Viral and Bacterial Co-Infections in the Lungs: Dangerous Liaisons

Cortactin: A major cellular target of viral, protozoal, and fungal pathogens

Many viral, protozoal, and fungal pathogens represent major human and animal health problems due to their great potential of causing infectious diseases. Research on these pathogens has contributed substantially to our current understanding of both microbial virulence determinants and host key factors during infection. Countless studies have also shed light on the molecular mechanisms of host-pathogen interactions that are employed by these microbes. For example, actin cytoskeletal dynamics play critical roles in effective adhesion, host cell entry, and intracellular movements of intruding pathogens. Cortactin is an eminent host cell protein that stimulates actin polymerization and signal transduction, and recently emerged as fundamental player during host-pathogen crosstalk. Here we review the important role of cortactin as major target for various prominent viral, protozoal and fungal pathogens in humans, and its role in human disease development and cancer progression. Most if not all of these important classes of pathogens have been reported to hijack cortactin during infection through mediating up- or downregulation of cortactin mRNA and protein expression as well as signaling. In particular, pathogen-induced changes in tyrosine and serine phosphorylation status of cortactin at its major phospho-sites (Y-421, Y-470, Y-486, S-113, S-298, S-405, and S-418) are addressed. As has been reported for various Gram-negative and Gram-positive bacteria, many pathogenic viruses, protozoa, and fungi also control these regulatory phospho-sites, for example, by activating kinases such as Src, PAK, ERK1/2, and PKD, which are known to phosphorylate cortactin. In addition, the recruitment of cortactin and its interaction partners, like the Arp2/3 complex and F-actin, to the contact sites between pathogens and host cells is highlighted, as this plays an important role in the infection process and internalization of several pathogens. However, there are also other ways in which the pathogens can exploit the function of cortactin for their needs, as the cortactin-mediated regulation of cellular processes is complex and involves numerous different interaction partners. Here, the current state of knowledge is summarized.

Along with PaO2/FiO2 ratio and lymphopenia, low HLA-DR monocytes are the only additional parameter that independently predicts the clinical course of undifferentiated SARS-CoV-2 patients in emergency departments

Because one-third of patients deteriorate after their admission to the emergency department, assessing the prognosis of COVID-19 patients is of great importance. However, to date, only lymphopenia and the partial pressure of oxygen/fraction of inspired oxygen (PaO2/FiO2) ratio have been reported as partly predictive of COVID-19-related further deterioration, and their association has not been evaluated. We asked whether other key biomarkers of SARS-CoV-2 immunologic defects-increase in circulating immature granulocytes, loss of monocyte HLA-DR (mHLA-DR) expression, and monocyte differentiation blockade-could also predict further COVID-19 deterioration. A series of 284 consecutive COVID-19 patients, with the sole inclusion criterion of being an adult, were prospectively enrolled at emergency department admission (day 0) of 2 different hospitals: 1 for the exploratory cohort (180 patients) and 1 for the confirmatory cohort (104 patients). Deterioration was assessed over the next 7 days. Neither increased immature granulocyte levels nor monocyte differentiation blockade predicted patient worsening. Among more than 30 clinical, biological, and radiological parameters, the value of decreased P/F ratio and lymphopenia for prediction of further COVID-19 deterioration was strongly confirmed, and the loss of mHLA-DR was the only additional independent marker. Combined together in a simple OxyLymphoMono score, the 3 variables perfectly predicted patients who did not worsen and correctly predicted worsening in 59% of cases. By highlighting lymphocyte and monocyte defects as preceding COVID-19 deterioration, these results point on early immunosuppression in COVID-19 deterioration. Combining P/F ratio, lymphopenia, and loss of mHLA-DR together in a simple and robust score could offer a pragmatic method for COVID-19 patient stratification.

4-Trifluoromethyl bithiazoles as broad-spectrum antimicrobial agents for virus-related bacterial infections or co-infections

Respiratory tract infections involving a variety of microorganisms such as viruses, bacteria, and fungi are a prominent cause of morbidity and mortality globally, exacerbating various pre-existing respiratory and non-respiratory conditions. Moreover, the ability of bacteria and viruses to coexist might impact the development and severity of lung infections, promoting bacterial colonization and subsequent disease exacerbation. Secondary bacterial infections following viral infections represent a complex challenge to be overcome from a therapeutic point of view. We report herein our efforts in the development of new bithiazole derivatives showing broad-spectrum antimicrobial activity against both viruses and bacteria. A series of 4-trifluoromethyl bithiazole analogues was synthesized and screened against selected viruses (hRVA16, EVD68, and ZIKV) and a panel of Gram-positive and Gram-negative bacteria. Among them, two promising broad-spectrum antimicrobial compounds (8a and 8j) have been identified: both compounds showed low micromolar activity against all tested viruses, 8a showed synergistic activity against E. coli and A. baumannii in the presence of a subinhibitory concentration of colistin, while 8j showed a broader spectrum of activity against Gram-positive and Gram-negative bacteria. Activity against antibiotic-resistant clinical isolates is also reported. Given the ever-increasing need to adequately address viral and bacterial infections or co-infections, this study paves the way for the development of new agents with broad antimicrobial properties and synergistic activity with common antivirals and antibacterials.

Epidemiological and etiological characteristics of 1266 patients with severe acute respiratory infection in central China, 2018-2020: a retrospective survey

BACKGROUND

Severe acute respiratory infection (SARI), a significant global health concern, imposes a substantial disease burden. In China, there is inadequate data concerning the monitoring of respiratory pathogens, particularly bacteria, among patients with SARI. Therefore, this study aims to delineate the demographic, epidemiological, and aetiological characteristics of hospitalised SARI patients in Central China between 2018 and 2020.

METHODS

Eligible patients with SARI admitted to the First Affiliated Hospital of Zhengzhou University between 1 January 2018 and 31 December 2020 were included in this retrospective study. Within the first 24 h of admission, respiratory (including sputum, nasal/throat swabs, bronchoalveolar lavage fluid, thoracocentesis fluid, etc.), urine, and peripheral blood specimens were collected for viral and bacterial testing. A multiplex real-time polymerase chain reaction (PCR) diagnostic approach was used to identify human influenza virus, respiratory syncytial virus, parainfluenza virus, adenovirus, human bocavirus, human coronavirus, human metapneumovirus, and rhinovirus. Bacterial cultures of respiratory specimens were performed with a particular focus on pathogenic microorganisms, including S. pneumoniae, S. aureus, K. pneumoniae, P. aeruginosa, Strep A, H. influenzae, A. baumannii, and E. coli. In cases where bacterial culture results were negative, nucleic acid extraction was performed for PCR to assay for the above-mentioned eight bacteria, as well as L. pneumophila and M. pneumoniae. Additionally, urine specimens were exclusively used to detect Legionella antigens. Furthermore, epidemiological, demographic, and clinical data were obtained from electronic medical records.

RESULTS

The study encompassed 1266 patients, with a mean age of 54 years, among whom 61.6% (780/1266) were males, 61.4% (778/1266) were farmers, and 88.8% (1124/1266) sought medical treatment in 2020. Moreover, 80.3% (1017/1266) were housed in general wards. The most common respiratory symptoms included fever (86.8%, 1122/1266) and cough (77.8%, 986/1266). Chest imaging anomalies were detected in 62.6% (792/1266) of cases, and 58.1% (736/1266) exhibited at least one respiratory pathogen, with 28.5% (361/1266) having multiple infections. Additionally, 95.7% (1212/1266) of the patients were from Henan Province, with the highest proportion (38.3%, 486/1266) falling in the 61-80 years age bracket, predominantly (79.8%, 1010/1266) seeking medical aid in summer and autumn. Bacterial detection rate (39.0%, 495/1266) was higher than viral detection rate (36.9%, 468/1266), with the primary pathogens being influenza virus (13.8%, 175/1266), K. pneumoniae (10.0%, 127/1266), S. pneumoniae (10.0%, 127/1266), adenovirus (8.2%, 105/1266), P. aeruginosa (8.2%, 105/1266), M. pneumoniae (7.8%, 100/1266), and respiratory syncytial virus (7.7%, 98/1266). During spring and winter, there was a significant prevalence of influenza virus and human coronavirus, contrasting with the dominance of parainfluenza viruses in summer and autumn. Respiratory syncytial virus and rhinovirus exhibited higher prevalence across spring, summer, and winter. P. aeruginosa, K. pneumoniae, and M. pneumoniae were identified at similar rates throughout all seasons without distinct spikes in prevalence. However, S. pneumoniae showed a distinctive pattern with a prevalence that doubled during summer and winter. Moreover, the positive detection rates of various other viruses and bacteria were lower, displaying a comparatively erratic prevalence trend. Among patients admitted to the intensive care unit, the predominant nosocomial bacteria were K. pneumoniae (17.2%, 43/249), A. baumannii (13.6%, 34/249), and P. aeruginosa (12.4%, 31/249). Conversely, in patients from general wards, predominant pathogens included influenza virus (14.8%, 151/1017), S. pneumoniae (10.4%, 106/1017), and adenovirus (9.3%, 95/1017). Additionally, paediatric patients exhibited significantly higher positive detection rates for influenza virus (23.9%, 11/46) and M. pneumoniae (32.6%, 15/46) compared to adults and the elderly. Furthermore, adenovirus (10.0%, 67/669) and rhinovirus (6.4%, 43/669) were the primary pathogens in adults, while K. pneumoniae (11.8%, 65/551) and A. baumannii (7.1%, 39/551) prevailed among the elderly, indicating significant differences among the three age groups.

DISCUSSION

In Central China, among patients with SARI, the prevailing viruses included influenza virus, adenovirus, and respiratory syncytial virus. Among bacteria, K. pneumoniae, S. pneumoniae, P. aeruginosa, and M. pneumoniae were frequently identified, with multiple infections being very common. Additionally, there were substantial variations in the pathogen spectrum compositions concerning wards and age groups among patients. Consequently, this study holds promise in offering insights to the government for developing strategies aimed at preventing and managing respiratory infectious diseases effectively.

Immunomodulatory Effects of Fluoroquinolones in Community-Acquired Pneumonia-Associated Acute Respiratory Distress Syndrome

Community-acquired pneumonia is reported as one of the infectious diseases that leads to the development of acute respiratory distress syndrome. The innate immune system is the first line of defence against microbial invasion; however, its dysregulation during infection, resulting in an increased pathogen load, stimulates the over-secretion of chemokines and pro-inflammatory cytokines. This phenomenon causes damage to the epithelial-endothelial barrier of the pulmonary alveoli and the leakage of the intravascular protein into the alveolar lumen. Fluoroquinolones are synthetic antimicrobial agents with immunomodulatory properties that can inhibit bacterial proliferation as well as exhibit anti-inflammatory activities. It has been demonstrated that the structure of fluoroquinolones, particularly those with a cyclopropyl group, exerts immunomodulatory effects. Its capability to inhibit phosphodiesterase activity leads to the accumulation of intracellular cAMP, which subsequently enhances PKA activity, resulting in the inhibition of transcriptional factor NF-κB and the activation of CREB. Another mechanism reported is the inhibition of TLR and ERK signalling pathways. Although the sequence of events has not been completely understood, significant progress has been made in comprehending the specific mechanisms underlying the immunomodulatory effects of fluoroquinolones. Here, we review the indirect immunomodulatory effects of FQs as an alternative to empirical therapy in patients diagnosed with community-acquired pneumonia.

The breathtaking world of human respiratory in vitro models: Investigating lung diseases and infections in 3D models, organoids, and lung-on-chip

The COVID-19 pandemic illustrated an urgent need for sophisticated, human tissue models to rapidly test and develop effective treatment options against this newly emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Thus, in particular, the last 3 years faced an extensive boost in respiratory and pulmonary model development. Nowadays, 3D models, organoids and lung-on-chip, respiratory models in perfusion, or precision-cut lung slices are used to study complex research questions in human primary cells. These models provide physiologically relevant systems for studying SARS-CoV-2 and, of course, other respiratory pathogens, but they are, too, suited for studying lung pathologies, such as CF, chronic obstructive pulmonary disease, or asthma, in more detail in terms of viral infection. With these models, the cornerstone has been laid for further advancing the organs by, for example, inclusion of several immune cell types or humoral immune components, combination with other organs in microfluidic organ-on-chip devices, standardization and harmonization of the devices for reliable and reproducible drug and vaccine testing in high throughput.

Bacterial Community- and Hospital-Acquired Pneumonia in Patients with Critical COVID-19-A Prospective Monocentric Cohort Study

The impact of bacterial pneumonia on patients with COVID-19 infection remains unclear. This prospective observational monocentric cohort study aims to determine the incidence of bacterial community- and hospital-acquired pneumonia (CAP and HAP) and its effect on mortality in critically ill COVID-19 patients admitted to the intensive care unit (ICU) at University Hospital Olomouc between 1 November 2020 and 31 December 2022. The secondary objectives of this study include identifying the bacterial etiology of CAP and HAP and exploring the capabilities of diagnostic tools, with a focus on inflammatory biomarkers. Data were collected from the electronic information hospital system, encompassing biomarkers, microbiological findings, and daily visit records, and subsequently evaluated by ICU physicians and clinical microbiologists. Out of 171 patients suffering from critical COVID-19, 46 (27%) had CAP, while 78 (46%) developed HAP. Critically ill COVID-19 patients who experienced bacterial CAP and HAP exhibited higher mortality compared to COVID-19 patients without any bacterial infection, with rates of 38% and 56% versus 11%, respectively. In CAP, the most frequent causative agents were chlamydophila and mycoplasma; Enterobacterales, which were multidrug-resistant in 71% of cases; Gram-negative non-fermenting rods; and Staphylococcus aureus. Notably, no strains of Streptococcus pneumoniae were detected, and only a single strain each of Haemophilus influenzae and Moraxella catarrhalis was isolated. The most frequent etiologic agents causing HAP were Enterobacterales and Gram-negative non-fermenting rods. Based on the presented results, commonly used biochemical markers demonstrated poor predictive and diagnostic accuracy. To confirm the diagnosis of bacterial CAP in our patient cohort, it was necessary to assess the initial values of inflammatory markers (particularly procalcitonin), consider clinical signs indicative of bacterial infection, and/or rely on positive microbiological findings. For HAP diagnostics, it was appropriate to conduct regular detailed clinical examinations (with a focus on evaluating respiratory functions) and closely monitor the dynamics of inflammatory markers (preferably Interleukin-6).

Co-Occurrence of Gram-Negative Rods in Patients with Hematologic Malignancy and Sinopulmonary Mucormycosis

Both Mucorales and Gram-negative rods (GNRs) commonly infect patients with hematological malignancies (HM); however, their co-occurrence is understudied. Therefore, we retrospectively reviewed the records of 63 patients with HM and proven or probable sinopulmonary mucormycosis at MD Anderson Cancer Center (Houston, Texas) from 2000-2020. Seventeen out of sixty-three reviewed patients (27.0%) had sinopulmonary co-occurrence of GNRs (most commonly Pseudomonas aeruginosa and Stenotrophomonas maltophilia) within 30 days of a positive Mucorales culture or histology demonstrating Mucorales species. Eight of seventeen co-isolations of Mucorales and GNRs were found in same-day samples. All 15 patients with GNR co-occurrence and reported antimicrobial data had received anti-Pseudomonal agents within 14 days prior to diagnosis of mucormycosis and 5/15 (33.3%) had received anti-Stenotrophomonal agents. Demographic and clinical characteristics of patients with and without GNR co-occurrence were comparable. Forty-two-day all-cause mortality was high (34.9%) and comparable in patients with (41.2%) and without (32.6%) GNR detection (p = 0.53). In summary, over a quarter of heavily immunosuppressed patients with sinopulmonary mucormycosis harbored GNRs in their respiratory tract. Although no impact on survival outcomes was seen in a background of high mortality in our relatively underpowered study, pathogenesis studies are needed to understand the mutualistic interplay of GNR and Mucorales and their influence on host responses.

Interferon signaling drives epithelial metabolic reprogramming to promote secondary bacterial infection

Clinical studies report that viral infections promote acute or chronic bacterial infections at multiple host sites. These viral-bacterial co-infections are widely linked to more severe clinical outcomes. In experimental models in vitro and in vivo, virus-induced interferon responses can augment host susceptibility to secondary bacterial infection. Here, we used a cell-based screen to assess 389 interferon-stimulated genes (ISGs) for their ability to induce chronic Pseudomonas aeruginosa infection. We identified and validated five ISGs that were sufficient to promote bacterial infection. Furthermore, we dissected the mechanism of action of hexokinase 2 (HK2), a gene involved in the induction of aerobic glycolysis, commonly known as the Warburg effect. We report that HK2 upregulation mediates the induction of Warburg effect and secretion of L-lactate, which enhances chronic P. aeruginosa infection. These findings elucidate how the antiviral immune response renders the host susceptible to secondary bacterial infection, revealing potential strategies for viral-bacterial co-infection treatment.

Deadly interactions: Synergistic manipulations of concurrent pathogen infections potentially enabling future pandemics

Certain mono-infections of influenza viruses and novel coronaviruses, including severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) are significant threats to human health. Concurrent infections by influenza viruses and coronaviruses increases their danger. Influenza viruses have eight manipulations capable of assisting SARS-CoV-2 and other coronaviruses, and several of these manipulations, which are not specific to viruses, can also directly or indirectly boost dangerous secondary bacterial pneumonias. The influenza virus manipulations include: inhibiting transcription factors and cytokine expression; impairing defensive protein expression; increasing RNA viral replication; inhibiting defenses by manipulating cellular sensors and signaling pathways; inhibiting defenses by secreting exosomes; stimulating cholesterol production to increase synthesized virion infectivities; increasing cellular autophagy to assist viral replication; and stimulating glucocorticoid synthesis to suppress innate and adaptive immune defenses by inhibiting cytokine, chemokine, and adhesion molecule production. Teaser: Rapidly spreading multidrug-resistant respiratory bacteria, combined with influenza virus's far-reaching cellular defense manipulations benefiting evolving SARS-CoV-2 or other coronaviruses and/or respiratory bacteria, can enable more severe pandemics or co-pandemics.

Performance of targeted next-generation sequencing in the detection of respiratory pathogens and antimicrobial resistance genes for children

Introduction. Respiratory tract infection, which is associated with high morbidity and mortality, occurs frequently in children. At present, the main diagnostic method is culture. However, the low pathogen detection rate of the culture approach prevents timely and accurate diagnosis. Fortunately, next-generation sequencing (NGS) can compensate for the deficiency of culture, and its application in clinical diagnostics has become increasingly available.Gap Statement. Targeted NGS (tNGS) is a platform that can select and enrich specific regions before data enter the NGS pipeline. However, the performance of tNGS in the detection of respiratory pathogens and antimicrobial resistance genes (ARGs) in infections in children is unclear.Aim and methodology. In this study, we estimated the performance of tNGS in the detection of respiratory pathogens and ARGs in 47 bronchoalveolar lavage fluid (BALF) specimens from children using conventional culture and antimicrobial susceptibility testing (AST) as the gold standard.Results. RPIP (Respiratory Pathogen ID/AMR enrichment) sequencing generated almost 500 000 reads for each specimen. In the detection of pathogens, RPIP sequencing showed targeted superiority in detecting difficult-to-culture bacteria, including Mycoplasma pneumoniae. Compared with the results of culture, the sensitivity and specificity of RPIP were 84.4 % (confidence interval 70.5-93.5 %) and 97.7 % (95.9 -98.8%), respectively. Moreover, RPIP results showed that a single infection was detected in 10 of the 47 BALF specimens, and multiple infections were detected in 34, with the largest number of bacterial/viral coinfections. Nevertheless, there were also three specimens where no pathogen was detected. Furthermore, we analysed the drug resistance genes of specimens containing Streptococcus pneumoniae, which was detected in 25 out of 47 specimens in the study. A total of 58 ARGs associated with tetracycline, macrolide-lincosamide-streptogramin, beta-lactams, sulfonamide and aminoglycosides were identified by RPIP in 19 of 25 patients. Using the results of AST as a standard, the coincidence rates of erythromycin, tetracycline, penicillin and sulfonamides were 89.5, 79.0, 36.8 and 42.1 %, respectively.Conclusion. These results demonstrated the superiority of RPIP in pathogen detection, particularly for multiple and difficult-to-culture pathogens, as well as in predicting resistance to erythromycin and tetracycline, which has significance for the accurate diagnosis of pathogenic infection and in the guidance of clinical treatment.

Immunomodulatory effects of inactivated Ligilactobacillus salivarius CECT 9609 on respiratory epithelial cells

The microbiota in humans and animals play crucial roles in defense against pathogens and offer a promising natural source for immunomodulatory products. However, the development of physiologically relevant model systems and protocols for testing such products remains challenging. In this study, we present an experimental condition where various natural products derived from the registered lactic acid bacteria Ligilactobacillus salivarius CECT 9609, known for their immunomodulatory activity, were tested. These products included live and inactivated bacteria, as well as fermentation products at different concentrations and culture times. Using our established model system, we observed no morphological changes in the airway epithelium upon exposure to Pasteurella multocida, a common respiratory pathogen. However, early molecular changes associated with the innate immune response were detected through transcript analysis. By employing diverse methodologies ranging from microscopy to next-generation sequencing (NGS), we characterized the interaction of these natural products with the airway epithelium and their potential beneficial effects in the presence of P. multocida infection. In particular, our discovery highlights that among all Ligilactobacillus salivarius CECT 9609 products tested, only inactivated cells preserve the conformation and morphology of respiratory epithelial cells, while also reversing or altering the natural immune responses triggered by Pasteurella multocida. These findings lay the groundwork for further exploration into the protective role of these bacteria and their derivatives.

Using risk factors and markers to predict bacterial respiratory co-/superinfections in COVID-19 patients: is the antibiotic steward's toolbox full or empty?

BACKGROUND

Adequate diagnosis of bacterial respiratory tract co-/superinfection (bRTI) in coronavirus disease (COVID-19) patients is challenging, as there is insufficient knowledge about the role of risk factors and (para)clinical parameters in the identification of bacterial co-/superinfection in the COVID-19 setting. Empirical antibiotic therapy is mainly based on COVID-19 severity and expert opinion, rather than on scientific evidence generated since the start of the pandemic.

PURPOSE

We report the best available evidence regarding the predictive value of risk factors and (para)clinical markers in the diagnosis of bRTI in COVID-19 patients.

METHODS

A multidisciplinary team identified different potential risk factors and (para)clinical predictors of bRTI in COVID-19 and formulated one or two research questions per topic. After a thorough literature search, research gaps were identified, and suggestions concerning further research were formulated. The quality of this narrative review was ensured by following the Scale for the Assessment of Narrative Review Articles.

RESULTS

Taking into account the scarcity of scientific evidence for markers and risk factors of bRTI in COVID-19 patients, to date, COVID-19 severity is the only parameter which can be associated with higher risk of developing bRTI.

CONCLUSIONS

Evidence on the usefulness of risk factors and (para)clinical factors as predictors of bRTI in COVID-19 patients is scarce. Robust studies are needed to optimise antibiotic prescribing and stewardship activities in the context of COVID-19.

Mapping spatial morbidity patterns for bronchiolitis related to socioeconomic estimators: A spatial epidemiology approach to identify health disparities in Puerto Madryn, Argentina

OBJECTIVES

To describe the frequency of hospitalizations of infants under 1 year of age with bronchiolitis in Puerto Madryn, Argentina, and to study the spatial distribution of cases throughout the city in relation to socioeconomic indicators. To visualize and better understand the underlying processes behind the local manifestation of the disease by creating a vulnerability map of the city.

METHODS

We performed a cross-sectional study of all patients discharged for bronchiolitis from the local public Hospital in 2017, considering length of hospital stay, readmission rate, patient age, home address and socioeconomic indicators (household overcrowding). To understand the local spatial distribution of the disease and its relationship to overcrowding, we used GIS and Moran's global and local spatial autocorrelation indices.

RESULTS

The spatial distribution of bronchiolitis cases was not random, but significantly aggregated. Of the 120 hospitalized children, 100 infants (83.33%) live in areas identified as having at least one unsatisfied basic need (UBN). We found a positive and statistically significant relationship between frequency of cases and percentage of overcrowded housing by census radius.

CONCLUSIONS

A clear association was found between bronchiolitis and neighborhoods with UBNs, and overcrowding is likely to be a particularly important explanatory factor in this association. By combining GIS tools, spatial statistics, geo-referenced epidemiological data, and population-level information, vulnerability maps can be created to facilitate visualization of priority areas for development and implementation of more effective health interventions. Incorporating the spatial and syndemic perspective into health studies makes important contributions to the understanding of local health-disease processes.

Comparative analysis of clinical features of lower respiratory tract infection with respiratory syncytial virus and influenza virus in adults: a retrospective study

BACKGROUND

Respiratory syncytial virus (RSV) infection in adults remains less recognized and understood, both socially and clinically, compared to influenza virus infection. This retrospective study aims to delineate and compare the clinical manifestations of adult RSV and influenza virus infections in the lower respiratory tract, thereby enhancing awareness of RSV lower respiratory tract infection and providing strategic insights for its prevention and treatment.

METHODS

Clinical data from January 2019 to December 2020 were analyzed for 74 patients with RSV and 129 patients with influenza A/B virus lower respiratory tract infections who were admitted to respiratory or intensive care units. All patients had complete clinical data with positive IgM and negative IgG viral antibodies. Comparison parameters included onset timing, baseline data, clinical manifestations, supplementary examination results, treatment methods, and prognosis, while logistic regression was employed to ascertain the correlation of clinical features between the two patient groups.

RESULTS

In comparison to the influenza group, the RSV group presented less frequently with fever at admission but exhibited a higher incidence of dyspnea and wheezing on pulmonary auscultation (P < 0.01). RSV infection was more prevalent among patients with underlying diseases, particularly chronic obstructive pulmonary disease (COPD) and demonstrated a higher probability of co-infections, most notably with Mycoplasma (P < 0.01). The RSV group had significantly higher lymphocyte counts (P < 0.01) and exhibited more incidences of pleural thickening, pulmonary fibrosis, and emphysema (P < 0.05). The use of non-invasive mechanical ventilation was more common, and hospital stays were longer in the RSV group compared to the influenza group (P < 0.05). Logistic multivariate regression analysis further revealed that age and tachypnea incidence were significantly higher in the RSV group (P < 0.05).

CONCLUSION

Compared to influenza virus infection, adults with COPD are more susceptible to RSV infection. Moreover, RSV infection elevates the risk of co-infection with Mycoplasma and may lead to conditions such as pleural thickening, pulmonary fibrosis, and emphysema. The requirement for non-invasive mechanical ventilation is higher in RSV-infected patients, who also tend to have longer hospital stays. Therefore, greater awareness and preventive strategies against RSV infection are imperative.

Co-infection of SARS-CoV-2 with human coronavirus OC43 in a patient with underlying lung disease: A case report

Co-infections with SARS-CoV-2 remain relatively rare and there is limited published data on the consequences of these events. We present the case of a 26-year-old man with SARS-CoV-2 and human coronavirus OC43 who had a severe infection resulting in prolonged hospitalization. Consideration of co-infections should be considered in high-risk patients.

The impact of concurrent bacterial lung infection on immunotherapy in patients with non-small cell lung cancer: a retrospective cohort study

Objective

To find out how bacterial lung infections (BLI) affect the effectiveness of therapy and the rate of pneumonia caused by pneumonia related to checkpoint inhibitors (CIP) in patients with non-small cell lung cancer (NSCLC) who are getting immunotherapy with checkpoint inhibitors (ICIs).

Patients and methods

507 NSCLC patients who received at least two ICI treatments between June 2020 and December 2022 at the Affiliated Hospital of Kunming University of Science and Technology(AHKUST) were included in a retrospective cohort study. Based on whether there was a concurrent BLI diagnosis from high-resolution CT scans of the chest, the patients were divided into two groups: 238 in the NSCLC with BLI group (NSCLC-BLI group), and 269 in the NSCLC alone group. The collected therapeutic outcome measures included the objective response rate (ORR), progression-free survival (PFS), overall survival (OS), and the incidence rate of CIP. We analyzed the effect of BLI on the therapeutic efficacy of ICI treatment and the incidence rate of CIP in NSCLC patients.Inclusion criteria based on NSCLC patients staged I to IV according to the 8th edition of the International Association for Lung Cancer Research (IASLC).

Results

The NSCLC-BLI group showed superior ORR to the NSCLC group when treated with ICIs. Multifactorial logistic regression and Cox analyses, adjusted for confounders, identified BLI as an independent positive prognostic factor for ORR (HR=0.482, 95%CI: 0.391-0.550; P<0.001) and PFS (HR=0.619; 95%CI: 0.551-0.771; P<0.001). No correlation between BLI and OS was found. Out of 26 cases of CIP, 12 were in the NSCLC-BLI group and 14 in the NSCLC group, with no significant difference in incidence (P=0.145).

Conclusion

NSCLC patients with BLI receiving ICI treatment show superior ORR and PFS compared to NSCLC alone without an increased CIP risk, positioning BLI as a predictive factor for improved outcomes in NSCLC patients receiving ICIs. However, the study has limitations including its retrospective nature and lacking data on BLI bacteria types and levels, which could influence therapy outcomes.

Nucleoside Derivatives of 2,6-Diaminopurine Antivirals: Base-Modified Nucleosides with Broad-Spectrum Antimicrobial Properties

The plethora of viral outbreaks experienced in the last decade, together with the widespread distribution of many re-emerging and newly emerging viruses, emphasize the urgent need for novel broad-spectrum antivirals as tools for early intervention in case of future epidemics. Non-natural nucleosides have been at the forefront for the treatment of infectious diseases for many years and still represent one of the most successful classes of antiviral molecules on the market. In the attempt to explore the biologically relevant chemical space of this class of antimicrobials, we describe herein the development of novel base-modified nucleosides by converting previously identified 2,6-diaminopurine antivirals into the corresponding D/L ribonucleosides, acyclic nucleosides and prodrug derivatives. A phenotypic screening against viruses belonging to different families (Flaviviridae, Coronaviridae, Retroviridae) and against a panel of Gram-positive and Gram-negative bacteria, allowed to identify a few interesting molecules with broad-spectrum antimicrobial activities.

Functional diversity of staphylococcal surface proteins at the host-microbe interface

Surface proteins of Gram-positive pathogens are key determinants of virulence that substantially shape host-microbe interactions. Specifically, these proteins mediate host invasion and pathogen transmission, drive the acquisition of heme-iron from hemoproteins, and subvert innate and adaptive immune cell responses to push bacterial survival and pathogenesis in a hostile environment. Herein, we briefly review and highlight the multi-facetted roles of cell wall-anchored proteins of multidrug-resistant Staphylococcus aureus, a common etiological agent of purulent skin and soft tissue infections as well as severe systemic diseases in humans. In particular, we focus on the functional diversity of staphylococcal surface proteins and discuss their impact on the variety of clinical manifestations of S. aureus infections. We also describe mechanistic and underlying principles of staphylococcal surface protein-mediated immune evasion and coupled strategies S. aureus utilizes to paralyze patrolling neutrophils, macrophages, and other immune cells. Ultimately, we provide a systematic overview of novel therapeutic concepts and anti-infective strategies that aim at neutralizing S. aureus surface proteins or sortases, the molecular catalysts of protein anchoring in Gram-positive bacteria.

The complement system and human autoimmune diseases

Genetic deficiencies of early components of the classical complement activation pathway (especially C1q, r, s, and C4) are the strongest monogenic causal factors for the prototypic autoimmune disease systemic lupus erythematosus (SLE), but their prevalence is extremely rare. In contrast, isotype genetic deficiency of C4A and acquired deficiency of C1q by autoantibodies are frequent among patients with SLE. Here we review the genetic basis of complement deficiencies in autoimmune disease, discuss the complex genetic diversity seen in complement C4 and its association with autoimmune disease, provide guidance as to when clinicians should suspect and test for complement deficiencies, and outline the current understanding of the mechanisms relating complement deficiencies to autoimmunity. We focus primarily on SLE, as the role of complement in SLE is well-established, but will also discuss other informative diseases such as inflammatory arthritis and myositis.

The Activation of the RIG-I/MDA5 Signaling Pathway upon Influenza D Virus Infection Impairs the Pulmonary Proinflammatory Response Triggered by Mycoplasma bovis Superinfection

Concurrent infections with multiple pathogens are often described in cattle with respiratory illness. However, how the host-pathogen interactions influence the clinical outcome has been only partially explored in this species. Influenza D virus (IDV) was discovered in 2011. Since then, IDV has been detected worldwide in different hosts. A significant association between IDV and bacterial pathogens in sick cattle was shown in epidemiological studies, especially with Mycoplasma bovis. In an experimental challenge, IDV aggravated M. bovis-induced pneumonia. However, the mechanisms through which IDV drives an increased susceptibility to bacterial superinfections remain unknown. Here, we used the organotypic lung model precision-cut lung slices to study the interplay between IDV and M. bovis coinfection. Our results show that a primary IDV infection promotes M. bovis superinfection by increasing the bacterial replication and the ultrastructural damages in lung pneumocytes. In our model, IDV impaired the innate immune response triggered by M. bovis by decreasing the expression of several proinflammatory cytokines and chemokines that are important for immune cell recruitment and the bacterial clearance. Stimulations with agonists of cytosolic helicases and Toll-like receptors (TLRs) revealed that a primary activation of RIG-I/MDA5 desensitizes the TLR2 activation, similar to what was observed with IDV infection. The cross talk between these two pattern recognition receptors leads to a nonadditive response, which alters the TLR2-mediated cascade that controls the bacterial infection. These results highlight innate immune mechanisms that were not described for cattle so far and improve our understanding of the bovine host-microbe interactions and IDV pathogenesis. IMPORTANCE Since the spread of the respiratory influenza D virus (IDV) infection to the cattle population, the question about the impact of this virus on bovine respiratory disease (BRD) remains still unanswered. Animals affected by BRD are often coinfected with multiple pathogens, especially viruses and bacteria. In particular, viruses are suspected to enhance secondary bacterial superinfections. Here, we use an ex vivo model of lung tissue to study the effects of IDV infection on bacterial superinfections. Our results show that IDV increases the susceptibility to the respiratory pathogen Mycoplasma bovis. In particular, IDV seems to activate immune pathways that inhibit the innate immune response against the bacteria. This may allow M. bovis to increase its proliferation and to delay its clearance from lung tissue. These results suggest that IDV could have a negative impact on the respiratory pathology of cattle.

Risk Factors for Influenza-Induced Exacerbations and Mortality in Non-Cystic Fibrosis Bronchiectasis

Influenza infection is a cause of exacerbations in patients with chronic pulmonary diseases. The aim of this study was to investigate the clinical outcomes and identify risk factors associated with hospitalization and mortality following influenza infection in adult patients with bronchiectasis. Using the Chang Gung Research Database, we identified patients with bronchiectasis and influenza-related infection (ICD-9-CM 487 and anti-viral medicine) between 2008 and 2017. The main outcomes were influenza-related hospitalization and in-hospital mortality rate. Eight hundred sixty-five patients with bronchiectasis and influenza infection were identified. Five hundred thirty-six (62%) patients with bronchiectasis were hospitalized for influenza-related infection and 118 (22%) patients had respiratory failure. Compared to the group only seen in clinic, the hospitalization group was older, with more male patients, a lower FEV_1, higher bronchiectasis aetiology comorbidity index (BACI), and more acute exacerbations in the previous year. Co-infections were evident in 55.6% of hospitalized patients, mainly caused by Pseudomonas aeruginosa (15%), fungus (7%), and Klebsiella pneumoniae (6%). The respiratory failure group developed acute kidney injury (36% vs. 16%; p < 0.001), and shock (47% vs. 6%; p < 0.001) more often than influenza patients without respiratory failure. The overall mortality rate was 10.8% and the respiratory failure group exhibited significantly higher in-hospital mortality rates (27.1% vs. 6.2%; p < 0.001). Age, BACI, and previous exacerbations were independently associated with influenza-related hospitalization. Age, presence of shock, and low platelet counts were associated with increased hospital mortality. Influenza virus caused severe exacerbation in bronchiectasis, especially in those who were older and who had high BACI scores and previous exacerbations. A high risk of respiratory failure and mortality were observed in influenza-related hospitalization in bronchiectasis. We highlight the importance of preventing or treating influenza infection in bronchiectasis.

Co-infection of the respiratory epithelium, scene of complex functional interactions between viral, bacterial, and human neuraminidases

The activity of sialic acids, known to play critical roles in biology and many pathological processes, is finely regulated by a class of enzymes called sialidases, also known as neuraminidases. These are present in mammals and many other biological systems, such as viruses and bacteria. This review focuses on the very particular situation of co-infections of the respiratory epithelium, the scene of complex functional interactions between viral, bacterial, and human neuraminidases. This intrinsically multidisciplinary topic combining structural biology, biochemistry, physiology, and the study of host-pathogen interactions, opens up exciting research perspectives that could lead to a better understanding of the mechanisms underlying virus-bacteria co-infections and their contribution to the aggravation of respiratory pathology, notably in the context of pre-existing pathological contexts. Strategies that mimic or inhibit the activity of the neuraminidases could constitute interesting treatment options for viral and bacterial infections.

Lianhuaqingwen capsule inhibits non-lethal doses of influenza virus-induced secondary Staphylococcus aureus infection in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Lianhuaqingwen capsule (LH-C) is a traditional Chinese medicine (TCM), consisting of two prescriptions, Ma-xing-shi-gan-tang (MXSGT) and Yinqiao San. It has been proven to have antiviral, antibacterial, and immunomodulatory effects in recent years. Clinically, it is commonly used in the treatment of respiratory tract infections.

AIM OF THE STUDY

It was demonstrated in our previous studies that LH-C has an effect of antivirus and inhibits influenza virus-induced bacterial adhesion to respiratory epithelial cells through down-regulation of cell adhesion molecules in vitro. However, LH-C's effect against influenza-induced secondary bacterial infection in animal studies remains unclear. Therefore, in the present study, we established a mouse model of infection with non-lethal doses of influenza virus(H1N1) and secondary infection of Staphylococcus aureus (S. aureus), to investigate the potential effects of LH-C.

METHODS

Experiments were carried out on BALB/c mice infecting non-lethal doses of H1N1 and non-lethal doses of S. aureus, and the viral, and bacterial doses were determined by observing and recording changes in the body weight, mortality, and pathological changes. Moreover, after LH-C treatment, the survival rate, body weight, lung index, viral titers, bacterial colonies, pathological changes, and the inflammatory cytokines in the mouse model have all been systematically determined.

RESULTS

In the superinfection models of H1N1 and S. aureus, the mortality rate was 100% in groups of mice infected with 20 PFU/50 μL of H1N1 and 10⁵ CFU/mL of S. aureus, 20 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus, 4 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus. The mortality rate was 50% in the group of mice infected with 4 PFU/50 μL of H1N1 and 10⁵ CFU/mL of S. aureus. The mortality rate was 37.5% in the group of mice infected with 20 PFU/50 μL of H1N1 alone and in the group of mice infected with 2 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus. The mortality rate in the group of mice infected with 2 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus was 30%. The infected mice of 2 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus had a weight loss of nearly 10%. About the histopathological changes in the lung tissue of infection mice, severe lung lesions were found in the superinfection models. LH-C improved survival in the superinfected mice, significantly reduced lung index, lowered viral titers and bacterial loads, and alleviated lung damage. It reduced lung inflammation by down-regulating mRNA expression levels of inflammatory mediators like IL-6, IL-1β, IL-10, TNF-α, IFN-β, MCP-1, and RANTES.

CONCLUSIONS

We found that superinfection from non-lethal doses of S. aureus following non-lethal doses of H1N1 was equally fatal in mice, confirming the severity of secondary infections. The ability of LH-C to alleviate lung injury resulting from secondary S. aureus infection induced by H1N1 was confirmed. These findings provided a further assessment of LH-C, suggesting that LH-C may have good therapeutic efficacy in influenza secondary bacterial infection disease.

Understanding the mechanisms of viral and bacterial coinfections in bovine respiratory disease: a comprehensive literature review of experimental evidence

Bovine respiratory disease (BRD) is one of the most important diseases impacting the global cattle industry, resulting in significant economic loss. Commonly referred to as shipping fever, BRD is especially concerning for young calves during transport when they are most susceptible to developing disease. Despite years of extensive study, managing BRD remains challenging as its aetiology involves complex interactions between pathogens, environmental and host factors. While at the beginning of the twentieth century, scientists believed that BRD was only caused by bacterial infections (“bovine pasteurellosis”), we now know that viruses play a key role in BRD induction. Mixtures of pathogenic bacteria and viruses are frequently isolated from respiratory secretions of animals with respiratory illness. The increased diagnostic screening data has changed our understanding of pathogens contributing to BRD development. In this review, we aim to comprehensively examine experimental evidence from all existing studies performed to understand coinfections between respiratory pathogens in cattle. Despite the fact that pneumonia has not always been successfully reproduced by in vivo calf modelling, several studies attempted to investigate the clinical significance of interactions between different pathogens. The most studied model of pneumonia induction has been reproduced by a primary viral infection followed by a secondary bacterial superinfection, with strong evidence suggesting this could potentially be one of the most common scenarios during BRD onset. Different in vitro studies indicated that viral priming may increase bacterial adherence and colonization of the respiratory tract, suggesting a possible mechanism underpinning bronchopneumonia onset in cattle. In addition, a few in vivo studies on viral coinfections and bacterial coinfections demonstrated that a primary viral infection could also increase the pathogenicity of a secondary viral infection and, similarly, dual infections with two bacterial pathogens could increase the severity of BRD lesions. Therefore, different scenarios of pathogen dynamics could be hypothesized for BRD onset which are not limited to a primary viral infection followed by a secondary bacterial superinfection.

Early predictors of lung necrosis severity in children with community-acquired necrotizing pneumonia

OBJECTIVE

To analyze baseline clinical and laboratory characteristics and explore the possible predictors of lung necrosis severity in children with community-acquired necrotizing pneumonia (NP).

METHODOLOGY

This retrospective observational study was performed in a tertiary referral center. A total of 104 patients aged <15 years with community-acquired pneumonia and radiologically confirmed NP by computed tomography (CT) were included. Patients were classified into the mild, moderate, or massive necrosis groups.

RESULTS

Among them, 29, 41, and 34 patients had mild, moderate, and massive necrosis, respectively. Moreover, 34.6% of the patients were admitted to pediatric intensive care unit. Massive necrosis was more likely to occur during winter (p < 0.05) and was associated with more severe clinical outcomes, such as longer duration of fever, longer hospitalization, increased mortality, and a higher risk of subsequent surgical intervention (p < 0.05). Multivariate analysis demonstrated that the following were independent risk factors for massive necrosis in this study: C-reactive protein (CRP) (p = 0.036), serum albumin (p = 0.009), and immunoglobulin M (IgM) (p = 0.022). Receiver operating characteristic analysis showed that when the cut-off value for CRP, serum albumin, and IgM were set at 122 mg/L, 30.8 g/L, and 95.7 mg/dl, respectively, they showed good diagnostic performance for differentiating patients with massive necrosis from all patients with NP.

CONCLUSION

NP is a potentially severe complication of pediatric community-acquired pneumonia. Different severities of lung necrosis can lead to different clinical outcomes. CRP, serum albumin, and IgM levels are independent predictors of the degree of lung necrosis.

Heterotypic Influenza Infections Mitigate Susceptibility to Secondary Bacterial Infection

Influenza-associated bacterial superinfections have devastating impacts on the lung and can result in increased risk of mortality. New strains of influenza circulate throughout the population yearly, promoting the establishment of immune memory. Nearly all individuals have some degree of influenza memory before adulthood. Due to this, we sought to understand the role of immune memory during bacterial superinfections. An influenza heterotypic immunity model was established using influenza A/Puerto Rico/8/34 and influenza A/X31. We report in this article that influenza-experienced mice are more resistant to secondary bacterial infection with methicillin-resistant Staphylococcus aureus as determined by wasting, bacterial burden, pulmonary inflammation, and lung leak, despite significant ongoing lung remodeling. Multidimensional flow cytometry and lung transcriptomics revealed significant alterations in the lung environment in influenza-experienced mice compared with naive animals. These include changes in the lung monocyte and T cell compartments, characterized by increased expansion of influenza tetramer-specific CD8+ T cells. The protection that was seen in the memory-experienced mouse model is associated with the reduction in inflammatory mechanisms, making the lung less susceptible to damage and subsequent bacterial colonization. These findings provide insight into how influenza heterotypic immunity reshapes the lung environment and the immune response to a rechallenge event, which is highly relevant to the context of human infection.

The Impact of Multiplex PCR in Diagnosing and Managing Bacterial Infections in COVID-19 Patients Self-Medicated with Antibiotics

The multiplex PCR is a powerful and efficient tool that was widely used during the COVID-19 pandemic to diagnose SARS-CoV-2 infections and that has applications for bacterial identification, as well as determining bacterial resistance to antibiotics. Therefore, this study aimed to determine the usability of multiplex PCR, especially in patients self-medicated with antibiotics, where bacterial cultures often give false-negative results. A cross-sectional study was developed in two COVID-19 units, where 489 eligible patients were included as antibiotic takers and non-antibiotic takers. Antibiotic takers used mostly over-the-counter medication; they suffered significantly more chronic respiratory conditions and were self-medicated most often with cephalosporins (41.4%), macrolide (23.2%), and penicillin (19.7%). The disease severity in these patients was significantly higher than in non-antibiotic takers, and bacterial superinfections were the most common finding in the same group (63.6%). Antibiotic takers had longer hospital and ICU admissions, although the mortality rate was not significantly higher than in non-antibiotic takers. The most common bacteria involved in secondary infections were Staphylococcus aureus (22.2%), Pseudomonas aeruginosa (27.8%), and Klebsiellaspp (25.0%). Patients self-medicating with antibiotics had significantly higher rates of multidrug resistance. The multiplex PCR test was more accurate in identifying multidrug resistance and resulted in a quicker initiation of therapeutic antibiotics compared with instances where a bacterial culture was initially performed, with an average of 26.8 h vs. 40.4 h, respectively. The hospital stay was also significantly shorter by an average of 2.5 days when PCR was used as an initial assessment tool for secondary bacterial infections. When adjusted for age, COVID-19 severity, and pulmonary disease, over-the-counter use of antibiotics represented a significant independent risk factor for a prolonged hospitalization (AOR = 1.21). Similar findings were observed for smoking status (AOR = 1.44), bacterial superinfection (AOR = 1.52), performing only a conventional bacterial culture (AOR = 1.17), and a duration of more than 48 h for bacterial sampling from the time of hospital admission (AOR = 1.36). Multiplex PCR may be a very effective method for diagnosing secondary bacterial infections in COVID-19 individuals self-medicating with antibiotics. Utilizing this strategy as an initial screen in COVID-19 patients who exhibit signs of sepsis and clinical deterioration will result in a faster recovery time and a shorter period of hospitalization.