Evolving epidemiology of pneumocystis pneumonia: Findings from a longitudinal population-based study and a retrospective multi-center study in Germany

A nomogram-based clinical prediction model for adverse clinical outcomes in non-HIV Pneumocystis jirovecii pneumonia patients

BACKGROUND

Non-human immunodeficiency virus (HIV) immunocompromised patients with Pneumocystis jirovecii pneumonia (PJP) face rapid progression and high mortality, necessitating a predictive model to identify patients at risk of adverse clinical outcomes for timely interventions and improved stratification.

METHODS

Patients admitted between January 2011 and June 2024 at Beijing Chao-Yang Hospital were retrospectively analyzed. Collected data included patients' demographics, smoking status, comorbidities, immunosuppressive diseases, blood laboratory tests, in-hospital treatment, and adverse clinical outcomes. Predictor selection was performed using the least absolute shrinkage and selection operator (LASSO) and logistic regression, with selected features incorporated into a nomogram. Internal validation was conducted using a 500-bootstrap resampling method to ensure model robustness. Model performance was assessed via the area under the receiver operating curve (AUC), calibration plots, decision curve analysis (DCA), and clinical impact curve (CIC).

RESULTS

Among the 431 patients, 243 (56.4%) experienced adverse clinical outcomes. LASSO regression screened 21 variables, selecting 9 predictors with non-zero coefficients through 10-fold cross-validation at lambda.1se = 0.0453 (log(lambda.1se) = -3.092). Multivariate logistic regression identified 7 independent risk factors for adverse clinical outcomes: smoking status, cytomegalovirus infection, diabetes, neutrophil-lymphocyte ratio (NLR), lactate dehydrogenase (LDH), PaO2/FiO2 (PFR), and lymphocyte subset. These factors were incorporated into a nomogram, achieving an AUC of 0.89 (95% CI: 0.86-0.92), with the Hosmer-Lemeshow test (p = 0.134) and calibration curves showing strong agreement between predicted and observed outcomes. Internal validation via 500-bootstrap resampling yielded a bias-corrected AUC of 0.83 (95% CI: 0.80-0.86). DCA demonstrated strong clinical decision-making utility, while the CIC confirmed its practical reliability.

CONCLUSIONS

Regression analysis identified smoking status, CMV infection, diabetes, NLR, LDH, PFR, and lymphocyte subset as independent risk factors for adverse clinical outcomes in non-HIV PJP patients. The predictive model constructed from these factors exhibited robust accuracy and reliability.

Key fungal coinfections: epidemiology, mechanisms of pathogenesis, and beyond

Coinfection is defined as the occurrence of at least two genetically distinct infectious agents within the same host. Historically, fungal infections have been neglected, leading to an underestimation of their impact on public health systems. However, fungal coinfections have become increasingly prevalent, emerging as a significant global health concern. This review explores fungal coinfections commonly associated with HIV, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza, Mycobacterium tuberculosis, and Pseudomonas species. These include candidiasis, aspergillosis, paracoccidioidomycosis, cryptococcosis, histoplasmosis, pneumocystosis, sporotrichosis, and mucormycosis. We discuss the key local and systemic mechanisms that contribute to the occurrence of these coinfections. HIV infects CD4+ cells, causing systemic immunosuppression, particularly impairing the adaptive immune response. The inflammatory response to SARS-CoV-2 infection disrupts both pulmonary and systemic homeostasis, rendering individuals more vulnerable to local and disseminated fungal coinfections. Severe influenza promotes fungal coinfections by triggering the production of pro-inflammatory cytokines, which damage the epithelial-endothelial barrier and impair the recognition and phagocytosis of fungal cells. Tuberculosis can replace normal lung parenchyma with collagen tissue, leading to alterations in lung architecture, compromising its function. Interaction between Pseudomonas and Aspergillus during coinfection involves the competition for iron availability and an adaptive response to its deprivation. Therefore, the specific interactions between each underlying disease and fungal coinfections are detailed in this review. In addition, we highlight the risk factors associated with coinfections, pathophysiology, epidemiology, and the challenges of early diagnosis. Recognizing the substantial worldwide public health burden posed by fungal coinfections is crucial to improve survival rates.

Isavuconazole as an optimal treatment option for multiple pathogens induced severe pneumonia in immunocompromised hosts: a case series report

Background

Treating severe pneumonia caused by multiple pathogens in immunocompromised hosts (ICHs) presents significant challenges. Isavuconazole (ISA), a next-generation triazole antifungal agent, has shown promise in managing fungal infections. However, clinical evidence regarding its efficacy in cases of complex infections involving multiple pathogens in ICHs remains limited.

Case presentation

This study describes a case series of three ICHs diagnosed with severe pneumonia, including invasive aspergillosis (IA). All three patients received ISA-based personalized antimicrobial regimens. Alleviation of symptoms was observed in all patients following antimicrobial treatment, with notable absorption of pulmonary lesions and no significant hepatorenal toxic side effects, with no recurrence observed.

Conclusion

ICHs are highly susceptible to fungal infections, and the severity of their condition can escalate dramatically, with a significant risk of mortality, when severe pneumonia caused by multiple pathogens occurs concurrently. A stepwise treatment strategy, which balances the use between immunosuppressant and effective antimicrobial treatment, is crucial. The selection of appropriate drugs should account for potential adverse drug reactions (ADRs). In this case series, ISA exhibited robust efficacy in treating IA with minimal ADRs. Therefore, ISA represents a valuable option for managing severe pneumonia in ICHs, particularly in the context of IA and co-infections caused by multiple pathogens.

Pneumocystis Infection in Pregnant Women: A Scoping Review

Pneumocystis jirovecii is an opportunistic fungus that causes severe pneumonia in immunosuppressed individuals. While Pneumocystis colonization, a subclinical form of infection, has been studied in different populations, its implications during pregnancy remain poorly understood. Given the immune modulation of pregnancy, maternal colonization or infection may contribute to vertical transmission and neonatal respiratory complications. This scoping review aims to map the existing evidence on Pneumocystis colonization/infection during pregnancy, identifying knowledge gaps, prevalence, risk factors, and potential neonatal outcomes. A systematic literature search was conducted in three databases following PRISMA-ScR guidelines. A total of 26 studies were included, covering Pneumocystis pneumonia cases (n = 19) and Pneumocystis colonization (n = 7). The review found that most Pneumocystis pneumonia cases in pregnant women were associated with HIV before antiretroviral therapy. More recent cases were related to hematologic malignancies. Pneumocystis colonization rates varied widely (5.4-46.5%). Evidence of vertical transmission was observed, but neonatal impact remains underexplored. This review highlights the need for HIV screening in pregnant women and the need to include Pneumocystis in the diagnosis of pregnant women with pneumonia. Increased awareness and research on Pneumocystis in pregnancy are necessary to improve maternal and neonatal outcomes. Future studies should focus on vertical transmission and neonatal respiratory health.

Clinical Factors Associated With Pneumocystis Pneumonia Despite Its Primary Prophylaxis: When to Stop Prophylaxis?

OBJECTIVE

Although previous studies show that primary prophylaxis against Pneumocystis jirovecii pneumonia (PJP) is effective in patients with rheumatic diseases receiving immunosuppressive treatment, there is limited evidence regarding the optimal timing for prophylaxis withdrawal. This study aimed to identify the risk factors for PJP despite prophylaxis and provide evidence for an optimal prophylaxis schedule.

METHODS

This case-control study included 1,294 prophylactic episodes in 1,148 patients with rheumatic disease who received immunosuppressants and prophylactic trimethoprim-sulfamethoxazole (TMP-SMX). The primary outcome was a one-year incidence of PJP. A Cox proportional hazards model with least absolute shrinkage and selection operator was used to evaluate clinical factors associated with outcomes.

RESULTS

During 1,174 person-years of observation, 10 cases of PJP were identified, with an incidence rate of 0.85 per 100 person-years. The mean ± SD duration of TMP-SMX prophylaxis was 181.9 ± 128.7 days. Except in one case, PJP occurred after discontinuation of TMP-SMX, with a median (interquartile range [IQR]) interval of 117.0 (86.0-161.0) days. The dose of glucocorticoids at the time of TMP-SMX discontinuation was significantly higher in the PJP group relative to the control group (median [IQR]: 22 [20-40] vs 10 [5-15] mg). Discontinuing TMP-SMX while on a glucocorticoid dose >12.5 mg/day of prednisone equivalent significantly increased the risk of PJP (adjusted hazard ratio: 13.84; 95% confidence interval, 1.71-111.80). There were 63 cases of adverse events during the observation period, and 10 (15.9%) were attributed to TMP-SMX with probable causality.

CONCLUSION

Tapering glucocorticoids with 12.5 mg/day of prednisone equivalent could be a reasonable timepoint to initiate the withdrawal of PJP prophylaxis in patients with rheumatic diseases.

Critical Insights: Severe Outcomes of Pneumocystis Pneumonia: A 10-year Retrospective Cohort Study

BACKGROUND

A considerable knowledge gap exists in predicting severe Pneumocystis pneumonia (PCP) outcomes following PCP diagnosis.

METHODS

In this retrospective cohort, we studied immunocompromised patients with PCP admitted to 5 University Health Network centers in Canada (2011-2022). The study outcome included severe PCP, a composite of 21-day ICU admission or 28-day all-cause mortality. Adjusted odds ratios (aOR) estimated the association between severe PCP and comorbidities as well as clinical and laboratory variables at diagnosis.

RESULTS

A total of 44 out of 182 (24.2%) immunocompromised patients (19 [10.4%] HIV-infected, 55 [30.2%] hematologic malignancies, 32 [17.6%] hematopoietic stem cell transplants, 32 [17.6% solid tumors, 26 solid organ transplants [14.3%], 12 (6.6%) autoimmune diseases, and 6 (3.3%) other immunosuppressive conditions) developed composite outcomes (40 ICU admissions [21.9%], 18 deaths [9.9%]). Patients with composite outcomes more often had acute-onset PCP (< 7 days) (18/34 [52.9%] vs. 38/126 [30.1%], p = 0.013), shortness of breath (39/44 [88.6%] vs. 96/136 [70.6%], p = 0.002), chronic liver disease (15/44 [34.1%] vs. 9/138 [6.5%], p < 0.001), hypoalbuminemia (median [IQR] albumin (g/L): 27 [25-31] vs. 32 [29-35], p < 0.001), elevated lactate dehydrogenase (median [IQR] LDH (U/L): 537 [324-809] vs. 340 [237-475], p < 0.001), lymphopenia (median [IQR] absolute lymphocyte count [(10*9/L),]: 0.4 [0.2-0.6] vs. 0.7 [0.3-1.2], p < 0.001), or required supplemental oxygen (39/44 [88.6%] vs. 60/136 [44.1%], p < 0.001) than those without composite outcomes. In multivariable analysis, chronic liver disease (aOR: 11.6, 95% CI: 2.2-61.3) and requiring supplemental oxygen on admission (aOR: 19.7, 95% CI: 3.0-128.5) were significantly associated with severe PCP.

CONCLUSIONS

Alongside hypoxemia upon admission, chronic liver disease appears to significantly predict severe PCP in immunocompromised patients. This biologically plausible finding warrants further investigation.

Multicentric prospective evaluation of Pneumocystis jirovecii fungal load in bronchoalveolar lavage fluid fractions using qPCR

Bronchoalveolar lavage fluid (BALF) is the key sample type for diagnosing Pneumocystis jirovecii pneumonia, with quantitative PCR (qPCR) providing high sensitivity and specificity. However, sample processing varies considerably between laboratories, and optimal nucleic acid extraction method for BALF remains undetermined. This retrospective multicenter study, conducted in 12 centers as part of the fungal PCR initiative, assessed the efficacy of P. jirovecii detection by qPCR in different BALF fractions, including whole (WHO), pellet (PEL), and supernatant (SUP). Samples that were P. jirovecii-qPCR-positive during routine testing were divided into the three predefined fractions prior to nucleic acid extraction and qPCR, comparing detection rates and quantification cycle (Cq) values. Out of 113 P. jirovecii-qPCR-positive BALF samples, 339 qPCR measurements were analyzed. The PEL fraction demonstrated a similar detection rate to the WHO fraction, with positivity rates of 92.9% and 88.5%, respectively. The SUP fraction showed a lower positivity rate of 71.7%, dropping to 47% for high Cq values (Cq > 35). Quantitative analysis showed that the SUP fraction consistently yielded higher Cq values, trailing by 3.05 cycles compared to WHO, while PEL showed a smaller deviation (0.49 cycles), confirming its efficiency in retaining P. jirovecii genetic material for qPCR detection. The study concludes that the SUP fraction is suboptimal for P. jirovecii detection due to higher Cq values, suggesting lower fungal loads. The PEL and WHO fractions are comparable, suggesting that the PEL is a viable alternative, permitting the concentration of larger BALF volumes to levels that can be extracted across a range of platforms.

Pulmonary Coinfection of Pneumocystis jirovecii and Aspergillus Species

In this multicenter study of 387 patients who were immunocompromised, 4.5% with invasive pulmonary aspergillosis also had Pneumocystis jirovecii pneumonia. Predictors of coinfection included elevated β-D-glucan and prolonged corticosteroid use. Coinfection correlated with reduced 30-day survival (22% vs 57%), suggesting that early identification and prophylaxis may improve outcomes.

Insights into Pneumocystis jirovecii pneumonia in South Africa (2018-2022)

Pneumocystis jirovecii causes P. jirovecii pneumonia (PJP)-a leading opportunistic infection among persons with advanced human immunodeficiency virus. Furthermore, individuals with underlying conditions such as cancer and transplant recipients are susceptible to PJP. Most data on PJP come from other countries, with limited knowledge about its prevalence in Africa. The aim was to describe changes in the proportion of positive PJP tests in South Africa from 2018 to 2022. A 5-year retrospective study was conducted on patients with suspected P. jirovecii, detected by polymerase chain reaction. Data were obtained from the National Health Laboratory Service, where laboratory diagnostics were done as part of routine patient care. Mann-Whitney test and Χ2 tests were used to compare the age, sex, and wards with both the negative and positive results of PJP. From 2018 to 2022, a total of 8110 patients' results were retrieved, and 8059 met the inclusion criteria. The positive test proportions of PJP in South Africa were 32.66%, 29.93%, 34.02%, 24.98%, and 25.78%, respectively. The median age was 35 years, with interquartile range of 24-43 years (P = .002). Female patients had a higher positive test proportion than males (59.39% vs. 38.74%, P < .001). The proportion of positive PJP tests was higher in general wards (48.54%) and intensive care units (18.99%) (P = .012). The epidemiology of PJP in South Africa is similar to that of other countries in some respects but is influenced by unique factors specific to the country. These findings are crucial for public health planning, emphasising the need for targeted PJP prevention strategies considering sex- and age-specific vulnerabilities in South Africa.

Use of echinocandins combined with clindamycin in Pneumocystis pneumonia: a case series of 14 patients

BACKGROUND

Pneumocystis jirovecii pneumonia (PcP) is an opportunistic infection for which the standard of care is co-trimoxazole. However, safety concerns and intolerance may compromise its utility.

OBJECTIVES

To evaluate the safety and efficacy of the combination of echinocandins and clindamycin to treat PcP.

PATIENTS AND METHODS

We investigated 14 patients treated with a co-trimoxazole-free combined regimen that included echinocandins and clindamycin.

RESULTS

Clinical cure was achieved in 8 out of 14 patients, while 5 had a fatal outcome due to their primary disease; however, only one patient died due to PcP.

CONCLUSIONS

Echinocandin and clindamycin may be a safe and effective alternative treatment for patients who cannot be given co-trimoxazole for PcP.

Epidemiology and risk factors of community-acquired pneumonia in patients with different causes of immunosuppression

Immunosuppression constitutes a significant risk for community-acquired pneumonia (CAP). Nevertheless, specific causes of immunosuppression and their relevance for incidence, etiology and prognosis of CAP are insufficiently investigated.We conducted a population-based cohort study within a statutory health insurance in Germany from 2015 to 2018. CAP was retrieved by ICD-10-GM codes. Episodes of immunosuppression were identified by coded conditions (hematologic neoplasms, stem cell or organ transplantation, neutropenia, HIV, primary immunosuppressive syndromes) or treatments (immunosuppressants, antineoplastic drugs, systemic steroids). Endpoints were defined as occurrence of CAP (primary), hospitalization, 30-day mortality and CAP associated with rare pathogens. Our analysis utilized the Andersen-Gill model adjusted for sex, age, level of long-term care, vaccination status, community type and comorbidities.942,008 individuals with 54,781 CAPs were included (hospitalization 55%, 30-day mortality 14.5%). 6% of individuals showed at least one episode of immunosuppression during the study period with systemic steroids (39.8%) and hematologic neoplasms (26.7%) being most common. Immunosuppression was recorded in 7.7% of CAPs. Besides classical risk factors such as age and level of long-term care, immunosuppressed patients were most prone to CAP (HR 2.4[2.3-2.5]) and consecutive death (HR 1.9[1.8-2.1]). Organ and stem cell transplantation (HR 3.2[2.6-4.0] and 2.8[2.1-3.7], respectively), HIV (HR 3.2[1.9-5.4]) and systemic steroids (> 20 mg prednisone daily dose equivalent (HR 2.7[2.4-3.1])) showed the highest risk for contracting CAP. CAP by rare pathogens was strongly associated with immunosuppression (HR 17.1[12.0-24.5]), especially HIV (HR 34.1[7.6-153]) and systemic steroids (HR 8.2[4.6-14.8]).Our study elucidates the relevance of particular immunosuppressive conditions including systemic steroids for occurrence and prognosis of CAP.

Variable reliability of the (1,3)-β-d-glucan test for screening Pneumocystis pneumonia in HIV-negative patients depending on the underlying condition

(1,3)-β-d-Glucan (BG) assay is a non-invasive test commonly used in the diagnostic of invasive fungal diseases. Given its high sensitivity, it was suggested that a negative BG result is sufficient for excluding the diagnosis of Pneumocystis pneumonia (PCP). However, suboptimal performance has been described in human immunodeficiency virus (HIV)-negative patients, particularly those with haematological malignancies. We aimed to assess the sensitivity of the BG assay for diagnosing PCP in HIV-negative patients based on their underlying PCP risk factors. We conducted a single-center, retrospective study (2009-2021) enrolling HIV-negative patients diagnosed with PCP and who underwent BG testing. Patients colonized with Pneumocystis jirovecii were included as a control group. In all, 55 PCP patients and 61 colonized patients met the inclusion criteria. Patients were further categorized according to the underlying condition that exposes patients to PCP. Median BG concentration was significantly higher in the PCP group than in the colonization group (500 vs. 31 pg/ml; P < 10-4, Mann-Whitney test) and the BG assay demonstrated a sensitivity of 85% and a specificity of 82% for PCP diagnosis. Notably, sensitivity was significantly higher in non-cancer patients (100%) compared to those with solid cancer (72%) and haematologic cancer (79%) (P < .05, Fischer's exact test). These findings strengthen the high performance of BG testing for screening PCP in non-cancer patients, comparable to that observed in HIV-infected individuals. In contrast, they highlight its low reliability in patients with malignancies, emphasizing the importance of considering underlying conditions when interpreting BG results and refining the role of the test in PCP diagnosis.

Fungal lung disease

Fungal lung disease encompasses a wide spectrum of organisms and associated clinical conditions, presenting a significant global health challenge. The type and severity of disease are determined by underlying host immunity and infecting fungal strain. The most common group of diseases are associated with the filamentous fungus Aspergillus species and include allergic bronchopulmonary aspergillosis, sensitisation, aspergilloma and chronic and invasive pulmonary aspergillosis. Fungal lung disease remains epidemiologically heterogenous and is influenced by geography, environment and host comorbidities. Diagnostic modalities continue to evolve and now include novel molecular assays and biomarkers; however, persisting challenges include achieving rapid and accurate diagnosis, particularly in resource-limited settings, and in differentiating fungal infection from other pulmonary conditions. Treatment strategies for fungal lung diseases rely mainly on antifungal agents but the emergence of drug-resistant strains poses a substantial global threat and adds complexity to existing therapeutic challenges. Emerging antifungal agents and increasing insight into the lung mycobiome may offer fresh and personalised approaches to diagnosis and treatment. Innovative methodologies are required to mitigate drug resistance and the adverse effects of treatment. This state-of-the-art review describes the current landscape of fungal lung disease, highlighting key clinical insights, current challenges and emerging approaches for its diagnosis and treatment.

Strengths and limitations of molecular diagnostics for Pneumocystis jirovecii pneumonia

INTRODUCTION

While Pneumocystis pneumonia (PcP) remains a major AIDS-defining disease, the majority of cases of PcP now present in the HIV-negative cohort, causing significant mortality. PcP PCR diagnosis is not novel, and the optimal route of diagnosis remains unclear, with an imperfect reference method and complexity in result interpretation for alternative tests.

AREAS COVERED

This extensive review utilizing a literature search underpinning a recent systematic review/meta-analysis discusses the technical and clinical performance of PcP PCR, the added benefits of PCR testing, future aspects/considerations, and how PCR may be best used in clinical algorithms to provide a probability of PcP.

EXPERT OPINION

Given the current imperfect reference test for PcP, an alternative would be beneficial. Concerns over PcP PCR generating false positive results are valid but can be resolved by using positivity thresholds that drive specificity. Unfortunately, the extensive range of PCR assays complicates the provision of a PCR reference method. Combination testing incorporating PCR and B-D-Glucan, along with clinical and host risk factors, is key to understanding the individual probability of PcP. It is critical that access to PcP PCR testing is improved through technical and logistical development. Conversely, syndromic approaches including PcP need to be fully evaluated.

Development of a clinical risk score for the prediction of Pneumocystis jirovecii pneumonia in hospitalised patients

BACKGROUND

The performance and availability of invasive and non-invasive investigations for the diagnosis of Pneumocystis jirovecii pneumonia (PCP) vary across clinical settings. Estimating the pre-test probability of PCP is essential to the optimal selection and interpretation of diagnostic tests, such as the 1,3-β-D-glucan assay (BDG), for the prioritization of bronchoscopy, and to guide empiric treatment decisions. We aimed to develop a multivariable risk score to estimate the pre-test probability of PCP.

METHODS

The score was developed from a cohort of 626 individuals who underwent bronchoscopy for the purposes of identifying PCP in a Canadian tertiary-care centre, between 2015 and 2018. We conducted a nested case-control study of 57 cases and 228 unmatched controls. Demographic, clinical, laboratory, and radiological data were included in a multivariable logistic regression model to estimate adjusted odds ratios for PCP diagnosis. A clinical risk score was derived from the multivariable model and discrimination was assessed by estimating the score's receiver operating characteristic curve.

RESULTS

Participants had a median age of 60 years (interquartile range [IQR] 49-68) and 115 (40%) were female; 40 (14%) had HIV and 49 (17%) had a solid organ transplant (SOT). The risk score included prior SOT or HIV with CD4 ≤ 200/µL (+ 2), serum lactate dehydrogenase ≥ 265.5 IU/mL (+ 2), radiological pattern typical of PCP on chest x-ray (+ 2) or CT scan (+ 2.5), and PCP prophylaxis with trimethoprim-sulfamethoxazole (-3) or other antimicrobials (-2). The median score was 4 points (IQR, 2-4.5) corresponding to a 28% probability of PCP. The risk prediction model had good discrimination with a c-statistic of 0.79 (0.71-0.84). Given the operating characteristics of the BDG assay, scores ≤ 3 in patients without HIV, and ≤ 5.5 in those with HIV, paired with a negative BDG, would be expected to rule out PCP with 95% certainty.

CONCLUSION

We propose the PCP Score to estimate pre-test probability of PCP. Once validated, it should help clinicians determine which patients to refer for invasive investigations, when to rely on serological testing, and in whom to consider pre-emptive treatment.

Pneumocystis murina promotes inflammasome formation and NETosis during Pneumocystis pneumonia

Pneumocystis jirovecii pneumonia (PjP) poses a serious risk to individuals with compromised immune systems, such as individuals with HIV/AIDS or undergoing immunosuppressive therapies for cancer or solid organ transplants. Severe PjP triggers excessive lung inflammation, resulting in lung function decline and consequential alveolar damage, potentially culminating in acute respiratory distress syndrome. Non-HIV patients face a 30%-60% mortality rate, emphasizing the need for a deeper understanding of inflammatory responses in PjP. Prior research emphasized macrophages in Pneumocystis infections, neglecting neutrophils' role in tissue damage. Consequently, the overemphasis on macrophages led to an incomplete understanding of the role of neutrophils and inflammatory responses. In the current investigation, our RNAseq studies on a murine surrogate model of PjP revealed heightened activation of the NLRP3 inflammasome and NETosis cell death pathways in their lungs. Immunofluorescence staining confirmed neutrophil extracellular trap (NET) presence in the lungs of the P. murina-infected mice, validating our findings. Moreover, isolated neutrophils exhibited NETosis when directly stimulated with P. murina. Isolated NETs compromised P. murina viability in vitro, highlighting the potential role of neutrophils in controlling fungal growth and promoting inflammation during P. murina pneumonia through NLRP3 inflammasome assembly and NETosis. These pathways, essential for inflammation and pathogen elimination, bear the risk of uncontrolled activation leading to excessive tissue damage and persistent inflammation. This pioneering study is the first to identify the formation of NETs and inflammasomes during Pneumocystis infection, paving the way for comprehensive investigations into treatments aimed at mitigating lung damage and augmenting survival rates for individuals with PjP.IMPORTANCEPneumocystis jirovecii pneumonia (PjP) affects individuals with weakened immunity, such as HIV/AIDS, cancer, and organ transplant patients. Severe PjP triggers lung inflammation, impairing function and potentially causing acute respiratory distress syndrome. Non-HIV individuals face a 30%-60% mortality rate, underscoring the need for deeper insight into PjP's inflammatory responses. Past research focused on macrophages in managing Pneumocystis infection and its inflammation, while the role of neutrophils was generally overlooked. In contrast, our findings in P. murina-infected mouse lungs showed neutrophil involvement during inflammation and increased expression of NLRP3 inflammasome and NETosis pathways. Detection of neutrophil extracellular traps further indicated their involvement in the inflammatory process. Although beneficial in combating infection, unregulated neutrophil activation poses a potential threat to lung tissues. Understanding the behavior of neutrophils in Pneumocystis infections is crucial for controlling detrimental reactions and formulating treatments to reduce lung damage, ultimately improving the survival rates of individuals with PjP.

Pneumocystis pneumonia in intensive care: clinical spectrum, prophylaxis patterns, antibiotic treatment delay impact, and role of corticosteroids. A French multicentre prospective cohort study

PURPOSE

Severe Pneumocystis jirovecii pneumonia (PJP) requiring intensive care has been the subject of few prospective studies. It is unclear whether delayed curative antibiotic therapy may impact survival in these severe forms of PJP. The impact of corticosteroid therapy combined with antibiotics is also unclear.

METHODS

This multicentre, prospective observational study involving 49 adult intensive care units (ICUs) in France was designed to evaluate the severity, the clinical spectrum, and outcomes of patients with severe PJP, and to assess the association between delayed curative antibiotic treatment and adjunctive corticosteroid therapy with mortality.

RESULTS

We included 158 patients with PJP from September 2020 to August 2022. Their main reason for admission was acute respiratory failure (n = 150, 94.9%). 12% of them received antibiotic prophylaxis for PJP before ICU admission. The ICU, hospital, and 6-month mortality were 31.6%, 35.4%, and 40.5%, respectively. Using time-to-event analysis with a propensity score-based inverse probability of treatment weighting, the initiation of curative antibiotic treatment after 96 h of ICU admission was associated with faster occurrence of death [time ratio: 6.75; 95% confidence interval (95% CI): 1.48-30.82; P = 0.014]. The use of corticosteroids for PJP was associated with faster occurrence of death (time ratio: 2.48; 95% CI 1.01-6.08; P = 0.048).

CONCLUSION

This study showed that few patients with PJP admitted to intensive care received prophylactic antibiotic therapy, that delay in curative antibiotic treatment was common and that both delay in curative antibiotic treatment and adjunctive corticosteroids for PJP were associated with accelerated mortality.

Polymerase Chain Reaction on Respiratory Tract Specimens of Immunocompromised Patients to Diagnose Pneumocystis Pneumonia: A Systematic Review and Meta-analysis

BACKGROUND

This meta-analysis examines the comparative diagnostic performance of polymerase chain reaction (PCR) for the diagnosis of Pneumocystis pneumonia (PCP) on different respiratory tract samples, in both human immunodeficiency virus (HIV) and non-HIV populations.

METHODS

A total of 55 articles met inclusion criteria, including 11 434 PCR assays on respiratory specimens from 7835 patients at risk of PCP. QUADAS-2 tool indicated low risk of bias across all studies. Using a bivariate and random-effects meta-regression analysis, the diagnostic performance of PCR against the European Organisation for Research and Treatment of Cancer-Mycoses Study Group definition of proven PCP was examined.

RESULTS

Quantitative PCR (qPCR) on bronchoalveolar lavage fluid provided the highest pooled sensitivity of 98.7% (95% confidence interval [CI], 96.8%-99.5%), adequate specificity of 89.3% (95% CI, 84.4%-92.7%), negative likelihood ratio (LR-) of 0.014, and positive likelihood ratio (LR+) of 9.19. qPCR on induced sputum provided similarly high sensitivity of 99.0% (95% CI, 94.4%-99.3%) but a reduced specificity of 81.5% (95% CI, 72.1%-88.3%), LR- of 0.024, and LR+ of 5.30. qPCR on upper respiratory tract samples provided lower sensitivity of 89.2% (95% CI, 71.0%-96.5%), high specificity of 90.5% (95% CI, 80.9%-95.5%), LR- of 0.120, and LR+ of 9.34. There was no significant difference in sensitivity and specificity of PCR according to HIV status of patients.

CONCLUSIONS

On deeper respiratory tract specimens, PCR negativity can be used to confidently exclude PCP, but PCR positivity will likely require clinical interpretation to distinguish between colonization and active infection, partially dependent on the strength of the PCR signal (indicative of fungal burden), the specimen type, and patient population tested.

Immune checkpoint inhibitor increased mortality in lung cancer patients with Pneumocystis jirovecii pneumonia: a comparative retrospective cohort study

Introduction

Pneumocystis jirovecii pneumonia (PJP) is a life-threatening infection in immunocompromised individuals. Immune checkpoint inhibitor (ICI) has brought significant survival benefit in lung cancer patients. Although the few studies showed there was high mortality in PJP patients with ICI use, these studies had no comparative control groups.

Methods

A retrospective study was conducted to compare the mortality in PJP patients with lung cancer between those treated with ICI and a concurrent control group treated without ICI.

Results

A total number of 20 non-human immunodeficiency virus (HIV) patients with confirmed PJP and co-existing lung cancer were included in the current study, and classified into ICI group (n=9) and non-ICI group (n=11).There was a clear trend to a shorter onset of PJP in ICI group than non-ICI group (118.9 ± 60.9 vs 253.0 ± 185.1 days), although without statistical significance (p=0.053). Bronchoscopic alveolar lavage fluid were collected from all patients and used to identify Pneumocystis jirovecii. In both groups, metagenomics next-generation sequencing (mNGS) were the most used diagnostic techniques. Within 28 days after the onset of PJP, mortality was significantly higher in the ICI group than non-ICI group (33.3% vs 0, p=0.042).

Conclusion

Lung cancer patients with ICI use had a higher mortality rate after PJP infection than patients without ICI use. Prospective studies with larger sample size and a multi-center design are warranted to further verify the present results.

Pneumocystis jirovecii pneumonia in non-HIV patients: need for a more extended prophylaxis

Background

Pneumocystis jirovecii pneumonia (PCP) has a significant mortality rate for non-HIV immunocompromised patients. Prevention is primarily based on combined trimethoprim and sulfamethoxazole (TMP-SMX) but guidelines on pneumocystosis prophylaxis are scattered and not consensual.

Objectives

This study aims to describe PCP in non-HIV patients and to review case by case the prior indication of prophylaxis according to specific guidelines.We included patients with confirmed diagnosis of PCP admitted to one university hospital from 2007 to 2020. Prior indication for pneumocystis prophylaxis was assessed according to the specific guidelines for the underlying pathology or treatment.

Results

Of 150 patients with a medical diagnosis of PCP, 78 were included. Four groups of underlying pathologies were identified: hematological pathologies (42%), autoimmune diseases (27%), organ transplantation (17%), and other pathologies at risk of PCP (14%). A small subgroup of 14 patients (18%) had received a prior prescription of pneumocystis prophylaxis but none at the time of the episode. Transfer to intensive care was necessary for 33 (42%) patients, and the mortality rate at 3 months was 20%. According to international disease society guidelines, 52 patients (59%) should have been on prophylaxis at the time of the pneumocystis episode. Lowest compliance with guidelines was observed in the hematological disease group for 24 patients (72%) without prescription of indicated prophylaxis.

Conclusion

Infectious disease specialists should draw up specific prophylactic guidelines against pneumocystis to promote a better prevention of the disease and include additional criteria in their recommendations according to individual characteristics to prevent fatal cases.

Pneumocystis pneumonia in French intensive care units in 2013-2019: mortality and immunocompromised conditions

PURPOSE

The recent epidemiology of Pneumocystis pneumonia (PCP) requiring intensive care unit (ICU) admission and the associated spectrum of immunocompromising conditions are poorly described.

METHODS

We analyzed all adult PCP cases admitted to French ICUs via the French medical database system (PMSI), over the period from 2013 to 2019.

RESULTS

French ICUs admitted a total of 4055 adult patients with PCP. Among all hospitalized PCP cases, the proportion requiring ICU admission increased from 17.8 in 2014 to 21.3% in 2019 (P < 0.001). The incidence of severe PCP rose from 0.85 in 2013 to 1.32/100,000 adult inhabitants in 2019 (P < 0.0001), primarily due to the proportion of HIV-negative patients that increased from 60.6% to 74.4% (P < 0.0001). Meanwhile, the annual number of severe PCP cases among patients with HIV infection remained stable over the years. In-hospital mortality of severe PCP cases was 28.5% in patients with HIV infection and 49.7% in patients without. Multivariable logistic analysis showed that patients with HIV infection had a lower adjusted risk of death than patients without HIV infection (Odds Ratio [OR]: 0.30, 95% confidence interval [95CI]: 0.17-0.55). Comorbidities or conditions strongly associated with hospital mortality included the patient's age, Simplified Acute Physiologic Score II, congestive heart failure, coagulopathy, solid organ cancer, and cirrhosis. A vast array of autoimmune inflammatory diseases affected 19.9% of HIV-negative patients.

CONCLUSIONS

The number of PCP cases requiring ICU admission in France has risen sharply. While the yearly count of severe PCP cases in HIV-infected patients has remained steady, this rise predominantly affects cancer patients, with a recent surge observed in patients with autoimmune inflammatory diseases, affecting one in five individuals.

Deep mutational scanning of Pneumocystis jirovecii dihydrofolate reductase reveals allosteric mechanism of resistance to an antifolate

Pneumocystis jirovecii is a fungal pathogen that causes pneumocystis pneumonia, a disease that mainly affects immunocompromised individuals. This fungus has historically been hard to study because of our inability to grow it in vitro. One of the main drug targets in P. jirovecii is its dihydrofolate reductase (PjDHFR). Here, by using functional complementation of the baker's yeast ortholog, we show that PjDHFR can be inhibited by the antifolate methotrexate in a dose-dependent manner. Using deep mutational scanning of PjDHFR, we identify mutations conferring resistance to methotrexate. Thirty-one sites spanning the protein have at least one mutation that leads to resistance, for a total of 355 high-confidence resistance mutations. Most resistance-inducing mutations are found inside the active site, and many are structurally equivalent to mutations known to lead to resistance to different antifolates in other organisms. Some sites show specific resistance mutations, where only a single substitution confers resistance, whereas others are more permissive, as several substitutions at these sites confer resistance. Surprisingly, one of the permissive sites (F199) is without direct contact to either ligand or cofactor, suggesting that it acts through an allosteric mechanism. Modeling changes in binding energy between F199 mutants and drug shows that most mutations destabilize interactions between the protein and the drug. This evidence points towards a more important role of this position in resistance than previously estimated and highlights potential unknown allosteric mechanisms of resistance to antifolate in DHFRs. Our results offer unprecedented resources for the interpretation of mutation effects in the main drug target of an uncultivable fungal pathogen.

Extracellular vesicles from Pneumocystis carinii-infected rats impair fungal viability but are dispensable for macrophage functions

Pneumocystis spp. are host obligate fungal pathogens that can cause severe pneumonia in mammals and rely heavily on their host for essential nutrients. The lack of a sustainable in vitro culture system poses challenges in understanding their metabolism, and the acquisition of essential nutrients from host lungs remains unexplored. Transmission electron micrographs show that extracellular vesicles (EVs) are found near Pneumocystis spp. within the lung. We hypothesized that EVs transport essential nutrients to the fungi during infection. To investigate this, EVs from P. carinii- and P. murina-infected rodents were biochemically and functionally characterized. These EVs contained host proteins involved in cellular, metabolic, and immune processes as well as proteins with homologs found in other fungal EV proteomes, indicating that Pneumocystis may release EVs. Notably, EV uptake by P. carinii indicated their potential involvement in nutrient acquisition and a possibility for using engineered EVs for efficient therapeutic delivery. However, EVs added to P. carinii in vitro did not show increased growth or viability, implying that additional nutrients or factors are necessary to support their metabolic requirements. Exposure of macrophages to EVs increased proinflammatory cytokine levels but did not affect macrophages' ability to kill or phagocytose P. carinii. These findings provide vital insights into P. carinii and host EV interactions, yet the mechanisms underlying P. carinii's survival in the lung remain uncertain. These studies are the first to isolate, characterize, and functionally assess EVs from Pneumocystis-infected rodents, promising to enhance our understanding of host-pathogen dynamics and therapeutic potential.IMPORTANCEPneumocystis spp. are fungal pathogens that can cause severe pneumonia in mammals, relying heavily on the host for essential nutrients. The absence of an in vitro culture system poses challenges in understanding their metabolism, and the acquisition of vital nutrients from host lungs remains unexplored. Extracellular vesicles (EVs) are found near Pneumocystis spp., and it is hypothesized that these vesicles transport nutrients to the pathogenic fungi. Pneumocystis proteins within the EVs showed homology to other fungal EV proteomes, suggesting that Pneumocystis spp. release EVs. While EVs did not significantly enhance P. carinii growth in vitro, P. carinii displayed active uptake of these vesicles. Moreover, EVs induced proinflammatory cytokine production in macrophages without compromising their ability to combat P. carinii. These findings provide valuable insights into EV dynamics during host-pathogen interactions in Pneumocystis pneumonia. However, the precise underlying mechanisms remain uncertain. This research also raises the potential for engineered EVs in therapeutic applications.

Determining Pneumocystis jirovecii Colonisation from Infection Using PCR-Based Diagnostics in HIV-Negative Individuals

BACKGROUND

Pneumocystis jirovecii pneumonia is increasingly diagnosed with highly sensitive PCR diagnostics in immunocompromised, HIV-negative individuals. We assessed the performance of our in-house quantitative PCR with the aim to optimise interpretation.

METHODS

Retrospective audit of all positive P. jirovecii qPCRs on induced sputum or BAL fluid at a single centre from 2012 to 2023. Medical and laboratory records were analysed and people with HIV were excluded. Cases were categorised as colonisation, high-probability PCP or uncertain PCP infection against a clinical gold standard incorporating clinico-radiological data. Quantitative PCR assay targeting the 5s gene was utilised throughout the time period.

RESULTS

Of the 82 positive qPCRs, 28 were categorised as high-probability PCP infection, 30 as uncertain PCP and 24 as colonisation. There was a significant difference in qPCR values stratified by clinical category but not respiratory sample type. Current assay performance with a cutoff of 2.5 × 105 copies/mL had a sensitivity of 50% (95% CI, 30.65-69.35%) and specificity of 83.33% (95% CI, 62.62-95.26%). Youden Index calculated at 6.5 × 104 copies/mL had a sensitivity of 75% (56.64-87.32%, 95% CI) and specificity of 66.67% (46.71-82.03%, 95% CI). High and low cutoffs were explored. Significant variables associated with infection were age > 70 years old, the presence of fever, hypoxia or ground glass changes.

CONCLUSIONS

A single qPCR cutoff cannot reliably determine P. jirovecii infection from colonisation. Low and high cutoffs are useful, however, a large "possible infection" cohort will remain where interpretation of clinic-radiological factors remains essential. Standardisation of assays with prospective validation in specific immunocompromised groups will allow greater generalisability and allow large-scale prospective assay validation to be performed.

Glucose Transporter and Sensor Mechanisms in Fungal Pathogens as Potential Drug Targets

Fungal infections are emerging as major health challenges in recent years. The development of resistance against existing antifungal agents needs urgent attention and action. The limited classes of antifungal drugs available, their tendency to cause adverse effects, lack of effectiveness, etc., are the major limitations of current therapy. Thus, there is a pressing demand for new antifungal drug classes to cope with the present circumstances. Glucose is the key source of energy for all organisms, including fungi. Glucose plays a crucial role as a source of carbon and energy for processes like virulence, growth, invasion, biofilm formation, and resistance development. The glucose transport and sensing mechanisms are well developed in these organisms as an important strategy to sustain survival. Modulating these transport or sensor mechanisms may serve as an important strategy to inhibit fungal growth. Moreover, the structural difference between human and fungal glucose transporters makes them more appealing as drug targets. Limited literature is available for fungal glucose entry mechanisms. This review provides a comprehensive account of sugar transport mechanisms in common fungal pathogens.

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.

Risk-Benefit Analysis of Primary Prophylaxis Against Pneumocystis Jirovecii Pneumonia in Patients With Rheumatic Diseases Receiving Rituximab

OBJECTIVE

To identify a specific population of patients with rheumatic diseases receiving rituximab treatment for whom the benefit from primary prophylaxis against Pneumocystis jirovecii pneumonia (PJP) outweighs the risk of adverse events (AEs).

METHODS

This study included 818 patients treated with rituximab for rheumatic diseases, among whom 419 received prophylactic trimethoprim/sulfamethoxazole (TMP/SMX) with rituximab, while the remainder did not. Differences in 1-year PJP incidence between the groups were estimated using Cox proportional hazards regression. Risk-benefit assessment was performed in subgroups stratified according to risk factors based on the number needed to treat (NNT) to prevent 1 case of PJP and the number needed to harm (NNH) due to severe AEs. Inverse probability of treatment weighting was applied to minimize the confounding by indication.

RESULTS

During the 663.1 person-years, there were 11 PJP cases, with a mortality rate of 63.6%. Concomitant use of high-dose glucocorticoids (≥30 mg/day of prednisone or equivalent during 4 weeks after rituximab administration) was the most important risk factor. The PJP incidence (per 100 person-years) was 7.93 (95% confidence interval [95% CI] 2.91-17.25) in the subgroup receiving high-dose glucocorticoids compared with 0.40 (95% CI 0.01-2.25) in the subgroup without high-dose glucocorticoid use. Although prophylactic TMP/SMX significantly reduced the overall PJP incidence (HR 0.11 [95% CI 0.03-0.43]), the NNT to prevent 1 case of PJP (146) was higher than the NNH (86). In contrast, the NNT fell to 20 (95% CI 10.7-65.7) in patients receiving concomitant high-dose glucocorticoids.

CONCLUSION

The benefit associated with primary PJP prophylaxis outweighs the risk of severe AEs in patients with rheumatic diseases receiving rituximab and concomitant high-dose glucocorticoid treatment.

How metals fuel fungal virulence, yet promote anti-fungal immunity

Invasive fungal infections represent a significant global health problem, and present several clinical challenges, including limited treatment options, increasing rates of antifungal drug resistance and compounding comorbidities in affected patients. Metals, such as copper, iron and zinc, are critical for various biological and cellular processes across phyla. In mammals, these metals are important determinants of immune responses, but pathogenic microbes, including fungi, also require access to these metals to fuel their own growth and drive expression of major virulence traits. Therefore, host immune cells have developed strategies to either restrict access to metals to induce starvation of invading pathogens or deploy toxic concentrations within phagosomes to cause metal poisoning. In this Review, we describe the mechanisms regulating fungal scavenging and detoxification of copper, iron and zinc and the importance of these mechanisms for virulence and infection. We also outline how these metals are involved in host immune responses and the consequences of metal deficiencies or overloads on how the host controls invasive fungal infections.

Role of fungal burden in risk stratification of HIV-negative patients with Pneumocystis pneumonia: A 12-year, retrospective, observational, multicenter cohort

OBJECTIVES

This study aimed to explore the role of fungal burden in risk stratification of patients without HIV-negative patients with Pneumocystis pneumonia (PCP).

METHODS

This was a retrospective analysis of the characteristics associated with 30-day mortality in patients who were positive for P. jirovecii using polymerase chain reaction in bronchoalveolar lavage fluid between 2006 and 2017 in a multicenter cohort from Central Norway. The fungal burden was indicated by the cycle threshold (CT) values from semiquantitative real-time polymerase chain reaction targeting the β-tubulin gene.

RESULTS

We included 170 patients with proven or probable PCP. The all-cause 30-day mortality was 18.2%. After adjusting for host characteristics and premorbid corticosteroid use, a higher fungal burden was associated with a higher risk of dying: adjusted odds ratio 1.42 (95% confidence interval 0.48-4.25) for a CT value 31-36, increasing to odds ratio 5.43 (95% confidence interval 1.48-19.9) for a CT value ≤30 compared with patients with a CT value ≥37. The Charlson comorbidity index (CCI) improved the risk stratification: patients with a CT value ≥37 and CCI ≤2 had a 9% mortality risk compared with 70% among those with a CT value ≤30 and CCI ≥6. Comorbid cardiovascular disease, solid tumors, immunological disorders, premorbid corticosteroids, hypoxemia, abnormal leukocyte counts, low serum albumin, and C-reactive protein ≥100 were also independently associated with 30-day mortality. The sensitivity analyses did not suggest selection bias.

CONCLUSION

Fungal burden may improve the risk stratification of patients without HIV-negative patients with PCP.

Burden of fungal infections in Kenya

The burden of fungal infections has been on the rise globally and remains a significant public health concern in Kenya. We estimated the incidence and prevalence of fungal infections using all mycology publications in Kenya up to January 2023, and from neighbouring countries where data lacked. We used deterministic modelling using populations at risk to calculate the disease burden. The total burden of serious fungal infections is estimated to affect 6,328,294 persons which translates to 11.57% of the Kenyan population. Those suffering from chronic infections such as chronic pulmonary aspergillosis are estimated to be 100,570 people (0.2% of the population) and probably nearly 200,000 with fungal asthma, all treatable with oral antifungal therapy. Serious acute fungal infections secondary to HIV (cryptococcal meningitis, disseminated histoplasmosis, pneumocystis pneumonia, and mucosal candidiasis) affect 196,543 adults and children (0.4% of the total population), while cancer-related invasive fungal infection cases probably exceed 2,299 and those in intensive care about 1,230 incident cases, including Candida auris bloodstream infection. The burden of fungal infections in Kenya is high; however, limited diagnostic test availability, low clinician awareness and inadequate laboratory capacity constrain the country's health system in responding to the syndemic of fungal disease in Kenya.

Microbial lectome versus host glycolipidome: How pathogens exploit glycosphingolipids to invade, dupe or kill

Glycosphingolipids (GSLs) are ubiquitous components of the cell membranes, found across several kingdoms of life, from bacteria to mammals, including humans. GSLs are a subclass of major glycolipids occurring in animal lipid membranes in clusters named "lipid rafts." The most crucial functions of GSLs include signal transduction and regulation as well as participation in cell proliferation. Despite the mainstream view that pathogens rely on protein-protein interactions to survive and thrive in their hosts, many also target the host lipids. In particular, multiple pathogens produce adhesion molecules or toxins that bind GSLs. Attachment of pathogens to cell surface receptors is the initial step in infections. Many mammalian pathogens have evolved to recognize GSL-derived receptors. Animal glycosphingolipidomes consist of multiple types of GSLs differing in terminal glycan and ceramide structures in a cell or tissue-specific manner. Interspecies differences in GSLs dictate host specificity as well as cell and tissue tropisms. Evolutionary pressure exerted by pathogens on their hosts drives changes in cell surface glycoconjugates, including GSLs, and has produced a vast number of molecules and interaction mechanisms. Despite that abundance, the role of GSLs as pathogen receptors has been largely overlooked or only cursorily discussed. In this review, we take a closer look at GSLs and their role in the recognition, cellular entry, and toxicity of multiple bacterial, viral and fungal pathogens.

Exploring the Differences in Pneumocystis Pneumonia Infection Between HIV and Non-HIV Patients

Pneumocystis pneumonia (PCP) is one of the most common opportunistic infections worldwide that affects the lung. Pneumocystis leads to pneumonia, caused by Pneumocystis jirovecii, formerly known as Pneumocystis carinii. In recent decades, PCP has been a major health problem for human immunodeficiency virus (HIV) patients and is responsible for most of mortality and morbidity. However, the increasing number of immunosuppressive-related diseases has led to outbreaks in other patient populations, raising the concern for PCP as it becomes a major concern among those patients. These changes led to marked changes in the prevalence and mortality rates of PCP. Huge variations in those parameters among HIV and non-HIV patients have been seen also. Historically, the diagnosis was made by staining and direct visualization of the organism within the bronchoalveolar lavage (BAL) fluid. The diagnosis is now made by microscopic examination and a real-time polymerase chain reaction (PCR) of BAL. Serum (1,3)-β-D-glucan, which is a component of the Pneumocystis jirovecii cell wall that distinguishes it from other fungi, has become an important diagnostic tool. Early diagnosis and treatment play a vital role in the patient’s survival and in the infection outcome; hence, empirical PCP therapy should be started immediately when the infection is suspected without waiting for the results of the diagnostic test. Steroids play an important role in the treatment of HIV patients, especially patients who present with hypoxia and respiratory failure. Prophylaxis is very effective and should be given to all patients at high risk of PCP. Antiretroviral therapy (ART) should be started as soon as possible in newly diagnosed HIV-infected patients with PCP, and the immune status of immunocompromised patients with PCP should be improved by temporarily withholding immunosuppressive drugs or reducing their doses.