Bacterial coinfection in influenza pneumonia: Rates, pathogens, and outcomes

Impact of antibiotic therapy in patients with respiratory viral infections: a retrospective cohort study

OBJECTIVES

The impact of antibiotics in patients with positive polymerase chain reaction (PCR) for respiratory viruses without evidence of a respiratory bacterial co-infection is largely unknown. The aim of this study was to assess the association of antibiotics on 30-day mortality and length of hospital stay in patients with an acute respiratory infection and PCR documented presence of respiratory viruses.

METHODS

We conducted a retrospective cohort study of adult patients admitted to hospital between 2012 and 2021 with positive PCR for influenza virus (H3N2, H1N1, influenza B), respiratory syncytial virus, human metapneumovirus or severe acute respiratory syndrome coronavirus 2. We used logistic regression, the Kaplan-Meier estimator and Poisson's regression to assess the impact of antibiotic therapy on outcomes.

RESULTS

Among 3979 patients, 67.7% received antibiotics. In adjusted analyses, antibiotics initiated in the emergency department (adjusted OR 1.23, 95% CI 0.77-1.96) and days of antibiotic therapy (adjusted OR per day of therapy 0.98, 95% CI 0.95-1.00) had no significant impact on mortality, whereas antibiotics initiated later during admission (adjusted OR 2.25, 95% CI 1.26-4.02) was associated with increased mortality. Patients prescribed antibiotics had longer duration of hospital admission.

CONCLUSIONS

We observed no protective association between in-hospital antibiotic therapy and outcomes, suggesting overuse of antibiotics in respiratory infections with proven respiratory viruses. A restrictive antibiotic strategy may be warranted.

Rescue of alveolar wall liquid secretion blocks fatal lung injury due to influenza-staphylococcal coinfection

Secondary lung infection by inhaled Staphylococcus aureus (SA) is a common and lethal event for individuals infected with influenza A virus (IAV). How IAV disrupts host defense to promote SA infection in lung alveoli, where fatal lung injury occurs, is not known. We addressed this issue using real-time determinations of alveolar responses to IAV in live, intact, perfused lungs. Our findings show that IAV infection blocked defensive alveolar wall liquid (AWL) secretion and induced airspace liquid absorption, thereby reversing normal alveolar liquid dynamics and inhibiting alveolar clearance of inhaled SA. Loss of AWL secretion resulted from inhibition of the cystic fibrosis transmembrane conductance regulator (CFTR) ion channel in the alveolar epithelium, and airspace liquid absorption was caused by stimulation of the alveolar epithelial Na+ channel (ENaC). Loss of AWL secretion promoted alveolar stabilization of inhaled SA, but rescue of AWL secretion protected against alveolar SA stabilization and fatal SA-induced lung injury in IAV-infected mice. These findings reveal a central role for AWL secretion in alveolar defense against inhaled SA and identify AWL inhibition as a critical mechanism of IAV lung pathogenesis. AWL rescue may represent a new therapeutic approach for IAV-SA coinfection.

Severe community-acquired pneumonia in the post COVID-19 era

PURPOSE OF REVIEW

The aim was to examine and summarize the most recent published literature in the last years stating the advances for treatment options and adjunctive therapies in patients hospitalized with severe community-acquired pneumonia (sCAP). Search was performed in PubMed, including observational studies, randomized controlled trials, systematic reviews and meta-analyses, and international guidelines.

RECENT FINDINGS

Regardless of a large number of published CAP guidelines, most of their recommendations are based on low-level evidence.Viruses have an increasing role as sCAP etiology with an impact on mortality. Accordingly, it is imperative to strengthen the demand for vaccines and newer antivirals. Considering an early monitoring of the immune response in patients with severe Influenza, may help to evaluate a personalized immunomodulatory strategy. Despite growing evidence, the use of corticosteroids as an adjunctive therapy in bacterial sCAP continues to be controversial.

SUMMARY

Mortality due to sCAP still remains undesirably high. This fact strengthens the need for more high-quality research to increase evidence. It also highlights the need for clinicians to be aware of the level of evidence of the stated recommendations, taking this into consideration before decision making.

Respiratory infections predominate after day 100 following B-cell maturation antigen-directed CAR T-cell therapy

Infections are an important complication after B-cell maturation antigen (BCMA)-directed chimeric antigen receptor (CAR) T-cell therapy and risks may differ between the early and late periods. We evaluated infections in 99 adults who received a first BCMA-directed CAR T-cell therapy (commercial and investigational autologous BCMA CAR T-cell products at the recommended phase 2 dose) for relapsed/refractory multiple myeloma between November 2016 and May 2022. Infections were recorded until day 365, if patients experienced symptoms with a microbiologic diagnosis, or for symptomatic site-specific infections treated with antimicrobials. One-year cumulative incidence functions were calculated based on time to first respiratory infection using dates of infection-free death and receipt of additional antineoplastic therapies as competing risks. Secondary analysis evaluated risk factors for late respiratory infections using univariate and multivariable Cox regression models. Thirty-seven patients (37%) experienced 64 infectious events over the first year after BCMA-directed CAR T-cell therapy, with 42 early infectious events (days, 0-100), and 22 late infectious events (days, 101-365). Respiratory infections were the most common site-specific infection and the relative proportion of respiratory infections increased in the late period (31% of early events vs 77% of late events). On multivariable analysis, hypogammaglobulinemia (hazard ratio [HR], 6.06; P = .044) and diagnosis of an early respiratory viral infection (HR, 2.95; P = .048) were independent risk factors for late respiratory infection. Respiratory infections predominate after BCMA CAR T-cell therapy, particularly after day 100. Hypogammaglobulinemia and diagnosis of an early respiratory infection are risk factors for late respiratory infections that may be used to guide targeted preventive strategies.

Memory Th17 cell-mediated protection against lethal secondary pneumococcal pneumonia following influenza infection

Streptococcus pneumoniae (Sp) frequently causes secondary pneumonia after influenza A virus (IAV) infection, leading to high morbidity and mortality worldwide. Concomitant pneumococcal and influenza vaccination improves protection against coinfection but does not always yield complete protection. Impaired innate and adaptive immune responses have been associated with attenuated bacterial clearance in influenza virus-infected hosts. In this study, we showed that preceding low-dose IAV infection caused persistent Sp infection and suppression of bacteria-specific T-helper type 17 (Th17) responses in mice. Prior Sp infection protected against subsequent IAV/Sp coinfection by improving bacterial clearance and rescuing bacteria-specific Th17 responses in the lungs. Furthermore, blockade of IL-17A by anti-IL-17A antibodies abrogated the protective effect of Sp preinfection. Importantly, memory Th17 responses induced by Sp preinfection overcame viral-driven Th17 inhibition and provided cross-protection against different Sp serotypes following coinfection with IAV. These results indicate that bacteria-specific Th17 memory cells play a key role in providing protection against IAV/Sp coinfection in a serotype-independent manner and suggest that a Th17-based vaccine would have excellent potential to mitigate disease caused by coinfection. IMPORTANCE Streptococcus pneumoniae (Sp) frequently causes secondary bacterial pneumonia after influenza A virus (IAV) infection, leading to increased morbidity and mortality worldwide. Current pneumococcal vaccines induce highly strain-specific antibody responses and provide limited protection against IAV/Sp coinfection. Th17 responses are broadly protective against Sp single infection, but whether the Th17 response, which is dramatically impaired by IAV infection in naïve mice, might be effective in immunization-induced protection against pneumonia caused by coinfection is not known. In this study, we have revealed that Sp-specific memory Th17 cells rescue IAV-driven inhibition and provide cross-protection against subsequent lethal coinfection with IAV and different Sp serotypes. These results indicate that a Th17-based vaccine would have excellent potential to mitigate disease caused by IAV/Sp coinfection.

Influenza A-induced cystic fibrosis transmembrane conductance regulator dysfunction increases susceptibility to Streptococcus pneumoniae

Influenza A virus (IAV) infection is commonly complicated by secondary bacterial infections that lead to increased morbidity and mortality. Our recent work demonstrates that IAV disrupts airway homeostasis, leading to airway pathophysiology resembling cystic fibrosis disease through diminished cystic fibrosis transmembrane conductance regulator (CFTR) function. Here, we use human airway organotypic cultures to investigate how IAV alters the airway microenvironment to increase susceptibility to secondary infection with Streptococcus pneumoniae (Spn). We observed that IAV-induced CFTR dysfunction and airway surface liquid acidification is central to increasing susceptibility to Spn. Additionally, we observed that IAV induced profound transcriptional changes in the airway epithelium and proteomic changes in the airway surface liquid in both CFTR-dependent and -independent manners. These changes correspond to multiple diminished host defense pathways and altered airway epithelial function. Collectively, these findings highlight both the importance of CFTR function during infectious challenge and demonstrate a central role for the lung epithelium in secondary bacterial infections following IAV.

Clinical Features of COVID-19 and Differentiation from Other Causes of CAP

Community-acquired pneumonia (CAP) is a significant cause of morbidity and mortality, one of the most common reasons for infection-related death worldwide. Causes of CAP include numerous viral, bacterial, and fungal pathogens, though frequently no specific organism is found. Beginning in 2019, the COVID-19 pandemic has caused incredible morbidity and mortality. COVID-19 has many features typical of CAP such as fever, respiratory distress, and cough, and can be difficult to distinguish from other types of CAP. Here, we highlight unique clinical features of COVID-19 pneumonia such as olfactory and gustatory dysfunction, lymphopenia, and distinct imaging appearance.

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.

Antibiotic use and Influencing Factors Among Hospitalized Patients with COVID-19: A Multicenter Point-Prevalence Study from Turkey

Background

Broad-spectrum empirical antimicrobials are frequently prescribed for patients with coronavirus disease 2019 (COVID-19) despite the lack of evidence for bacterial coinfection.

Aims

We aimed to cross-sectionally determine the frequency of antibiotics use, type of antibiotics prescribed, and the factors influencing antibiotics use in hospitalized patients with COVID-19 confirmed by polymerase chain reaction.

Study Design

The study was a national, multicenter, retrospective, and single-day point prevalence study.

Methods

This was a national, multicenter, retrospective, and single-day point-prevalence study, conducted in the 24-h period between 00:00 and 24:00 on November 18, 2020, during the start of the second COVID-19 peak in Turkey.

Results

A total of 1500 patients hospitalized with a diagnosis of COVID-19 were included in the study. The mean age ± standard deviation of the patients was 65.0 ± 15.5, and 56.2% (n = 843) of these patients were men. Of these hospitalized patients, 11.9% (n = 178) were undergoing invasive mechanical ventilation or ECMO. It was observed that 1118 (74.5%) patients were receiving antibiotics, of which 416 (37.2%) were prescribed a combination of antibiotics. In total, 71.2% of the patients had neither a clinical diagnosis nor microbiological evidence for prescribing antibiotics. In the multivariate logistic regression analysis, hospitalization in a state hospital (p < 0.001), requiring any supplemental oxygen (p = 0.005), presence of moderate/diffuse lung involvement (p < 0.001), C-reactive protein > 10 ULT coefficient (p < 0.001), lymphocyte count < 800 (p = 0.007), and clinical diagnosis and/or confirmation by culture (p < 0.001) were found to be independent factors associated with increased antibiotic use.

Conclusion

The necessity of empirical antibiotics use in patients with COVID-19 should be reconsidered according to their clinical, imaging, and laboratory findings.

Community-Acquired Pneumonia

Community-acquired pneumonia is an important cause of morbidity and mortality. It can be caused by bacteria, viruses, or fungi and can be prevented through vaccination with pneumococcal, influenza, and COVID-19 vaccines. Diagnosis requires suggestive history and physical findings in conjunction with radiographic evidence of infiltrates. Laboratory testing can help guide therapy. Important issues in treatment include choosing the proper venue, timely initiation of the appropriate antibiotic or antiviral, appropriate respiratory support, deescalation after negative culture results, switching to oral therapy, and short treatment duration.

Lower antibiotic prescription rates in hospitalized COVID-19 patients than influenza patients, a prospective study

BACKGROUND

COVID-19 patients are extensively treated with antibiotics despite few bacterial complications. We aimed to study antibiotic use in hospitalized COVID-19 patients compared to influenza patients in two consecutive years. Furthermore, we investigated changes in antibiotic use from the first to second pandemic wave.

METHODS

This prospective study included both patients from two referral hospitals in Bergen, Norway, admitted with influenza (n = 215) during the 2018/2019 epidemic and with COVID-19 (n = 82) during spring/summer 2020, and national data on registered Norwegian COVID-19 hospital admissions from March 2020 to January 2021 (n = 2300). Patient characteristics were compared, and logistic regression analysis was used to identify risk factors for antibiotic use.

RESULTS

National and local COVID-19 patients received significantly less antibiotics (53% and 49%) than influenza patients (69%, p < .001). Early antibiotics contributed to >90% of antibiotic prescriptions in the two local hospitals, and >70% of prescriptions nationally. When adjusted for age, comorbidities, symptom duration, chest X-ray infiltrates and oxygen treatment, local COVID-19 patients still had significantly lower odds of antibiotic prescription than influenza patients (aOR 0.21, 95%CI 0.09-0.50). At the national level, we observed a significant reduction in antibiotic prescription rates in the second pandemic wave compared to the first (aOR 0.35, 95% CI 0.29-0.43).

CONCLUSION

Fewer COVID-19 patients received antibiotics compared to influenza patients admitted to the two local hospitals one year earlier. The antibiotic prescription rate was lower during the second pandemic wave, possibly due to increased clinical experience and published evidence refuting the efficacy of antibiotics in treating COVID-19 pneumonia.