Non-bacterial infections in allogeneic non-myeloablative stem cell transplant recipients

Overview of Infections in the Immunocompromised Host

Understanding the components of the immune system that contribute to host defense against infection is key to recognizing infections that are more likely to occur in an immunocompromised patient. In this review, we discuss the integrated system of physical barriers and of innate and adaptive immunity that contributes to host defense. Specific defects in the components of this system that predispose to particular infections are presented. This is followed by a review of primary immunodeficiency diseases and secondary immunodeficiencies, the latter of which develop because of a specific illness or condition or are treatment-related. The effects of treatment for neoplasia, autoimmune diseases, solid organ and stem cell transplants on host defenses are reviewed and associated with susceptibility to particular infections. In conclusion, an approach to laboratory screening for a suspected immunodeficiency is presented. Knowledge of which host defects predispose to specific infections allows clinicians to prevent, diagnose, and manage infections in their immunocompromised patients most effectively.

Invasive diagnostic strategies in immunosuppressed patients with acute respiratory distress syndrome

Immunosuppression predisposes the host to development of pulmonary infections, which can lead to respiratory failure and the development of acute respiratory distress syndrome (ARDS). There are multiple mechanisms by which a host can be immunosuppressed and each is associated with specific infectious pathogens. Early invasive diagnostic modalities such as fiber-optic bronchoscopy with bronchoalveolar lavage, transbronchial biopsy, and open lung biopsy are complementary to serologic and noninvasive studies and assist in rapidly establishing an accurate diagnosis, which allows initiation of appropriate therapy and may improve outcomes with relative safety.

Diagnostic bronchoscopy in solid-organ and hematopoietic stem cell transplantation

Fiberoptic bronchoscopy is a valuable diagnostic tool in solid-organ and hematopoietic stem cell transplant recipients presenting with a range of pulmonary complications. This article provides a comprehensive overview of the utility and potential adverse effects of diagnostic bronchoscopy for transplant recipients. Recommendations are offered on the selection of patients, the timing of bronchoscopy, and the samples to be obtained across the spectrum of suspected pulmonary complications of transplantation. Based on review of the literature, the authors recommend early diagnostic bronchoscopy over empiric treatment in transplant recipients with evidence of certain acute, subacute, or chronic pulmonary processes. This approach may be most critical when an underlying infectious etiology is suspected. In the absence of prompt diagnostic information on which to base effective treatment, the risks associated with empiric antimicrobial therapy, including medication side effects and the development of antibiotic resistance, compound the potential harm of delaying targeted management.

Neurological complications of transplantation: part I: hematopoietic cell transplantation

Hematopoietic cell transplantation (HCT) is the preferred treatment for an expanding range of neoplastic and nonmalignant conditions. Increasing numbers of solid organ transplantations (SOTs) add an additional population of immunosuppressed patients with multiple potential neurological problems. While the spectrum of neurological complications varies with conditioning procedure and hematopoietic cell or solid organ source, major neurological complications occur with all transplantation procedures. This 2 part review emphasizes a practical consultative approach to central and peripheral nervous system problems related to HCT or SOT with clinical and neuroimaging examples from the authors' institutional experience with the following conditions: the diversity of manifestations of common infections such as varicella zoster virus, Aspergillus, and progressive multifocal leukoencephalopathy (PML), drug therapy-related complications, stroke mechanisms, the spectrum of graft versus host disease (GVHD), and neurologically important syndromes of immune reconstitution inflammatory syndrome (IRIS), posterior reversible encephalopathy syndrome (PRES), and posttransplantation lymphoproliferative disorder (PTLD). These complications preferentially occur at specific intervals after HCT and SOT, and neurological consultants must recognize an extensive spectrum of syndromes in order to effect timely diagnosis and expedite appropriate treatment.

Fatal BK virus pneumonia following stem cell transplantation

We report the case of a 39-year-old male patient who died of severe BK virus (BKV) pneumonia 168 days after hematopoietic stem cell transplantation (HSCT) for acute lymphoblastic leukemia. After suffering from BKV-associated late-onset hemorrhagic cystitis (HC) with long-term sustained BKV viremia, he died of rapidly progressive pneumonia. On autopsy, numerous viral intranuclear inclusions were seen in his lungs and bladder. An immunohistochemical examination of his lungs was positive for simian virus 40. Based on these pathological results and the high sustained BKV viral load in his blood, we reached a diagnosis of BKV pneumonia. Viral infection can occasionally become life threatening among HSCT recipients. It is widely known that BKV can cause late-onset HC, but BKV-associated pneumonia is rare. Because of its rapid progression and poor prognosis, it is difficult to make an antemortem diagnosis of BKV pneumonia. A treatment strategy for BKV pneumonia also needs to be formulated. Similar to other viral pathogens, BKV can cause pneumonia and the clinician should therefore be aware of it in immunocompromised patients.

Infectious complications following allogeneic stem cell transplantation: reduced-intensity vs. myeloablative conditioning regimens

BACKGROUND

In allogeneic stem cell transplantation (allo-SCT), reduced-intensity conditioning (RIC) is known for producing less regimen-related toxicity. However, whether or not RIC reduces the risk for infection and infection-related mortality (IRM) remains controversial.

METHODS

We retrospectively analyzed infectious episodes and IRMs after allo-SCTs by time period and by the intensity of the conditioning regimen (RIC [n = 81] vs. myeloablative conditioning, MAC [n = 150]).

RESULTS

The cumulative incidence of any kind of infection was lower in the RIC group through the entire period (72% vs. 87%; P = 0.007). The onset of infections was deferred in the RIC group as compared with the MAC group (P = 0.012). Bacteremia occurred less frequently in the RIC group through the entire period (5% vs. 14%; P = 0.044). However, the incidences of cytomegalovirus reactivation and disease, herpes zoster, virus-associated hemorrhagic cystitis, and invasive fungal infection were not different between the two groups. Furthermore, there was no difference in relapse-free survival and IRM between the two conditioning regimens.

CONCLUSION

Careful monitoring and appropriate preventive/therapeutic strategies for infectious complications, comparable to those for allo-SCT recipients with MAC, should also be applied to those with RIC, especially after engraftment.