Antibiotic susceptibility patterns of bacterial isolates of patients with upper respiratory tract infections

Abstract To evaluate the antibiotic susceptibility patterns in URTIs reporting to tertiary hospitals of Lahore. A cross-sectional study employing 259 culture sensitivity reports obtained from tertiary care hospitals of Lahore. Using SPSS, descriptive statistics were used to estimate frequencies and percentages. In URTIs, S. aureus (5%) was the frequent gram-positive isolate followed by MRSA (1.5%) and MSSA (1.5%), while P. aeruginosa (15.8%) was the prevalent gram-negative isolate followed by Klebsiella (13.1%) and E. coli (6.9%). Against P. aeruginosa, ceftazidime (7.7%), cefuroxime/ceftriaxone (4.6%), amoxicillin (4.3%) and ciprofloxacin (4.2%), were tested resistant, while imipenem (11.2%), ciprofloxacin (9.2%), amikacin (9.2%), meropenem/ levofloxacin/gentamicin (8.1%) and piptaz (6.9%) were found sensitive. Against Klebsiella, carbepenems (7.3%), amikacin (6.5%), ciprofloxacin (5.4%) and gentamicin (5%) were tested sensitive, whereas, ceftazidime (8.5%), ceftriaxone (5.8%), cefaclor (5.5%), ampicillin (4.6%), co-amoxiclave (4.2%) and ciftazidime/ciprofloxacin (3.8%) were found resistant. Overall, imipenem (35%), meropenem (30.8%) and amikacin (31.9%) were the three most sensitive antibiotics, while ceftazidime (25.4%), ceftriaxone (19.2%) and ampicillin (18.5%) were the three most resistant antibiotics. Data suggested that P.aeruginosa and Klebsiella, were the most frequent bacterial isolates in URTIs of Lahore. These isolates were resistant to ampicillin, cefuroxime and ceftazidime, but were sensitive to carbapenem and aminoglycosides

Retrospective study on the efficacy of monocyte distribution width (MDW) as a screening test for COVID-19.

BACKGROUND: Pathogenic genetic testing for coronavirus disease 2019 (COVID-19) can detect viruses with high sensitivity; however, there are several challenges. In the prevention, testing, and treatment of COVID-19, more effective, safer, and convenient methods are desired. We evaluated the possibility of monocyte distribution width (MDW) as an infection biomarker in COVID-19 testing. METHODS: The efficacy of MDW as a screening test for COVID-19 was retrospectively assessed in 80 patients in the COVID-19 group and 232 patients in the non-COVID-19 group (141 patients with acute respiratory infection, 19 patients with nonrespiratory infection, one patient with a viral infection, 11 patients who had received treatment for COVID-19, one patient in contact with COVID-19 patients, and 59 patients with noninfectious disease). RESULTS: The median MDW in 80 patients in the COVID-19 group was 23.3 (17.2-33.6), and the median MDW in 232 patients in the non-COVID-19 group was 19.0 (13.6-30.2) (P < 0.001). When the COVID-19 group was identified using the MDW cut-off value of 21.3 from the non-COVID-19 group, the area under the curve (AUC) was 0.844, and the sensitivity and specificity were 81.3% and 78.2%, respectively. Comparison of MDW by severity between the COVID-19 group and patients with acute respiratory infection in the non-COVID-19 group showed that MDW was significantly higher in the COVID-19 group for all mild, moderate I, and moderate II disease. CONCLUSIONS: MDW (cut-off value: 21.3) may be used as a screening test for COVID-19 in fever outpatients. Trial registration This study was conducted after being approved by the ethics committee of National Hospital Organization Omuta National Hospital (Approval No. 3-19). This study can be accessed via https://omuta.hosp.go.jp/files/000179721.pdf .

Respiratory infections and type 1 diabetes: Potential roles in pathogenesis.

Among the environmental factors associated with type 1 diabetes (T1D), viral infections of the gut and pancreas has been investigated most intensely, identifying enterovirus infections as the prime candidate trigger of islet autoimmunity (IA) and T1D development. However, the association between respiratory tract infections (RTI) and IA/T1D is comparatively less known. While there are significant amounts of epidemiological evidence supporting the role of respiratory infections in T1D, there remains a paucity of data characterising infectious agents at the molecular level. This gap in the literature precludes the identification of the specific infectious agents driving the association between RTI and T1D. Furthermore, the effect of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections on the development of IA/T1D remains undeciphered. Here, we provide a comprehensive overview of the evidence to date, implicating RTIs (viral and non-viral) as potential risk factors for IA/T1D.

Recapitulating infection, thermal sensitivity and antiviral treatment of seasonal coronaviruses in human airway organoids.

BACKGROUND: Human seasonal coronaviruses usually cause mild upper-respiratory tract infection, but severe complications can occur in specific populations. Research into seasonal coronaviruses is limited and robust experimental models are largely lacking. This study aims to establish human airway organoids (hAOs)-based systems for seasonal coronavirus infection and to demonstrate their applications in studying virus-host interactions and therapeutic development. METHODS: The infections of seasonal coronaviruses 229E, OC43 and NL63 in 3D cultured hAOs with undifferentiated or differentiated phenotypes were tested. The kinetics of virus replication and production was profiled at 33 °C and 37 °C. Genome-wide transcriptome analysis by RNA sequencing was performed in hAOs under various conditions. The antiviral activity of molnupiravir and remdesivir, two approved medications for treating COVID19, was tested. FINDINGS: HAOs efficiently support the replication and infectious virus production of seasonal coronaviruses 229E, OC43 and NL63. Interestingly, seasonal coronaviruses replicate much more efficiently at 33 °C compared to 37 °C, resulting in over 10-fold higher levels of viral replication. Genome-wide transcriptomic analyses revealed distinct patterns of infection-triggered host responses at 33 °C compared to 37 °C temperature. Treatment of molnupiravir and remdesivir dose-dependently inhibited the replication of 229E, OC43 and NL63 in hAOs. INTERPRETATION: HAOs are capable of modeling 229E, OC43 and NL63 infections. The intriguing finding that lower temperature resembling that in the upper respiratory tract favors viral replication may help to better understand the pathogenesis and transmissibility of seasonal coronaviruses. HAOs-based innovative models shall facilitate the research and therapeutic development against seasonal coronavirus infections. FUNDING: This research is supported by funding of a VIDI grant (No. 91719300) from the Netherlands Organization for Scientific Research and the Dutch Cancer Society Young Investigator Grant (10140) to Q.P., and the ZonMw COVID project (114025011) from the Netherlands Organization for Health Research and Development to R.R.

Evaluation of the SARS-CoV-2 positivity ratio and upper respiratory tract viral load among asymptomatic individuals screened before hospitalization or surgery in Flanders, Belgium.

INTRODUCTION: The incidence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infections in the Belgian community is mainly estimated based on test results of patients with coronavirus disease (COVID-19)-like symptoms. The aim of this study was to investigate the evolution of the SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) positivity ratio and distribution of viral loads within a cohort of asymptomatic patients screened prior hospitalization or surgery, stratified by age category. MATERIALS/METHODS: We retrospectively studied data on SARS-CoV-2 real-time RT-PCR detection in respiratory tract samples of asymptomatic patients screened pre-hospitalization or pre-surgery in nine Belgian hospitals located in Flanders over a 12-month period (1 April 2020-31 March 2021). RESULTS: In total, 255925 SARS-CoV-2 RT-PCR test results and 2421 positive results for which a viral load was reported, were included in this study. An unweighted overall SARS-CoV-2 real-time RT-PCR positivity ratio of 1.27% was observed with strong spatiotemporal differences. SARS-CoV-2 circulated predominantly in 80+ year old individuals across all time periods except between the first and second COVID-19 wave and in 20-30 year old individuals before the second COVID-19 wave. In contrast to the first wave, a significantly higher positivity ratio was observed for the 20-40 age group in addition to the 80+ age group compared to the other age groups during the second wave. The median viral load follows a similar temporal evolution as the positivity rate with an increase ahead of the second wave and highest viral loads observed for 80+ year old individuals. CONCLUSION: There was a high SARS-CoV-2 circulation among asymptomatic patients with a predominance and highest viral loads observed in the elderly. Moreover, ahead of the second COVID-19 wave an increase in median viral load was noted with the highest overall positivity ratio observed in 20-30 year old individuals, indicating they could have been the hidden drivers of this wave.

A multilevel analysis of the social determinants associated with symptoms of acute respiratory infection among preschool age children in Pakistan: A population-based survey.

BACKGROUND: As advocated by WHO in "Closing the Health Gap in a Generation", dramatic differences in child health are closely linked to degrees of social disadvantage, both within and between communities. Nevertheless, research has not examined whether child health inequalities include, but are not confined to, worse acute respiratory infection (ARI) symptoms among the socioeconomic disadvantaged in Pakistan. In addition to such disadvantages as the child's gender, maternal education, and household poverty, the present study also examined the linkages between the community environment and ARI symptoms among Pakistan children under five. Furthermore, we have assessed gender contingencies related to the aforementioned associations. METHODS: Using data from the nationally representative 2017-2018 Pakistan Demographic and Health Survey, a total of 11,908 surviving preschool age children (0-59 months old) living in 561 communities were analyzed. We employed two-level multilevel logistic regressions to model the relationship between ARI symptoms and individual-level and community-level social factors. RESULTS: The social factors at individual and community levels were found to be significantly associated with an increased risk of the child suffering from ARI symptoms. A particularly higher risk was observed among girls who resided in urban areas (AOR = 1.42; p<0.01) and who had a birth order of three or greater. DISCUSSIONS: Our results underscore the need for socioeconomic interventions in Pakistan that are targeted at densely populated households and communities within urban areas, with a particular emphasis on out-migration, in order to improve unequal economic underdevelopment. This could be done by targeting improvements in socio-economic structures, including maternal education.

Impact of Bacterial Toxins in the Lungs.

Bacterial toxins play a key role in the pathogenesis of lung disease. Based on their structural and functional properties, they employ various strategies to modulate lung barrier function and to impair host defense in order to promote infection. Although in general, these toxins target common cellular signaling pathways and host compartments, toxin- and cell-specific effects have also been reported. Toxins can affect resident pulmonary cells involved in alveolar fluid clearance (AFC) and barrier function through impairing vectorial Na+ transport and through cytoskeletal collapse, as such, destroying cell-cell adhesions. The resulting loss of alveolar-capillary barrier integrity and fluid clearance capacity will induce capillary leak and foster edema formation, which will in turn impair gas exchange and endanger the survival of the host. Toxins modulate or neutralize protective host cell mechanisms of both the innate and adaptive immunity response during chronic infection. In particular, toxins can either recruit or kill central players of the lung's innate immune responses to pathogenic attacks, i.e., alveolar macrophages (AMs) and neutrophils. Pulmonary disorders resulting from these toxin actions include, e.g., acute lung injury (ALI), the acute respiratory syndrome (ARDS), and severe pneumonia. When acute infection converts to persistence, i.e., colonization and chronic infection, lung diseases, such as bronchitis, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) can arise. The aim of this review is to discuss the impact of bacterial toxins in the lungs and the resulting outcomes for pathogenesis, their roles in promoting bacterial dissemination, and bacterial survival in disease progression.

Metabolic Modifications by Common Respiratory Viruses and Their Potential as New Antiviral Targets.

Respiratory viruses are known to be the most frequent causative mediators of lung infections in humans, bearing significant impact on the host cell signaling machinery due to their host-dependency for efficient replication. Certain cellular functions are actively induced by respiratory viruses for their own benefit. This includes metabolic pathways such as glycolysis, fatty acid synthesis (FAS) and the tricarboxylic acid (TCA) cycle, among others, which are modified during viral infections. Here, we summarize the current knowledge of metabolic pathway modifications mediated by the acute respiratory viruses respiratory syncytial virus (RSV), rhinovirus (RV), influenza virus (IV), parainfluenza virus (PIV), coronavirus (CoV) and adenovirus (AdV), and highlight potential targets and compounds for therapeutic approaches.

Chest Radiological Findings and Clinical Characteristics of Laboratory-Confirmed COVID-19 Patients from Saudi Arabia.

BACKGROUND Coronavirus disease 2019 (COVID-19) is a viral respiratory disease that first emerged in China in December 2019 and quickly spread worldwide. As the prevalence of COVID-19 increases, radiological examination is becoming an essential diagnostic tool for identifying and managing the disease's progression. Therefore, we aimed to identify the chest imaging features and clinical characteristics of patients with laboratory-confirmed COVID-19 in Saudi Arabia. MATERIAL AND METHODS In this retrospective study, data of laboratory-confirmed COVID-19 patients were collected from 4 hospitals in Jeddah, Saudi Arabia. Their common clinical characteristics, as well as imaging features of chest X-rays and computed tomography (CT) images, were analyzed. RESULTS A total of 297 patients with laboratory-confirmed COVID-19 who underwent chest imaging were investigated in this study. Of these patients, 77.9% were male and 22.2% were female. Their mean age was 48 years old. The most common clinical symptoms were fever (187 patients; 63%) and cough (174 patients; 58.6%). The predominant descriptive chest imaging findings were ground-glass opacities and consolidation. Locations of abnormalities were bilateral, mainly distributed peripherally, in the lower lung zones, and in the middle lung zones. CONCLUSIONS This study provides an understanding of the most common clinical and radiological features of patients with laboratory-confirmed COVID-19 in Saudi Arabia. The majority of COVID-19 patients in our study cohort had either stable or worse progression of lung lesions during follow-ups; thus, they presented moderate disease cases. Elderly males were more affected by COVID-19 than females, with fever and cough being the most common clinical symptoms.

Emerging Advances of Nanotechnology in Drug and Vaccine Delivery against Viral Associated Respiratory Infectious Diseases (VARID).

Viral-associated respiratory infectious diseases are one of the most prominent subsets of respiratory failures, known as viral respiratory infections (VRI). VRIs are proceeded by an infection caused by viruses infecting the respiratory system. For the past 100 years, viral associated respiratory epidemics have been the most common cause of infectious disease worldwide. Due to several drawbacks of the current anti-viral treatments, such as drug resistance generation and non-targeting of viral proteins, the development of novel nanotherapeutic or nano-vaccine strategies can be considered essential. Due to their specific physical and biological properties, nanoparticles hold promising opportunities for both anti-viral treatments and vaccines against viral infections. Besides the specific physiological properties of the respiratory system, there is a significant demand for utilizing nano-designs in the production of vaccines or antiviral agents for airway-localized administration. SARS-CoV-2, as an immediate example of respiratory viruses, is an enveloped, positive-sense, single-stranded RNA virus belonging to the coronaviridae family. COVID-19 can lead to acute respiratory distress syndrome, similarly to other members of the coronaviridae. Hence, reviewing the current and past emerging nanotechnology-based medications on similar respiratory viral diseases can identify pathways towards generating novel SARS-CoV-2 nanotherapeutics and/or nano-vaccines.

The First Pediatric Patients with Coronavirus Disease 2019 (COVID-19) in Japan: Risk of Co-Infection with Other Respiratory Viruses.

Coronavirus disease 2019 (COVID-19) is a severe infectious disease of the respiratory tract caused by a novel coronavirus, severe acute respiratory syndrome coronavirus 2, and has a high mortality rate. The disease emerged from Wuhan, China, in late 2019, and spread to Japan, including Hokkaido, in January 2020. In February 2020, 3 children were diagnosed with COVID-19 in Furano, Hokkaido, Japan. During this period, influenza and human metapneumovirus infections were prevalent among children in the Furano region. Two of the 3 patients experienced co-infection with other respiratory viruses, including influenza virus A or human metapneumovirus. To the authors' knowledge, the cases described in the present report were the first pediatric patients with COVID-19 in Japan. In children with COVID-19, the possibility of co-infection with other respiratory pathogens should be considered.

Comparative Pathogenesis of Bovine and Porcine Respiratory Coronaviruses in the Animal Host Species and SARS-CoV-2 in Humans.

Discovery of bats with severe acute respiratory syndrome (SARS)-related coronaviruses (CoVs) raised the specter of potential future outbreaks of zoonotic SARS-CoV-like disease in humans, which largely went unheeded. Nevertheless, the novel SARS-CoV-2 of bat ancestral origin emerged to infect humans in Wuhan, China, in late 2019 and then became a global pandemic. Less than 5 months after its emergence, millions of people worldwide have been infected asymptomatically or symptomatically and at least 360,000 have died. Coronavirus disease 2019 (COVID-19) in severely affected patients includes atypical pneumonia characterized by a dry cough, persistent fever, and progressive dyspnea and hypoxia, sometimes accompanied by diarrhea and often followed by multiple organ failure, especially of the respiratory and cardiovascular systems. In this minireview, we focus on two endemic respiratory CoV infections of livestock: bovine coronavirus (BCoV) and porcine respiratory coronavirus (PRCV). Both animal respiratory CoVs share some common features with SARS-CoV and SARS-CoV-2. BCoV has a broad host range including wild ruminants and a zoonotic potential. BCoV also has a dual tropism for the respiratory and gastrointestinal tracts. These aspects, their interspecies transmission, and certain factors that impact disease severity in cattle parallel related facets of SARS-CoV or SARS-CoV-2 in humans. PRCV has a tissue tropism for the upper and lower respiratory tracts and a cellular tropism for type 1 and 2 pneumocytes in lung but is generally a mild infection unless complicated by other exacerbating factors, such as bacterial or viral coinfections and immunosuppression (corticosteroids).

A Descriptive and Quantitative Immunohistochemical Study Demonstrating a Spectrum of Platelet Recruitment Patterns Across Pulmonary Infections Including COVID-19.

OBJECTIVES: Pulmonary platelet deposition and microangiopathy are increasingly recognized components of coronavirus disease 2019 (COVID-19) infection. Thrombosis is a known component of sepsis and disseminated intravascular coagulation. We sought to compare the level of platelet deposition in the pulmonary vasculature in cases of confirmed COVID-19 infection to other lung injuries and infections. METHODS: Immunohistochemistry was performed on 27 autopsy cases and 2 surgical pathology cases targeting CD61. Multiple cases of normal lung, diffuse alveolar damage, COVID-19, influenza, and bacterial and fungal infections, as well as one case of pulmonary emboli, were included. The levels of CD61 staining were compared quantitatively in the autopsy cases, and patterns of staining were described. RESULTS: Nearly all specimens exhibited an increase in CD61 staining relative to control lung tissue. The area of CD61 staining in COVID-19 infection was higher than influenza but still comparable to many other infectious diseases. Cases of aspiration pneumonia, Staphylococcus aureus infection, and blastomycosis exhibited the highest levels of CD61 staining. CONCLUSIONS: Platelet deposition is a phenomenon common to many pulmonary insults. A spectrum of staining patterns was observed, suggestive of pathogen-specific mechanisms of platelet deposition. Further study into the mechanisms driving platelet deposition in pulmonary injuries and infections is warranted.

Coronavirus Surveillance in a Pediatric Population in Jordan From 2010 to 2013: A Prospective Viral Surveillance Study.

BACKGROUND: Human coronaviruses (HCoVs) are a significant cause of acute respiratory illness (ARI) in children; however, the role of HCoVs in ARI among hospitalized children in the Middle East is not well defined. METHODS: Children under 2 years admitted with fever and/or respiratory symptoms were enrolled from 2010 to 2013 in Amman, Jordan. Nasal/throat swabs were collected and stored for testing. Demographic and clinical characteristics were collected through parent/guardian interviews and medical chart abstractions. Prior stored specimens were tested for HCoVs (HKU1, OC43, 229E and NL63) by qRT-PCR. RESULTS: Of the 3168 children enrolled, 6.7% were HCoVs-positive. Among HCoV-positive children, the median age was 3.8 (1.9-8.4) months, 59% were male, 14% were premature, 11% had underlying medical conditions and 76% had viral-codetection. The most common presenting symptoms were cough, fever, wheezing and shortness of breath. HCoVs were detected year-round, peaking in winter-spring months. Overall, 56%, 22%, 13% and 6% were OC43, NL63, HKU1 and 229E, respectively. There was no difference in disease severity between the species, except higher intensive care unit admission frequency in NL63-positive subjects. CONCLUSIONS: HCoVs were detected in around 7% of children enrolled in our study. Despite HCoV detection in children with ARI with highest peaks in respiratory seasons, the actual burden and pathogenic role of HCoVs in ARI merits further evaluation given the high frequency of viral codetection.

Clinical impact of monocyte distribution width and neutrophil-to-lymphocyte ratio for distinguishing COVID-19 and influenza from other upper respiratory tract infections: A pilot study.

The coronavirus disease 2019 (COVID-19) has become a pandemic. Rapidly distinguishing COVID-19 from other respiratory infections is a challenge for first-line health care providers. This retrospective study was conducted at the Taipei Medical University Hospital, Taiwan. Patients who visited the outdoor epidemic prevention screening station for respiratory infection from February 19 to April 30, 2020, were evaluated for blood biomarkers to distinguish COVID-19 from other respiratory infections. Monocyte distribution width (MDW) ≥ 20 (odds ratio [OR]: 8.39, p = 0.0110, area under curve [AUC]: 0.703) and neutrophil-to-lymphocyte ratio (NLR) < 3.2 (OR: 4.23, p = 0.0494, AUC: 0.673) could independently distinguish COVID-19 from common upper respiratory tract infections (URIs). Combining MDW ≥ 20 and NLR < 3.2 was more efficient in identifying COVID-19 (AUC: 0.840). Moreover, MDW ≥ 20 and NLR > 5 effectively identified influenza infection (AUC: 0.7055). Thus, MDW and NLR can distinguish COVID-19 from influenza and URIs.

Pneumonia and respiratory infections in Down syndrome: A scoping review of the literature.

Pneumonia and respiratory infections impact infants and children with Down syndrome; pneumonia is a leading cause of mortality in adults with Down syndrome. We aimed to review the literature to evaluate gaps and address key questions. A series of key questions were formulated a priori to inform the search strategy and review process; addressed prevalence, severity, etiology, risk factors, preventive methods, screening, and financial costs, potential benefits or harms of screening. Using the National Library of Medicine database, PubMed, detailed literature searches on pneumonia and respiratory infections in Down syndrome were performed. Previously identified review articles were also assessed. The quality of available evidence was then evaluated and knowledge gaps were identified. Forty-two relevant original articles were identified which addressed at least one key question. Study details including research design, internal validity, external validity, and relevant results are presented. Pneumonia and respiratory infections are more prevalent and more severe in individuals with Down syndrome compared to healthy controls through literature review, yet there are gaps in the literature regarding the etiology of pneumonia, the infectious organism, risk factors for infection, and to guide options for prevention and screening. There is urgent need for additional research studies in Down syndrome, especially in the time of the current COVID-19 pandemic.

Severity of Respiratory Infections With Seasonal Coronavirus Is Associated With Viral and Bacterial Coinfections.

The clinical presentation of human coronavirus (HCoV) infections in children varies strongly. We show that children with an HCoV-associated lower respiratory tract infection more frequently had respiratory syncytial virus codetected and higher abundance of Haemophilus influenzae/haemolyticus than asymptomatic HCoV carriers as well as children with a non-HCoV-associated lower respiratory tract infection. Viral and bacterial cooccurrence may drive symptomatology of HCoV-associated infections including coronavirus disease 2019.

Cellular senescence: friend or foe to respiratory viral infections?

Cellular senescence permanently arrests the replication of various cell types and contributes to age-associated diseases. In particular, cellular senescence may enhance chronic lung diseases including COPD and idiopathic pulmonary fibrosis. However, the role cellular senescence plays in the pathophysiology of acute inflammatory diseases, especially viral infections, is less well understood. There is evidence that cellular senescence prevents viral replication by increasing antiviral cytokines, but other evidence shows that senescence may enhance viral replication by downregulating antiviral signalling. Furthermore, cellular senescence leads to the secretion of inflammatory mediators, which may either promote host defence or exacerbate immune pathology during viral infections. In this Perspective article, we summarise how senescence contributes to physiology and disease, the role of senescence in chronic lung diseases, and how senescence impacts acute respiratory viral infections. Finally, we develop a potential framework for how senescence may contribute, both positively and negatively, to the pathophysiology of viral respiratory infections, including severe acute respiratory syndrome due to the coronavirus SARS-CoV-2.

Generation of Complete Multi-Cell Type Lung Organoids From Human Embryonic and Patient-Specific Induced Pluripotent Stem Cells for Infectious Disease Modeling and Therapeutics Validation.

The normal development of the pulmonary system is critical to transitioning from placental-dependent fetal life to alveolar-dependent newborn life. Human lung development and disease have been difficult to study due to the lack of an in vitro model system containing cells from the large airways and distal alveolus. This article describes a system that allows human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs) to differentiate and form three-dimensional (3D) structures that emulate the development, cytoarchitecture, and function of the lung ("organoids"), containing epithelial and mesenchymal cell populations, and including the production of surfactant and presence of ciliated cells. The organoids can also be invested with mesoderm derivatives, differentiated from the same human pluripotent stem cells, such as alveolar macrophages and vasculature. Such lung organoids may be used to study the impact of environmental modifiers and perturbagens (toxins, microbial or viral pathogens, alterations in microbiome) or the efficacy and safety of drugs, biologics, and gene transfer. © 2020 Wiley Periodicals LLC. Basic Protocol: hESC/hiPSC dissection, definitive endoderm formation, and lung progenitor cell induction.