candida albicans hsp90 promoter resulted in hypersensitivity to caspofungin and abolition of the paradoxical effect (resistance at high caspofungin concentrations). By inducing truncations in the hsp90 promoter, we identified a 100-base pair proximal sequence that triggers a significant increase of hsp90 expression (≥1.5-fold) and is essential for the paradoxical effect. Preventing this increase of hsp90 expression was sufficient to abolish the paradoxical effect and therefore optimize the antifungal activity of caspofungin.

Antifungal use and therapeutic monitoring of plasma concentrations of itraconazole in heart and lung transplantation patients

BACKGROUND

The prophylactic use of itraconazole has dramatically reduced the incidence of fungal infections in patients after solid-organ transplantation. To further reduce this incidence, it has been suggested that plasma concentrations of itraconazole be monitored and maintained above a putative minimum target concentration of 500 ng/mL.

METHODS

A retrospective audit was undertaken of patients who had had a heart or lung transplant over a 14-month period (between January 1, 2010 and March 31, 2011). The itraconazole prophylaxis regimen (dose, time of last dose, time of blood collection) and plasma concentrations were recorded together with the use of concomitant antacid medication. Details of breakthrough fungal infections were documented.

RESULTS

Eighty-four heart or lung organ transplantations were undertaken in the study period; 57 were treated prophylactically with itraconazole. Plasma concentrations of itraconazole were monitored in 56% (n = 32) of these cases. Considerable interpatient (range, 50-2000 ng/mL) and intrapatient variability in plasma concentrations was observed. The putative target was not achieved consistently in the majority of cases. All patients were taking a proton pump inhibitor. Six of the cohort developed an invasive fungal infection. None of the 3 patients for whom plasma concentrations were monitored was above the target concentration.

CONCLUSIONS

Further clinical studies, involving monitoring of the active metabolite and attention to the importance of the stereoisomers of itraconazole, may give better insight into the appropriateness of the currently suggested minimum target concentration, whose validity remains uncertain. Formulations with improved absorption characteristics could reduce the variability of absorption with the goal of further reducing the incidence of infrequent, but life-threatening, invasive fungal infections.

Histoplasmosis after solid organ transplant

BACKGROUND

To improve our understanding of risk factors, management, diagnosis, and outcomes associated with histoplasmosis after solid organ transplant (SOT), we report a large series of histoplasmosis occurring after SOT.

METHODS

All cases of histoplasmosis in SOT recipients diagnosed between 1 January 2003 and 31 December 2010 at 24 institutions were identified. Demographic, clinical, and laboratory data were collected.

RESULTS

One hundred fifty-two cases were identified: kidney (51%), liver (16%), kidney/pancreas (14%), heart (9%), lung (5%), pancreas (2%), and other (2%). The median time from transplant to diagnosis was 27 months, but 34% were diagnosed in the first year after transplant. Twenty-eight percent of patients had severe disease (requiring intensive care unit admission); 81% had disseminated disease. Urine Histoplasma antigen detection was the most sensitive diagnostic method, positive in 132 of 142 patients (93%). An amphotericin formulation was administered initially to 73% of patients for a median duration of 2 weeks; step-down therapy with an azole was continued for a median duration of 12 months. Ten percent of patients died due to histoplasmosis with 72% of deaths occurring in the first month after diagnosis; older age and severe disease were risk factors for death from histoplasmosis. Relapse occurred in 6% of patients.

CONCLUSIONS

Although late cases occur, the first year after SOT is the period of highest risk for histoplasmosis. In patients who survive the first month after diagnosis, treatment with an amphotericin formulation followed by an azole for 12 months is usually successful, with only rare relapse.

Crossover fungal pathogens: the biology and pathogenesis of fungi capable of crossing kingdoms to infect plants and humans

The outbreak of fungal meningitis associated with contaminated methylprednisolone acetate has thrust the importance of fungal infections into the public consciousness. The predominant pathogen isolated from clinical specimens, Exserohilum rostratum (teleomorph: Setosphaeria rostrata), is a dematiaceous fungus that infects grasses and rarely humans. This outbreak highlights the potential for fungal pathogens to infect both plants and humans. Most crossover or trans-kingdom pathogens are soil saprophytes and include fungi in Ascomycota and Mucormycotina phyla. To establish infection, crossover fungi must overcome disparate, host-specific barriers, including protective surfaces (e.g. cuticle, skin), elevated temperature, and immune defenses. This review illuminates the underlying mechanisms used by crossover fungi to cause infection in plants and mammals, and highlights critical events that lead to human infection by these pathogens. Several genes including veA, laeA, and hapX are important in regulating biological processes in fungi important for both invasive plant and animal infections.

Epidemiology and treatment of mucormycosis

Mucormycosis is an uncommon but aggressive opportunistic fungal infection that afflicts patients with severe underlying immunosuppression, uncontrolled hyperglycemia and/or ketoacidosis, patients with iron overload resulting from frequent blood transfusions or blood disorders and occasionally healthy patients who are inoculated with fungal spores through traumatic injuries. The clinical presentation of mucormycosis is initially indistinguishable from other common infections, and if not diagnosed early and aggressively treated, it is almost always fatal. In this article we summarize recent changes in the epidemiology of mucormycosis, discuss diagnostic and clinical clues suggestive of the infection and provide a general strategy for managing the infection in the absence of data from well-controlled, prospective clinical trials.

Opportunistic infections of the central nervous system in the transplant patient

Therapeutic advances in transplantation medicine have resulted in ever expanding patient populations that receive organ or stem cell transplantation. Modern potent immunomodulatory therapies have resulted in improvements in allograft and patient survival, but, consequently, as a result of the immunosuppressive state, transplant recipients are highly vulnerable to infection, including those that affect the central nervous system (CNS). CNS infections present a diagnostic and therapeutic challenge for clinicians involved in the care of the transplant patient, with a propensity to result in profound morbidity and often high mortality in this patient population. Here, we review major opportunistic pathogens of the CNS seen in transplant patients, highlighting distinguishing epidemiologic and clinical features.

Donor-derived Cryptococcus infection in liver transplant: case report and literature review

Cryptococcosis occurring within 30 days after transplant is unusual. We present a case of cryptococcosis diagnosed within 2 weeks of liver transplant and cryptococcal infection transmitted by liver transplant is considered as the cause. A 63-year-old woman with hepatitis C virus-related cirrhosis and hepatocellular carcinoma had an orthotopic liver transplant from a 45-year-old donor. The immediate postoperative course was smooth, although she was confused with a fever, tachycardia, respiratory failure of 1 week's duration after the orthotopic liver transplant. A liver biopsy was performed for hyperbilirubinemia 2 weeks after the orthotopic liver transplant that showed a Cryptococcus-like yeast. Her blood culture was reexamined, and it was confirmed as Cryptococcus neoformans that had been misinterpreted as candida initially. At the time of the re-examination, her sputum was clear. We checked her preoperative blood sample, retrospectively, for serum cryptococcal antigen with negative result. She was on liposomal amphotericin treatment for 1 month when her blood culture became negative. She was discharged home, with good liver function and a low antigen titer for cryptococcal infection. Cryptococcal disease usually develops at a mean of 5.6 months after transplant. However an early occurrence is rare. Apart from that, its variable clinical presentations make early detection difficult. It might be an early reactivation or a donor-derived infection. The latter usually occurs in unusual sites (eg, the transplanted organ as the sole site of involvement). Our case presented as cryptococcoma and liver involvement was diagnosed by an unintentional liver biopsy.

An autopsy case of pulmonary fissure induced by zygomycosis

For immunodeficient patients, fungi are life-threatening pathogens. In this paper, we present an autopsy case of combined zygomycosis and aspergillosis. A female in her 70s on chronic hemodialysis was admitted to a hospital suffering bloody sputum, dyspnea, and fever, probably due to perinuclear anti-neutrophil cytoplasmic antibody-related vasculitis. Antibiotics were administered and immunosuppressive therapy was started, resulting in an improvement in her condition. Pneumonia later developed, followed by pulmonary bleeding and intractable pneumothorax from which she ultimately died. On autopsy, the upper lobe of the left lung was found to have hemorrhagic necrosis and showed a large longitudinal fissure. Microscopically, Zygomycota were observed in both the lungs and heart, while Aspergillus was found in the middle lobe of the right lung. Zygomycosis, which usually has a poor prognosis, is assumed to have induced hemorrhagic infarction of the lungs, inducing pulmonary bleeding and necrosis, despite the use of lipid formulations of amphotericin B, which are effective medicines against Zygomycota.

Relationship between trough plasma and epithelial lining fluid concentrations of voriconazole in lung transplant recipients

Trough (predose) voriconazole concentrations in plasma and pulmonary epithelial lining fluid (ELF) of lung transplant recipients receiving oral voriconazole preemptive treatment were determined. The mean (± standard deviation [SD]) ELF/plasma ratio was 12.5 ± 6.3. A strong positive linear relationship was noted between trough plasma and ELF voriconazole concentrations (r(2) = 0.87), suggesting the feasibility of using trough plasma voriconazole concentration as a surrogate to estimate the corresponding concentration in ELF of lung transplant recipients.