New insights into transmission, diagnosis, and drug treatment of Pneumocystis carinii pneumonia

Molecular Analysis of Dihydropteroate Synthase Gene Mutations in Pneumocystis jirovecii Isolates among Bulgarian Patients with Pneumocystis Pneumonia

Pneumocystis jirovecii pneumonia (PCP) is a significant cause of morbidity and mortality in immunocompromised people. The widespread use of trimethoprim-sulfamethoxazole (TMP-SMZ) for the treatment and prophylaxis of opportunistic infections (including PCP) has led to an increased selection of TMP-SMZ-resistant microorganisms. Sulfa/sulfone resistance has been demonstrated to result from specific point mutations in the DHPS gene. This study aims to investigate the presence of DHPS gene mutations among P. jirovecii isolates from Bulgarian patients with PCP. A total of 326 patients were examined via real-time PCR targeting the P. jirovecii mitochondrial large subunit rRNA gene and further at the DHPS locus. P. jirovecii DNA was detected in 50 (15.34%) specimens. A 370 bp DHPS locus fragment was successfully amplified in 21 samples from 19 PCP-positive patients, which was then purified, sequenced, and used for phylogenetic analysis. Based on the sequencing analysis, all (n = 21) P. jirovecii isolates showed DHPS genotype 1 (the wild type, with the nucleotide sequence ACA CGG CCT at codons 55, 56, and 57, respectively). In conclusion, infections caused by P. jirovecii mutants potentially resistant to sulfonamides are still rare events in Bulgaria. DHPS genotype 1 at codons 55 and 57 is the predominant P. jirovecii strain in the country.

Emergence of infectious diseases and role of advanced nanomaterials in point-of-care diagnostics: a review

Infectious outbreaks are the foremost global public health concern, challenging the current healthcare system, which claims millions of lives annually. The most crucial way to control an infectious outbreak is by early detection through point-of-care (POC) diagnostics. POC diagnostics are highly advantageous owing to the prompt diagnosis, which is economical, simple and highly efficient with remote access capabilities. In particular, utilization of nanomaterials to architect POC devices has enabled highly integrated and portable (compact) devices with enhanced efficiency. As such, this review will detail the factors influencing the emergence of infectious diseases and methods for fast and accurate detection, thus elucidating the underlying factors of these infections. Furthermore, it comprehensively highlights the importance of different nanomaterials in POCs to detect nucleic acid, whole pathogens, proteins and antibody detection systems. Finally, we summarize findings reported on nanomaterials based on advanced POCs such as lab-on-chip, lab-on-disc-devices, point-of-action and hospital-on-chip. To this end, we discuss the challenges, potential solutions, prospects of integrating internet-of-things, artificial intelligence, 5G communications and data clouding to achieve intelligent POCs.

Co-Infection of COVID-19 and Pneumocystosis Following Rituximab Infusion—A Case Report

Immunocompromised patients with respiratory viral infections are at increased risk of fungal superinfections, including Pneumocystosis. Within the scope of the COVID-19 pandemic, Pneumocystis jirovecii co-infections are being increasingly reported. Differential diagnosis often creates a dilemma, due to multiple overlapping clinical and radiographic features. Awareness of fungal co-infections in the context of the COVID-19 pandemic is crucial to initiate prophylactic measures, especially in high-risk individuals. We report the second case of Pneumocystis jirovecii pneumonia and COVID-19 co-infection in a renal transplant recipient in Poland.

Clinical Performance of BAL Metagenomic Next-Generation Sequence and Serum (1,3)-β-D-Glucan for Differential Diagnosis of Pneumocystis jirovecii Pneumonia and Pneumocystis jirovecii Colonisation

Background

Differentiating Pneumocystis jirovecii infection from colonisation is crucial for appropriate therapy administration. In this study, we evaluated the performance of bronchoalveolar lavage fluid (BAL) metagenomic next-generation sequencing (mNGS) and serum 1,3-β-D-glucan (BDG) tests in differentiating colonisation and infection with P. jirovecii.

Methods

From January 2018 to March 2021, 47 patients were enrolled in this study at the Hunan Provincial People’s Hospital. The final diagnosis was used as a reference, and cases were classified into the P. jirovecii pneumonia (PJP) group or the P. jirovecii colonisation (PJC) group. Clinical data were recorded. The performances of mNGS and BDG were compared.

Result

The fungal load significantly differed between patients with PJP and PJC, with median reads of 3,215.79 ± 1,797 vs. 5.61 ± 0.88 in the PJP and PJC groups, respectively (P < 0.0001). BDG also significantly differed between the two groups, with a median titre of 233.60 ± 39.65 pg/ml in the PJP group and 68.48 ± 19.21 pg/ml in the PJC group (P = 0.0006). The area under the curve was 0.973 (95%CI: 0.868–1.007) for mNGS of the BAL and 0.879 (95%CI: 0.769–0.989) for the serum BDG. The optimal threshold value for discriminating P. jirovecii infection from colonisation appeared to be 14 reads (sensitivity, 83.3%; specificity, 95.7%; positive likelihood ratio, 19.2) and BDG = 88.6 pg/ml (sensitivity, 79.2%; specificity, 92.9%; positive likelihood ratio, 18.2). No correlation between mNGS reads and the BDG titre was found in mNGS-positive patients (r² = 0.0076, P = 0.583). The levels of lactate dehydrogenase and C-reactive protein were significantly higher in the PJP group than in the PJC group.

Conclusion

BAL mNGS and serum BDG are useful adjunct tests that can assist with differentiating between colonisation and infection of P. jirovecii.

Fungal pneumonia in kidney transplant recipients

Fungal pneumonia is a dreaded complication encountered after kidney transplantation, complicated by increased mortality and often associated with graft failure. Diagnosis can be challenging because the clinical presentation is non-specific and diagnostic tools have limited sensitivity and specificity in kidney transplant recipients and must be interpreted in the context of the clinical setting. Management is difficult due to the increased risk of dissemination and severity, multiple comorbidities, drug interactions and reduced immunosuppression which should be applied as an important adjunct to therapy. This review will focus on the main causes of fungal pneumonia in kidney transplant recipients including Pneumocystis, Aspergillus, Cryptococcus, mucormycetes and Histoplasma. Epidemiology, clinical presentation, laboratory and radiographic features, specific characteristics will be discussed with an update on diagnostic procedures and treatment.

Diagnostic accuracy of the 1,3-beta-D-glucan test and lactate dehydrogenase for pneumocystis pneumonia in non-HIV patients

We evaluated the serum levels of (1–3)-beta-d-glucan (BG) and lactate dehydrogenase (LDH) as a tool to support pneumocystis pneumonia (PCP) diagnostic procedures in non-HIV patients. We retrospectively collected non-HIV (human immunodeficiency virus) patients presenting clinical features of PCP between April 1st, 2013, and December 31st, 2018. A total of 225 included patients were tested for Pneumocystis jirovecii by polymerase chain reaction (PCR) and methenamine silver staining. Based on different exclusion criteria, 179 cases were included in the BG group, and 196 cases were included in the LDH group. In each group, cases with positive immunofluorescence (IF) microscopy and PCR were considered proven PCP, while cases with only positive PCR were considered probable PCP. Fifty patients with negative IF and PCR results and proven to be non-PCP infection were chosen randomly as the control group. The cut-off levels of BG and LDH to distinguish non-PCP from probable PCP were 110 pg/mL and 296 U/L with 88% sensitivity and 86% specificity, and 66% sensitivity and 88% specificity, respectively. The cut-off levels of BG and LDH to distinguish non-PCP from proven PCP were 285.8 pg/mL and 379 U/L with 92% sensitivity and 96% specificity, and 85% sensitivity and 77% specificity, respectively. The cut-off levels of BG and LDH to distinguish non-PCP from proven/probable PCP were 144.1 pg/mL and 363 U/L with 90% sensitivity, 86% specificity and 80% sensitivity, 76% specificity respectively. BG and LDH are reliable indicators for detecting P. jirovecii infection in HIV-uninfected immunocompromised patients.

COVID-19 and Pneumocystis jirovecii Pulmonary Coinfection-The First Case Confirmed through Autopsy

Background: Establishing the diagnosis of COVID-19 and Pneumocystisjirovecii pulmonary coinfection is difficult due to clinical and radiological similarities that exist between the two disorders. For the moment, fungal coinfections are underestimated in COVID-19 patients. Case presentation: We report the case of a 52-year-old male patient, who presented to the emergency department for severe dyspnea and died 17 h later. The RT-PCR test performed at his admission was negative for SARS-CoV-2. Retesting of lung fragments collected during autopsy revealed a positive result for SARS-CoV-2. Histopathological examination showed preexisting lesions, due to comorbidities, as well as recent lesions: massive lung thromboses, alveolar exudate rich in foam cells, suprapleural and intra-alveolar Pneumocystisjirovecii cystic forms, and bilateral adrenal hemorrhage. Conclusion: COVID-19 and P.jirovecii coinfection should be considered, particularly in critically ill patients, and we recommend the systematic search for P. jirovecii in respiratory samples.

A Comprehensive Evaluation of Risk Factors for Pneumocystis Jirovecii Pneumonia in Adult Solid Organ Transplant Recipients: a Systematic Review and Meta-Analysis

BACKGROUND

There is no consensus guidance on when to reinitiate Pneumocystis jirovecii pneumonia (PJP) prophylaxis in solid organ transplant (SOT) recipients at increased risk. The 2019 American Society of Transplantation Infectious Diseases Community of Practice (AST IDCOP) guidelines suggested to continue or reinstitute PJP prophylaxis in those receiving intensified immunosuppression for graft rejection, CMV infection, higher dose of corticosteroids, or prolonged neutropenia.

METHODS

A literature search was conducted evaluating all literature from existence through April 22, 2020 using MEDLINE and EMBASE. (PROSPERO: CRD42019134204) RESULTS:: A total of 30 studies with 413 276 SOT recipients were included. The following factors were associated with PJP development: acute rejection (pooled odds ratio (pOR) = 2.35 (1.69, 3.26), study heterogeneity index (I)= 23.4%), cytomegalovirus (CMV)-related illnesses (pOR = 3.14 (2.30, 4.29), I=48%), absolute lymphocyte count < 500 cells/mm (pOR = 6.29[3.56, 11.13], I 0%), BK-related diseases (pOR = 2.59[1.22, 5.49], I 0%), HLA mismatch ≥ 3 (pOR = 1.83 [1.06, 3.17], I= 0%), rituximab use (pOR =3.03 (1.82, 5.04); I =0%) and polyclonal antibodies use for rejection (pOR = 3.92 [1.87, 8.19], I= 0%). On the other hand, sex, CMV mismatch, interleukin-2 inhibitors, corticosteroids for rejection, and plasmapheresis were not associated with developing PJP.

CONCLUSION

PJP prophylaxis should be considered in SOT recipients with lymphopenia, BK-related infections and rituximab exposure in addition to the previously mentioned risk factors in the AST IDCOP guidelines.

Pneumocystis jirovecii Pneumonia in Children with Hematological Malignancies: Diagnosis and Approaches to Management

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic infection that mostly affects children with suppressed cellular immunity. PJP was the most common cause of infectious death in children with acute lymphoblastic leukemia prior to the inclusion of cotrimoxazole prophylaxis as part of the standard medical care in the late 1980s. Children with acute leukemia, lymphomas, and those undergoing hematopoietic stem cell transplantation, especially allogeneic transplantation, are also at high risk of PJP. Persistent lymphopenia, graft versus host disease, poor immune reconstitution, and lengthy use of corticosteroids are significant risk factors for PJP. Active infection may be due to reactivation of latent infection or recent acquisition from environmental exposure. Intense hypoxemia and impaired diffusing capacity of the lungs are hallmarks of PJP, while computerized tomography of the lungs is the diagnostic technique of choice. Immunofluorescence testing with monoclonal antibodies followed by fluorescent microscopy and polymerase chain reaction testing of respiratory specimens have emerged as the best diagnostic methods. Measurement of (1-3)-β-D-glucan in the serum has a high negative predictive value in ruling out PJP. Oral cotrimoxazole is effective for prophylaxis, but in intolerant patients, intravenous and aerosolized pentamidine, dapsone, and atovaquone are effective alternatives. Ιntravenous cotrimoxazole is the treatment of choice, but PJP has a high mortality even with appropriate therapy.

Role of Serum (1,3)-Β-D-Glucan to Screen for Pneumocystis Pneumonia in Kidney Transplant Recipients

BACKGROUND

Pneumocystis pneumonia is a common opportunistic infection in kidney transplant recipients caused by the ascomycetous fungi Pneumocystis jirovecii. Its clinical presentation of a progressive nonproductive cough, shortness of breath, and fever is nonspecific and often delays diagnosis and appropriate treatment. Moreover, the plain radiograph may show a spectrum of findings from normal to bilateral diffuse infiltrates. Detection of serum (1,3)-β-D-glucan along with consistent clinical findings can be used as early screening tools to diagnose and initiate treatment for Pneumocystis pneumonia pending confirmation by bronchoscopy.

METHODS

This case series describes 6 kidney transplant recipients who were diagnosed as having Pneumocystis pneumonia. The baseline demographic variables, presenting symptoms, radiographic findings, laboratory findings including lactate dehydrogenase and serum (1,3)-β-D-glucan levels, bronchoscopy findings, and its timing in relation to a positive serum (1,3)-β-D-glucan test, and response to treatment were collected.

RESULTS

All 6 patients who completed the first 3 months of prophylaxis against Pneumocystis pneumonia with sulfamethoxazole-trimethoprim were diagnosed as having Pneumocystis pneumonia between 2 to 24 years post transplant. They initiated treatment early based on a positive serum (1,3)-β-D-glucan and negative Histoplasma antigen and serum galactomannan test with a presumptive diagnosis of Pneumocystis pneumonia, which was later confirmed with a positive polymerase chain reaction on bronchoalveolar lavage fluid.

CONCLUSIONS

Pneumocystis pneumonia is a common opportunistic fungal infection in immunosuppressed kidney transplant recipients, and use of serum (1,3)-β-D-glucan can be used as an initial screening test for its early diagnosis and treatment.

Safety and efficacy of reduced-dose pentamidine as second-line treatment for HIV-related pneumocystis pneumonia

OBJECTIVES

Parenteral pentamidine isethionate (PM) 4 mg/kg/day is recommended as an alternative therapeutic regimen after failure of first-line treatment for pneumocystis pneumonia (PCP). However, the dose is often reduced to 3 mg/kg/day in clinical settings because of high rates of adverse events and drug toxicity. Although considered equally efficacious, this lower dose has not been well evaluated.

METHODS

This was a single-center, retrospective cohort study that analyzed 75 patients with HIV-PCP who were treated with trimethoprim-sulfamethoxazole, but discontinued treatment because of treatment failure or adverse events; they were then administered 3 mg/kg/day of intravenous PM as a salvage therapy. The primary outcomes were the regimen completion rate with the reduced PM dose.

RESULTS AND CONCLUSIONS

In total, 40 (53.3%) of the eligible patients completed PCP therapy with reduced-dose PM salvage treatment. The overall survival rate of PCP was 73 (97.3%). The median duration of second-line PM treatment was 8.0 days (interquartile range: 6.0-10.0). Although, the adverse events with reduced-dose PM were observed in 41 (54.7%), including 35 treatment-limiting adverse events, grade 3 or 4 adverse events occurred in only three patients (thrombocytopenia, one patient; neutropenia, two patients). Life-threating adverse events, such as hypoglycemia and arrhythmia, were not observed with reduced-dose PM. Salvage therapy with reduced-dose PM for patients with HIV-PCP is relatively safe and effective; moreover, life-threating adverse events did not occur. This therapy could be recommended for patients with HIV-PCP who fail to respond to first-line treatment with trimethoprim-sulfamethoxazole.

Molecular diagnosis and genotyping of Pneumocystis jirovecii in bronchoalveolar lavage samples obtained from patients with pulmonary disorder

Background and Purpose:

Pneumocystis pneumonia (PCP) is one of the most common and life-threatening fungal diseases in patients with human immunodeficiency, treated with immunosuppressive medications. Immunocompetent people can also be a spreading agent for PCP. Regarding this, the aim of the present study was to diagnose and identify Pneumocystis jirovecii in bronchoalveolar lavage (BAL) samples obtained from patients with pulmonary disorder using a molecular method.

Materials and Methods:

For the purpose of the study, BAL samples (n=138) were collected from patients, undergoing bronchoscopy at the different departments of university hospitals affiliated to Mashhad University of Medical Sciences, Mashhad, Iran, during a period of one year (i.e., April 2014 until May 2015). Giemsa staining and molecular identification were carried out for each sample. The samples were also subjected to nested polymerase chain reaction (PCR), sequencing, and genotyping based on mitochondrial ribosomal large subunit (mtLSU rRNA) of P. jirovecii. The phylogenic tree was constructed by MEGA6 software.

Results:

The results of direct microscopic examination revealed the presence of P. jirovecii in 3 (2.2%) out of 138 samples; in addition, nested PCR and sequencing led to the detection of species in 17 (12.3%) samples. Out of patients with positive results, 10 (25%) and 7 (7.1%) cases were immunosuppressed and immunocompetent, respectively. The most common clinical symptoms among patients with pneumocystis were fever, dyspnea, and dry cough. In addition, genotypes III and II were the dominant genotypes in our dataset.

Conclusion:

Nested PCR and sequencing methods showed higher sensitivity and specificity as compared with a direct staining technique. Genotype III was identified as the most dominant type in patients with pulmonary disorder in Mashhad.

A Multivariable Prediction Model for Pneumocystis jirovecii Pneumonia in Hematology Patients with Acute Respiratory Failure

RATIONALE

The incidence of Pneumocystis jirovecii pneumonia (PjP) is rising. Longer time to treatment is associated with higher mortality.

OBJECTIVES

To develop a multivariable risk prediction model for PjP diagnosis.

METHODS

In a prospective multicenter cohort of ICU patients with hematological malignancies and acute respiratory failure, factors associated with documented PjP were identified. The risk prediction model was tested in an independent prospective multicenter cohort. We assessed discrimination (by areas under the receiver operating characteristic curves [AUCs]) and goodness of fit (by Hosmer-Lemeshow statistics). Model performance was assessed using 30 sets of imputed data sets.

MEASUREMENTS AND MAIN RESULTS

Among the 1,330 patients, 134 of 1,092 (12.3%; 95% confidence interval [CI], 10.4-14.4%) had proven PjP in the derivation cohort, as did 15 of 238 (6.3%, 95% CI, 3.6-10.2%) in the validation cohort. The model included age, lymphoproliferative disease, anti-Pneumocystis prophylaxis, the number of days between respiratory symptom onset and ICU admission, shock, chest radiograph pattern, and pleural effusion. The median (interquartile range) score was 3.5 (1.5-5.0) (range, -3.5 to 8.5) in the derivation cohort and 1.0 (0-2.0) (range, -3.5 to 6.0) in the validation cohort. The best threshold was defined on the validation sample as 3, allowing us to reach 86.7% sensitivity and 67.7% specificity for PjP, with a negative predictive value of 97.9% in the case of 10% prevalence. The score had good calibration (goodness of fit, -0.75) and discrimination in the derivation cohort (mean AUC, 0.80; 95% CI, 0.76-0.84) and validation cohort (mean AUC, 0.83; 95% CI, 0.72-0.93).

CONCLUSIONS

The PjP score for hematology patients with acute respiratory failure can be computed at admission, based on readily available variables. Potential clinical benefits of using this score deserve assessment.

Pneumocystis jiroveci in solid organ transplantation: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of Pneumocystis jiroveci fungal infection transplant recipients. Pneumonia (PJP) may develop via airborne transmission or reactivation of prior infection. Nosocomial clusters of infection have been described among transplant recipients. PJP should not occur during prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMX). Without prophylaxis, PJP risk is greatest in the first 6 months after organ transplantation but may develop later. Risk factors include low lymphocyte counts, cytomegalovirus infection (CMV), hypogammaglobulinemia, treated graft rejection or corticosteroids, and advancing patient age (>65). Presentation typically includes fever, dyspnea with hypoxemia, and cough. Chest radiographic patterns generally reveal diffuse interstitial processes best seen by CT scans. Patients generally have PO₂  < 60 mm Hg, elevated serum lactic dehydrogenase (LDH), and elevated serum (1 → 3) β-d-glucan assay. Specific diagnosis uses respiratory specimens with direct immunofluorescent staining; invasive procedures may be required. Quantitative PCR is a useful adjunct to diagnosis. TMP-SMX is the drug of choice for therapy; drug allergy should be documented before resorting to alternative therapies. Adjunctive corticosteroids may be useful early. Routine PJP prophylaxis is recommended for at least 6-12 months post-transplant, preferably with TMP-SMX.

Impact of Pneumocystis jirovecii pneumonia on kidney transplant outcome

Backgrounds

Pneumocystis jirovecii pneumonia (PCP) remains an important cause of morbidity and mortality in kidney transplant recipients. While the acute phase toxicity in patients with PCP is well-characterized, there is a lack of data on the effects of PCP on long-term graft outcome.

Method

This retrospective observational study analyzed 1502 adult patients who underwent kidney transplantation at Seoul National University Hospital between 2000 and 2017. After a propensity score matching was performed, the graft and survival outcomes were compared between PCP-negative and PCP-positive groups.

Results

A total of 68 patients (4.5%) developed PCP after transplantation. The multivariable Cox analysis showed that positivity for cytomegalovirus and lack of initial oral antibiotic prophylaxis were risk factors of post-transplant PCP. The PCP-positive group had higher hazard ratios of graft failure [adjusted hazard ratio (HR), 3.1 (1.14–8.26); P = 0.027] and mortality [adjusted HR, 11.0 (3.68–32.80); P < 0.001] than the PCP-negative group. However, the PCP event was not related with subsequent development of de novo donor-specific antibodies or pathologic findings, such as T-cell or antibody mediated rejection and interstitial fibrosis and tubular atrophy.

Conclusions

PCP is a risk factor of long-term graft failure and mortality, irrespective of rejection. Accordingly, appropriate prophylaxis and treatment is needed to avoid adverse transplant outcomes of PCP.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1407-x) contains supplementary material, which is available to authorized users.

Pneumocystis pneumonia in HIV-1-infected patients

Pneumocystis pneumonia (PCP) is an opportunistic disease that mainly affects patients with a deficiency of cell-mediated immunity, especially acquired immunodeficiency syndrome (AIDS). The incidence of PCP in these patients has declined substantially owing to the widespread use of antiretroviral therapy and PCP prophylaxis. However, PCP is still a major AIDS-related opportunistic infection, particularly in patients with advanced immunosuppression in whom human immunodeficiency virus type 1 (HIV-1) infection remains undiagnosed or untreated. The clinical manifestations, diagnosis, treatment, and prevention of PCP in patients with HIV-1 infection are addressed in this review.

Site-Directed Mutagenesis of the 1,3-β-Glucan Synthase Catalytic Subunit of Pneumocystis jirovecii and Susceptibility Assays Suggest Its Sensitivity to Caspofungin

The echinocandin caspofungin inhibits the catalytic subunit Gsc1 of the enzymatic complex synthesizing 1,3-β-glucan, an essential compound of the fungal wall. Studies with rodents showed that caspofungin is effective against Pneumocystis asci. However, its efficacy against asci of Pneumocystis jirovecii, the species infecting exclusively humans, remains controversial. The aim of this study was to assess the sensitivity to caspofungin of the P. jirovecii Gsc1 subunit, as well as of those of Pneumocystis carinii and Pneumocystis murina infecting, respectively, rats and mice. In the absence of an established in vitro culture method for Pneumocystis species, we used functional complementation of the Saccharomyces cerevisiae gsc1 deletant. In the fungal pathogen Candida albicans, mutations leading to amino acid substitutions in Gsc1 confer resistance to caspofungin. We introduced the corresponding mutations into the Pneumocystis gsc1 genes using site-directed mutagenesis. In spot dilution tests, the sensitivity to caspofungin of the complemented strains decreased with the number of mutations introduced, suggesting that the wild-type enzymes are sensitive. The MICs of caspofungin determined by Etest and YeastOne for strains complemented with Pneumocystis enzymes (respectively, 0.125 and 0.12 μg/ml) were identical to those upon complementation with the enzyme of C. albicans, for which caspofungin presents low MICs. However, they were lower than the MICs upon complementation with the enzyme of the resistant species Candida parapsilosis (0.19 and 0.25 μg/ml). Sensitivity levels of Gsc1 enzymes of the three Pneumocystis species were similar. Our results suggest that P. jirovecii is sensitive to caspofungin during infections, as are P. carinii and P. murina.

A Molecular Window into the Biology and Epidemiology of Pneumocystis spp

Pneumocystis, a unique atypical fungus with an elusive lifestyle, has had an important medical history. It came to prominence as an opportunistic pathogen that not only can cause life-threatening pneumonia in patients with HIV infection and other immunodeficiencies but also can colonize the lungs of healthy individuals from a very early age. The genus Pneumocystis includes a group of closely related but heterogeneous organisms that have a worldwide distribution, have been detected in multiple mammalian species, are highly host species specific, inhabit the lungs almost exclusively, and have never convincingly been cultured in vitro, making Pneumocystis a fascinating but difficult-to-study organism. Improved molecular biologic methodologies have opened a new window into the biology and epidemiology of Pneumocystis. Advances include an improved taxonomic classification, identification of an extremely reduced genome and concomitant inability to metabolize and grow independent of the host lungs, insights into its transmission mode, recognition of its widespread colonization in both immunocompetent and immunodeficient hosts, and utilization of strain variation to study drug resistance, epidemiology, and outbreaks of infection among transplant patients. This review summarizes these advances and also identifies some major questions and challenges that need to be addressed to better understand Pneumocystis biology and its relevance to clinical care.

Prophylaxis and treatment of Pneumocystis Jirovecii pneumonia after solid organ transplantation

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic infection diagnosed in immunocompromized patients. After solid organ transplantation, early infection has decreased as a result of effective prophylaxis, but late infections and even outbreaks caused by interpatient transmission of pneumocystis by air are present in the SOT community. Different risk factors for PJP have been described and several indications for PJP prophylaxis have to be considered by clinicians in patients even years after transplantation. Diagnosis of PJP is confirmed by microscopy and immunofluorescence staining of bronchial fluid but PCR as well as serum ß-D-Glucan analysis have become increasingly valuable diagnostic tools. Treatment of choice is Trimethoprim/sulfamethoxazole and early treatment improves prognosis. However, mortality of PJP in solid organ transplant patients is still high and many aspects including the optimal management of immunosuppression during PJP treatment require further investigations.

Treatment of Pneumocystis jirovecii pneumonia in HIV-infected patients: a review

INTRODUCTION

Pneumocystis pneumonia is a potentially life-threatening pulmonary infection that occurs in immunocompromised individuals and HIV-infected patients with a low CD4 cell count. Trimethoprim-sulfamethoxazole has been used as the first-line agent for treatment, but mutations within dihydropteroate synthase gene render potential resistance to sulfamide. Despite advances of combination antiretroviral therapy (cART), Pneumocystis pneumonia continues to occur in HIV-infected patients with late presentation for cART or virological and immunological failure after receiving cART. Areas covered: This review summarizes the diagnosis and first-line and alternative treatment and prophylaxis for Pneumocystis pneumonia in HIV-infected patients. Articles for this review were identified through searching PubMed. Search terms included: 'Pneumocystis pneumonia', 'Pneumocystis jirovecii pneumonia', 'Pneumocystis carinii pneumonia', 'trimethoprim-sulfamethoxazole', 'primaquine', 'trimetrexate', 'dapsone', 'pentamidine', 'atovaquone', 'echinocandins', 'human immunodeficiency virus infection', 'acquired immunodeficiency syndrome', 'resistance to sulfamide' and combinations of these terms. We limited the search to English language papers that were published between 1981 and March 2017. We screened all identified articles and cross-referenced studies from retrieved articles. Expert commentary: Trimethoprim-sulfamethoxazole will continue to be the first-line agent for Pneumocystis pneumonia given its cost, availability of both oral and parenteral formulations, and effectiveness or efficacy in both treatment and prophylaxis. Whether resistance due to mutations within dihydropteroate synthase gene compromises treatment effectiveness remains controversial. Continued search for effective alternatives with better safety profiles for Pneumocystis pneumonia is warranted.

Immunization with Pneumocystis Cross-Reactive Antigen 1 (Pca1) Protects Mice against Pneumocystis Pneumonia and Generates Antibody to Pneumocystis jirovecii

Pneumocystis pneumonia (PcP) is a life-threatening infection that affects immunocompromised individuals. Nearly half of all PcP cases occur in those prescribed effective chemoprophylaxis, suggesting that additional preventive methods are needed. To this end, we have identified a unique mouse Pneumocystis surface protein, designated Pneumocystis cross-reactive antigen 1 (Pca1), as a potential vaccine candidate. Mice were immunized with a recombinant fusion protein containing Pca1. Subsequently, CD4⁺ T cells were depleted, and the mice were exposed to Pneumocystis murina Pca1 immunization completely protected nearly all mice, similar to immunization with whole Pneumocystis organisms. In contrast, all immunized negative-control mice developed PcP. Unexpectedly, Pca1 immunization generated cross-reactive antibody that recognized Pneumocystis jirovecii and Pneumocystis carinii Potential orthologs of Pca1 have been identified in P. jirovecii Such cross-reactivity is rare, and our findings suggest that Pca1 is a conserved antigen and potential vaccine target. The evaluation of Pca1-elicited antibodies in the prevention of PcP in humans deserves further investigation.

Identification and Functional Ascertainment of the Pneumocystis jirovecii Potential Drug Targets Gsc1 and Kre6 Involved in Glucan Synthesis

The most efficient drug against the human pathogenic fungus Pneumocystis jirovecii is cotrimoxazole targeting the folate biosynthesis. However, resistance toward it is emerging and adverse effects occur in some patients. Studies in rodent models suggested that echinocandins could be useful to treat Pneumocystis pneumonia. Echinocandins inhibit the catalytic subunit Gsc1 of the enzymatic complex ensuring the synthesis of 1,3-β glucan, an essential constituent of cell walls of most fungi. Besides, inhibitors of the enzyme Kre6 involved in the synthesis of 1,6-β glucan, another essential component of fungal walls, were recently described. We identified and functionally characterized these two potential drug targets in the human pathogen P. jirovecii by rescue of the null allele of the orthologous gene in Saccharomyces cerevisiae. The P. jirovecii proteins Gsc1 and Kre6 identified using those of the relative Pneumocystis carinii as the query sequence showed high sequence identity to the putative fungal orthologs (53-97% in conserved functional domains). The expression of their encoding genes on plasmid rescued the increased sensitivity to, respectively, caspofungin or calcofluor white of the corresponding S. cerevisiae null allele. The uniqueness and likely essentiality of these proteins suggest that they are potential good drug targets.

Lower Respiratory Tract Infections

This review will focus on the infectious etiologies and more common noninfectious causes of lower respiratory tract syndromes among major immunosuppressed populations. The changing epidemiology of infections in the era of highly active antiretroviral therapy (HAART) in the case of HIV-positive patients and the impacts of both newer immune-suppressant therapies and anti-infective prophylaxis for other immunocompromised hosts will be discussed, with emphasis on diagnostic approaches and practice algorithms.

A Review of Pneumocystis Pneumonia

Pneumocystis pneumonia remains one of the leading causes of morbidity and mortality in the HIV-infected population. Trimethoprim-sulfamethoxazole remains the drug of choice for both the treatment and prevention of this infection, although a high rate of side effects in HIV-infected patients often necessitates alternative treatment regimens. This article will review pneumocystis pneumonia, with a focus on the various therapeutic options, their side effects, and the immune reconstitution inflammatory syndrome as it relates to pneumocystis pneumonia infection.

Cost-effectiveness of Prophylaxis Against Pneumocystis jiroveci Pneumonia in Patients with Crohn's Disease

BACKGROUND

Emerging evidence suggests that Pneumocystis jiroveci pneumonia is occurring more frequently in Crohn's disease patients on immunosuppressive medications, especially corticosteroids. Considering its excess mortality and the efficacy of chemoprophylaxis in reducing P. jiroveci pneumonia in acquired immunodeficiency syndrome, there is debate without consensus on the need for chemoprophylaxis in Crohn's disease patients on corticosteroids.

AIMS

We sought to address this debate using insights from simulation modeling.

METHODS

We used a Markov microsimulation model to simulate the natural history of Crohn's disease in 1 million virtual patients receiving appropriate care and who faced P. jiroveci pneumonia risks that varied with corticosteroid use. We examined several chemoprophylaxis strategies and compared their population-level economic and clinical impact using various indices including costs, quality-adjusted life expectancy, and incremental cost-effectiveness ratios. We also performed several nested probabilistic sensitivity analyses to estimate the health and economic impact of chemoprophylaxis in patients on triple immunosuppressive therapy.

RESULTS

At the current PJP incidence, no PJP chemoprophylaxis was the preferred strategy from a population perspective. Considered chemoprophylactic strategies led to higher average costs and fewer P. jiroveci pneumonia cases. However, they also led to lower average quality-adjusted life expectancy and were thus dominated. Nevertheless, these alternative strategies became preferred with progressively higher risks of P. jiroveci pneumonia. Our results also suggest that PJP chemoprophylaxis may be cost-effective in patients on triple immunosuppressive therapy.

CONCLUSION

Our findings support a case-by-case consideration of P. jiroveci pneumonia chemoprophylaxis in Crohn's disease patients receiving corticosteroids.

Development of Novel Chitosan Microcapsules for Pulmonary Delivery of Dapsone: Characterization, Aerosol Performance, and In Vivo Toxicity Evaluation

Pneumocystis carinii pneumonia (PCP) is a major opportunistic infection that affects patients with human immunodeficiency virus. Although orally administered dapsone leads to high hepatic metabolism, decreasing the therapeutic index and causing severe side effects, this drug is an effective alternative for the treatment of PCP. In this context, microencapsulation for pulmonary administration can offer an alternative to increase the bioavailability of dapsone, reducing its adverse effects. The aim of this work was to develop novel dapsone-loaded chitosan microcapsules intended for deep-lung aerosolized drug delivery. The geometric particle size (D 4,3) was approximately 7 μm, the calculated aerodynamic diameter (d aero) was approximately 4.5 μm, and the mass median aerodynamic diameter from an Andersen cascade impactor was 4.7 μm. The in vitro dissolution profile showed an efficient dapsone encapsulation, demonstrating the sustained release of the drug. The in vitro deposition (measured by the Andersen cascade impactor) showed an adequate distribution and a high fine particles fraction (FPF = 50%). Scanning electron microscopy of the pulmonary tissues demonstrated an adequate deposition of these particles in the deepest part of the lung. An in vivo toxicity experiment showed the low toxicity of the drug-loaded microcapsules, indicating a protective effect of the microencapsulation process when the particles are microencapsulated. In conclusion, the pulmonary administration of the novel dapsone-loaded microcapsules could be a promising alternative for PCP treatment.

[Pulmonary manifestations in HIV-infected patients: a diagnostic approach]

The spectrum of pulmonary diseases that can affect human immunodeficiency virus (HIV)-infected patients is wide and includes both HIV and non-HIV-related conditions. Opportunistic infections and neoplasms remain a major concern even in the current era of combination antiretroviral therapy. Although these diseases have characteristic clinical and radiological features, there can be considerable variation in these depending on the patient's CD4 lymphocyte count. The patient's history, physical examination, CD4 count and chest radiograph features must be considered in establishing an appropriate diagnostic algorithm. In this article, we propose different diagnostic approaches HIV infected to patients with respiratory symptoms depending on their clinico-radiological pattern.

Antimicrobial Dihydrofolate Reductase Inhibitors - Achievements and Future Options: Review

Despite all progress made in the fight against infections caused by bacteria, fungi, protozoa or viruses, there is a need for more and new active agents. Intensive efforts are currently directed against many new and attractive targets, and are hoped to result in new useful agents. The opportunities offered by some known and validated targets are, however, by far not exhausted. Dihydrofolate reductase (DHFR, EC 1.5.1.3) attracted much attention over several decades, which yielded several useful agents. There are excellent chances for new drugs in this field, and they are thought to increase by limiting the spectrum of activity. Whereas trimethoprim seems to present the optimum which can be achieved for a broad spectrum antibacterial agent, specific agents could probably be designed for well defined groups or specific organisms, such as staphylococci among the bacteria, or for a number of parasites, such as Plasmodium falciparum, the fungus Pneumocystis carinii, and several protozoa, such as Trypanosoma, Toxoplasma, and others. This would even extend to herbicides or specific plant pathogens. Achievements and current efforts directed against new DHFR-inhibitors are reviewed, considering only the most recent literature.

Decision making and management of gliomas: practical considerations

Over the last decade, diagnostic options and introduction of novel treatments have expanded the armamentarium in the management of malignant glioma. Combined chemoradiotherapy has become the standard of care in glioblastoma up to the age of 70 years, while treatment in elderly patients or with lower grade glioma is less well defined. Molecular markers define different disease subtypes and allow for adapted treatment selection. This review focuses on simple questions arising in the daily management of patients.

Kinetic and structural analysis for potent antifolate inhibition of Pneumocystis jirovecii, Pneumocystis carinii, and human dihydrofolate reductases and their active-site variants

A major concern of immunocompromised patients, in particular those with AIDS, is susceptibility to infection caused by opportunistic pathogens such as Pneumocystis jirovecii, which is a leading cause of pneumonia in immunocompromised patients. We report the first kinetic and structural data for 2,4-diamino-6-[(2',5'-dichloro anilino)methyl]pyrido[2,3-d]pyrimidine (OAAG324), a potent inhibitor of dihydrofolate reductase (DHFR) from P. jirovecii (pjDHFR), and also for trimethoprim (TMP) and methotrexate (MTX) with pjDHFR, Pneumocystis carinii DHFR (pcDHFR), and human DHFR (hDHFR). OAAG324 shows a 9.0-fold selectivity for pjDHFR (Ki, 2.7 nM) compared to its selectivity for hDHFR (Ki, 24.4 nM), whereas there is only a 2.3-fold selectivity for pcDHFR (Ki, 6.3 nM). In order to understand the determinants of inhibitory potency, active-site mutations of pj-, pc-, and hDHFR were explored to make these enzymes more like each other. The most unexpected observations were that the variant pcDHFR forms with K37Q and K37Q/F69N mutations, which made the enzyme more like the human form, also made these enzymes more sensitive to the inhibitory activity of OAAG324, with Ki values of 0.26 and 0.71 nM, respectively. A similar gain in sensitivity was also observed for the hDHFR N64F variant, which showed a lower Ki value (0.58 nM) than native hDHFR, pcDHFR, or pjDHFR. Structural data are reported for complexes of OAAG324 with hDHFR and its Q35K and Q35S/N64F variants and for the complex of the K37S/F69N variant of pcDHFR with TMP. These results provide useful insight into the role of these residues in the optimization of highly selective inhibitors of DHFR against the opportunistic pathogen P. jirovecii.

Test performance of blood beta-glucan for Pneumocystis jirovecii pneumonia in patients with AIDS and respiratory symptoms

OBJECTIVE

The objective of this study was to define the test characteristics of plasma beta-glucan for diagnosis of Pneumocystis jirovecii pneumonia (PCP) in AIDS patients with respiratory symptoms.

DESIGN

Analysis of baseline blood samples in a randomized strategy study of patients with acute opportunistic infections, limited to participants with respiratory symptoms.

METHODS

Participants in the 282-person ACTG A5164 trial had baseline plasma samples assayed for beta-glucan testing. As part of A5164 trial, two study investigators independently adjudicated the diagnosis of PCP. Respiratory symptoms were identified by investigators from a list of all signs and symptoms with an onset or resolution in the 21 days prior to or 14 days following study entry. Beta-glucan was defined as positive if at least 80 pg/ml and negative if less than 80 pg/ml.

RESULTS

Of 252 study participants with a beta-glucan result, 159 had at least one respiratory symptom, 139 of whom had a diagnosis of PCP. The sensitivity of beta-glucan for PCP in participants with respiratory symptoms was 92.8% [95% confidence interval (CI) 87.2-96.5], and specificity 75.0% (95% CI 50.9-91.3). Among 134 individuals with positive beta-glucan and respiratory symptoms, 129 had PCP, for a positive predictive value of 96.3% (95% CI 91.5-98.8). Fifteen of 25 patients with a normal beta-glucan did not have PCP, for a negative predictive value of 60% (95% CI 38.7-78.9).

CONCLUSION

Elevated plasma beta-glucan has a high predictive value for diagnosis of PCP in AIDS patients with respiratory symptoms. We propose an algorithm for the use of beta-glucan as a diagnostic tool on the basis of the pretest probability of PCP in such patients.

Non-HIV Pneumocystis pneumonia: do conventional community-acquired pneumonia guidelines under estimate its severity?

Background

Non-HIV Pneumocystis pneumonia (PCP) can occur in immunosuppressed patients having malignancy or on immunosuppressive agents. To classify severity, the A-DROP scale proposed by the Japanese Respiratory Society (JRS), the CURB-65 score of the British Respiratory Society (BTS) and the Pneumonia Severity Index (PSI) of the Infectious Diseases Society of America (IDSA) are widely used in patients with community-acquired pneumonia (CAP) in Japan. To evaluate how correctly these conventional prognostic guidelines for CAP reflect the severity of non-HIV PCP, we retrospectively analyzed 21 patients with non-HIV PCP.

Methods

A total of 21 patients were diagnosed by conventional staining and polymerase chain reaction (PCR) for respiratory samples with chest x-ray and computed tomography (CT) findings. We compared the severity of 21 patients with PCP classified by A-DROP, CURB-65, and PSI. Also, patients’ characteristics, clinical pictures, laboratory results at first visit or admission and intervals from diagnosis to start of specific-PCP therapy were evaluated in both survivor and non-survivor groups.

Results

Based on A-DROP, 18 patients were classified as mild or moderate; respiratory failure developed in 15 of these 18 (83.3%), and 7/15 (46.7%) died. Based on CURB-65, 19 patients were classified as mild or moderate; respiratory failure developed in 16/19 (84.2%), and 8 of the 16 (50%) died. In contrast, PSI classified 14 as severe or extremely severe; all of the 14 (100%) developed respiratory failure and 8/14 (57.1%) died. There were no significant differences in laboratory results in these groups. The time between the initial visit and diagnosis, and the time between the initial visit and starting of specific-PCP therapy were statistically shorter in the survivor group than in the non-survivor group.

Conclusions

Conventional prognostic guidelines for CAP could underestimate the severity of non-HIV PCP, resulting in a therapeutic delay resulting in high mortality. The most important factor to improve the mortality of non-HIV PCP is early diagnosis and starting of specific-PCP therapy as soon as possible.

Structural analysis of human dihydrofolate reductase as a binary complex with the potent and selective inhibitor 2,4-diamino-6-{2'-O-(3-carboxypropyl)oxydibenz[b,f]-azepin-5-yl}methylpteridine reveals an unusual binding mode

In order to understand the structure-activity profile observed for a series of substituted dibenz[b,f]azepine antifolates, the crystal structure of the binary complex of human dihydrofolate reductase (hDHFR) with the potent and selective inhibitor 2,4-diamino-6-{2'-O-(3-carboxypropyl)oxydibenz[b,f]-azepin-5-yl}methylpteridine (PT684) was determined to 1.8 Å resolution. These data revealed that the carboxylate side chain of PT684 occupies two alternate positions, neither of which interacts with the conserved Arg70 in the active-site pocket, which in turn hydrogen bonds to water. These observations are in contrast to those reported for the ternary complex of mouse DHFR (mDHFR) with NADPH [Cody et al. (2008), Acta Cryst. D64, 977-984], in which the 3-carboxypropyl side chain of PT684 was hydrolyzed to its hydroxyl derivative, PT684a. The crystallization conditions differed for the human and mouse DHFR crystals (100 mM K2HPO4 pH 6.9, 30% ammonium sulfate for hDHFR; 15 mM Tris pH 8.3, 75 mM sodium cacodylate, PEG 4K for mDHFR). Additionally, the side chains of Phe31 and Gln35 in the hDHFR complex have a single conformation, whereas in the mDHFR complex they occupied two alternative conformations. These data show that the hDHFR complex has a decreased active-site volume compared with the mDHFR complex, as reflected in a relative shift of helix C (residues 59-64) of 1.2 Å, and a shift of 1.5 Å compared with the ternary complex of Pneumocystis carinii DHFR (pcDHFR) with the parent dibenz[b,f]azepine PT653. These data suggest that the greater inhibitory potency of PT684 against pcDHFR is consistent with the larger active-site volume of pcDHFR and the predicted interactions of the carboxylate side chain with Arg75.

Medical management of patients with brain tumors

OPINION STATEMENT

Patients with brain tumors require meticulous attention to medical issues resulting from their disease or its therapy. The following specific issues are the ones most frequently arising in the purview of neurologists: (1) Vasogenic edema: Corticosteroids should be used in divided doses in the minimum amount required to control symptoms and should be tapered as quickly as possible. Some patients may require long-term steroid supplementation, and symptoms of adrenal insufficiency should be investigated with 8 AM: cortisol measurement and treated with appropriate repletion. (2) Seizures: Patients with brain tumors should receive antiepileptic drugs only if they have had seizures, and the drugs should be chosen to minimize cognitive effects and interactions with concurrently administered chemotherapy. Levetiracetam is an excellent choice for patients with partial seizures and is available both orally and parenterally. Lamotrigine is another reasonable choice but requires slow titration. (3) Venous thromboembolism: All brain tumor patients should receive perioperative venous thrombosis prophylaxis with compression boots and enoxaparin or dalteparin. Lifelong treatment with low molecular weight heparinoids or warfarin is required for those developing venous thromboembolism. (4) Other problems: Long-term survivors of brain tumors should be monitored indefinitely for cognitive problems, endocrine dysfunction, and development of secondary neoplasms. Modafinil can improve mood and attention impairments.

Crystallographic analysis reveals a novel second binding site for trimethoprim in active site double mutants of human dihydrofolate reductase

In order to produce a more potent replacement for trimethoprim (TMP) used as a therapy for Pneumocystis pneumonia and targets dihydrofolate reductase from Pneumocystis jirovecii (pjDHFR), it is necessary to understand the determinants of potency and selectivity against DHFR from the mammalian host and fungal pathogen cells. To this end, active site residues in human (h) DHFR were replaced with those from pjDHFR. Structural data are reported for two complexes of TMP with the double mutants Gln35Ser/Asn64Phe (Q35S/N64F) and Gln35Lys/Asn64Phe (Q35K/N64F) of hDHFR that unexpectedly show evidence for the binding of two molecules of TMP: one molecule that binds in the normal folate binding site and the second molecule that binds in a novel subpocket site such that the mutated residue Phe64 is involved in van der Waals contacts to the trimethoxyphenyl ring of the second TMP molecule. Kinetic data for the binding of TMP to hDHFR and pjDHFR reveal an 84-fold selectivity of TMP against pjDHFR (K(i) 49 nM) compared to hDHFR (K(i) 4093 nM). Two mutants that contain one substitution from pj--and one from the closely related Pneumocystis carinii DHFR (pcDHFR) (Q35K/N64F and Q35S/N64F) show K(i) values of 593 and 617 nM, respectively; these K(i) values are well above both the K(i) for pjDHFR and are similar to pcDHFR (Q35K/N64F and Q35S/N64F) (305nM). These results suggest that active site residues 35 and 64 play key roles in determining selectivity for pneumocystis DHFR, but that other residues contribute to the unique binding of inhibitors to these enzymes.

A limited number of ITS haplotypes defines the diversity of Pneumocystis jirovecii strains in Sweden

The infectious fungus Pneumocystis jirovecii remains an important cause of pneumonia (PCP) in the immunocompromised host. To study the biodiversity of P. jirovecii in Sweden the internal transcribed spacers (ITS) of the rDNA locus were amplified, cloned and sequenced from a set of diagnostic respiratory specimens obtained from 64 patients with P. jirovecii infection during the years 1996-2003. The analysis of 408 cloned sequences from amplified products resulted in the identification of 10 ITS1 and 12 ITS2 established genotypes. Twelve ITS haplotypes (combinations of ITS1 and ITS2) were identified of which nine were found to recur during the time span of the study. Haplotype Eg was the most common, followed by Ne, Bi and Eb. A new ITS2 genotype denoted v was identified in specimens from four patients. There was no association between ITS haplotype and patient age, sex, underlying disease or geographical origin. Shannon and Simpson index analysis revealed no difference in diversity in Sweden compared to other countries studied and no changes in diversity were found during the study period in Sweden. Criteria were defined to enable the discrimination of genuine ITS types and a more accurate assessment of the previously overestimated genetic diversity of P. jirovecii populations. A model depicting the phylogenetic and genealogic relationships in a revised set of global types of this fungus is presented.

Pneumocystis infection in an immunocompetent host can promote collateral sensitization to respiratory antigens

Infection with the opportunistic fungal pathogen Pneumocystis is assumed to pass without persistent pathology in immunocompetent hosts. However, when immunocompetent BALB/c mice were inoculated with Pneumocystis, a vigorous Th2-like pulmonary inflammation ensued and peaked at 14 days postinfection. This coincided with a 10-fold increase in the number of antigen-presenting cells (APCs) in the lung, and these cells were capable of presenting antigen in vitro, as well as greater uptake of antigen in vivo. When mice were presented with exogenous antigen at the 14-day time point of the infection, they developed respiratory sensitization to that antigen, in the form of increased airway hyperresponsiveness upon a later challenge, whereas mice not infected but presented with antigen did not. Like other forms of collateral sensitization, this response was dependent on interleukin-4 receptor signaling. This ability to facilitate sensitization to exogenous antigen has been previously reported for other infectious disease agents; however, Pneumocystis appears to be uniquely capable in this respect, as a single intranasal dose without added adjuvant, when it was administered at the appropriate time, was sufficient to initiate sensitization. Pneumocystis infection probably occurs in most humans during the first few years of life, and in the vast majority of cases, it fails to cause any overt direct pathology. However, as we show here, Pneumocystis can be an agent of comorbidity at this time by facilitating respiratory sensitization that may relate to the later development or exacerbation of obstructive airway disease.

Minimally Invasive Diagnostic Strategy in Immunocompromised Patients with Pulmonary Infiltrates

Acute respiratory failure (ARF) is the main reason for ICU admission in patients with haematological malignancies. High mortality rates of up to 50% are reported in this situation, and mortality is highest when mechanical ventilation is needed. Rapid and accurate diagnostic methods are needed in these vulnerable patients to ensure the prompt initiation of effective treatment. However, the broad array of possible cause of ARF raises diagnostic challenges. In this review, we discuss the DIRECT strategy, which identifies the most plausible diagnosis in each patient based on the type of immune deficiency and clinical presentation. We will focus on non-invasive laboratory tests developed in recent years, discussing their sensitivity and specificity. We also discuss the usefulness in cancer patients with specific organ dysfunctions of biomarkers introduced over the past few years.

Kinetics of serum β-D-glucan after Pneumocystis pneumonia treatment in patients with AIDS

OBJECTIVE

Serum β-D-glucan has been demonstrated as a reliable, adjunct diagnostic marker for PCP, but its kinetics after PCP treatment are poorly understood. To evaluate the correlation between the levels of β-D-glucan and the clinical response, we investigated the individual transition of serum β-D-glucan levels after the initiation of PCP treatment.

METHODS

Retrospective study

PATIENTS

Seventeen PCP patients with AIDS who were admitted to our hospital were analyzed.

RESULTS

All subjects showed the serum β-D-glucan levels above the cut-off value, and the median level was 224 pg/mL [IQR: 78-597] at the time of PCP diagnosis. There were no correlations between serum β-D-glucan levels and CRP, LDH, or AaDO(2) at room air. Although there was a downward trend in serum β-D-glucan level as PCP treatment was initiated, a significant number of subjects showed a marked increase in the serum β-D-glucan levels despite their evident clinical improvement.

CONCLUSION

The serum β-D-glucan level does not reflect the severity and prognosis of PCP infection, and thus it may not be suitable for monitoring the response to treatment.