Invasive aspergillosis in the immunocompromised host: utility of computed tomography and bronchoalveolar lavage

Approach to Peribronchovascular Disease on CT

Diseases that are predominantly peribronchovascular in distribution on computed tomography by definition involve the bronchi, adjacent vasculature, and associated lymphatics involving the central or axial lung interstitium. An understanding of diseases that can present with focal peribronchovascular findings is useful for establishing diagnoses and guiding patient management. This review will cover clinical and imaging features that may assist in differentiating amongst the various causes of primarily peribronchovascular disease.

The pathogenicity ofAspergillus fumigatus, drug resistance, and nanoparticle delivery

The genus Aspergillus includes fungal species that cause major health issues of significant economic importance. These microorganisms are also the culprit for production of carcinogenic aflatoxins in grain storages, contaminating crops, and economically straining the production process. Aspergillus fumigatus is a very important pathogenic species, being responsible for high human morbidity and mortality on a global basis. The prevalence of these infections in immunosuppressed individuals is on the rise, and physicians struggle with the diagnosis of these deadly pathogens. Several virulence determinants facilitate fungal invasion and evasion of the host immune response. Metabolic functions are also important for virulence and drug resistance, since they allow fungi to obtain nutrients for their own survival and growth. Following a positive diagnostic identification, mortality rates remain high due, in part, to emerging resistance to frequently used antifungal drugs. In this review, we discuss the role of the main virulence, drug target, and drug resistance determinants. We conclude with the review of new technologies being developed to treat aspergillosis. In particular, microsphere and nanoparticle delivery systems are discussed in the context of improving drug bioavailability. Aspergillus will likely continue to cause problematic infections in immunocompromised patients, so it is imperative to improve treatment options.

Pulmonary Aspergillosis: What CT can Offer Before it is too Late!

Aspergillus is a large genus of saprophytic fungi which are present everywhere in the environment. However, in persons with underlying weakened immune response this innocent bystander can cause fatal illness if timely diagnosis and management is not done. Chest infection is the most common infection caused by Aspergillus in human beings. Radiological investigations particularly Computed Tomography (CT) provides the easiest, rapid and decision making information where tissue diagnosis and culture may be difficult and time-consuming. This article explores the crucial role of CT and offers a bird's eye view of all the radiological patterns encountered in pulmonary aspergillosis viewed in the context of the immune derangement associated with it.

Multidetector CT of pulmonary cavitation: filling in the holes

Pulmonary cavitation causes significant morbidity and mortality. Early diagnosis of the presence and aetiology of a cavity is therefore crucial in order to avoid further demise in both the localized pulmonary and systemic disorders that may manifest with pulmonary cavity formation. Multidetector CT has become the principal diagnostic technique for detecting pulmonary cavitation and its complications. This review provides an overview of the aetiologies and their imaging findings using this technique. Combining a literature review with case illustration, a synopsis of the different imaging features and constellations is provided, which may suggest a particular cause and aid the differentiation from diseases with similar findings.

Incidence of pulmonary aspergillosis and correlation of conventional diagnostic methods with nested PCR and real-time PCR assay using BAL fluid in intensive care unit patients

BACKGROUND

Although the incidence of invasive aspergillosis in the intensive care unit (ICU) is scarce, it has emerged as major problems in critically ill patients. In this study, the incidence of pulmonary aspergillosis (PA) in ICU patients has evaluated and direct microscopy and culture has compared with nested polymerase chain reaction (PCR) and real-time PCR for detection of Aspergillus fumigatus and A. flavus in bronchoalveolar lavage (BAL) samples of the patients.

METHODS

Thirty BAL samples obtained from ICU patients during a 16-month period were subjected to direct examinations on 20% potassium hydroxide (KOH) and culture on two culture media. Nested PCR targeting internal transcribed spacer ribosomal DNA and TaqMan real-time PCR assay targeting β-tubulin gene were used for the detection of A. fumigatus and A. flavus.

RESULTS

Of 30 patients, 60% were men and 40% were women. The diagnosis of invasive PA was probable in 1 (3%), possible in 11 (37%), and not IPA in 18 (60%). Nine samples were positive in nested PCR including seven samples by A. flavus and two by A. fumigatus specific primers. The lowest amount of DNA that TaqMan real-time PCR could detect was ≥40 copy numbers. Only one of the samples had a positive result of A. flavus real-time PCR with Ct value of 37.5.

CONCLUSIONS

Although a significant number of specimens were positive in nested PCR, results of this study showed that establishment of a correlation between the conventional methods with nested PCR and real-time PCR needs more data confirmed by a prospective study with a larger sample group.

ACR appropriateness criteria(®)acute respiratory illness in immunocompromised patients

The respiratory system is often affected by complications of immunodeficiency, typically manifesting clinically as acute respiratory illness. Ongoing literature reviews regarding the appropriateness of imaging in these patients are critical, as advanced medical therapies such as stem cell transplantation, chemotherapy, and immunosuppressive therapies for autoimmune disease continue to keep high the population of immunosuppressed patients in our health care system today. This ACR Appropriateness Criteria(®) topic describes clinical scenarios of acute respiratory illness in immunocompromised patients with cough, dyspnea, chest pain, and fever; in those with negative, equivocal, or nonspecific findings on chest radiography; in those with diffuse or confluent opacities on chest radiography; and in those in whom noninfectious disease is suspected. The use of chest radiography, chest CT, transthoracic needle biopsy, and nuclear medicine imaging are all discussed in the contexts of these clinical scenarios. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Atypical invasive aspergillosis in a neutropenic child

Invasive aspergillosis (IA) is an aggressive disease with a high mortality rate requiring a high index of clinical suspicion in susceptible patients. We report an atypical presentation of IA, not previously published. A 2-year-old girl with underlying neuroblastoma developed IA, which manifested as fungal pneumonia associated with an intrabronchial polypoid mass.

Comparison of CT features of Aspergillus and bacterial pneumonia in severely neutropenic patients

PURPOSE

To establish whether a relationship exists between computed tomography features of lung opacities in severely neutropenic patients and their Aspergillus or bacterial etiology.

METHODS

Computed tomography scans of 124 patients with lung opacities larger than 5 mm occurring during severe (neutrophils <500/mm) and prolonged (>7 d) neutropenia-induced by bone marrow transplantation and/or high-dose chemotherapy for hematologic malignancies-were reviewed. Invasive pulmonary aspergillosis or bacterial pneumonia were assessed by means of bronchoalveolar lavage, bronchial washing, trans-bronchial biopsy or (for bacteria only) blood cultures. Pulmonary opacities were classified as nodules or as consolidations. The presence of a perinodular ground-glass halo, the similarity of consolidations to a pulmonary infarction and the presence of cavitation (crescent-shaped or not) were recorded.

RESULTS

Invasive pulmonary aspergillosis was diagnosed in 68 patients; bacterial pneumonia in 56. Nodules (85) were more common than consolidations (39); their distribution among the patients with aspergillosis (52 nodules and 16 consolidations) and those with bacterial pneumonia (33 nodules and 23 consolidations) was even. Out of the 19 nodules surrounded by a halo 17 were due to aspergillosis. Nine consolidations (3 due to aspergillosis) were infarctionlike shaped. Cavitation appeared during 22/68 aspergillosis and 31/56 bacterial pneumonias; an air-crescent in 6 patients with aspergillosis and in 24 with bacterial pneumonia.

CONCLUSIONS

Although rare enough, the perinodular halo is highly specific for invasive aspergillosis. The nodular pattern of lung opacities, their similarity to a pulmonary infarction, the occurrence of cavitation and the air-crescent are not related to aspergillosis.

Treatment of invasive pulmonary aspergillosis in neutropenic patients by additional bronchoscopic amphotericin B instillation

BACKGROUND

Invasive pulmonary aspergillosis (IPA) remains a life-threatening condition despite systemic antifungal therapy.

OBJECTIVES

This retrospective analysis investigated whether additional bronchoscopic instillation of amphotericin B (amB) would improve efficacy of antifungal treatment in patients with haematological malignancies suffering from IPA.

METHODS

Twenty patients (40.6 +/- 14.2 years, 14 male) with preceding chemotherapy, bone marrow or stem cell transplantation complicated by severe IPA who did not respond sufficiently to systemic antifungal therapy were additionally treated by repeated bronchoscopic instillations of amB solution (91 instillations, on average 4.6 +/- 2.2 instillations per patient over a period of 24.1 +/- 21.0 days). Therapeutic response to this combined treatment regimen was monitored by chest X-ray and CT scan.

RESULTS

The mean infiltration sizes during systemic antifungal therapy alone (mean duration 11.9 +/- 9.9 days) did not change significantly. However, after additional bronchoscopic instillation of amB solution infiltration sizes were reduced significantly (p < 0.05). A total resolution of infiltrates was seen in 3 and a partial reduction in 13 of 20 patients. Mean duration of total antifungal treatment was 50.1 +/- 24.0 days. The mean follow-up period was 34.1 +/- 31.2 months. The IPA-related mortality rate was 18.8% (3 of 16 patients).

CONCLUSIONS

Additional bronchoscopic instillation of amB may improve the efficacy of systemic antifungal therapy in patients with haematological malignancies complicated by severe IPA. Bronchoscopic instillation of amB should be considered as an additional treatment option in cases with IPA unresponsive to systemic therapy.

Radiología de las infecciones fúngicas invasoras del aparato respiratorio

Invasive fungal infections of the respiratory tract are a major cause of serious morbidity and mortality especially in immunocompromised patients due to neutropenia, corticosteroids, or hematologic malignancy. The role of imaging is very important in the management of patients with fungal infections and chest x-ray is still the most used exploration. Nevertheless, new approaches recommend the systematic use of computed tomography scan for early documentation of invasive fungal infection. Combination of clinical setting with recognition of radiological pattern is the best approach to pulmonary fungal diseases. The following is a review of the imaging features of different invasive fungal infections we can face in our daily practice.

Bronchoscopic diagnosis of pulmonary infiltrates in granulocytopenic patients with hematologic malignancies: BAL versus PSB and PBAL

BACKGROUND

Treatment of patients with hematologic malignancies is often complicated by severe respiratory infections. Bronchoscopy is generally to be used as a diagnostic tool in order to find a causative pathogen.

OBJECTIVES

In a prospective study the combination of protected specimen brush (PSB) and protected bronchoalveolar lavage (PBAL) was compared with bronchoalveolar lavage (BAL) for evaluated feasibility and diagnostic yield in granulocytopenic patients with hematologic malignancies and pulmonary infiltrates.

METHODS

All specimens from 63 bronchoscopic procedures (35 BAL and 28 PSB-PBAL) were investigated by cytological examination and various microbiological tests. If clinically relevant and feasible, based on the clinical condition and/or the presence of thrombocytopenia, lung tissue samples were obtained.

RESULTS

The majority of the 58 included patients were diagnosed as having acute myeloid leukaemia and developed a severe neutropenia (BAL-group: 27 days; PSB-PBAL group: 30 days). Microbiological and cytological examination of 63 bronchoscopic procedures (35 BAL and 28 PSB-PBAL) yielded causative pathogens in 9 (26%) patients of the BAL-group and 8 (29%) patients of the PSB-PBAL group (PSB and PBAL 4 each). Aspergillus fumigatus was the pathogen most frequently (13%) detected. Using all available examinations including the results of autopsy, a presumptive diagnosis was established in 43% of the patients in the BAL group and 57% of those in the PSB-PBAL group; in these cases microbial aetiology was correctly identified in 67% and 57%, respectively. The complication rate was of these procedures were low, and none of the patients experienced serious complications due to the invasive techniques.

CONCLUSIONS

Our results showed that modern bronchoscopic techniques such as PSB and PBAL did not yield better diagnostic results compared to BAL in granulocytopenic patients with hematologic malignancies and pulmonary infiltrates. In approximately half of the cases a presumptive diagnosis was made by bronchoscopic procedures.

Long-term CT follow-up in 40 non-HIV immunocompromised patients with invasive pulmonary aspergillosis: kinetics of CT morphology and correlation with clinical findings and outcome

OBJECTIVE

The aim of this study was to assess CT signs of invasive pulmonary aspergillosis (IPA) and their long-term kinetics in correlation with clinical findings and outcome.

MATERIALS AND METHODS

Three hundred ten serial CT scans (mean, 7.7) in 40 consecutive patients were reviewed retrospectively over a median follow-up of 112 days (range, 5-841 days). Along with underlying disease, hematopoietic stem cell transplantation, neutropenia, graft-versus-host disease or antifungal treatment, signs of IPA, and number or size of lesions were evaluated regarding outcome and radiologic dynamics.

RESULTS

On the day of IPA diagnosis, median lesion number and size were 3 or 3.1 cm(2), respectively. Irrespective of antifungal therapy, 90% of patients showed an increase in lesion size and number until day 9 (median and mean). Lesion size subsequently showed a median plateau phase of 3.5 days (mean, 7), during which median lesion numbers dropped by 17%. Consequently, 42.5% of patients showed a complete radiologic remission within a median 80 days. Of all parameters, formation of cavitation most strongly predicted time until radiologic remission, which was 2.5 times as long in patients with cavitary lesions. Likewise, cavitations were strong precursors of beneficial outcome (odds ratio, 8.4; confidence interval [CI], 1.07-176).

CONCLUSION

The kinetics of radiologic signs of IPA adheres to a distinctive pattern with initial rise in number and size, followed by a plateau phase of size and gradual reduction. Both time until complete radiologic remission and outcome are independent of initial or maximum lesion size and number yet strongly influenced by cavitation.

Laboratory diagnosis of invasive aspergillosis

Invasive aspergillosis occurs in a wide range of clinical scenarios, is protean in its manifestations, and is still associated with an unacceptably high mortality rate. Early diagnosis is critical to a favourable outcome, but is difficult to achieve with current methods. Deep tissue diagnostic specimens are often difficult to obtain from critically ill patients. Newer antifungal agents exhibit differential mould activity, thus increasing the importance of establishing a specific diagnosis of invasive aspergillosis. For these reasons, a range of alternate diagnostic strategies have been investigated. Most investigative efforts have focused on molecular and serological diagnostic techniques. The detection of metabolites produced by Aspergillus spp and a range of aspergillus-specific antibodies represent additional, but relatively underused, diagnostic avenues. The detection of galactomannan has been incorporated into diagnostic criteria for invasive aspergillosis, reflecting an increased understanding of the performance, utility, and limitations of this technique. Measurement of (1,3)-beta-D glucan in blood may be useful as a preliminary screening tool for invasive aspergillosis, despite the fact that this antigen can be detected in a number of other fungi. There have been extensive efforts directed toward the detection of Aspergillus spp DNA, but a lack of technical standardisation and relatively poor understanding of DNA release and kinetics continues to hamper the broad applicability of this technique. This review considers the application, utility, and limitations of the currently available and investigational diagnostic modalities for invasive aspergillosis.

Initial CT manifestations of invasive pulmonary aspergillosis in 45 non-HIV immunocompromised patients: association with patient outcome?

PURPOSE

To assess early high-resolution computer tomographic (CT) signs of invasive pulmonary aspergillosis (IPA) in non-HIV immunosuppressed patients and their potential association with patient's outcome, including frequency and severity of pulmonary hemorrhage, taking also in consideration the impact of other known risk factors contributory to IPA.

MATERIAL AND METHODS

A retrospective review of serial CT scans was performed in 45 immunocompromised patients with a total of 46 episodes of invasive pulmonary aspergillosis. All patients underwent CT beginning with the day they showed clinical or laboratory signs of infection. Serial follow-up CT included more than two, up to 12 CT examinations. Patient's outcome was judged by clinical and radiological follow-up and classified as survival, death by IPA, or death unrelated to IPA. The influence of patient's age, underlying disease, hematopoietic stem cell transplantation, neutropenia, graft versus host disease, and antifungal therapy onset was also statistically considered.

RESULTS

Three main CT findings were identified: small nodules (<1cm) 43% (20/46), large nodules 21% (10/46) and consolidations, either in patchy+/-segmental 26% (12/46), or peribronchial distribution+/-tree in bud 9% (4/46). In 11 patients (24%) we found a combination of two or more of these signs: 9 (19%) patients presented concurrent small nodules accompanied by reticulation, tree in bud or peribronchial infiltrates, while 2 (4%) patients showed large pulmonary nodules accompanied by large consolidations. An accompanying "halo" sign was observed in 38 patients (82%). Crescent sign followed by cavitation was encountered in 29 patients (63%). Two patients succumbed to massive pulmonary bleeding caused by IPA. Twenty-one patients (15/46) deceased in this series, 12 of them succumbed to IPA, 1 died from cerebral invasive aspergillosis, while in 9 patients the cause of death was not primarily IPA. Manifest pulmonary hemorrhage occurred in 19% (9/46) of IPA episodes.

CONCLUSION

Initial CT findings of invasive pulmonary aspergillosis consist mainly of small nodules or patchy consolidations, showing in 82% of cases an early halo sign. Serious pulmonary hemorrhage was an infrequent clinical complication in our series, with an attributable mortality of 4.3%. IPA-related lethality was 26%, in our cohort. None of the early HRCT signs seemed to predict outcome.

Oxidative and amphotericin B-mediated cell death in the opportunistic pathogen Aspergillus fumigatus is associated with an apoptotic-like phenotype

When protoplasts of the opportunistic fungal pathogen Aspergillus fumigatus were treated with low but toxic levels of hydrogen peroxide (0.1 mM) or amphotericin B (0.5 microg ml(-1)), loss of cell viability and death were associated with a number of phenotypic changes characteristic of apoptosis. The percentage of protoplasts staining positive with annexin V-FITC, an indicator of the externalization of phosphatidylserine and an early marker of apoptosis, rose to approximately 55 % within 1 h. This was followed by a similar increase in apoptotic DNA fragmentation detected by the TUNEL assay, and led to a loss of cell permeability and death in approximately 90 % of protoplasts, as indicated by the uptake of propidium iodide. The development of an apoptotic phenotype was blocked when protoplasts were pre-treated with the protein synthesis inhibitor cycloheximide, indicating active participation of the cell in the process. However, no significant activity against synthetic caspase substrates was detected, and the inclusion of the cell-permeant broad-spectrum caspase inhibitor Z-VAD-fmk did not block the development of the apoptotic-like phenotype. Higher concentrations of H(2)O(2) (1.8 mM) and amphotericin B (1 microg ml(-1)) caused protoplasts to die without inducing an apoptotic phenotype. As predicted, the fungistatic antifungal agent itraconazole, which inhibits growth without causing immediate cell death, did not induce an apoptotic-like phenotype.

Invasive aspergillosis in critically ill patients without malignancy

Using criteria designed for invasive aspergillosis (IA) in patients with cancer, we aimed to determine the impact of IA in patients without malignancy in a medical intensive care unit (ICU). In this retrospective study, 127 patients out of 1,850 admissions (6.9%) hospitalized between 2000 and 2003 had microbiological or histopathologic evidence of Aspergillus during their ICU stay. There were 89 cases (70%) without hematologic malignancy. These patients were classified as proven IA (n = 30), probable IA (n = 37), possible IA (n = 2), or colonization (n = 20). In these patients, mean SAPS II score was 52 with a predicted mortality of 48%. The observed mortality was 80% (n = 71). Mortality of the proven and the probable IA was 97 and 87%, respectively. Postmortem examination was done in 46 out of 71 patients, and 27 autopsies (59%) showed hyphael invasion with Aspergillus. Aspergillus infections occurred in five critically ill patients with proven IA who did not have any predisposing factors according to the currently available definitions. Three of these patients had Child C liver cirrhosis. IA is an emerging and devastating infectious disease in patients in the ICU without malignancy. In those patients, host criteria for probable fungal infections should probably be adapted.

Pulmonary nodules in lung transplant recipients: etiology and outcome

BACKGROUND

The pulmonary nodule (PN) poses a diagnostic and therapeutic challenge in the immunocompromised host. Common causes of PNs in lung transplant (LT) recipients include bacterial or fungal infections and posttransplant lymphoproliferative disorder (PTLD). However, experience in diagnosis and management of PNs is limited.

METHODS

Two hundred thirty-four LTs were performed between February 1990 and December 2000. Medical records of all patients with PNs were reviewed retrospectively. Data on presentation, radiographic features, diagnostic methods, therapy, and outcome were collected and analyzed.

RESULTS

Twenty-three patients had PNs after a follow-up of 20.1 +/- 20.1 months (mean +/- SD). The mean age was 45.5 +/- 14.4 years, with a male:female ratio of 17:6. Thirteen patients received single LT, 9 patients received bilateral LT, and 1 patient received heart-LT. Cough and dyspnea were the most common symptoms at presentation, and PNs were better detected by CT than chest radiography. Solitary PNs were due to bronchogenic carcinoma and PTLD, while multiple PNs were due to invasive pulmonary aspergillosis (IPA), cytomegalovirus pneumonitis, bronchiolitis obliterans, and metastatic carcinoma. Bronchoscopy with BAL and transbronchial lung biopsy was the usual method of diagnosis (n = 17, 74%), and our mortality rate was 70%.

CONCLUSION

PNs are not uncommon in patients following LT. The majority were due to IPA and PTLD. Prophylaxis with itraconazole against Aspergillus, and acyclovir for Epstein-Barr virus-negative LT recipients, serial CT and surveillance bronchoscopy for early detection of Aspergillus infections, and rituximab therapy for PTLD could improve the outcome of these patients.

Aspergillus in the lung: diverse and coincident forms

Pulmonary disease caused by the fungus Aspergillus has traditionally been regarded as belonging to one of the following, apparently distinct, entities: saprophytic aspergilloma; allergic bronchopulmonary aspergillosis (ABPA); and invasive aspergillosis (IPA); which may be further categorised as angioinvasive, acute or chronic airway invasive) [1]. It is not always obvious that there is overlap between these entities, and that in any given patient more than one Aspergillus-related pathological process can co-exist [2]. The aim of this article is to review the clinical and imaging features of the main categories of Aspergillus-related pulmonary disease and, in particular, to highlight the overlap between them.

Clinical utility of bronchoalveolar lavage in pediatric cancer patients

BACKGROUND

Pulmonary disease in the pediatric cancer patient continues to pose a difficult clinical dilemma. Bronchoalveolar lavage (BAL) is commonly utilized for the diagnosis of pulmonary complications in the immunocompromised child.

PROCEDURE

We retrospectively reviewed 53 BAL procedures performed in pediatric cancer patients with pulmonary disease between 1988 and 1998 to determine the diagnostic and clinical utility of BAL. Patients who had undergone prior myeloablative therapy were excluded from analysis.

RESULTS

The majority of patients (83%) had an underlying diagnosis of acute leukemia or lymphoma. BAL yielded a specific diagnosis in 16 patients (30%), including 15 infections and 1 malignant infiltration. Medical management was altered in an additional 14 patients (26%) as a consequence of a negative BAL result. Severe but transient complications associated with the BAL procedure occurred in four patients (8%). Minor complications following the BAL occurred in 21 patients (40%) and included transiently increased oxygen requirement and anesthesia-related gastrointestinal complaints. The mortality from lung disease in this patient population was 7.5%.

CONCLUSIONS

Both positive and negative BAL results contribute to the management of pediatric cancer patients with pulmonary disease. The low incidence of significant complications associated with BAL and the high mortality rate in this patient population support the choice of BAL as an initial diagnostic test in pediatric cancer patients with pulmonary disease.

Acute lung disease in the immunocompromised host

The immunocompromised host is an individual with a decreased defense mechanism or immunity. Pulmonary complications commonly seen in these patients include infections, neoplasms, drug-induced lung disease, and pulmonary hemorrhage. High-resolution CT plays an invaluable role in confirming the presence of pulmonary disease and narrowing down the differential diagnosis in this group of patients. It also is helpful as a guide to the optimal type and site of biopsy. The pattern and prevalence of disease varies considerably between the AIDS and the non-AIDS group, and therefore, these two groups are considered separately.

Detection of Aspergillus species in blood and bronchoalveolar lavage samples from immunocompromised patients by means of 2-step polymerase chain reaction: clinical results

Bronchoalveolar lavage (BAL) samples from 67 patients who were at high risk for invasive aspergillosis were examined using a recently developed 2-step polymerase chain reaction (PCR) that detects </=10 fg of Aspergillus DNA in blood and BAL samples in vitro. Thirteen of these patients had PCR and diagnostic results positive for Aspergillus infection. Four patients with possible invasive aspergillosis also had positive PCR results, and the remaining 50 had negative PCR results. In addition, 907 blood samples from 218 high-risk patients were screened. Thirty-three patients with positive PCR results had invasive aspergillosis; 148 patients had PCR and diagnostic results that were negative, and 34 patients with positive PCR results had nonconclusive clinical data. Both blood and BAL testing were performed for 45 patients. All 8 patients with proven invasive aspergillosis showed concordance of positive PCR results. Our data suggest that this PCR method has possible clinical value for confirming and improving the diagnosis of invasive aspergillosis in high-risk patients.

Spectrum of pulmonary aspergillosis: histologic, clinical, and radiologic findings

Aspergillosis is a serious pathologic condition caused by Aspergillus organisms and is frequently seen in immunocompromised patients. At computed tomography (CT), saprophytic aspergillosis (aspergilloma) is characterized by a mass with soft-tissue attenuation within a lung cavity. The mass is typically separated from the cavity wall by an airspace ("air crescent" sign) and is often associated with thickening of the wall and adjacent pleura. CT findings in allergic bronchopulmonary aspergillosis consist primarily of mucoid impaction and bronchiectasis involving predominantly the segmental and subsegmental bronchi of the upper lobes. Aspergillus necrotizing bronchitis may manifest as an endobronchial mass, obstructive pneumonitis or collapse, or a hilar mass. Bronchiolitis is characterized by centrilobular nodules and branching linear or nodular areas of increased attenuation ("tree-in-bud" pattern). Obstructing bronchopulmonary aspergillosis mimics allergic bronchopulmonary aspergillosis at CT and manifests as bilateral bronchial and bronchiolar dilatation, large mucoid impactions, and diffuse lower lobe consolidation caused by postobstructive atelectasis. Characteristic CT findings in angioinvasive aspergillosis consist of nodules surrounded by a halo of ground-glass attenuation ("halo sign") or pleura-based, wedge-shaped areas of consolidation. Although imaging findings in pulmonary aspergillosis may be nonspecific, in the appropriate clinical setting, familiarity with the CT findings may suggest or even help establish the diagnosis.

Evaluation of pulmonary infiltrates in critically ill patients with cancer and marrow transplant

Pulmonary infiltrates in critically ill patients with cancer or marrow transplant can be evaluated by the differential diagnosis presented at the beginning of this article. The patient's quantitative immune system dysfunction, epidemiologic history and chest radiographic findings (pattern, rapidity, and time of onset) will help focus the differential diagnosis. In this patient population, however, common diagnoses can have atypical presentations, unusual diagnoses do occur, and more than one process may be responsible for a patient's infiltrates. Early bronchoscopy to rule out infection is the focus of diagnostic testing. Surgical lung biopsy in this patient population has a low yield.

Fungal infections in patients undergoing blood and marrow transplantation

Fungal infections are currently a leading cause of infectious morbidity and mortality in patients undergoing allogeneic blood and marrow transplantation (BMT). Although the introduction of azole antifungals for prophylaxis has had a significant impact on the incidence of candidal infections (especially those caused by C. albicans and C. tropicalis), invasive aspergillosis has increased in incidence in many centers worldwide. Given the long risk period corresponding with graft-versus-host disease, and the toxicities of currently available mold-active antifungals, the development of a prevention strategy for these angioinvasive molds remains a challenge. The introduction of new antifungal drugs and adjunctive therapy to improve immune function may be beneficial in decreasing mortality associated with these infections in the future. Most importantly, a greater understanding of the pathogenesis of fungal disease and specific host risks is necessary to impact this increasingly important infection in immunocompromised hosts.

The utility of CT in imaging chest infections in HIV-negative patients

This article focuses on the recent developments in CT imaging of chest infections in patients who are immunocompetent or immunosuppressed, but not infected with HIV. Although simple viral and bacterial infections predominate, more "exotic" infections are now being encountered. First, a re-emergence of mycobacterial disease has occurred. Second, a growing population of transplant recipients (i.e., lung, solid organ, and bone marrow) is susceptible to a wide range of pathogens. These trends are reflected in the forthcoming discussion. In particular, several important articles on immunosuppressed (HIV-negative) patients and on imaging fungal disease have been written within the past year.

Respiratory infections in immunocompromised patients

HIV disease has been dramatically reduced in the developed world by the introduction of highly active antiretroviral therapy, with implications that prophylactic therapy against opportunistic infections may be stopped; however, tuberculosis is an escalating problem in the HIV-infected and HIV-noninfected populations worldwide. Compliance with effective treatment regimens, especially through directly observed therapy, remains the cornerstone of tuberculosis control strategies. Although tuberculosis prophylaxis is of benefit for tuberculin skin reactors with HIV in the developed world, several reservations are voiced about this approach in resource-poor settings. Recent advances in technology, particularly in antigen-specific systems, have revolutionized the understanding of HIV immunology and helped to elucidate the mechanisms of pathogenesis in diseases such as cytomegalovirus. In bone marrow transplantation and solid-organ transplantation patients, quantitative polymerase chain reaction (PCR) to predict cytomegalovirus disease is an important advance, and patients who undergo bone marrow transplantation, CT scanning has proven useful in the diagnosis of pulmonary aspergillosis.

Aspergillus fumigatus and aspergillosis

Aspergillus fumigatus is one of the most ubiquitous of the airborne saprophytic fungi. Humans and animals constantly inhale numerous conidia of this fungus. The conidia are normally eliminated in the immunocompetent host by innate immune mechanisms, and aspergilloma and allergic bronchopulmonary aspergillosis, uncommon clinical syndromes, are the only infections observed in such hosts. Thus, A. fumigatus was considered for years to be a weak pathogen. With increases in the number of immunosuppressed patients, however, there has been a dramatic increase in severe and usually fatal invasive aspergillosis, now the most common mold infection worldwide. In this review, the focus is on the biology of A. fumigatus and the diseases it causes. Included are discussions of (i) genomic and molecular characterization of the organism, (ii) clinical and laboratory methods available for the diagnosis of aspergillosis in immunocompetent and immunocompromised hosts, (iii) identification of host and fungal factors that play a role in the establishment of the fungus in vivo, and (iv) problems associated with antifungal therapy.