Polybacterial aetiology and outcomes in patients with community-acquired pneumonia

Aetiological agents of adult community-acquired pneumonia in Japan: systematic review and meta-analysis of published data

OBJECTIVE

Epidemiological information is essential in providing appropriate empiric antimicrobial therapy for pneumonia. This study aimed to clarify the epidemiology of community-acquired pneumonia (CAP) by conducting a systematic review of published studies in Japan.

DESIGN

Systematic review.

DATA SOURCE

PubMed and Ichushi web database (January 1970 to October 2022).

ELIGIBILITY CRITERIA

Clinical studies describing pathogenic micro-organisms in CAP written in English or Japanese, excluding studies on pneumonia other than adult CAP, investigations limited to specific pathogens and case reports.

DATA EXTRACTION AND SYNTHESIS

Patient setting (inpatient vs outpatient), number of patients, concordance with the CAP guidelines, diagnostic criteria and methods for diagnosing pneumonia pathogens as well as the numbers of each isolate. A meta-analysis of various situations was performed to measure the frequency of each aetiological agent.

RESULTS

Fifty-six studies were included and 17 095 cases of CAP were identified. Pathogens were undetectable in 44.1% (95% CI 39.7% to 48.5%). Streptococcus pneumoniae was the most common cause of CAP requiring hospitalisation or outpatient care (20.0% (95% CI 17.2% to 22.8%)), followed by Haemophilus influenzae (10.8% (95% CI 7.3% to 14.3%)) and Mycoplasma pneumoniae (7.5% (95% CI 4.6% to 10.4%)). However, when limited to CAP requiring hospitalisation, Staphylococcus aureus was the third most common at 4.9% (95% CI 3.9% to 5.8%). Pseudomonas aeruginosa was more frequent in hospitalised cases, while atypical pathogens were less common. Methicillin-resistant S. aureus accounted for 40.7% (95% CI 29.0% to 52.4%) of S. aureus cases. In studies that used PCR testing for pan-respiratory viral pathogens, human enterovirus/human rhinovirus (9.4% (95% CI 0% to 20.5%)) and several other respiratory pathogenic viruses were detected. The epidemiology varied depending on the methodology and situation.

CONCLUSION

The epidemiology of CAP varies depending on the situation, such as in the hospital versus outpatient setting. Viruses are more frequently detected by exhaustive genetic searches, resulting in a significant variation in epidemiology.

Burden of illness associated with pneumococcal infections in Japan - a targeted literature review

INTRODUCTION

Pneumococcal diseases (PDs) are among the leading causes of mortality and morbidity worldwide. However, the evidence on epidemiology, health economic, and patient-reported outcomes has not been systematically reviewed and published in Japan. This study aimed to assess the burden, treatment adherence and compliance, and serotype distribution associated with PDs in Japan.

METHOD

One hundred and eight studies were identified between January 2005 and June 2020. The identified studies were mostly regional and with a limited scale, clinical settings, and populations.

RESULTS

In 2013-2017, invasive PD incidence rates were 4.98-9.47/100,000 in <4-year-olds, 0.36/100,000 in 5-14-year-olds, 0.46/100,000 in 15-64-year-olds, and 1.50-5.38/100,000 in the elderly. The incidence of invasive PDs in children decreased from 24.6/100,000 in 2008 to 10.7/100,000 in 2013 after the introduction of PCV7 and further declined to 10.3/100,000 in 2014 after PCV13 was introduced. From 2014, the prevalence of PCV13 serotypes decreased across all age groups along with a decrease of PPV23 serotypes, but an increase of PPV23 serotypes not included in PCV13 among adults and the elderly. No study reported health-related quality-of-life data for PDs. In children, direct costs were 340,905-405,978 JPY (3,099-3,691 USD) per pneumococcal bacteraemia, 767,447-848,255 JPY (6,977-7,711 USD) per pneumococcal meningitis, and 79,000 JPY (718 USD) per pneumococcal acute otitis media episodes. In adults and the elderly, the direct cost of pneumococcal pneumonia was 348,280-389,630 JPY (3,166-3,542 USD). The average hospital stay length was 7.2-31.9 days in children, 9.0 days in adults and 9.0-28.7 days in adults and the elderly.

CONCLUSIONS

The epidemiological burden of PDs remains high in Japan, especially among children and the elderly with invasive PDs accounting for a very small proportion of all PDs. A significant impact of the PCV13 vaccine program was reported, while the PPV23's impact remains unclear. A substantial decrease in quality-adjusted life years in adults and the elderly and a high economic burden may exist.

Poverty as an independent risk factor for in-hospital mortality in community-acquired pneumonia: A study in a developing country population

BACKGROUND

Community-acquired pneumonia (CAP) is one of the most severe lower respiratory tract infections with a high in-hospital mortality. The aim of this study was to investigate the socioeconomic and medical risk factors affecting the prognosis of acute pneumonia. The results of this study can mention the value of socioeconomic backgrounds like poverty and illiteracy in clinical practice, even in a well-known biological phenomenon (eg acute pneumonia).

METHODS

In this cross-sectional study, all admitted patients to a tertiary teaching hospital with a diagnosis of community acquired pneumonia in a 12-month period were enrolled. Socioeconomic and demographic characteristics, underlying conditions, clinical manifestations and para-clinical test results at admission registered prospectively. A logistic regression model was conducted using in-hospital mortality as the dependent variable.

RESULTS

A total of 621 patients was included in this study. Among them, 47 patients (7.6%) died during the hospitalisation period. In multiple logistic regression analysis, pleural effusion, a higher CURB-65 score, hyponatremia, hyperglycaemia and poverty (being in the lower economic class) were identified as independent risk factors for in-hospital mortality in community-acquired pneumonia.

CONCLUSION

Numerous factors can influence the prognosis of CAP. In addition to the CURB-65 score and some other medical risk factors, socioeconomic backgrounds can also affect the early outcome in CAP. In this study, being in the lower economic class (as an indicator of poverty) is interpreted as an independent risk factor for a poor prognosis in CAP.

Steroid-induced Deficiency of Mucosal-associated Invariant T Cells in the Chronic Obstructive Pulmonary Disease Lung. Implications for Nontypeable Haemophilus influenzae Infection

RATIONALE

Mucosal-associated invariant T (MAIT) cells are a recently described abundant, proinflammatory T-cell subset with unknown roles in pulmonary immunity. Nontypeable Haemophilus influenzae (NTHi) is the leading bacterial pathogen during chronic obstructive pulmonary disease (COPD) exacerbations and is a plausible target for MAIT cells.

OBJECTIVES

To investigate whether MAIT cells respond to NTHi and the effects of inhaled corticosteroids (ICS) on their frequency and function in COPD.

METHODS

Eleven subjects with COPD receiving ICS, 8 steroid-naive subjects with COPD, and 21 healthy control subjects underwent phlebotomy, sputum induction, bronchoalveolar lavage, and endobronchial biopsy. Pulmonary and monocyte-derived macrophages were cultured in vitro with NTHi.

MEASUREMENTS AND MAIN RESULTS

Frequencies of Vα7.2⁺CD161⁺ MAIT cells, surface expression of the major histocompatibility complex-related protein 1 (MR1), and intracellular IFN-γ expression were measured by flow cytometry. MAIT-cell frequencies were reduced in peripheral blood of ICS-treated subjects with COPD (median 0.38%; interquartile range [IQR], 0.25-0.96) compared with healthy control subjects (1.8%; IQR, 1.4-2.5; P = 0.001) or steroid-naive patients with COPD (1.8%; IQR, 1.2-2.3; P = 0.04). MAIT cells were reduced in bronchial biopsies from subjects with COPD treated with steroids (0.73%; IQR, 0.46-1.3) compared with healthy control subjects (4.0%; IQR, 1.6-5.0; P = 0.02). Coculture of live NTHi increased macrophage surface expression of MR1 and induced IFN-γ from CD4 cells and CD8 cells, but most potently from MAIT cells (median IFN-γ-positive frequencies, 2.9, 8.6, and 27.6%, respectively). In vitro fluticasone and budesonide reduced MR1 surface expression twofold and decreased NTHi-induced IFN-γ secretion eightfold.

CONCLUSIONS

MAIT cells are deficient in blood and bronchial tissue in steroid-treated, but not steroid-naive, COPD. NTHi constitutes a target for pulmonary MAIT-cell immune responses, which are significantly impaired by corticosteroids.