BACKGROUND: Despite improvements in health care, pneumonia-associated mortality remains high. The objective of this study was to analyze the factors associated with mortality in bacteremic pneumonia caused by pneumococcus.
METHODS: Retrospective cohort study in adult patients with pneumonia diagnosis and isolation of pneumococcus in blood cultures, between January 2012 and May 2021, was carried out. Clinical and laboratory variables, radiological involvement, evolution and mortality during hospitalization were analyzed. The group of deceased patients was compared with that of survivors.
RESULTS: 152 patients were included. Median age: 58 years; men: 58.9%; 33% presented a CURB-65 > than 2 at admission. Overall mortality: 34% (n=52). Deceased patients were more tachypneic on admission (respiratory rate 26 vs. 22; p=0.003), presented sensory alteration more frequently (58% vs. 14%; p< 0.001), PaO2/fraction of inspired oxygen ratio < 250 (58% vs. 22%; p<0.001), bilateral radiological compromise (50% vs. 32%; p=0.03), needed mechanical ventilation (50% vs 12%; p< 0.001), higher blood creatinine values (1.6 vs. 1.15; p=0.01), lower white blood cell count (10 900 vs 17 400; p=0.002), a lower glucose dosage (111 vs. 120; p=0.01), and fewer days of hospital stay (6 vs. 9; p=0.015). In logistic regression model, significant differences were maintained in the following factors associated with mortality: mechanical ventilation (OR=3.54), altered mental status (OR=5.95), chest X-ray with bilateral compromise (OR 3.20) and PAFI less than 250 (OR=3.62).
CONCLUSIONS: In our series, the factors related to mortality, despite the presence of bacteremia, do not differ from those published in the literature and which are part of the different prognostic scores used in routine practice.
Introducción: A pesar de las mejoras en los cuidados de la salud, la mortalidad asociada a neumonía continúa siendo alta. El objetivo de este estudio fue analizar los factores asociados a mortalidad en neumonía bacteriémica por neumococo. Métodos: Estudio de cohorte retrospectiva en pacientes adultos con diagnóstico de neumonía y neumococo aislado en hemocultivos, entre enero 2012 y mayo 2021. Se analizaron: variables clínicas y de laboratorio, compromiso radiológico, evolución y mortalidad durante la internación. Se comparó el grupo de pacientes fallecidos con el de sobrevivientes. Resultados: Se incluyeron 152 pacientes. La mediana de edad fue de 58 años y el 58.9% fueron hombres. El 33% presentó un CURB-65 mayor a 2 al momento de internación. La mortalidad global fue 34% (n=52). Los pacientes fallecidos se encontraban más frecuentemente taquipneicos al ingreso (frecuencia respiratoria 26 vs. 22; p=0.003), presentaban más frecuentemente alteración del sensorio (58% vs. 14%; p< 0.001), PaO2/fracción inspirada de oxígeno (PAFI) < 250 (58% vs. 22%; p<0.001), compromiso radiológico bilateral (50% vs. 32%; p=0.03), necesidad de asistencia respiratoria mecánica (ARM) (50% vs. 12%; p< 0.001), mayor valor de creatinina en sangre (1.6 vs. 1.15; p=0.01), menor recuento de glóbulos blancos (10 900 vs. 17 400; p=0.002), menor valor de glucemia (111 vs. 120; p=0.01) y menos días de estancia hospitalaria (6 vs. 9; p=0.015). En el análisis de regresión logística multivariable se mantuvieron diferencias significativas en los siguientes factores asociados a mortalidad: ventilación mecánica (OR=3.54), confusión (OR=5.95), radiografía con compromiso bilateral (OR= 3.20) y PAFI < 250 (OR=3.62). Conclusión: Los factores relacionados con mortalidad, a pesar de la presencia de bacteriemia, no difieren de los publicados en la literatura y forman parte de los scores pronósticos de práctica habitual.

BACKGROUND: Pneumococcal pneumonia (PP) is a serious infection caused by Streptococcus pneumoniae (pneumococcus), with a wide spectrum of clinical manifestations. The aim of this study was to analyze the comorbidity factors that influenced the mortality in patients with asplenia according to PP.
METHODS: Discharge reports from the Spanish Minimum Basic Data Set (MBDS) was used to retrospectively analyze patients with asplenia and PP, from 1997 to 2021. Elixhauser Comorbidity Index (ECI) was calculated to predict in-hospital mortality (IHM).
RESULTS: 97,922 patients with asplenia were included and 381 cases of PP were identified. The average age for men was 63.87 years and for women 65.99 years. In all years, ECI was larger for splenectomized than for non-splenectomized patients, with men having a higher mean ECI than women. An association was found between risk factors ECI, splenectomy, age group, sex, pneumococcal pneumonia, and increased mortality (OR = 0.98; 95% CI: 0.97-0.99; p < 0.001). The IHM increased steadily with the number of comorbidities and index scores in 1997-2021.
CONCLUSIONS: Asplenia remain a relevant cause of hospitalization in Spain. Comorbidities reflected a great impact in patients with asplenia and PP, which would mean higher risk of mortality.

Streptococcus pneumoniae is the most common bacterial cause of community acquired pneumonia and the acute respiratory distress syndrome (ARDS). Some clinical trials have demonstrated a beneficial effect of corticosteroid therapy in community acquired pneumonia, COVID-19, and ARDS, but the mechanisms of this benefit remain unclear. The primary objective of this study was to investigate the effects of corticosteroids on the pulmonary biology of pneumococcal pneumonia in a mouse model. A secondary objective was to identify shared transcriptomic features of pneumococcal pneumonia and steroid treatment in the mouse model and clinical samples.
We carried out comprehensive physiologic, biochemical, and histological analyses in mice to identify the mechanisms of lung injury in Streptococcus pneumoniae with and without adjunctive steroid therapy. We also studied lower respiratory tract gene expression from a cohort of 15 mechanically ventilated patients (10 with Streptococcus pneumoniae and 5 controls) to compare with the transcriptional studies in the mice.
In mice with pneumonia, dexamethasone in combination with ceftriaxone reduced (1) pulmonary edema formation, (2) alveolar protein permeability, (3) proinflammatory cytokine release, (4) histopathologic lung injury score, and (5) hypoxemia but did not increase bacterial burden. Transcriptomic analyses identified effects of steroid therapy in mice that were also observed in the clinical samples.
In combination with appropriate antibiotic therapy in mice, treatment of pneumococcal pneumonia with steroid therapy reduced hypoxemia, pulmonary edema, lung permeability, and histologic criteria of lung injury, and also altered inflammatory responses at the protein and gene expression level. The transcriptional studies in patients suggest that the mouse model replicates some of the features of pneumonia in patients with Streptococcus pneumoniae and steroid treatment. Overall, these studies provide evidence for the mechanisms that may explain the beneficial effects of glucocorticoid therapy in patients with community acquired pneumonia from Streptococcus Pneumoniae.

IL-22 plays a critical role in defending against mucosal infections, but how IL-22 production is regulated is incompletely understood. Here, we show that mice lacking IL-33 or its receptor ST2 (IL-1RL1) were more resistant to Streptococcus pneumoniae lung infection than wild-type animals and that single-nucleotide polymorphisms in IL33 and IL1RL1 were associated with pneumococcal pneumonia in humans. The effect of IL-33 on S. pneumoniae infection was mediated by negative regulation of IL-22 production in innate lymphoid cells (ILCs) but independent of ILC2s as well as IL-4 and IL-13 signaling. Moreover, IL-33\'s influence on IL-22-dependent antibacterial defense was dependent on housing conditions of the mice and mediated by IL-33\'s modulatory effect on the gut microbiota. Collectively, we provide insight into the bidirectional crosstalk between the innate immune system and the microbiota. We conclude that both genetic and environmental factors influence the gut microbiota, thereby impacting the efficacy of antibacterial immune defense and susceptibility to pneumonia.

Resolving inflammation is thought to return the affected tissue back to homoeostasis but recent evidence supports a non-linear model of resolution involving a phase of prolonged immune activity. Here we show that within days following resolution of Streptococcus pneumoniae-triggered lung inflammation, there is an influx of antigen specific lymphocytes with a memory and tissue-resident phenotype as well as macrophages bearing alveolar or interstitial phenotype. The transcriptome of these macrophages shows enrichment of genes associated with prostaglandin biosynthesis and genes that drive T cell chemotaxis and differentiation. Therapeutic depletion of post-resolution macrophages, inhibition of prostaglandin E2 (PGE2) synthesis or treatment with an EP4 antagonist, MF498, reduce numbers of lung CD4+/CD44+/CD62L+ and CD4+/CD44+/CD62L-/CD27+ T cells as well as their expression of the α-integrin, CD103. The T cells fail to reappear and reactivate upon secondary challenge for up to six weeks following primary infection. Concomitantly, EP4 antagonism through MF498 causes accumulation of lung macrophages and marked tissue fibrosis. Our study thus shows that PGE2 signalling, predominantly via EP4, plays an important role during the second wave of immune activity following resolution of inflammation. This secondary immune activation drives local tissue-resident T cell development while limiting tissue injury.

We evaluated whether the quantification of IgG to pneumococcal capsular polysaccharides is an accurate diagnostic test for pneumococcal infection in children with pneumonia in Nepal. Children with pneumococcal pneumonia did not have higher convalescent, or higher fold change, IgG to pneumococcal polysaccharides than children with other causes of pneumonia. Caution is needed in interpreting antibody responses in pneumococcal infections.

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BACKGROUND: Streptococcus pneumoniae is a global cause of community-acquired pneumonia (CAP) and invasive disease in children. The CAP-IT trial (grant No. 13/88/11; https://www.capitstudy.org.uk/ ) collected nasopharyngeal swabs from children discharged from hospitals with clinically diagnosed CAP, and found no differences in pneumococci susceptibility between higher and lower antibiotic doses and shorter and longer durations of oral amoxicillin treatment. Here, we studied in-depth the genomic epidemiology of pneumococcal (vaccine) serotypes and their antibiotic resistance profiles.
METHODS: Three-hundred and ninety pneumococci cultured from 1132 nasopharyngeal swabs from 718 children were whole-genome sequenced (Illumina) and tested for susceptibility to penicillin and amoxicillin. Genome heterogeneity analysis was performed using long-read sequenced isolates (PacBio, n = 10) and publicly available sequences.
RESULTS: Among 390 unique pneumococcal isolates, serotypes 15B/C, 11 A, 15 A and 23B1 were most prevalent (n = 145, 37.2%). PCV13 serotypes 3, 19A, and 19F were also identified (n = 25, 6.4%). STs associated with 19A and 19F demonstrated high genome variability, in contrast to serotype 3 (n = 13, 3.3%) that remained highly stable over a 20-year period. Non-susceptibility to penicillin (n = 61, 15.6%) and amoxicillin (n = 10, 2.6%) was low among the pneumococci analysed here and was independent of treatment dosage and duration. However, all 23B1 isolates (n = 27, 6.9%) were penicillin non-susceptible. This serotype was also identified in ST177, which is historically associated with the PCV13 serotype 19F and penicillin susceptibility, indicating a potential capsule-switch event.
CONCLUSIONS: Our data suggest that amoxicillin use does not drive pneumococcal serotype prevalence among children in the UK, and prompts consideration of PCVs with additional serotype coverage that are likely to further decrease CAP in this target population. Genotype 23B1 represents the convergence of a non-vaccine genotype with penicillin non-susceptibility and might provide a persistence strategy for ST types historically associated with vaccine serotypes. This highlights the need for continued genomic surveillance.

Multiplex panel tests identify many individual pathogens at once, using a set of component tests. In some panels the number of components can be large. If the panel is detecting causative pathogens for a single syndrome or disease then we might estimate the burden of that disease by combining the results of the panel, for example determining the prevalence of pneumococcal pneumonia as caused by many individual pneumococcal serotypes. When we are dealing with multiplex test panels with many components, test error in the individual components of a panel, even when present at very low levels, can cause significant overall error. Uncertainty in the sensitivity and specificity of the individual tests, and statistical fluctuations in the numbers of false positives and false negatives, will cause large uncertainty in the combined estimates of disease prevalence. In many cases this can be a source of significant bias. In this paper we develop a mathematical framework to characterise this issue, we determine expressions for the sensitivity and specificity of panel tests. In this we identify a counter-intuitive relationship between panel test sensitivity and disease prevalence that means panel tests become more sensitive as prevalence increases. We present novel statistical methods that adjust for bias and quantify uncertainty in prevalence estimates from panel tests, and use simulations to test these methods. As multiplex testing becomes more commonly used for screening in routine clinical practice, accumulation of test error due to the combination of large numbers of test results needs to be identified and corrected for.

OBJECTIVE: The objective of this review was to gain new insight into the rare condition, Austrian syndrome: the triad of endocarditis, meningitis and pneumonia caused by Streptococcus pneumoniae.
METHODS: A systematic review of case reports was conducted using the PRISMA guideline. Cases were rigorously screened to meet a set of well-defined inclusion criteria. Relevant data was aggregated and reported using descriptive statistics.
RESULTS: Seventy-one cases from 69 case reports were included in the final review. The mean age was 56.5 years with a male-to-female ratio of 2.4:1. Alcoholism was reported in 41% of patients. Altered mental state (69%) and fever (65%) (mean temperature on admission = 38.9°C) were the commonest presenting symptoms. The mean duration of symptoms before presentation to the hospital was 8 days. The aortic valve was most commonly affected (56%). The mean duration of antibiotic therapy was 5.6 weeks. Seventy percent of patients were admitted to the intensive care unit (ICU). Fifty-six percent of patients had valvular surgery. The average length of stay in the hospital was 36.9 days. Mortality was recorded in 28% of patients.
CONCLUSIONS: Austrian syndrome is rare but deadly. The true incidence is unknown but is commoner in middle-aged men and in alcoholics. Affected patients are usually critically unwell, often requiring ICU admission and prolonged hospital stays. Treatment is aggressive including prolonged courses of antibiotics and often, surgery. Despite these, the case fatality rate is high, with death occurring in over a quarter of patients. Surgery appears to be associated with better prognosis.