Aspergillus antigen detection in the diagnosis of invasive aspergillosis

Opportunistic infection in the patients with acute liver failure: a report of three cases with one fatality

We report three cases of severe opportunistic infection in patients with acute liver failure (ALF). These cases included a 56-year-old man infected with Cryptococcus neoformans, cytomegarovirus (CMV), Candida albicans and Aspergillus fumigates, as well as a 62-year-old man and a 54-year-old woman infected with pneumocystis pneumonia, CMV and Aspergillus fumigatus. One patient died as a result of the infection rather than liver failure. We stress the importance of opportunistic infection as a consideration in the use of immunosuppressive agents for the treatment of ALF.

Aspergillus fumigatus endocarditis in a pediatric liver transplant recipient: favorable outcome without cardiac surgery

Transplant recipients are very susceptible to invasive aspergillosis, which increases mortality rate. Disseminated aspergillosis in the liver transplant recipient can affect virtually any organ and endocarditis is often lethal despite cardiac surgery and antifungal therapy. We report the case of a eight-month-old girl who presented with Aspergillus fumigatus endocarditis 18 days after liver transplantation that was successfully treated by a combination of antifungal drugs associated to a low dosage of immunosuppressive therapy.

Endobronchial Fungal Disease: An Under-Recognized Entity

Most fungi enter the human body via inhalation; however, endobronchial fungal infection (EBFI) seems to be a rare manifestation compared to pulmonary or systemic disease. This presentation seems to be related to environmental factors as well as to the host status. With the increasing popularity of flexible bronchoscopy, it is being recognized with a higher frequency. Bronchoscopic findings in EBFI vary from mild mucosal inflammation to central airway obstruction. We searched English literature related to the topic and found 228 total cases of EBFI: Aspergillus species (121), Coccidioides immitis (38), Zygomycetes (31), Candida species (14) Cryptococcus neoformans (13), and Histoplasma capsulatum (11). We have also included a single case of endobronchial Pseudallescheria boydii infection in a lung transplant recipient that has not been reported previously. Most patients were immunocompromised, exhibited systemic manifestations of the primary infection, and responded to appropriate therapy. EBFI should be included in the differential diagnosis of any form of airway lesions in immunocompromised patients, especially among residents from the endemic areas.

Fungal infections of the spine

Fungal infections of the spine are relatively uncommon. Fungi such as Coccidioides immitis and Blastomyces dermatitidis are limited to specific geographical areas whereas cryptococcus, candida, and aspergillus are found worldwide. Candida and aspergillus are normal commensals of the body and produce disease in susceptible organisms when they gain access to the vascular system through intravenous lines, during implantation of prosthetic devices, or during surgery. For the other fungi, spinal involvement usually is the result of hematogenous or direct spread of organisms from an initial pulmonary source of infection. Involvement of the vertebral bodies can lead to vertebral compression fractures and gross deformity of the spine. Spread of infection along the anterior longitudinal ligament can lead to psoas or paravertebral abscesses. Early recognition of the disease requires a high index of suspicion, proper travel history, and a detailed physical examination. Treatment relies on the prompt institution of appropriate pharmacotherapy and constant monitoring of clinical progress. Resistance to medical therapy, spinal instability, and neurologic deficits are indications for débridement and stabilization with spinal fusion. Prognosis depends on the premorbid state of the patient, the type of fungal organism, and the timing of treatment.

LEVEL OF EVIDENCE

Level V (expert opinion). Please see the Guidelines for Authors for a complete description of levels of evidence.

The future of animal models of invasive aspergillosis

The diagnosis of invasive aspergillosis remains very difficult, coupled with limited treatment options. Animal models have been utilized to evaluate both the diagnosis and treatment of infection and to assess the pathogenicity and virulence of the organism. However, animal models have not been standardized and have been used in only a limited fashion for genomic evaluation in this disease. Extensive efforts are underway to expand significantly the Aspergillus genomic information. Thus, the standardization of animal models of invasive aspergillosis is critical to create a unified platform to enhance evaluation of newer genomic information and allow assessment of pathogenicity and virulence factors. Proposed models, supported by a recently awarded National Institutes of Health/National Institute of Allergy and Infectious Diseases contract, will be developed in close interaction with the extended Aspergillus community (including academia and industry) to answer key questions in this disease. The goal of this work is to provide the framework to evaluate genomic targets in animal models in order to improve the diagnosis and treatment of invasive aspergillosis that will ultimately result in improved outcomes of patients with this frequently fatal infection.

Choices aplenty: antifungal prophylaxis in hematopoietic stem cell transplant recipients

The incidence of invasive fungal infection (IFIs) in hematopoietic stem cell transplantation (HSCT) recipients ranges from 10 to 25% with an overall case fatality rate of up to 70-90%. Candida and Aspergillus genera remain the two most common pathogens. Although fluconazole prophylaxis in this population has been moderately effective in reducing mortality due to invasive candidiasis, this agent does not have activity against invasive aspergillosis (IA) and other mould. Several new agents such as voriconazole and caspofungin have enhanced potency and broad-spectrum antifungal activity and show promising results against yeasts and filamentous fungi when given as therapy and as chemoprophylaxis. Further, new diagnostic tools to detect circulating fungal antigens in biological fluids and PCR-based methods to detect species or genus-specific DNA or RNA have been developed. Incorporating these techniques along with clinical criteria appear to improve the accuracy of preclinical diagnosis of IFIs. Such approaches may alter the current treatment strategy from prophylaxis to pre-emptive therapy, thereby potentially decreasing cost and toxicity in high-risk patients.

Risk factors for invasive aspergillosis in liver transplant recipients

Aspergillosis is a potential, severe, and usually early complication of liver transplantation. New promising strategies, such as detecting Aspergillus antigenemia, have been used for the diagnosis of aspergillosis in immunosuppressed patients, but the impact in solid organ transplantation is not well known. A case-control study in 260 adults who underwent liver transplantation from January 1994 to June 2000 was performed. A case was defined as any liver transplant recipient with a proven or probable diagnosis of invasive aspergillosis. Controls were defined as a liver transplant recipient without aspergillosis infection with a survival longer than two months after transplantation. Clinical and analytical variables, including Aspergillus antigenemia, were compared. A special analysis was performed in patients in whom late aspergillosis developed (after day 100 posttransplantation). Among 260 patients, invasive aspergillosis developed in 15 (5.6%). Median time from transplantation to aspergillosis in 13 patients with sufficient data for analysis was 126 days (range, 22 to 1117). Seven (54%) developed the infection after day 100 posttransplantation. Thirty-eight patients were used as controls. Antigenemia was available in nine of 13 cases and in 33 of 38 controls. By multivariate analysis, retransplantation (OR, 29.9 [95% CI, 2.1 to 425.1]), dialysis requirements after transplantation (OR, 24.5 [95% CI, 1.25 to 354]), and the presence of Aspergillus antigenemia in serum at any time point after transplantation (OR, 50.0 [95% CI, 3.56 to 650]) were independently associated to aspergillosis. In the subgroup of patients that developed late aspergillosis, cytomegalovirus infection (OR, 6.7 [95% CI, 1.0 to 42.5]) was the only independent factor associated. Hepatic and renal dysfunction predispose to Aspergillus infection in liver transplant recipients. Cytomegalovirus infection and increased immunosuppression favor invasive aspergillosis during the late posttransplantation period. Aspergillus antigenemia seems to be a good predictor of invasive aspergillosis.

Follow-up of anti-Aspergillus IgG and IgA antibodies in bone marrow transplanted patients with invasive aspergillosis

A total of 89 patients at risk for, or with invasive aspergillosis (IA) were recruited from bone marrow transplantation (BMT) units in two Lisbon hospitals, and followed for 2(1/2) years to monitor their immune response. Of these patients, six developed probable IA, from which five died. The presence of serum IgG or IgA antibodies against seven Aspergillus recombinant antigens was assessed in patients with IA, using an enzyme-linked immunosorbent assay (ELISA). In parallel, the serum levels of galactomannan (GM) were also monitored, using the Platelia Aspergillus kit (Sanofi Pasteur, Marnes-la-Coquette, France). Superoxide dismutase (Sod) and 94 kDa were the most immunogenic antigens for IgA, while the IgG pattern of recognition changed from patient to patient. From our results we conclude that although follow-up of antibodies against these antigens should not be used as a diagnostic method, patients with IA do produce an immune response that may influence disease outcome.

Critical assessment of issues in the diagnosis of invasive aspergillosis

Invasive aspergillosis remains a devastating disease, which is partly because of the inability to identify infected patients at an early stage of the disease. Recently, new diagnostic tests and procedures have been developed to help in identifying high-risk patients. High-resolution computed tomography has been shown to be a potent tool for detecting pulmonary abnormalities in neutropenic patients. Assays for the detection of circulating markers such as fungal antigens or Aspergillus DNA have been developed and show that markers can be detected in the blood at an early stage of infection. Also, the markers correlate with the fungal burden in the tissue, which allows monitoring of response to antifungal therapy. The tests and procedures that are now available need to be incorporated into management strategies for at-risk patients and evaluated in clinical trials. Although we now have markers that allow the early detection of fungal products, many questions remain unanswered with respect to the kinetics of the markers in different patient groups, the optimal management strategy and the effect of prophylaxis and treatment on the markers. Nevertheless, the implementation of new approaches for the management of invasive aspergillosis offers opportunities to improve outcome of patients.

Galactomannan enzyme immunoassay for monitoring systemic infection with Aspergillus fumigatus in mice

Intravenous (i.v.) infection of immunocompetent mice with Aspergillus fumigatus was used to investigate the ability of a commercial galactomannan enzyme-linked immunosorbent assay (ELISA) to monitor the course of organ infection after dissemination. The test detected 100% of the fungemias which occurred for up to 5 days after infection. When blood-cultures became negative but there was a high load of fungi in the parenchymal organs and a positive culture from the brain, the ELISA was again positive in all animals. However, when blood cultures as well as brain cultures were negative and lower amounts of fungi demarcated by immune cells were present in the liver and kidneys which was the case between day 5 and 30 of infection, the test was negative in most of the animals. Therefore, the test was excellent for detection of early i.v. infection with Aspergillus fumigatus but not suited for detection of limited organ infection in immunocompetent mice.

Invasive pulmonary aspergillosis in neutropenic patients during hospital construction: before and after chemoprophylaxis and institution of HEPA filters

Between September 1993 and December 1993, during extensive hospital construction and indoor renovation, a nosocomial outbreak of invasive pulmonary aspergillosis occurred in acute leukemia patients treated in a regular ward that has only natural ventilation. The observed infection rate was 50%. Chemoprophylaxis with intravenous continuous low-dose amphotericin B was then instituted as a preventive measure. During the next 18 months invasive pulmonary aspergillosis developed in 43% of acute leukemia patients. After that period a new hematology ward was opened with an air filtration system through high-efficiency particulate air filtration (HEPA) filters, and a bone marrow transplantation program was started on the hematology service. During the following three years, none of the acute leukemia or bone marrow transplantation patients who were hospitalized exclusively in the hematology ward developed invasive pulmonary aspergillosis, although 29% of acute leukemia patients who were housed in a regular ward, because of shortage of space in the new facility, still contracted invasive pulmonary aspergillosis. Overall, 31 patients were diagnosed with invasive pulmonary aspergillosis during almost five years: 74% of patients recovered from invasive pulmonary aspergillosis, and 42% are long-term survivors; 26% of patients died of resistant leukemia with aspergillosis, but no one died of invasive pulmonary aspergillosis alone. In conclusion, during an on-going construction period, an extremely high incidence rate of invasive pulmonary aspergillosis in acute leukemia patients undergoing intensive chemotherapy was observed. Institution of low-dose intravenous amphotericin B prophylaxis marginally reduced the incidence rate of invasive pulmonary aspergillosis. Keeping patients in a special ward with air filtration through a HEPA system eliminated invasive pulmonary aspergillosis completely. Among patients who developed invasive pulmonary aspergillosis, early diagnosis and treatment are probably the explanation for the favorable outcome.

Aspergillus antigenemia sandwich-enzyme immunoassay test as a serodiagnostic method for invasive aspergillosis in liver transplant recipients

BACKGROUND

Invasive aspergillosis (IA) is an important cause of mortality in liver transplant patients. Clinical and microbiological diagnosis is difficult, and it is frequently achieved only after autopsy. Early diagnosis and antifungal therapy could improve the survival of these patients.

METHODS

A retrospective case-control study of IA in liver transplant recipients (OLT) was performed to determine the value of the detection of galactomannan Aspergillus antigen in serum using a sandwich-ELISA test (Platelia, Sanofi Diagnostic Pasteur). Stored frozen serum specimens obtained during the posttransplantation period were used.

RESULTS

Fourteen cases of IA were diagnosed in 240 OLT recipients (IA incidence: 5.8%) during 5 years with 13 deaths (mortality: 93%). Nine case patients and 33 control patients met the criteria required for being considered "valid" for antigenemia analysis. In five of the nine case patients, a serum sample was positive for Aspergillus antigenemia detection. The median value was 5.7 ng/ml (range: 1.6-6.6). Sensitivity of the test was 55.6%, specificity was 93.9%, the positive predictive value was 71.4%, and the negative predictive value was 88.6%. The likelihood ratio of a positive test was 9.2.

CONCLUSIONS

Galactomannan detection in serum could be useful for an early diagnosis of IA in OLT recipients.

Value of antigen detection using an enzyme immunoassay in the diagnosis and prediction of invasive aspergillosis in two adult and pediatric hematology units during a 4-year prospective study

BACKGROUND

Invasive aspergillosis (IA) is a well recognized, life-threatening infection in neutropenic patients and stem cell transplantation recipients. Early diagnosis is important to achieve the best outcome for these patients; however, definite proof often is difficult to obtain due to counterindicated invasive procedures.

METHODS

This study evaluated the specificity and sensitivity of the detection of galactomannan (GM) for the diagnostic and prediction of IA in 347 children from the Pediatric Hematology Service and 450 patients from the Bone Marrow Transplantation Unit at the Hôpital Saint-Louis in Paris. Serial screening of Aspergillus GM circulating antigen was evaluated using a double sandwich ELISA assay (Platelia Aspergillus) on 6209 sera. Among the patients studied, 53 presented with confirmed IA (n = 27 patients) or probable IA (n = 26 patients).

RESULTS

Antigen was detected on at least two sequential sera in 48 of 53 patients, with a sensitivity of 90.6%. GM antigenemia was detected before the onset of radiologic signs in 31 of 48 patients (64.6%), with a mean of -8.4 days, and before clinical symptoms in 18 of 48 patients (39.6%), with a mean of -6.9 days. In patients without IA, 44 of 744 had positive antigenemia, resulting in a specificity of 94%. False positive results could not be related to the presence of a concurrent mucositis.

CONCLUSIONS

This large, prospective study allowed the authors to define better the conditions for the use of GM immunocapture ELISA in surveying patients who are at high risk for IA. The presence of antigen has a good diagnostic value mainly when there is an increase in the titer on two consecutive sera samples. A repeated negative result is a strong argument against the diagnosis of IA; however, an awareness of the possibility of unexplained false negative results is important.

Invasive aspergillosis. Disease spectrum, treatment practices, and outcomes. I3 Aspergillus Study Group

A review of representative cases of invasive aspergillosis was conducted to describe current treatment practices and outcomes. Eighty-nine physicians experienced with aspergillosis completed case forms on 595 patients with proven or probable invasive aspergillosis diagnosed using modifications of the Mycoses Study Group criteria. Pulmonary disease was present in 56%, with disseminated infection in 19%. The major risk factors for aspergillosis were bone marrow transplantation (32%) and hematologic malignancy (29%), but patients had a variety of underlying conditions including solid organ transplants (9%), AIDS (8%), and pulmonary diseases (9%). Overall, high antifungal failure rates occurred (36%), and complete antifungal responses were noted in only 27%. Treatment practices revealed that amphotericin B alone (187 patients) was used in most severely immunosuppressed patients while itraconazole alone (58 patients) or sequential amphotericin B followed by itraconazole (93 patients) was used in patients who were less immunosuppressed than patients receiving amphotericin B alone. Response rate for patients receiving amphotericin B alone was poor, with complete responses noted in only 25% and death due to or with aspergillosis in 65%. In contrast, patients receiving itraconazole alone or following amphotericin B had death due to or with Aspergillus in 26% and 36%, respectively. These results confirm that mortality from invasive aspergillosis in severely immunosuppressed patients remains high even with standard amphotericin B. Improved responses were seen in the less immunosuppressed patients receiving sequential amphotericin B followed by itraconazole and those receiving itraconazole alone. New approaches and new therapies are needed to improve the outcome of invasive aspergillosis in high-risk patients.

Microbiological diagnosis of invasive fungal infections in transplant recipients

Invasive fungal infections remain an important cause of morbidity and mortality in transplant recipients. Since conventional diagnostic tools such as culture lack sensitivity and specificity, alternative diagnostic assays have been developed. Among the most promising techniques are the detection of fungal DNA and serology. Fungal DNA can be detected with high sensitivity and specificity when performed with specimens from sterile sites such as blood. Polymerase chain reaction (PCR) assays can be used to detect a broad range of fungal pathogens and combined with species identification. Multicenter diagnostic studies are needed to establish the diagnostic value of PCR but lack of standardization hampers such studies. The serodiagnosis of invasive fungal infections has become an important tool in the management of invasive fungal infections. Especially the detection of circulating galactomannan has been shown to be a sensitive marker for invasive aspergillosis. Both serology and PCR can be used to monitor the response to antifungal therapy. The optimal use of non-culture-based methods is in prospective screening of patients at high risk. Since the incidence of disease greatly influences the positive predictive value, screening should take place only in those patients at very high risk for invasive fungal disease.

Aspects of Pulmonary Infections After Solid Organ Transplantation

The increasing number of solid organ transplant (SOT) recipients have high rates of pulmonary infections due to bacterial, fungal, and viral pathogens. These patients have unique sets of factors predisposing to infection. Lung and heart-lung transplants are associated with particularly high infection rates. The prominence of cytomegalovirus (CMV) as a pathogen in all subsets of SOT patients has led to new strategies for prophylaxis, detection, and treatment of CMV pneumonitis. Progress is similarly being made in managing fungal and bacterial infections. Advances in liver, kidney, heart, and lung transplantation are being discussed, with further attention to specific pathogens (ie, CMV, Aspergillus, Pneumocystis carinii, and Mycobacterium tuberculosis).

Comparison of commercial latex agglutination and sandwich enzyme immunoassays with a competitive binding inhibition enzyme immunoassay for detection of antigenemia and antigenuria in a rabbit model of invasive aspergillosis

A commercial latex agglutination assay (LA) and a sandwich enzyme immunoassay (SEIA) (Sanofi Diagnostics Pasteur, Marnes-la-Coquette, France) were compared with a competitive binding inhibition assay (enzyme immunoassay [EIA]) to determine the potential uses and limitations of these antigen detection tests for the sensitive, specific, and rapid diagnosis of invasive aspergillosis (IA). Toward this end, well-characterized serum and urine specimens were obtained by using a rabbit model of IA. Serially collected serum or urine specimens were obtained daily from control rabbits or from rabbits immunosuppressed and infected systemically with Aspergillus fumigatus. By 4 days after infection, EIA, LA, and SEIA detected antigen in the sera of 93, 93, and 100% of A. fumigatus-infected rabbits, respectively, whereas antigen was detected in the urine of 93, 100, and 100% of the rabbits, respectively. False-positive results for non-A. fumigatus-infected rabbits for EIA, LA, and SEIA were as follows: for serum, 14, 11, and 23%, respectively; for urine, 14, 84, and 90%, respectively. Therefore, although the sensitivities of all three tests were similar, the specificity was generally greater for EIA than for LA or SEIA. Infection was also detected earlier by EIA, by which the serum of 53% of A. fumigatus-infected rabbits was positive as early as 1 day after infection, whereas the serum of only 27% of the rabbits tested by LA was positive. Although the serum of 92% of A. fumigatus-infected rabbits was positive by SEIA as early as 1 day after infection, the serum of a high percentage (50%) was false positive before infection. The urine of 21% of A. fumigatus-infected rabbits was positive by EIA as early as 1 day after infection, and the urine of none of the rabbits was false positive before infection. When EIA results for urine specimens were combined with those for serum, sensitivity was improved (i.e., 67% of rabbits were positive by 1 day after infection and only one rabbit gave a false-positive result). A total of 93% of A. fumigatus-infected rabbits were positive for antigen in urine as early as 1 day after infection and the urine of 100% of the rabbits was positive by SEIA. However, before infection, 79% of A. fumigatus-infected rabbits were false positive for antigen in urine by LA and 90% were false positive for antigen in urine by SEIA. These data indicate that the EIA has the potential to be used to diagnose IA with both serum and urine specimens and to detect a greater number of infections earlier with greater specificity than the specificities achieved with the commercial tests.

Aspergillosis in bone marrow transplant recipients

Invasive aspergillosis in bone marrow transplant recipient is associated with a high mortality. Diagnosis is often delayed because the inflammatory response is blunted by immunosuppression. The gold standard of tissue biopsy is often considered too in invasive as the procedure is often complicated by bleeding and secondary infection. Recent finding on non-invasive tests such as serial measurement of peripheral blood galactomannan antigen or DNA appears to be promising. However, the limited availability of such tests and requirement for expertise are still hampering their use in routine clinical management. More often than not, initiation of antifungal therapy is empirical and based on suggestive radiological changes. Amphotericin B remains the gold standard of therapy but liposconal preparation may prove to be less nephrotoxic and equally effective. Treatment outcome depends more on the acceleration of the recovery of the immune system and the reduction of anti-GVHD therapy than the antifungal agent followed by surgical resection. The efficacy of many reported anti-aspergillosis prophylactic regimen has not been proved in randomized control trials. Despite the absence of data, such policy should still be considered in transplant units with high incidence of aspergillus or undergoing renovation.

Aspergillus Fumigatus antigen detection in sera from patients at risk for invasive aspergillosis

We have developed an inhibition enzyme immunoassay (inhibition-EIA) to monitor for the occurrence of invasive aspergillosis (IA) in sera from 45 immunocompromised (IC) patients. The test uses rabbit polyclonal antibodies and a mixture of components from Aspergillus fumigatus, containing three predominant antigens with molecular weights of 18,000, 33,000, and 56,000. Circulating antigens were found in five of seven proven cases of IA due to A. fumigatus. In two of the five positive cases, antigenemia was detected with inhibition-EIA earlier than with X ray or other biological methods. No antigens were detected in the sera from two patients with proven IA due to Aspergillus flavus and Aspergillus terreus nor in the sera from four patients with probable IA. Circulating antigens were not detected in the control group, composed of 30 healthy adult blood donors. Four of the 32 at-risk patients examined, though they displayed no definite evidence of IA, gave a positive result in this test. The sensitivity, specificity, and positive predictive value of inhibition-EIA were 71.4, 94.4, and 71.2%, respectively. The data were compared with those obtained by a latex agglutination assay of galactomannan (GM) that was positive in only one patient with probable IA. The higher sensitivity obtained by inhibition-EIA may well be due to its ability to detect circulating antigens other than GM in the sera of IC patients with IA. Detecting these antigens may improve the diagnosis of IA, as they may serve as markers of this infection.

Specific detection of Aspergillus species in blood and bronchoalveolar lavage samples of immunocompromised patients by two-step PCR

The increasing incidence of aspergillosis, a life-threatening infection in immunocompromised patients, emphasizes the need to improve the currently limited diagnostic tools. We developed a two-step PCR assay that specifically amplifies a region of the 18S rRNA gene that is highly conserved in Aspergillus species. A number of primers with the least homology to equivalent human or Candida gene sequences were screened for the pairs that gave the highest sensitivity and specificity. No cross-reaction with the wide range of fungal and bacterial pathogens so far tested was observed. This assay allows direct and rapid detection of down to 10 fg of Aspergillus DNA corresponding to 1 to 5 CFU per ml of blood. A total of 315 blood and bronchoalveolar lavage samples from 140 subjects, including 93 patients at risk for invasive fungal disease, were screened. The result was a 100% correlation between positive histology, culture, or high-resolution computed tomography findings and PCR results. The test specificity was 89%. Our data point to the considerable potential clinical value of this simple, specific, rapid, and inexpensive PCR assay for improving the means of early diagnosis of systemic aspergillosis in high-risk patients.

Approaches to fungal diagnosis in transplantation

The diagnosis of invasive fungal infection in patients undergoing solid organ or bone marrow transplantation remains a significant clinical challenge. Consideration of the epidemiology of these infections and host risk factors may be an important clue to a specific fungal diagnosis. Despite extensive investigation on methods such as serologic techniques to improve the rapid diagnosis of these infections, the diagnosis of invasive mycoses remains largely dependent on clinical presentation. For example, the signs and symptoms that result from angioinvasion of fungal organisms include pleuritic chest pain or hemoptysis. In a high-risk patient these findings can be important clues to invasive fungal infection. Cultures of opportunistic fungi in certain settings, such as Aspergillus in respiratory samples from immunosuppressed patients, may be associated with infection. Radiographic findings can also be useful to establish a diagnosis of infection. In patients with invasive aspergillosis as well as other angioinvasive moulds, chest CT scans may demonstrate lesions that are not visible on plain radiographs. Serodiagnosis of these infections remains largely investigational. Microbiological antifungal resistance has increasingly been reported, but in patients at high risk for serious fungal infection, including patients undergoing bone marrow and organ transplantation, antifungal resistance remains uncommon, particularly in Candida albicans. Higher doses of azoles should be used to treat patients with infections due to less susceptible yeasts and those with more serious infection. Prompt recognition of fungal infection combined with intensive antifungal therapy is needed for successful therapy.

Aspergillus meningitis: diagnosis by non-culture-based microbiological methods and management

The performance of antibody detection, antigen detection, and Aspergillus genus-specific PCR for diagnosing Aspergillus meningitis was investigated with 26 cerebrospinal fluid (CSF) samples obtained from a single patient with proven infection caused by Aspergillus fumigatus. Immunoglobulin G antibodies directed against Aspergillus were not detected by enzyme-linked immunosorbent assay in CSF or serum. The antigen galactomannan was detected in the CSF 45 days before a culture became positive, and Aspergillus DNA was detected 4 days prior to culture. Decline of the galactomannan antigen titer in the CSF during treatment with intravenous and intraventricular amphotericin B and intravenous voriconazole corresponded with the clinical response to treatment.

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.

PCR detection of DNA specific for Trichosporon species in serum of patients with disseminated trichosporonosis

Deep-seated trichosporonosis is a lethal opportunistic infection that disseminates rapidly and widely in immunocompromised patients, and early diagnosis is crucial for the treatment of this infection. We developed a novel nested-PCR assay that detects DNA specific for clinically important strains of Trichosporon in serum samples from patients with disseminated trichosporonosis. In this assay, two sets of oligonucleotide primers were derived from the sequence of 26S rRNA genes of Trichosporon asahii. The specific fragment was amplified from T. asahii and T. mucoides, but not from other microorganisms, including some other basidiomycetous fungi (Cryptococcus, Malassezia, Rhodotorula, and Sporobolomyces). Target DNA was detected by the nested PCR with as little as 5 fg of the extracted DNA of T. asahii. In a study using 11 clinical samples, the specific fragment was detected by the nested PCR in 64% (7 of 11) of sera from patients with histologically diagnosed disseminated trichosporonosis, while glucuronoxylomannan antigen was detected in only 54% (6 of 11) of the samples. Our new nested-PCR assay using serum samples can be performed repeatedly throughout the course of the disease. In addition, not only can it be used for early diagnosis of trichosporonosis, but it may also be beneficial for monitoring its progress or response to therapy.

Detection of PCR-amplified fungal DNA by using a PCR-ELISA system

In order to speed up and standardize polymerase chain reaction (PCR)-based detection of medically important fungi in clinical samples we established a combination of commercially available kits for DNA extraction, PCR amplification and detection of the amplicons. The PCR plate assay proved to be as sensitive and specific as our previously published assay (5 cfu ml(-1) blood). Moreover, in a selected group of patients, all patients with proven and probable invasive fungal infection were found to be PCR-positive. Thus the PCR plate assay was found to be a sensitive, technically simplified and standardized method with potential for adaptation to automation.

Lack of utility of the lysis-centrifugation blood culture method for detection of fungemia in immunocompromised cancer patients

We retrospectively compared the utility of a fungal isolation device (Isolator) versus conventional techniques for recovering fungal organisms from blood cultures obtained from neutropenic cancer patients. Positive cultures were deemed true pathogens, possible pathogens, or contaminants according to laboratory and clinical criteria. Fifty-three patients had 66 positive blood cultures for fungi, nine on multiple occasions. In 20 episodes true pathogens were recovered, 6 from broth medium alone, 4 from the Isolator system alone, and 10 from both systems. False-negative cultures were noted in 4 of 20 (20%) cases in which broth medium was used and in 6 of 20 (30%) cases in which the Isolator system was used. Possible pathogens were detected in 4 of 66 blood culture-positive cases. Forty-two positive cultures were considered contaminants, 1 collected from standard medium and 41 of 42 (98%) which grew only in Isolators. Eleven of 18 patients with true fungal infections expired as a result of infection, while 4 of 33 patients with a contaminant expired, none from a fungal cause. We do not advocate the routine use of Isolator tubes in the evaluation of the febrile, neutropenic patient due to the high rates of false positives and of contamination.

Serum Aspergillus galactomannan antigen testing by sandwich ELISA: practical use in neutropenic patients

The double sandwich ELISA detecting Aspergillus galactomannan (GM) was prospectively evaluated for the diagnosis of invasive aspergillosis (IA) in 50 haematological patients at risk for IA. Serum samples were collected once weekly as long as the risk factors persisted. Six patients had proven or probable IA (3 A. fumigatus, 1 A. flavus, 1 A. niger, 1 A. ustus) and the GM titres were parallel to the clinical evolution of IA. Six of nine patients with suspected IA had at least two consecutive serum GM titres above 1 ng/ml and died with increasing titres, whereas the GM-negative patients survived. Positive GM titres did not anticipate the isolation of fungi. Unfortunately, positive GM titres did not anticipate the initiation of antifungal therapy, based on clinical suspicion. Moreover, if a true-positive result was defined as two consecutive positive serum samples, four patients out of 35 without proven, probable or suspected IA were positive. Then, the rate of false-positive results was high (12%) in the range previously reported. Nevertheless, the GM ELISA appears useful to assess IA and to follow the efficacy of antifungal treatment.

Murine macrophage elastolytic activity induced by Aspergillus fumigatusstrains in vitro: evidence of the expression of two macrophage-induced protease genes

The interaction between Aspergillus fumigatus conidia and murine macrophages of various origins was investigated. Cocultures were carried out between A. fumigatus strains and freshly isolated murine pulmonary alveolar macrophages or two murine macrophage cell-lines: murine alveolar cell-line MALU and murine astrocytoma cell-line J774. By measuring the variation of elastolytic activity in the coculture supernatants with two elastin substrates, we demonstrated that either viable or fixed A. fumigatus or C. albicans yeasts or nonspecific particles induced significant macrophage elastolytic activity. The effect of A. fumigatus supernatant or the purified A. fumigatus galactomannan suggested also the possible involvement of this polysaccharide in macrophage-protease gene expression, release, and activity in invasive aspergillosis. The effect of inhibitory compounds demonstrated the potential implication of a macrophagic metalloprotease and a macrophagic cysteine protease. RNA analysis allowed us to demonstrate the induction of expression of two macrophagic protease genes in stimulated macrophages. Two distinctive mechanisms appeared to be implicated in macrophage protease induction: nonspecific phagocytosis in the earliest times of the coculture and (or) specific galactomannan recognition after its gradual release by the mycelium.

Detection and identification of fungal pathogens in blood by using molecular probes

A PCR assay was developed for the detection and identification of Candida and Aspergillus species. The design of the oligonucleotide primer pair as well as the species-specific probes used for species identification was derived from a comparison of the sequences of the 18S rRNA genes of various fungal pathogens. The primers targeted a consensus sequence for a variety of fungal pathogens. The assay was tested for sensitivity and specificity with 134 fungal and 85 nonfungal isolates. To assess clinical applicability, 601 blood samples from four defined groups were tested: group A (n = 35), controls; groups B to D (n = 86), patients with febrile neutropenia, without fungal colonization (group B; n = 29) and with fungal colonization (group C; n = 36); and patients with documented invasive fungal infection (IFI) (group D; n = 21). The assay detected and, by species-specific hybridization, identified most of the clinically relevant Candida and Aspergillus species at 1 CFU/ml of blood. Amplification was 100% sensitive for all molds and yeasts tested, with Histoplasma capsulatum being the only non-Aspergillus species hybridizing with the Aspergillus spp. probe. None of 35 group A patients and only 3 of 65 group B and C patients were PCR positive. The sensitivity of the assay for specimens from patients with IFI (21 patients in group D) was 100% if two specimens were tested. For specificity, 3 of 189 specimens from patients at risk but with negative cultures were positive by the assay, for a specificity of 98%. PCR preceded radiological signs by a median of 4 days (range, 4 to 7 days) for 12 of 17 patients with hepatosplenic candidiasis or pulmonary aspergillosis. For the 10 patients with IFI responding to antifungal therapy, PCR assays became persistently negative after 14 days of treatment, in contrast to the case for 11 patients, who remained PCR positive while not responding to antifungal therapy. Thus, the described PCR assay allows for the highly sensitive and specific detection and identification of fungal pathogens in vitro and in vivo. Preliminary data from the screening of a selected group of patients revealed some value in the early diagnosis and monitoring of antifungal therapy.

Prevention of infections in bone marrow transplant recipients

Bone marrow transplantation (BMT) is increasingly used in the treatment of hematologic malignancies, solid tumors, and congenital diseases. The number of patients receiving a BMT increased from approximately 5000 in 1989 to 12,000 in 1995. Infectious complications are the most common cause of morbidity and mortality in the peritransplant period in patients undergoing autologous BMT. Additionally, infectious complications are a serious cause of complications in recipients of matched sibling allogeneic BMT, unrelated BMT, and related mismatched BMT.

Serial monitoring of Aspergillus antigen in the early diagnosis of invasive aspergillosis. Preliminary investigations with two examples

A recently developed sandwich ELISA, which detects Aspergillus galactomannan, was tested retrospectively in serial serum samples from an allogeneic bone marrow transplant recipient with proven invasive aspergillosis (patient 1) and another with suspected disease (patient 2). Galactomannan was detected in the serum 4 and 28 days, respectively, before pulmonary infiltrates suggestive of fungal infection first became apparent on the chest X-ray. Aspergillus was detected by ELISA and PCR in BAL fluid samples from both patients, and in CSF from patient 1. The diagnosis was confirmed at autopsy for patient 1 by histopathology and the recovery of Aspergillus fumigatus from the lung and brain. Furthermore, in both patients the course of the antigen titer in the serum during antifungal treatment corresponded with the clinical outcome. These results confirm that the sandwich ELISA appears to be useful for the early diagnosis of invasive aspergillosis. The value of the test for monitoring the response to antifungal treatment remains to be established in prospective trials.

Fungal infections in lung and heart-lung transplant recipients. Report of 9 cases and review of the literature

We reviewed the pattern and incidence of fungal infections in patients undergoing lung and heart-lung transplantation at Duke University Medical Center from September 1992 until August 1995, and present here 9 illustrative cases. Of the 73 lung and heart-lung transplant recipients studied, 59 (81%) had positive fungal cultures at some point after transplantation. The cases presented here illustrate that lung transplant recipients are predisposed to a wide variety of fungal infections. The clinical pattern of these infections ranges from asymptomatic to rapidly progressive fatal disease. In addition to the reactivation of previous fungal infections and recent exposure to new environmental sources, the donor lung itself can be the source of fungal infection, as we showed by using molecular epidemiology techniques. Because of the associated morbidity and mortality, efforts should be directed at investigating prophylactic antifungal regimens in lung transplant recipients. Preliminary reports on the use of itraconazole and aerosolized amphotericin B have been encouraging. Prospective randomized studies are needed to assess the safety and cost effectiveness of different regimens. Fungal infections in patients after lung transplantation can significantly impede recovery and lead to substantial mortality.

Prospective sandwich enzyme-linked immunosorbent assay for serum galactomannan: early predictive value and clinical use in invasive aspergillosis

BACKGROUND

The delay between the onset of invasive aspergillosis and the start of antifungal therapy is crucial for the patient's recovery. Early diagnosis is difficult in cancer patients through lack of precocious specific signs. We have investigated the clinical usefulness of circulating Aspergillus antigen monitoring in pediatric hematology patients with a new sensitive sandwich enzyme-linked immunosorbent assay.

METHODS

A prospective study was conducted by assessing circulating galactomannan levels in high risk patients. Thirty-seven patients studied during an 18-month period were evaluated twice weekly during neutropenic phases with the sandwich enzyme-linked immunosorbent assay for serum Aspergillus galactomannan.

RESULTS

Twelve patients had one or more episodes of positive circulating galactomannan detection, 10 of whom developed presumptive invasive aspergillosis. The clinical and radiologic signs occurred at a mean of 13.4 days (range, 0 to 48) after circulating galactomannan detection and reversed in 6 patients treated with amphotericin B at the same time circulating galactomannan detection became negative. Reappearance of circulating galactomannan was observed during subsequent neutropenic periods in 3 patients.

CONCLUSIONS

The detection of galactomannan at concentrations as low as 1 ng/ml can be useful for the early initiation of antifungal therapy and monitoring treatment in clinically documented lung aspergillosis. This technique coupled with chest computed tomography could help to restrict the need of invasive diagnostic procedures in fragile patients.