Pneumocystis pneumonia: current concepts in pathogenesis, diagnosis, and treatment

Next-generation sequencing technology for the diagnosis of Pneumocystis pneumonia in an immunocompetent female: A case report

BACKGROUND

Pneumocystis pneumonia (PCP) is a serious fungal infection usually seen in patients with human immunodeficiency virus, and it is more frequently found and has a high fatality rate in immunocompromised people. Surprisingly, it rarely occurs in immunocompetent patients. However, the clinical diagnosis of this pathogen is made more difficult by the difficulty of obtaining accurate microbiological evidence with routine tests. This case reports a PCP patient with normal immune function who was diagnosed through next-generation sequencing (NGS).

CASE SUMMARY

A 23-year-old female who had no special disease in the past was admitted to the hospital with a persistent fever and cough. Based on the initial examination results, the patient was diagnosed with bipulmonary pneumonia, and empirical broad-spectrum antibiotic therapy was administered. However, due to the undetermined etiology, the patient's condition continued to worsen. She was transferred to the intensive care unit because of acute respiratory failure. After the diagnosis of Pneumocystis jirovecii infection through NGS in bronchoalveolar lavage fluid and treatment with trimethoprim/sulfamethoxazole and caspofungin, the patient gradually recovered and had a good prognosis.

CONCLUSION

This case emphasizes that, for patients with normal immune function the possibility of PCP infection, although rare, cannot be ignored. NGS plays an important role in the diagnosis of refractory interstitial pneumonia and acute respiratory failure.

The mycological and molecular study of Pneumocystis jiroveci pneumonia among HIV and non-HIV immunocompromised patients hospitalized in pulmonary units in Guilan, Northern Iran

Background and Objectives

Pneumocystis jirovecii pneumonia (PJP) is a serious infection that usually affects those with a weak immune system. Since the prevalence of this infection in Iran and in the world is not clearly defined, the present study aimed to evaluate the incidence, clinical spectrum, and demographic characteristics of PJP among HIV and non-HIV immunocompromised patients.

Materials and Methods

Bronchoalveolar Lavage (BAL) specimens were obtained from 3 groups of immunocompromised patients, including acquired immunodeficiency syndrome (AIDS) patients, diabetic patients, and patients receiving immunosuppressive therapies. All were hospitalized in pulmonary units. The specimens were examined using microscopic methods (Giemsa and calcofluor white staining) and the nested-PCR technique based on mtLSU-rRNA gene.

Results

A total of 120 BAL samples were collected. From 12.5% (5 from 40) of HIV-infected patients, 5% (2 from 40) of patients receiving immunosuppressive therapies, and 2.5% (1 from 40) of diabetic patients Pneumocystis jiroveci was isolated. There was not any association between the prevalence of PJP and the patient's gender (p= 0.557) and age (p= 0.681). Fever and dyspnea (n=7, 87.5%), nonproductive cough and abnormal auscultation sound (n=5, 62.5%), and also chills and weight loss (n=2, 25%) were the documented clinical symptoms of PJP. Also, the results showed that none of the samples had positive results for P. jiroveci with microscopic tests while using the nested-PCR method 8 samples had positive results.

Conclusion

Since PJP often causes symptoms that are similar to other illnesses, such as the flu or tuberculosis, clinical and laboratory findings should be used simultaneously for making the final decision on drug administration.

Pneumocystis Pneumonia: Immunity, Vaccines, and Treatments

For individuals who are immunocompromised, the opportunistic fungal pathogen Pneumocystis jirovecii is capable of causing life-threatening pneumonia as the causative agent of Pneumocystis pneumonia (PCP). PCP remains an acquired immunodeficiency disease (AIDS)-defining illness in the era of antiretroviral therapy. In addition, a rise in non-human immunodeficiency virus (HIV)-associated PCP has been observed due to increased usage of immunosuppressive and immunomodulating therapies. With the persistence of HIV-related PCP cases and associated morbidity and mortality, as well as difficult to diagnose non-HIV-related PCP cases, an improvement over current treatment and prevention standards is warranted. Current therapeutic strategies have primarily focused on the administration of trimethoprim-sulfamethoxazole, which is effective at disease prevention. However, current treatments are inadequate for treatment of PCP and prevention of PCP-related death, as evidenced by consistently high mortality rates for those hospitalized with PCP. There are no vaccines in clinical trials for the prevention of PCP, and significant obstacles exist that have slowed development, including host range specificity, and the inability to culture Pneumocystis spp. in vitro. In this review, we overview the immune response to Pneumocystis spp., and discuss current progress on novel vaccines and therapies currently in the preclinical and clinical pipeline.

Clinical characteristics and prognosis of patients with Pneumocystis jirovecii pneumonia without a compromised illness

Objective

Pneumocystis jirovecii pneumonia (PCP) is a fatal respiratory infection, mostly associated with immunocompromised conditions. Several reports have described PCP development in patients who were not immunocompromised, but the clinical course and prognosis of PCP are not well understood. We compared the clinical characteristics and prognoses between patients with and without immunocompromised conditions who developed PCP.

Methods

We retrospectively analyzed patients who had been treated for PCP from three hospitals. We defined immunocompromised (IC) status as following: human immunodeficiency virus (HIV) infection; hematological malignancy; solid organ tumor under chemotherapy; rheumatic disease; medication with immunosuppressive agents. Patients without immunocompromised status were defined as being non-immunocompromised (non-IC).

Results

The IC and non-IC groups comprised 173 and 14 patients. The median ages were 62.0 and 74.0 years in the IC and the non-IC group, respectively. The median interval between admission and anti-PCP treatment was significantly longer for patients in the non-IC group than that for patients in the IC group (7 vs. 2 days). The in-hospital mortality rates were significantly higher for patients in the non-IC group than that for patients in the IC group (71.4% vs. 43.9%; P = 0.047). A longer interval between admission and anti-PCP therapy was associated with increased 90-day mortality rate in patients with PCP (hazard ratio, 1.082; 95% confidence interval, 1.015–1.153; P = 0.016).

Conclusions

Patients with PCP with no predisposing illnesses were older and had higher mortality rates than IC patients with PCP. Delayed anti-PCP treatment was associated with increased 90-day mortality.

Invasive fungal disease in humans: are we aware of the real impact?

Despite the medical advances and interventions to improve the quality of life of those in intensive care, people with cancer or severely immunocompromised or other susceptible hosts, invasive fungal diseases (IFD) remain severe and underappreciated causes of illness and death worldwide. Therefore, IFD continue to be a public health threat and a major hindrance to the success of otherwise life-saving treatments and procedures. Globally, hundreds of thousands of people are affected every year with Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans, Pneumocystis jirovecii, endemic dimorphic fungi and Mucormycetes, the most common fungal species causing invasive diseases in humans. These infections result in morbidity and mortality rates that are unacceptable and represent a considerable socioeconomic burden. Raising the general awareness of the significance and impact of IFD in human health, in both the hospital and the community, is hence critical to understand the scale of the problem and to raise interest to help fighting these devastating diseases.

Clinical characteristics and prevalence of dihydropteroate synthase gene mutations in Pneumocystis jirovecii-infected AIDS patients from low endemic areas of China

Pneumocystis pneumonia (PCP) is an opportunistic and potentially life-threatening infection of AIDS patients caused by the fungus Pneumocystis jirovecii (P. jirovecii). Trimethoprim-sulfamethoxazole (TMP-SMX) is the most commonly used drug combination in the treatment and prophylaxis of PCP. However, with long-term use of this combination, mutations in the dihydropteroate synthase (DHPS) gene of P. jirovecii bring about the development of resistance. Data on the prevalence of P. jirovecii and its DHPS mutants in China, especially in low endemic areas, are still limited. Thus, in the present study, we measured the P. jirovecii infection rate among HIV-positive and AIDS (HIV/AIDS) patients with suspected PCP and investigated the relationship between CD4+ T cell count and PCP occurrence. As well as the polymerase chain reaction (PCR) analysis and sequencing, the restriction fragment length polymorphism (RFLP) method was used to analyze DHPS point mutation in P. jirovecii strains. P. jirovecii was detected in 40.82% of cases. The clinical symptoms and signs of PCP were not typical; with decreasing CD4+ T cell counts, PCP infection in HIV/AIDS patients increased. In only one case (1.67%), the patients' DHPS gene could not be cut by the Acc I restriction enzyme. Furthermore, mutation at codon 171 was detected in 11 cases and no mutation was found at codon 57. Patients treated with sulfamethoxazole combined with Voriconazole or Caspofungin exhibited favorable results. After treatment, the symptoms of dyspnea were alleviated, and chest computed tomography findings showed the improvement of lung shadows. These indicated that the prevalence of DHPS mutations in P. jirovecii isolates in AIDS-PCP patients in the region was low. Thus, the contribution of gene mutations to treatment failure requires further research.

Niflumic Acid Reverses Airway Mucus Excess and Improves Survival in the Rat Model of Steroid-Induced Pneumocystis Pneumonia

Although the role of adaptive immunity in fighting Pneumocystis infection is well known, the role of the innate, airway epithelium, responses remains largely unexplored. The concerted interaction of innate and adaptive responses is essential to successfully eradicate infection. Increased expression of goblet-cell-derived CLCA1 protein plus excess mucus in infant autopsy lungs and in murine models of primary Pneumocystis infection alert of innate immune system immunopathology associated to Pneumocystis infection. Nonetheless, whether blocking mucus-associated innate immune pathways decreases Pneumocystis-related immunopathology is unknown. Furthermore, current treatment of Pneumocystis pneumonia (PcP) relying on anti-Pneumocystis drugs plus steroids is not ideal because removes cellular immune responses against the fungal pathogen. In this study, we used the steroid-induced rat model of PcP to evaluate inflammation and mucus progression, and tested the effect of niflumic acid (NFA), a fenamate-type drug with potent CLCA1 blocker activity, in decreasing Pneumocystis-associated immunopathology. In this model, animals acquire Pneumocystis spontaneously and pneumonia develops owing to the steroids-induced immunodeficiency. Steroids led to decreased animal weight evidencing severe immunosuppression and to significant Pneumocystis-associated pulmonary edema as evidenced by wet-to-dry lung ratios that doubled those of uninfected animals. Inflammatory cuffing infiltrates were noticed first around lung blood vessels followed by bronchi, and both increased progressively. Similarly, airway epithelial and lumen mucus progressively increased. This occurred in parallel to increasing levels of MUC5AC and mCLCA3, the murine homolog of hCLCA1. Administration of NFA caused a significant decrease in total mucus, MUC5AC and mCLCA3 and also, in Pneumocystis-associated inflammation. Most relevant, NFA treatment improved survival at 8 weeks of steroids. Results suggest an important role of innate immune responses in immunopathology of steroid-induced PcP. They warrant evaluation of CLCA1 blockers as adjunctive therapy in this condition and describe a simple model to evaluate therapeutic interventions for steroid resistant mucus, a common condition in patients with chronic lung disease like asthma, chronic obstructive pulmonary disease (COPD) and cystic fibrosis.

Global and Multi-National Prevalence of Fungal Diseases-Estimate Precision

Fungal diseases kill more than 1.5 million and affect over a billion people. However, they are still a neglected topic by public health authorities even though most deaths from fungal diseases are avoidable. Serious fungal infections occur as a consequence of other health problems including asthma, AIDS, cancer, organ transplantation and corticosteroid therapies. Early accurate diagnosis allows prompt antifungal therapy; however this is often delayed or unavailable leading to death, serious chronic illness or blindness. Recent global estimates have found 3,000,000 cases of chronic pulmonary aspergillosis, ~223,100 cases of cryptococcal meningitis complicating HIV/AIDS, ~700,000 cases of invasive candidiasis, ~500,000 cases of Pneumocystis jirovecii pneumonia, ~250,000 cases of invasive aspergillosis, ~100,000 cases of disseminated histoplasmosis, over 10,000,000 cases of fungal asthma and ~1,000,000 cases of fungal keratitis occur annually. Since 2013, the Leading International Fungal Education (LIFE) portal has facilitated the estimation of the burden of serious fungal infections country by country for over 5.7 billion people (>80% of the world's population). These studies have shown differences in the global burden between countries, within regions of the same country and between at risk populations. Here we interrogate the accuracy of these fungal infection burden estimates in the 43 published papers within the LIFE initiative.

Human immunodeficiency virus and fungal infections

The discovery of HIV was largely due to the presence of Pneumocystis pneumonia (PCP) in young patients that did not have the usual known causes of immune deficiencies in the early 1980s. Currently, treatment with highly active anti-retroviral therapy (HAART) and the use of prophylaxis for PCP have lowered the frequency of fungal infections; however, these infections continue to cause morbidity and mortality in those patients that fall out or are not in care. The frequency of specific fungal diseases in HIV patients will depend on the prevalence of fungi in the particular geographic location. Nowadays, superficial and invasive Candida infections, PCP, and cryptococci are the most frequent fungal infections seen in HIV positive patients worldwide. The role of pathology in diagnosing fungal infections is crucial because a lesion may be biopsied without obtaining mycology cultures, certain organisms may take several weeks to grow, or the sample sent to the mycology laboratory may not have the organism. Following we will describe fungal infections that are particularly frequent in HIV infected patients and their key pathological features.

[Pneumocystis pneumonia in HIV-negative adults]

In HIV-negative adults, Pneumocystis jirovecii pneumonia can be observed when immunodeficiency is present, especially in case of drug-induced immune suppression (steroids, chemotherapy, transplantation). Clinical, radiological, and biological presentations are different in HIV-positive and HIV-negative individuals with different immunodeficiency profiles. In HIV-negative patients, dyspnea occurs more quickly (median duration of 5 days to get a diagnosis), diagnosis is more difficult because of less Pneumocystis in bronchoalveolar lavage, and mortality is higher than in HIV-positive individuals. Lung CT-scan typically shows diffuse ground glass opacities, but peri-bronchovascular condensations or ground glass opacities clearly limited by interlobular septa can also be observed. Lymphopenia is common but CD4+ T-cells count is rarely performed. HIV-negative patients with Pneumocystis pneumonia are co-infected with bacteria, viruses or fungi in about 30% cases. Bronchoalveolar lavage is often more neutrophilic than in HIV-positive individuals. PCR and β-D-glucan have good sensitivity but poor specificity to diagnose Pneumocystis pneumonia. Trimethoprim-sulfamethoxazole remains the first choice of treatment. Duration is 14 days in HIV-negative patients whereas it is typically of 21 days in HIV-positive individuals. Adjunctive corticosteroids are of beneficial effect in HIV-positive adult patients with substantial hypoxaemia but are not recommended in HIV-negative patients, as they could be deleterious in some individuals.

Type I IFNs Act upon Hematopoietic Progenitors To Protect and Maintain Hematopoiesis during Pneumocystis Lung Infection in Mice

Although acquired bone marrow failure (BMF) is considered a T cell-mediated autoimmune disease, few studies have considered contributing roles of innate immune deviations following otherwise innocuous infections as a cause underlying the immune defects that lead to BMF. Type I IFN signaling plays an important role in protecting hematopoiesis during systemic stress responses to the opportunistic fungal pathogen Pneumocystis. During Pneumocystis lung infection, mice deficient in both lymphocytes and type I IFN receptor (IFrag(-/-)) develop rapidly progressing BMF associated with accelerated hematopoietic cell apoptosis. However, the communication pathway eliciting the induction of BMF in response to this strictly pulmonary infection has been unclear. We developed a conditional-null allele of Ifnar1 and used tissue-specific induction of the IFrag(-/-) state and found that, following Pneumocystis lung infection, type I IFNs act not only in the lung to prevent systemic immune deviations, but also within the progenitor compartment of the bone marrow to protect hematopoiesis. In addition, transfer of sterile-filtered serum from Pneumocystis-infected mice as well as i.p. injection of Pneumocystis into uninfected IFrag(-/-) mice induced BMF. Although specific cytokine deviations contribute to induction of BMF, immune-suppressive treatment of infected IFrag(-/-) mice ameliorated its progression but did not prevent loss of hematopoietic progenitor functions. This suggested that additional, noncytokine factors also target and impair progenitor functions; and interestingly, fungal β-glucans were also detected in serum. In conclusion, our data demonstrate that type 1 IFN signaling protects hematopoiesis within the bone marrow compartment from the damaging effects of proinflammatory cytokines elicited by Pneumocystis in the lung and possibly at extrapulmonary sites via circulating fungal components.

Dapsone Hypersensitivity Syndrome in a Patient With Acquired Immunodeficiency Syndrome

Objective: A case of dapsone hypersensitivity syndrome (DHS) in an AIDS patient receiving dapsone for Pneumocystis pneumonia (PCP) prophylaxis is discussed. Case Summary: A 50-year-old Caucasian male with a history of AIDS was admitted with suspicion of pneumonia. The clinical presentation consisted of shortness of breath, occasional hemoptysis, odynophagia, skin rash, transaminitis, anemia, malaise, and peripheral neuropathy. His medications included nystatin, fluconazole, valacyclovir, and pantoprazole. For PCP prophylaxis, the patient was initiated on dapsone 100 mg daily approximately 4 weeks prior to admission. The patient was also on a 3-drug regimen for the treatment of mycobacterium avium complex: clarithromycin, rifabutin, and ethambutol. After extensive work up, DHS was diagnosed. Dapsone was immediately discontinued and the patient was started on intravenous methylprednisolone, gradually tapered, and transitioned to oral prednisone. On discontinuation of dapsone, the patient improved, evidenced by decreased need for oxygen and reversal of peripheral neuropathy, anemia, and transaminitis. The patient’s skin rash improved within a few days. An objective causality assessment, with the Naranjo scale, suggests that DHS was probably related to dapsone. Discussion: Our patient only exhibited some of the classic symptoms observed in DHS such as skin eruptions, malaise, hepatic failure, and hemolytic anemia. The patient, however, did not present with lymphadenopathy and fever commonly noted in DHS, which may be attributed to his immunosuppressed state, evidenced by a CD4 count of 7 cell/mm3. Conclusions: A patient on dapsone for PCP prophylaxis was diagnosed with DHS. Clinicians and patients should be educated on risk factors and clinical presentation of DHS so that when initial symptoms appear they can be treated promptly. Clinicians should also be aware that patients infected with HIV/AIDS may not present with all the classic symptoms of DHS due to their immunocompromised state. Therefore, practitioners should be vigilant when initiating dapsone in this patient population.

Prevalence and genotype distribution of Pneumocystis jirovecii in Cuban infants and toddlers with whooping cough

This study describes the prevalence and genotype distribution of Pneumocystis jirovecii obtained from nasopharyngeal (NP) swabs from immunocompetent Cuban infants and toddlers with whooping cough (WC). A total of 163 NP swabs from 163 young Cuban children with WC who were admitted to the respiratory care units at two pediatric centers were studied. The prevalence of the organism was determined by a quantitative PCR (qPCR) assay targeting the P. jirovecii mitochondrial large subunit (mtLSU) rRNA gene. Genotypes were identified by direct sequencing of mtLSU ribosomal DNA (rDNA) and restriction fragment length polymorphism (RFLP) analysis of the dihydropteroate synthase (DHPS) gene amplicons. qPCR detected P. jirovecii DNA in 48/163 (29.4%) samples. mtLSU rDNA sequence analysis revealed the presence of three different genotypes in the population. Genotype 2 was most common (48%), followed in prevalence by genotypes 1 (23%) and 3 (19%); mixed-genotype infections were seen in 10% of the cases. RFLP analysis of DHPS PCR products revealed four genotypes, 18% of which were associated with resistance to sulfa drugs. Only contact with coughers (prevalence ratio [PR], 3.51 [95% confidence interval {CI}, 1.79 to 6.87]; P = 0.000) and exposure to tobacco smoke (PR, 1.82 [95% CI, 1.14 to 2.92]; P = 0.009) were statistically associated with being colonized by P. jirovecii. The prevalence of P. jirovecii in infants and toddlers with WC and the genotyping results provide evidence that this population represents a potential reservoir and transmission source of P. jirovecii.

Delayed opportunistic infections in hematopoietic stem cell transplantation patients: a surmountable challenge

Changes in the transplantation procedure and the implementation of effective supportive care strategies have decreased the incidence of infectious complications early after conditioning therapy for allogeneic hematopoietic stem cell transplantation (HCT) and have extended the duration of risks later. Therefore, the types of infections that cause significant morbidity and the timing of risks have changed. These late infections are caused by all types of organisms, bacterial, viral, and fungal, but risks are predictable and surmountable with the use of tailored prevention strategies. Specifically, recent studies document prolonged risks for bacterial infections in the setting of GVHD, especially those caused by encapsulated organisms and those secondary to impaired Ab responses. Both prophylaxis and vaccination strategies can be used as a means to prevent infections, which typically manifest in the respiratory tract. Multiple viruses cause infection later after HCT, including several herpesviruses (eg, CMV and varicella zoster virus) and other respiratory viruses such as influenza and adenovirus. These infections can cause severe disease with diagnostic challenges, but prevention strategies using enhanced monitoring and/or prophylaxis may be effective. Finally, fungi also cause disease late after HCT, especially filamentous fungi (eg, Aspergillus species and Mucormycoses) and Pneumocystis jiroveci; prophylactic strategies may be used successfully to prevent invasive infection. Late infections and methods to prevent them are reviewed herein.

Specific detection of Pneumocystis jirovecii in clinical samples by flow cytometry

Pneumocystis jirovecii is an opportunistic pathogen responsible for severe pneumonia in immunocompromised patients. Flow cytometry (FC) is a method widely used in different areas of clinical diagnosis like hematology and immunology. Recently it has started to be used in microbiology with a great potential for diagnosis of emergent microorganisms in clinical samples, especially when present in low numbers. The detection of Pneumocystis jirovecii in respiratory samples can be performed by FC, using specific monoclonal antibodies. Considering clinical diagnosis as a reference method, we previously showed FC to be 100% sensitive and specific when compared to immunofluorescence. Being an automated method, it is faster and less subject to human error than microscopic evaluation.

Metagenomic profiles of free-living archaea, bacteria and small eukaryotes in coastal areas of Sichang island, Thailand

Background

Tha Wang and Tham Phang coasts, though situated at similar oceanographic positions on Sichang island, Chonburi province, Thailand, are different in bay geography and amount of municipal disturbances. These affect the marine ecosystems. The study used metagenomics combined with 16S and 18S rDNA pyrosequencing to identify types and distributions of archaea, bacteria, fungi and small eukaryotes of sizes ranges 0.45 and ~30 μm.

Results

Following the open bay geography and minimal municipal sewages, Tham Phang coast showed the cleaner water properties, described by color, salinity, pH, conductivity and percent dissolved oxygen. The 16S and 18S rDNA metagenomic profiles for Tha Wang and Tham Phang coasts revealed many differences, highlighting by low Lennon and Yue & Clayton theta similarity indices (66.03-73.03% for 16S rDNA profiles, 2.85-25.38% for 18S rDNA profiles). For 16S rDNA, the percent compositions of species belonging to Proteobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, Verrucomicrobia, Gammatimonadetes, Tenericutes, Acidobacteria, Spirochaetes, Chlamydiae, Euryarchaeota, Nitrospirae, Planctomycetes, Thermotogae and Aquificae were higher or distinctly present in Tha Wang. In Tham Phang, except Actinobacteria, the fewer number of prokaryotic species existed. For 18S rDNA, fungi represented 74.745% of the species in Tha Wang, whereas only 6.728% in Tham Phang. Basidiomycota (71.157%) and Ascomycota (3.060%) were the major phyla in Tha Wang. Indeed, Tha Wang-to-Tham Phang percent composition ratios for fungi Basidiomycota and Chytridiomycota were 1264.701 and 25.422, respectively. In Tham Phang, Brachiopoda (lamp shells) and Mollusca (snails) accounted for 80.380% of the 18S rDNA species detected, and their proportions were approximately tenfold greater than those in Tha Wang. Overall, coastal Tham Phang comprised abundant animal species.

Conclusions

Tha Wang contained numerous archaea, bacteria and fungi, many of which could synthesize useful biotechnology gas and enzymes that could also function in high-saline and high-temperature conditions. Tham Phang contained less abundant archaea, bacteria and fungi, and the majority of the extracted metagenomes belonged to animal kingdom. Many microorganisms in Tham Phang were essential for nutrient-recycling and pharmaceuticals, for instances, Streptomyces, Pennicilium and Saccharomyces. Together, the study provided metagenomic profiles of free-living prokaryotes and eukaryotes in coastal areas of Sichang island.

Delayed opportunistic infections in hematopoietic stem cell transplantation patients: a surmountable challenge

Changes in the transplantation procedure and the implementation of effective supportive care strategies have decreased the incidence of infectious complications early after conditioning therapy for allogeneic hematopoietic stem cell transplantation (HCT) and have extended the duration of risks later. Therefore, the types of infections that cause significant morbidity and the timing of risks have changed. These late infections are caused by all types of organisms, bacterial, viral, and fungal, but risks are predictable and surmountable with the use of tailored prevention strategies. Specifically, recent studies document prolonged risks for bacterial infections in the setting of GVHD, especially those caused by encapsulated organisms and those secondary to impaired Ab responses. Both prophylaxis and vaccination strategies can be used as a means to prevent infections, which typically manifest in the respiratory tract. Multiple viruses cause infection later after HCT, including several herpesviruses (eg, CMV and varicella zoster virus) and other respiratory viruses such as influenza and adenovirus. These infections can cause severe disease with diagnostic challenges, but prevention strategies using enhanced monitoring and/or prophylaxis may be effective. Finally, fungi also cause disease late after HCT, especially filamentous fungi (eg, Aspergillus species and Mucormycoses) and Pneumocystis jiroveci; prophylactic strategies may be used successfully to prevent invasive infection. Late infections and methods to prevent them are reviewed herein.

Pneumocystis jirovecii pneumonia associated with etanercept treatment in patients with rheumatoid arthritis: a retrospective review of 15 cases and analysis of risk factors

OBJECTIVES

The association of anti-tumor necrosis factor therapy with opportunistic infections in rheumatoid arthritis (RA) patients has been reported. The goal of this study was to clarify the clinical characteristics and the risk factors of RA patients who developed Pneumocystis jirovecii pneumonia (PCP) during etanercept therapy.

METHODS

We conducted a multicenter, case-control study in which 15 RA patients who developed PCP were compared with 74 RA patients who did not develop PCP during etanercept therapy.

RESULTS

PCP developed within 26 weeks following the first injection of etanercept in 86.7% of the patients. All PCP patients presented with a rapid and severe clinical course and the overall mortality was 6.7%. Independent risk factors were identified using multivariate analysis and included age ≥65 years [hazard ratio (HR) 3.35, p = 0.037], coexisting lung disease (HR 4.48, p = 0.009), and concomitant methotrexate treatment (HR 4.68, p = 0.005). In patients having a larger number of risk factors, the cumulative probability of developing PCP was significantly higher (p < 0.001 for patients with two or more risk factors vs. those with no risk factor, and p = 0.001 for patients with one risk factor vs. those with no risk factor).

CONCLUSION

Physicians must consider the possibility of PCP developing during etanercept therapy in RA patients, particularly if one or more risk factors are present.

A prognostic scoring tool for identification of patients at high and low risk of death from HIV-associated Pneumocystis jirovecii pneumonia

A prognostic scoring tool (PST) was created to aid prediction of outcome from HIV-associated Pneumocystis jirovecii pneumonia (PCP) using data obtained from 577 episodes of PCP among 540 patients presenting to a specialist HIV treatment centre in London, UK. It used risk factors identifiable at/soon after hospitalization, previously identified as being associated with mortality: repeat episode of PCP, patient's age, haemoglobin (Hb) and oxygen partial pressure (PaO2) on admission, presence of medical co-morbidity (Comorb) and of pulmonary Kaposi sarcoma (PKS). The derived PST was 25.5+(age in years/10) + 2 (if a repeat episode of PCP) + 3 (if Comorb present) + 4 (if PKS detected) – PaO2 (kPa) – Hb (g/dL), and produced scores that ranged between 0 and 19. Patients were divided into five groups according to their prognostic score: 0-3.9 = group 1 (0% mortality), 4-7.9 = group 2 (3% mortality), 8-10.9 = group 3 (9% mortality), 11-14.9 = group 4 (29% mortality) and ≥15 = group 5 (52% mortality). This PST facilitates rapid identification of patients early in their hospitalization who have mild or severe HIV-associated PCP and who are at high and low risk of in-hospital death from PCP. The PST may aid assessment of severity of illness and in directing treatment strategies, but requires validation in patient cohorts from other healthcare institutions.

Substrate analysis of the Pneumocystis carinii protein kinases PcCbk1 and PcSte20 using yeast proteome microarrays provides a novel method for Pneumocystis signalling biology

Pneumocystis carinii (Pc) undergoes morphological transitions between cysts and trophic forms. We have previously described two Pc serine/threonine kinases, termed PcCbk1 and PcSte20, with PcSte20 belonging to a family of kinases involved in yeast mating, while PcCbk1 is a member of a group of protein kinases involved in regulation of cell cycle, shape, and proliferation. As Pc remains genetically intractable, knowledge on specific substrates phosphorylated by these kinases remains limited. Utilizing the phylogenetic relatedness of Pc to Saccharomyces cerevisiae, we interrogated a yeast proteome microarray containing >4000 purified protein based peptides, leading to the identification of 18 potential PcCbk1 and 15 PcSte20 substrates (Z-score > 3.0). A number of these potential protein substrates are involved in bud site selection, polarized growth, and response to mating α factor and pseudohyphal and invasive growth. Full-length open reading frames suggested by the PcCbk1 and PcSte20 protoarrays were amplified and expressed. These five proteins were used as substrates for PcCbk1 or PcSte20, with each being highly phosphorylated by the respective kinase. Finally, to demonstrate the utility of this method to identify novel PcCbk1 and PcSte20 substrates, we analysed DNA sequence data from the partially complete Pc genome database and detected partial sequence information of potential PcCbk1 kinase substrates PcPxl1 and PcInt1. We additionally identified the potential PcSte20 kinase substrate PcBdf2. Full-length Pc substrates were cloned and expressed in yeast, and shown to be phosphorylated by the respective Pc kinases. In conclusion, the yeast protein microarray represents a novel crossover technique for identifying unique potential Pc kinase substrates.

Cost-effectiveness analysis of diagnostic options for pneumocystis pneumonia (PCP)

Background

Diagnosis of Pneumocystis jirovecii pneumonia (PCP) is challenging, particularly in developing countries. Highly sensitive diagnostic methods are costly, while less expensive methods often lack sensitivity or specificity. Cost-effectiveness comparisons of the various diagnostic options have not been presented.

Methods and Findings

We compared cost-effectiveness, as measured by cost per life-years gained and proportion of patients successfully diagnosed and treated, of 33 PCP diagnostic options, involving combinations of specimen collection methods [oral washes, induced and expectorated sputum, and bronchoalveolar lavage (BAL)] and laboratory diagnostic procedures [various staining procedures or polymerase chain reactions (PCR)], or clinical diagnosis with chest x-ray alone. Our analyses were conducted from the perspective of the government payer among ambulatory, HIV-infected patients with symptoms of pneumonia presenting to HIV clinics and hospitals in South Africa. Costing data were obtained from the National Institutes of Communicable Diseases in South Africa. At 50% disease prevalence, diagnostic procedures involving expectorated sputum with any PCR method, or induced sputum with nested or real-time PCR, were all highly cost-effective, successfully treating 77–90% of patients at $26–51 per life-year gained. Procedures using BAL specimens were significantly more expensive without added benefit, successfully treating 68–90% of patients at costs of $189–232 per life-year gained. A relatively cost-effective diagnostic procedure that did not require PCR was Toluidine Blue O staining of induced sputum ($25 per life-year gained, successfully treating 68% of patients). Diagnosis using chest x-rays alone resulted in successful treatment of 77% of patients, though cost-effectiveness was reduced ($109 per life-year gained) compared with several molecular diagnostic options.

Conclusions

For diagnosis of PCP, use of PCR technologies, when combined with less-invasive patient specimens such as expectorated or induced sputum, represent more cost-effective options than any diagnostic procedure using BAL, or chest x-ray alone.

Histopathologic diagnosis of fungal infections in the 21st century

Fungal infections are becoming more frequent because of expansion of at-risk populations and the use of treatment modalities that permit longer survival of these patients. Because histopathologic examination of tissues detects fungal invasion of tissues and vessels as well as the host reaction to the fungus, it is and will remain an important tool to define the diagnostic significance of positive culture isolates or results from PCR testing. However, there are very few instances where the morphological characteristics of fungi are specific. Therefore, histopathologic diagnosis should be primarily descriptive of the fungus and should include the presence or absence of tissue invasion and the host reaction to the infection. The pathology report should also include a comment stating the most frequent fungi associated with that morphology as well as other possible fungi and parasites that should be considered in the differential diagnosis. Alternate techniques have been used to determine the specific agent present in the histopathologic specimen, including immunohistochemistry, in situ hybridization, and PCR. In addition, techniques such as laser microdissection will be useful to detect the now more frequently recognized dual fungal infections and the local environment in which this phenomenon occurs.

Diagnosing invasive fungal disease in critically ill patients

Fungal infections are increasing, with a changing landscape of pathogens and emergence of new groups at risk for invasive disease. We review current diagnostic techniques, focusing on studies in critically ill patients. Microbiological cultures, the current "gold standard", demonstrate poor sensitivity, thus diagnosis of invasive disease in the critically ill is difficult. This diagnostic dilemma results in under- or over-treatment of patients, potentially contributing to poor outcomes and antifungal resistance. While other current diagnostic tests perform moderately well, many lack timeliness, efficacy, and are negatively affected by treatments common to critically ill patients. New nucleic acid-based research is promising.

Clinical characteristics of Pneumocystis pneumonia in non-HIV patients and prognostic factors including microbiological genotypes

Background

The number of patients with non-HIV Pneumocystis pneumonia (PCP) is increasing with widespread immunosuppressive treatment. We investigated the clinical characteristics of non-HIV PCP and its association with microbiological genotypes.

Methods

Between January 2005 and March 2010, all patients in 2 university hospitals who had been diagnosed with PCP by PCR were enrolled in this study. Retrospective chart review of patients, microbiological genotypes, and association with 30-day mortality were examined.

Results

Of the 82 adult patients investigated, 50 patients (61%) had inflammatory diseases, 17 (21%) had solid malignancies, 12 (15%) had hematological malignancies, and 6 (7%) had received transplantations. All patients received immunosuppressive agents or antitumor chemotherapeutic drugs. Plasma (1→3) β-D-glucan levels were elevated in 80% of patients, and were significantly reduced after treatment in both survivors and non-survivors. However, β-D-glucan increased in 18% of survivors and was normal in only 33% after treatment. Concomitant invasive pulmonary aspergillosis was detected in 5 patients. Fifty-six respiratory samples were stored for genotyping. A dihydropteroate synthase mutation associated with trimethoprim-sulfamethoxazole resistance was found in only 1 of the 53 patients. The most prevalent genotype of mitochondrial large-subunit rRNA was genotype 1, followed by genotype 4. The most prevalent genotype of internal transcribed spacers of the nuclear rRNA operon was Eb, followed by Eg and Bi. Thirty-day mortality was 24%, in which logistic regression analysis revealed association with serum albumin and mechanical ventilation, but no association with genotypes.

Conclusions

In non-HIV PCP, poorer general and respiratory conditions at diagnosis were independent predictors of mortality. β-D-glucan may not be useful for monitoring the response to treatment, and genotypes were not associated with mortality.

Seasonal variation in mortality of Pneumocystis jirovecii pneumonia in HIV-infected patients

A seasonal variation in the presentation of Pneumocystis jirovecii pneumonia (PCP) has been reported and a previous study from this centre noted a seasonal variation in mortality rates. This study examined seasonal influences (including climatic factors) within-host factors (clinical and laboratory-derived variables), the infectious burden of P. jirovecii in bronchoalveolar lavage (BAL) fluid, the presence of dihydropteroate synthase (DHPS) mutations in P. jirovecii, variations in knowledge and skills of junior medical staff, and mortality in 547 episodes of PCP occurring in 494 HIV-infected patients. The overall mortality rate was 13.5%. There was a seasonal variation in mortality: highest in autumn (21.2%) and lowest in spring (9.7%), P = 0.047. After adjustment was made for prognostic factors previously identified as being associated with mortality (increasing patient age, second/third episode of PCP, low haemoglobin, low PaO(2), presence of medical co-morbidity and pulmonary Kaposi sarcoma), there was no seasonal association with mortality, P = 0.249. The quantity of P. jirovecii DNA in BAL fluid showed no evidence of seasonal variation, P = 0.67; DHPS mutations were identified with equal frequency in each season and the mortality rate for February and August (when junior medical staff arrive in new posts) was 16.7%, only slightly greater than for other months (13.0%).

Serum antibody levels to the Pneumocystis jirovecii major surface glycoprotein in the diagnosis of P. jirovecii pneumonia in HIV+ patients

Background

Pneumocystis jirovecii remains an important cause of fatal pneumonia (Pneumocystis pneumonia or PcP) in HIV+ patients and other immunocompromised hosts. Despite many previous attempts, a clinically useful serologic test for P. jirovecii infection has never been developed.

Methods/Principal Findings

We analyzed serum antibody responses to the P. jirovecii major surface glycoprotein recombinant fragment C1 (MsgC1) in 110 HIV+ patients with active PcP (cases) and 63 HIV+ patients with pneumonia due to other causes (controls) by an enzyme-linked immunosorbent assay (ELISA). The cases had significantly higher IgG and IgM antibody levels to MsgC1 than the controls at hospital admission (week 0) and intervals up to at least 1 month thereafter. The sensitivity, specificity and positive predictive value (PPV) of IgG antibody levels increased from 57.2%, 61.7% and 71.5% at week 0 to 63.4%, 100%, and 100%, respectively, at weeks 3–4. The sensitivity, specificity and PPV of IgM antibody levels rose from 59.7%, 61.3%, and 79.3% at week 0 to 74.6%, 73.7%, and 89.8%, respectively, at weeks 3–4. Multivariate analysis revealed that a diagnosis of PcP was the only independent predictor of high IgG and IgM antibody levels to MsgC1. A high LDH level, a nonspecific marker of lung damage, was an independent predictor of low IgG antibody levels to MsgC1.

Conclusions/Significance

The results suggest that the ELISA shows promise as an aid to the diagnosis of PCP in situations where diagnostic procedures cannot be performed. Further studies in other patient populations are needed to better define the usefulness of this serologic test.

Late presentation of Pneumocystis jiroveci pneumonia after cardiac transplantation

We report the case of a 64-year-old man who had received a heart transplant 9 years previously and was on long-term immunosuppression. He was referred to the intensive care unit of our district general hospital with acute respiratory distress and was diagnosed with community-acquired pneumonia. He was treated with antimicrobials, whose spectrum was extended empirically to cover Pneumocystis jiroveci, and respiratory support was provided with continuous positive airway pressure (CPAP). PCR analysis subsequently confirmed a diagnosis of pneumocystis pneumonia (PCP). Despite appropriate therapy the patient unfortunately died 8 days after admission to the unit. To the author's knowledge, this is the first report in the literature of such a late presentation of PCP after cardiac transplantation. We discuss current diagnostic and treatment strategies for PCP.

Pneumocystis cell wall beta-glucan stimulates calcium-dependent signaling of IL-8 secretion by human airway epithelial cells

BACKGROUND

Respiratory failure secondary to alveolar inflammation during Pneumocystis pneumonia is a major cause of death in immunocompromised patients. Neutrophil infiltration in the lung of patients with Pneumocystis infection predicts severity of the infection and death. Several previous studies indicate that airway epithelial cells release the neutrophil chemoattractant proteins, MIP-2 (rodents) and IL-8 (humans), in response to Pneumocystis and purified Pneumocystis cell wall beta-glucans (PCBG) through the NF-kappaB-dependent pathway. However, little is known about the molecular mechanisms that are involved in the activation of airway epithelium cells by PCBG resulting in the secretion of IL-8.

METHOD

To address this, we have studied the activation of different calcium-dependent mitogen-activated protein kinases (MAPKs) in 1HAEo- cells, a human airway epithelial cell line.

RESULTS

Our data provide evidence that PCBG induces phosphorylation of the MAPKs, ERK, and p38, the activation of NF-kappaB and the subsequently secretion of IL-8 in a calcium-dependent manner. Further, we evaluated the role of glycosphingolipids as possible receptors for beta-glucans in human airway epithelial cells. Preincubation of the cells with D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) a potent inhibitor of the glycosphingolipids synthesis, prior to PCBG stimulation, significantly decreased IL-8 production.

CONCLUSION

These data indicate that PCBG activates calcium dependent MAPK signaling resulting in the release of IL-8 in a process that requires glycosphingolipid for optimal signaling.

A new method for the detection of Pneumocystis jirovecii using flow cytometry

Pneumocystis jirovecii is an opportunistic pathogen responsible for severe pneumonia in immunocompromised patients. Its diagnosis has been based upon direct microscopy either by classic staining (Gomori Grocott) or by epifluorescence microscopy (immunofluorescence staining, IFS), both of which are time-consuming and low on sensitivity. Our aim was to develop a flow cytometric (FC) protocol for the detection of P. jirovecii on respiratory samples. In our study, 420 respiratory samples were analysed in parallel by IFS and FC, and compared from clinical diagnosis to its resolution upon specific anti-Pneumocystis therapy. The optimum specific antibody concentration for FC analysis was determined to be 10 microg/ml, without any cross-reactions to bacteria or fungi. All positive cases detected by IFS were positive by FC; however, FC classified eight samples to be positive which were classified as negative by routine technique. These samples were obtained from patients with respiratory symptoms who responded favourably to Pneumocystis-specific therapy and were subsequently considered to be true-positives. Using clinical diagnosis as a reference method, FC showed 100% sensitivity and specificity, whereas IFS showed 90.9% sensitivity and 100% specificity. According to our results, a new diagnostic approach is now available to detect P. jirovecii in respiratory samples.

[Effects of combined addition of atovaquone and lithium on the in vitro cell growth of the pathogenic yeast Candida albicans]

Atovaquone, an analog of ubiquinone, binds tightly to the ubiquinol oxidation site (Qo site) of parasite cytochrome bc(1) complex to inhibit electron transport at concentrations far lower than those at which the mammalian system is affected. The mode of action is thought similar to that of myxothiazol. To treat Pneumocystis jirovecii and Plasmodium falciparum infections, atovaquone has been used worldwide whereas it is unapproved in Japan. Since the pathogenic Candida species fungi seem resistant to atovaquone, this drug is not clinically available for candidosis, particularly deep mycosis. We examined the effects of atovaquone on cellular respiration and in vitro growth of C. albicans to explore a new therapeutic possibility for fungal infections. Atovaquone strongly inhibited glucose-dependent cellular respiration similarly to antimycin A, stigmatellin, and myxothiazol, specific bc(1) complex inhibitors. However, atovaquone suppressed glucose-dependent cell growth to a much lesser extent versus the comparator agents. When added alone, lithium exerted slight growth inhibition. The combined addition of lithium with atovaquone showed a significant increase in inhibition of growth. Although the way lithium acts synergistically with atovaquone remains to be elucidated, our results suggest a new therapeutic possibility of this combination for the treatment of candidosis.