Possible pandemic HIN1 influenza complicated by Pneumocystis jirovecii pneumonia in an HIV-infected patient

Pneumocystis jirovecii Pneumonia after Heart Transplantation: Two Case Reports and a Review of the Literature

Post-transplant Pneumocystis jirovecii pneumonia (PcP) is an uncommon but increasingly reported disease among solid organ transplantation (SOT) recipients, associated with significant morbidity and mortality. Although the introduction of PcP prophylaxis has reduced its overall incidence, its prevalence continues to be high, especially during the second year after transplant, the period following prophylaxis discontinuation. We recently described two cases of PcP occurring more than one year after heart transplantation (HT) in patients who were no longer receiving PcP prophylaxis according to the local protocol. In both cases, the disease was diagnosed following the diagnosis of a viral illness, resulting in a significantly increased risk for PcP. While current heart transplantation guidelines recommend Pneumocystis jirovecii prophylaxis for up to 6-12 months after transplantation, after that period they only suggest an extended prophylaxis regimen in high-risk patients. Recent studies have identified several new risk factors that may be linked to an increased risk of PcP infection, including medication regimens and patient characteristics. Similarly, the indication for PcP prophylaxis in non-HIV patients has been expanded in relation to the introduction of new medications and therapeutic regimens for immune-mediated diseases. In our experience, the first patient was successfully treated with non-invasive ventilation, while the second required tracheal intubation, invasive ventilation, and extracorporeal CO2 removal due to severe respiratory failure. The aim of this double case report is to review the current timing of PcP prophylaxis after HT, the specific potential risk factors for PcP after HT, and the determinants of a prompt diagnosis and therapeutic approach in critically ill patients. We will also present a possible proposal for future investigations on indications for long-term prophylaxis.

Pathogenesis of Respiratory Viral and Fungal Coinfections

Individuals suffering from severe viral respiratory tract infections have recently emerged as "at risk" groups for developing invasive fungal infections. Influenza virus is one of the most common causes of acute lower respiratory tract infections worldwide. Fungal infections complicating influenza pneumonia are associated with increased disease severity and mortality, with invasive pulmonary aspergillosis being the most common manifestation. Strikingly, similar observations have been made during the current coronavirus disease 2019 (COVID-19) pandemic. The copathogenesis of respiratory viral and fungal coinfections is complex and involves a dynamic interplay between the host immune defenses and the virulence of the microbes involved that often results in failure to return to homeostasis. In this review, we discuss the main mechanisms underlying susceptibility to invasive fungal disease following respiratory viral infections. A comprehensive understanding of these interactions will aid the development of therapeutic modalities against newly identified targets to prevent and treat these emerging coinfections.

Pneumocystosis as a Complication of H1N1 Influenza A Infection in an HIV-Positive Patient on Effective cART

H1N1 influenza A virus can affect the immune system, causing lymphopenia. This might be of great concern for HIV individuals undergoing effective antireroviral therapy (cART). We report the first confirmed case of H1N1-induced AIDS and Pneumocystis jiroveci pneumonia in an HIV-positive woman on effective cART since 2006.

A Molecular Window into the Biology and Epidemiology of Pneumocystis spp

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

Influenza and Pneumocystis jirovecii pneumonia in an allogeneic hematopoietic stem cell transplantation recipient: Coinfection or superinfection?

Influenza infection and Pneumocystis jirovecii pneumonia (PJP) in hematopoietic stem cell transplant (HSCT) patients are well characterized; however, no dual infections have been reported in this patient population and little evidence of mechanisms of interaction between the two infections exists. We present a 53-year-old male allogeneic HSCT patient on immunosuppressive therapy for the treatment of graft versus host disease initially diagnosed with influenza A H3 and later PJP. Despite the development of acute respiratory distress syndrome, the patient was successfully treated with appropriate antimicrobial therapy and aggressive supportive care. This case demonstrates the necessity of maintaining a high index of suspicion for fungal (including PJP) coinfection or superinfection in the setting of worsening influenza infection.

First data on Pneumocystis jirovecii colonization in patients with respiratory diseases in North Lebanon

Pneumocystis colonization may play a role in transmission and local inflammatory response. It was explored in patients with respiratory diseases in North Lebanon. Overall prevalence reached only 5.2% (95% CI 2.13–10.47) but it was higher (17.3%) in the subpopulation of patients with chronic obstructive pulmonary disease (COPD). COPD was the only factor associated with a significantly increased risk of colonization. mtLSU genotyping revealed predominance of genotype 2, identified in five patients (71.4%), including one patient who had co-infection with genotype 3. These first data in North Lebanon confirm Pneumocystis circulation among patients with respiratory diseases and the potential for transmission to immunocompromised patients.