Infections in asplenic patients

Microbe capture by splenic macrophages triggers sepsis via T cell-death-dependent neutrophil lifespan shortening

The mechanisms linking systemic infection to hyperinflammation and immune dysfunction in sepsis are poorly understood. Extracellular histones promote sepsis pathology, but their source and mechanism of action remain unclear. Here, we show that by controlling fungi and bacteria captured by splenic macrophages, neutrophil-derived myeloperoxidase attenuates sepsis by suppressing histone release. In systemic candidiasis, microbial capture via the phagocytic receptor SIGNR1 neutralizes myeloperoxidase by facilitating marginal zone infiltration and T cell death-dependent histone release. Histones and hyphae induce cytokines in adjacent CD169 macrophages including G-CSF that selectively depletes mature Ly6G^high neutrophils by shortening their lifespan in favour of immature Ly6G^low neutrophils with a defective oxidative burst. In sepsis patient plasma, these mediators shorten mature neutrophil lifespan and correlate with neutrophil mortality markers. Consequently, high G-CSF levels and neutrophil lifespan shortening activity are associated with sepsis patient mortality. Hence, by exploiting phagocytic receptors, pathogens degrade innate and adaptive immunity through the detrimental impact of downstream effectors on neutrophil lifespan.

Hyperinflammation and immune dysfunction are key drivers of immunopathology in sepsis. Here the authors show microbial exploitation of phagocytic receptors is linked to triggering of sepsis and the immune cell mediated reduction in neutrophil life span.

Enhanced Bacteremia in Dextran Sulfate-Induced Colitis in Splenectomy Mice Correlates with Gut Dysbiosis and LPS Tolerance

Because both endotoxemia and gut dysbiosis post-splenectomy might be associated with systemic infection, the susceptibility against infection was tested by dextran sulfate solution (DSS)-induced colitis and lipopolysaccharide (LPS) injection models in splenectomy mice with macrophage experiments. Here, splenectomy induced a gut barrier defect (FITC-dextran assay, endotoxemia, bacteria in mesenteric lymph nodes, and the loss of enterocyte tight junction) and gut dysbiosis (increased Proteobacteria by fecal microbiome analysis) without systemic inflammation (serum IL-6). In parallel, DSS induced more severe mucositis in splenectomy mice than sham-DSS mice, as indicated by mortality, stool consistency, gut barrier defect, serum cytokines, and blood bacterial burdens. The presence of green fluorescent-producing (GFP) E. coli in the spleen of sham-DSS mice after an oral gavage supported a crucial role of the spleen in the control of bacteria from gut translocation. Additionally, LPS administration in splenectomy mice induced lower serum cytokines (TNF-α and IL-6) than LPS-administered sham mice, perhaps due to LPS tolerance from pre-existing post-splenectomy endotoxemia. In macrophages, LPS tolerance (sequential LPS stimulation) demonstrated lower cell activities than the single LPS stimulation, as indicated by the reduction in supernatant cytokines, pro-inflammatory genes (iNOS and IL-1β), cell energy status (extracellular flux analysis), and enzymes of the glycolysis pathway (proteomic analysis). In conclusion, a gut barrier defect after splenectomy was vulnerable to enterocyte injury (such as DSS), which caused severe bacteremia due to defects in microbial control (asplenia) and endotoxemia-induced LPS tolerance. Hence, gut dysbiosis and gut bacterial translocation in patients with a splenectomy might be associated with systemic infection, and gut-barrier monitoring or intestinal tight-junction strengthening may be useful.

The development of a quality improvement project to improve infection prevention and management in patients with asplenia or hyposplenia

Asplenia and hyposplenia (a/hyposplenia) are associated with increased morbidity and mortality from complications including infection. The recommended measures to reduce the risks associated with infection include patient education, vaccination and early initiation of antibiotic therapy for fever. Despite these recommendations, there is poor adherence to best practice management of patients with asplenia or hyposplenia (PWA/H). We present the development methodology and pilot data of a quality improvement project that explored whether a programme involving a novel medical alert card together with a patient and healthcare provider educational booklet increased vaccination rates and improved awareness and understanding of the infectious implications of a/hyposplenia. Our aim was to increase the proportion of those appropriately vaccinated and the proportion of patients with proper understanding of fever management by twofold in 18 months. Questionnaires were used locally as a root-cause-analysis to confirm the need for education and evaluate the effectiveness of the programme, as well as patient satisfaction. An interdisciplinary team developed a toolkit composed of a medical alert card and booklet. The toolkit was distributed to PWA/H who presented for a haematology clinic visit at a tertiary care centre. A separate set of questionnaires was then used to evaluate satisfaction and obtain feedback from patients and practitioners receiving the toolkit for the first time. Changes suggested by patients and practitioners with unanimous agreement among study investigators were made to the toolkit. The pilot study showed an increase in vaccination rates and awareness of vaccination status and appropriate fever management. The majority of the patients and practitioners found the information provided by the toolkit helpful. Given these promising single-centre findings, the intervention is being extended to another tertiary care centre with a large red blood cell disorders programme to evaluate its generalisability. The next step will be to expand the scope to paediatric PWA/H.

The management and outcome of paediatric splenic injuries in the Netherlands

Background

Non-operative management (NOM) is generally accepted as a treatment method of traumatic paediatric splenic rupture. However, considerable variations in management exist. This study analyses local trends in aetiology and management of paediatric splenic injuries and evaluates the implementation of the guidelines proposed by the American Paediatric Surgical Association (APSA) in a level 1 trauma centre.

Methods

The charts of paediatric patients with blunt splenic injury (BSI) who were admitted or transferred to a level 1 trauma centre between 2003 and 2020 were retrospectively assessed. Information pertaining to demographics, mechanism of injury, injury description, associated injuries, intervention and outcomes were analysed and compared to international literature.

Results

There were 130 patients with BSI identified (63.1% male), with a mean age of 11.3 ± 4.0 and a mean Injury Severity Score (ISS) of 21.6 ± 13.7. Bicycle accidents were the most common trauma mechanism (23.1%). Sixty-four percent were multi-trauma patients, 25% received blood transfusions, and 31% were haemodynamically unstable. Mean injury grade was 3.0, with 30% of patients having a high-grade injury. In total, 75% of patients underwent NOM with a 100% efficacy rate. Total splenectomy rate was 6.2%. Four patients died due to brain damage.

Patients with a high-grade BSI (grades IV–V) had a significantly higher ISS and longer bedrest and more often presented with an active blush on computed tomography (CT) scans than patients with a low-grade BSI (grades I–III). Non-operative management was mainly the choice of treatment in both groups (76.6% and 79.5%, respectively). Haemodynamic instability was a predictor for operative management (OM) (p = 0.001). Predictors for a longer length of stay (LOS) included concomitant injuries, haemodynamic instability and OM (all p < 0.02). Interobserver agreement in the grading of BSI is moderate, with a Cohens Kappa coefficient of 0.493.

Conclusion

Non-operative management has proven to be a realistic management approach in both low- and high-grade splenic injuries. Consideration for operative management should be based on haemodynamic instability. Compared to the anticipated length of bedrest and hospital stay outlined in the APSA guidelines, the Netherlands can reduce the length of bedrest and hospital stay through their non-operative management.

Level of evidence

Therapeutic study, level III

Supplementary Information

The online version contains supplementary material available at 10.1186/s13017-021-00353-4.

Streptococcus pneumoniae–induced purpura fulminans in a woman with functional asplenia

Purpura fulminans is a rare complication of septic shock, often associated withStreptococcus pneumoniae. Patients with anatomic or functional asplenia are at increased risk for infection because of impairment of their ability to defend against encapsulated pathogens. We report the case of a previously healthy, unimmunized 33-year-old female with functional asplenia who presented in septic shock and purpura fulminans and died in spite of maximal resuscitative measures. The clinical presentation, diagnosis, and management of purpura fulminans are reviewed. Purpura fulminans is a rare condition that requires early diagnosis and aggressive management by emergency physicians.

Bacterial meningitis in adults after splenectomy and hyposplenic states

OBJECTIVE

To examine the occurrence, disease course, prognosis, and vaccination status of patients with community-acquired bacterial meningitis with a history of splenectomy or functional hyposplenia.

PATIENTS AND METHODS

Patients with bacterial meningitis proven by cerebrospinal fluid culture were prospectively included in a nationwide cohort study between March 1, 2006, and September 1, 2011. Splenectomy or diseases associated with functional hyposplenia were scored for all patients. Vaccination status, clinical features, and outcome of patients with a history of splenectomy or functional hyposplenia were analyzed and compared with patients with normal spleen function.

RESULTS

Twenty-four of 965 patients (2.5%) had an abnormal splenic function: 16 had a history of splenectomy and 8 had functional hyposplenia. All patients had pneumococcal meningitis. Pre-illness vaccination status could be retrieved for 19 of 21 patients (90%), and only 6 patients (32%) were adequately vaccinated against pneumococci. Pneumococcal serotype was known in 21 patients; 52% of pneumococcal isolates had a serotype included in the 23-valent vaccine. Vaccine failure occurred in 3 patients. Splenectomized patients more often presented with signs of septic shock compared with patients with a normal spleen (63% vs 24%; P=.02). Outcome was unfavorable in 14 patients (58%), and 6 patients died (25%).

CONCLUSION

Splenectomy or functional hyposplenia is an uncommon risk factor for bacterial meningitis but results in a high rate of mortality and unfavorable outcome. Most patients were not adequately vaccinated against Streptococcus pneumoniae.

Overwhelming infection in asplenic patients: current best practice preventive measures are not being followed

AIMS

Patients without spleens are at increased risk of overwhelming infection. Recently, greater efforts, including the publication of national guidelines, have been made to improve the management of asplenic individuals. In theory, risks of serious sepsis can be reduced by good advice, immunisation, and antibiotic prophylaxis. In practice, such preventive measures might not be followed or may fail. A study of recent cases of overwhelming postsplenectomy infection (OPSI) was undertaken to examine specific associated factors and to determine whether currently recommended preventive measures are being followed.

METHODS

Cases of OPSI were identified and reported mainly by microbiologists across the country using a specifically designed proforma. Data including the nature of the infection and vaccination/ antibiotic prophylaxis history since splenectomy were obtained.

RESULTS

Seventy seven cases were reported. The age range varied from 3 months (congenital asplenia) to 87 years. In those who had undergone surgical splenectomy, the time interval between surgery and OPSI varied from 24 days to 65 years. Overall mortality reached 50%, with underlying haematological malignancy associated with the highest death rate. Streptococcus pneumoniae caused approximately 90% episodes. Only 31% individuals had received pneumococcal vaccination before OPSI. Seven of 17 pneumococcal infections in immunised cases could be considered vaccine failures. Few patients had been adequately advised on antibiotic prophylaxis or other measures.

CONCLUSIONS

Currently accepted best practice for managing asplenic patients is not being followed. Some OPSI cases may still be preventable but many asplenic individuals remain unrecognised. The compilation of asplenic patient registers might help to implement agreed policies with audit necessary to evaluate compliance. More is needed to ensure optimal management for this cohort of the population.

A study of 42 episodes of overwhelming post-splenectomy infection: is current guidance for asplenic individuals being followed?

Individuals without a spleen have an increased risk of overwhelming post-splenectomy infection (OPSI). Improved awareness in recent years has stimulated increased efforts to prevent OPSI. Published guidelines have described policies for immunization, chemoprophylaxis and other measures considered beneficial to asplenic patients, yet OPSI episodes continue to occur. In an attempt to investigate why serious infections are still being seen, we have conducted a nationally based survey of recent OPSI episodes, using mainly a network of medical microbiologists. Data including clinical background to both splenectomy and OPSI episode, immunization and chemoprophylaxis history have been collated. Forty-two cases of overwhelming infection were reported by June 1996. Patients of all ages were affected with OPSI occurring up to 59 years after splenectomy. A mortality rate of 45% was seen. Pneumococcal infection caused at least 37 of 42 episodes, but only 12 patients had received pneumococcal vaccine. Four cases were possible vaccine failures. Only 22% of individuals had taken any chemoprophylaxis since splenectomy, and only one carried a medical alert card. Much more needs to be done to ensure that asplenic patients are warned of the risks of infection, and given at least pneumococcal vaccine. The role of antibiotics for either continual prophylaxis or as a reserve supply for self-prescription at appropriate times also needs greater discussion. Further work on improving pneumococcal vaccine response together with suitable programmes for revaccination are required. Surveillance should continue until the incidence of OPSI reaches an irreducible minimum.