Secondary Bacterial Pneumonia Research Articles

Making Universal Influenza Vaccines: Lessons From the 1918 Pandemic.

The year 2018 marked the 100th anniversary of the deadliest event in human history. In 1918–1919, pandemic influenza spread globally and caused an estimated 50–100 million deaths associated with unexpected clinical and epidemiological features. The descendants of the 1918 virus continue to circulate as annual epidemic viruses causing significant mortality each year. The 1918 influenza pandemic serves as a benchmark for the development of universal influenza vaccines. Challenges to producing a truly universal influenza vaccine include eliciting broad protection against antigenically different influenza viruses that can prevent or significantly downregulate viral replication and reduce morbidity by preventing development of viral and secondary bacterial pneumonia. Perhaps the most important goal of such vaccines is not to prevent influenza, but to prevent influenza deaths.

Is Fever a Red Flag for Bacterial Pneumonia in Children With Viral Bronchiolitis?

We hypothesized that fever in children with viral bronchiolitis indicates the need for consideration of superimposed bacterial pneumonia. We conducted a retrospective study of 349 children aged 2 years and younger with diagnoses of respiratory syncytial virus (RSV) and viral upper respiratory infection. Data were analyzed using Pearson χ2 test. One hundred seventy-eight children had RSV with no other identified virus. The majority of children (56%) who had only RSV were afebrile. Febrile children with RSV were over twice as likely to be diagnosed with bacterial pneumonia as those who were afebrile (60% vs 27%, P < .001). In the 171 children who had bronchiolitis caused by a virus other than RSV, 51% were afebrile. These children were 8 times more likely to be diagnosed with pneumonia than those who were afebrile (65% vs 8%, P < .001). Evaluation of febrile children with viral bronchiolitis may allow early diagnosis and treatment of secondary bacterial pneumonia.

Pathogen analysis of bacterial pneumonia secondary to influenza

In human history, there have been several times of influenza raging, which have caused tens of millions of deaths and brought serious social and economic burdens. Although with the development of science, the emergence of vaccines has significantly reduced the incidence and mortality of influenza, due to the high variability of viruses, there is still a lack of effective treatment. More and more studies have found that bacterial pneumonia secondary to influenza was an important cause of the progression to critical illness or even death. Hence, diagnosis and treatment timely of secondary bacterial pneumonia are valuable. Therefore, we discuss the pathogens of bacterial pneumonia secondary to influenza, associated morbidity, mortality, and risk factors. Hopefully, it can provide some valuable references for clinical practice. Since some clinical studies have not separated pneumonia from lower respiratory tract infections, we will discuss these two situations together.

Innate Immune Cell Suppression and the Link With Secondary Lung Bacterial Pneumonia.

Secondary infections arise as a consequence of previous or concurrent conditions and occur in the community or in the hospital setting. The events allowing secondary infections to gain a foothold have been studied for many years and include poor nutrition, anxiety, mental health issues, underlying chronic diseases, resolution of acute inflammation, primary immune deficiencies, and immune suppression by infection or medication. Children, the elderly and the ill are particularly susceptible. This review is concerned with secondary bacterial infections of the lung that occur following viral infection. Using influenza virus infection as an example, with comparisons to rhinovirus and respiratory syncytial virus infection, we will update and review defective bacterial innate immunity and also highlight areas for potential new investigation. It is currently estimated that one in 16 National Health Service (NHS) hospital patients develop an infection, the most common being pneumonia, lower respiratory tract infections, urinary tract infections and infection of surgical sites. The continued drive to understand the mechanisms of why secondary infections arise is therefore of key importance.

On the Centenary of the Spanish Flu: Being Prepared for the Next Pandemic.

Influenza is one of the oldest infectious diseases affecting humans. Every influenza pandemic in history has ended with disastrous outcomes regarding public health and the social economy. This year marks the 100th anniversary of the Spanish flu (H1N1) outbreak of 1918, which is recognized as the most lethal natural event in recent history. In spite of limited travel and transportation at that time, the Spanish flu pandemic of 1918 reached peak activity on multiple continents simultaneously within several months after its emergence in late 1917 from different hypothesized origins, such as US military camps, the state of Kansas, or the troop staging and hospital camp in Extaples, France ( Patterson and Pyle 1991 ; Oxford et al. 2005 ; Shanks 2016 ). However, in some islands of the Pacific region, such as in New Caledonia, the pandemic's lethal effects lasted for over 3 years, until July 1921 ( Shanks et al. 2018 ). The pandemic flu is estimated to have infected more than 500 million people, causing between 50 and 100 million deaths globally ( Patterson and Pyle 1991 ; Guan et al. 2010 ). The evidence suggests that most pandemicrelated deaths were not caused by the direct pathological effects of the influenza virus, but rather by the lethal effects of secondary bacterial pneumonia ( Chien et al. 2009 ).

CCR2 mediates increased susceptibility to post-H1N1 bacterial pneumonia by limiting dendritic cell induction of IL-17.

Post Influenza bacterial pneumonia is associated with significant mortality and morbidity. Dendritic cells (DCs) play a crucial role in host defense against bacterial pneumonia, but their contribution to post influenza-susceptibility to secondary bacterial pneumonia is incompletely understood. WT and CCR2−/− mice were infected with 100 plaque forming units (pfu) H1N1 intranasally alone or were challenged on day 5 with 7×107 colony forming units (cfu) methicillin-resistant Staphylococcus aureus intratracheally. WT mice express abundant CCL2 mRNA and protein post-H1N1 alone or dual infection. CCR2−/− mice had significantly higher survival as compared to WT mice, associated with significantly improved bacterial clearance at 24 and 48 hours (10 fold and 14 fold, respectively) post-bacterial challenge. There was robust upregulation of IL-23 and IL-17 as well as down-regulation of IL-27 expression in CCR2−/− mice following sequential infection as compared to WT mice, which was also associated with significantly greater accumulation of CD103+ DC. Finally, WT mice treated with a CCR2 inhibitor showed improved bacterial clearance in association with similar cytokine profiles as CCR2−/− mice. Thus, CCR2 significantly contributes to increased susceptibility to bacterial infection after influenza pneumonia likely via altered dendritic cell responses and thus, CCR2 antagonism represents a potential therapeutic strategy.

Respiratory Viral Infection-Induced Microbiome Alterations and Secondary Bacterial Pneumonia.

Influenza and other respiratory viral infections are the most common type of acute respiratory infection. Viral infections predispose patients to secondary bacterial infections, which often have a more severe clinical course. The mechanisms underlying post-viral bacterial infections are complex, and include multifactorial processes mediated by interactions between viruses, bacteria, and the host immune system. Studies over the past 15 years have demonstrated that unique microbial communities reside on the mucosal surfaces of the gastrointestinal tract and the respiratory tract, which have both direct and indirect effects on host defense against viral infections. In addition, antiviral immune responses induced by acute respiratory infections such as influenza are associated with changes in microbial composition and function (“dysbiosis”) in the respiratory and gastrointestinal tract, which in turn may alter subsequent immune function against secondary bacterial infection or alter the dynamics of inter-microbial interactions, thereby enhancing the proliferation of potentially pathogenic bacterial species. In this review, we summarize the literature on the interactions between host microbial communities and host defense, and how influenza, and other acute respiratory viral infections disrupt these interactions, thereby contributing to the pathogenesis of secondary bacterial infections.

Inflammation induced by influenza virus impairs human innate immune control of pneumococcus.

Colonization of the upper respiratory tract by pneumococcus is important both as a determinant of disease and for transmission into the population. The immunological mechanisms that contain pneumococcus during colonization are well studied in mice but remain unclear in humans. Loss of this control of pneumococcus following infection with influenza virus is associated with secondary bacterial pneumonia. We used a human challenge model with type 6B pneumococcus to show that acquisition of pneumococcus induced early degranulation of resident neutrophils and recruitment of monocytes to the nose. Monocyte function was associated with the clearance of pneumococcus. Prior nasal infection with live attenuated influenza virus induced inflammation, impaired innate immune function and altered genome-wide nasal gene responses to the carriage of pneumococcus. Levels of the cytokine CXCL10, promoted by viral infection, at the time pneumococcus was encountered were positively associated with bacterial load.

STAT2 Signaling Regulates Macrophage Phenotype During Influenza and Bacterial Super-Infection.

Influenza is a common respiratory virus that infects between 5 and 20% of the US population and results in 30,000 deaths annually. A primary cause of influenza-associated death is secondary bacterial pneumonia. We have previously shown that influenza induces type I interferon (IFN)-mediated inhibition of Type 17 immune responses, resulting in exacerbation of bacterial burden during influenza and Staphylococcus aureus super-infection. In this study, we investigated the role of STAT2 signaling during influenza and influenza-bacterial super-infection in mice. Influenza-infected STAT2−/− mice had increased morbidity, viral burden, and inflammation when compared to wild-type mice. Despite an exaggerated inflammatory response to influenza infection, we found increased bacterial control and survival in STAT2 deficient mice during influenza-MRSA super-infection compared to controls. Further, we found that increased bacterial clearance during influenza-MRSA super-infection is not due to rescue of Type 17 immunity. Absence of STAT2 was associated with increased accumulation of M1, M2 and M1/M2 co-expressing macrophages during influenza-bacterial super-infection. Neutralization of IFNγ (M1) and/or Arginase 1 (M2) impaired bacterial clearance in Stat2−/− mice during super-infection, demonstrating that pulmonary macrophages expressing a mixed M1/M2 phenotype promote bacterial control during influenza-bacterial super-infection. Together, these results suggest that the STAT2 signaling is involved in suppressing macrophage activation and bacterial control during influenza-bacterial super-infection. Further, these studies reveal novel mechanistic insight into the roles of macrophage subpopulations in pulmonary host defense.

Influenza infection directly alters innate IL-23 and IL-12p70 and subsequent IL-17A and IFN-γ responses to pneumococcus in vitro in human monocytes.

It is well accepted that influenza A virus predisposes individuals to often more severe superinfections with Streptococcus pneumonia. However, the mechanisms that lead to this synergy are not clearly understood. Recent data suggests that competent Th17 immunity is crucial to clearance and protection from invasive pneumococcal disease of the lung. We demonstrate that early influenza infection significantly reduced levels of pneumococcus driven IL-12p70, IL-23 and IL-27 in human monocytes with significant impairment of IL-17A and IFN-γ in HKSP-treated allogeneic mixed lymphocyte cultures. We also provide evidence to suggest that the hemagglutinin component of the virus is at least partially responsible for this downward pressure on IL-17 responses but surprisingly this suppression occurs despite robust IL-23 levels in hemagglutinin-treated monocyte cultures. This study demonstrates that influenza can directly affect the immunological pathways that promote appropriate responses to Streptococcus pneumonia in human immune cells.ImportanceInfluenza virus is highly contagious and poses substantial public health problems due to its strong association with morbidity and mortality. Approximately 250,000–500,000 deaths are caused by seasonal influenza virus annually, and this figure increases during periods of pandemic infections. Most of these deaths are due to secondary bacterial pneumonia. Influenza-bacterial superinfection can result in hospitalisation and/or death of both patients with pre-existing lung disease or previously healthy individuals. The importance of our research is in determining that influenza and its component haemagglutinin has a direct effect on the classic pneumococcus induced pathways to IL-17A in our human ex vivo model.Our understanding of the mechanism which leaves people exposed to influenza infection during superinfection remain unresolved. This paper demonstrates that early infection of monocytes inhibits an arm of immunity crucial to bacterial clearance. Understanding this mechanism may provide alternative interventions in the case of superinfection with antimicrobial resistant strains of bacteria.

Clinical characteristics and severity of influenza infections by virus type, subtype, and lineage: A systematic literature review.

AimStudies carried out in the early 2000s found that the number of influenza‐associated hospitalizations and deaths was highest in seasons dominated by A(H3N2), suggesting that the clinical presentation and severity of influenza may differ across virus types, subtypes, and lineages. We aimed to review the studies that examined this hypothesis.MethodWe conducted a literature review of studies published until January 2017 that compared the clinical presentation, disease severity, and case‐fatality ratio of influenza patients infected with different virus types (A, B), subtypes (pre‐pandemic A(H1N1), A(H1N1)p, A(H3N2)), and lineages (Victoria, Yamagata).ResultsThe literature search resulted in over 1700 entries: After applying in‐ and exclusion criteria, 47 studies were included in the literature review. Studies showed a wide diversity in setting and populations. Only a minority of studies provided results adjusted by patient's age and other potential confounders. There were very few differences in the clinical presentation of patients infected with different influenza viruses. We found weak evidence that the A(H1N1)p subtype in the post‐pandemic period was more often associated with secondary bacterial pneumonia, ICU admission, and death, than the other influenza virus (sub)types.ConclusionContrary to what is commonly assumed, the causal virus subtype does not seem to be a major determinant of clinical presentation and severity of influenza illness. However, drawing conclusions was made difficult by the low comparability and methodological shortcomings of included studies, and more well‐designed studies are warranted.

Treatment with broadly neutralizing influenza antibodies reduces severity of secondary pneumococcal pneumonia in mice.

Secondary bacterial pneumonia is a frequent complication of influenza, associated with high morbidity and mortality. We hypothesized that treatment with neutralizing influenza A antibody AT10_002 protects against severe secondary pneumococcal infection in a mouse model of influenza A infection. Influenza A (H3N2) virus–infected male C57Bl6 mice were treated intravenously with either AT10_002 or a control 2 days postinfection. Seven days later, both groups were infected with Streptococcus pneumoniae and killed 18 hours later. Mice receiving AT10_002 showed less loss of bodyweight compared with controls (+1% vs −12%, P < .001), lower viral loads in bronchoalveolar lavage fluids (BALFs) (7 vs 194 RNA copies per µL; P < .001), and reduced bacterial outgrowth in lung homogenates (3.3 × 101 vs 2.5 × 105 colony‐forming units per mg; P < .001). The treatment group showed lower pulmonary wet weights, lower cell counts, and lower protein levels in BALF compared with controls. Treatment with AT10_002 was associated with lower levels of tumor necrosis factor‐α, interleukin (IL)‐6, cytokine‐induced neutrophil chemoattractant (KC), and interferon‐γ in BALF and lower IL‐6 and KC in lung homogenates. Treatment with anti‐influenza antibody AT10_002 is associated with reduced weight loss, viral load, bacterial outgrowth, and lung injury in a murine model of secondary pneumococcal pneumonia following influenza infection.

Gram-negative bacilli are a major cause of secondary pneumonia in patients with pulmonary tuberculosis: evidence from a cross-sectional study in a tertiary hospital in Nigeria.

This study was aimed at describing the profile of bacterial aetiology of secondary pneumonia in pulmonary tuberculosis (PTB) patients. A 22-month analysis of patients with PTB and secondary bacterial pneumonia was conducted. Data on isolates recovered and the antimicrobial susceptibility profile were recorded. Of the 141 patients, there were 79 (56%) males and the mean age was 35.98±15.93. Gram-negative bacilli were isolated with equal frequency as Streptococcus pneumoniae (63 [44.7%]). Most of the isolates tested were sensitive to levofloxacin, ceftriaxone or chloramphenicol. Gram-negative bacilli are a major cause of pneumonia in patients with PTB on treatment.

Mechanisms Regulating IL-1β Mediated Inflammation during Secondary Bacterial Pneumonia

Abstract Viral bacterial coinfections are known to cause severe pneumonia due to enhanced pathogen growth and excessive or altered immune responses. Despite knowing the overall causes for disease severity, current treatments fail to improve disease in many patients. Thus, an improved understanding of the specific immune pathways involved is needed to improve therapeutic treatment design. Interlukine-1β (IL-1β) is an important immune signaling cytokine responsible for inflammation. It exists as an inactive precursor that can be activated by caspase-1 containing inflammasomes. We found that coinfection of Influenza A virus and Streptococcus pneumoniae results in inflammasome activation mainly through the NOD-like receptor protein NLRP3. IL-1β levels are synergistically enhanced during coinfection, but not overall inflammasome activation. Instead, enhanced activation of the transcription factor NF-κB results in increased production of pro-IL-1β, which is subsequently processed into its active form by the inflammasome. In vivo, we discovered that IL-1β regulates lung pathology, and mice treated with a combination of antibiotics and IL-1β neutralizing antibodies have improved weight loss and mortality compared to either treatment individually.

Secondary Bacterial Pneumonia by Staphylococcus aureus Following Influenza A Infection Is SaeR/S Dependent.

Staphylococcus aureus is a predominant cause of fatal pneumonia following influenza A virus (IAV) infection. Herein we investigate the influence of antecedent IAV infection on S. aureus virulence gene expression. Using a murine model, comparing the USA300 and USA300ΔsaeR/S strains, we demonstrate that S. aureus pathogenesis following IAV infection is SaeR/S dependent. Furthermore, we show that IAV modulates the lung environment to rapidly up-regulate S. aureus virulence factors containing the SaeR-binding domain. Data demonstrate that the pathogen response to IAV infection impacts host outcome and provides evidence that the ability of S. aureus to sense and respond to the lung environment determines severity of pneumonia.

Risk factors affecting the mortality of HIV-infected patients with pulmonary tuberculosis in the cART era: a retrospective cohort study in China

BackgroundTuberculosis infection still places a great burden on HIV-infected individuals in China and other developing countries. Knowledge of the survival of HIV-infected patients with pulmonary tuberculosis (PTB) would provide important insights for the clinical management of this population, which remains to be well described in current China.MethodsHIV-infected patients with PTB admitted to Shanghai Public Health Clinical Center from January 2011 to December 2015 were retrospectively enrolled. In this cohort, the survival prognosis was estimated by the Kaplan-Meier method, while univariate and multivariate Cox proportional hazards models were used to determine the risk factors affecting mortality.ResultsAfter reviewing 4914 admitted patients with HIV infection, 359 PTB cases were identified. At the time of PTB diagnosis, the patients’ median CD4+ T cell count was 51 /mm3 (IQR: 23–116), and 27.30% of patients (98/359) were on combination antiretroviral therapy (cART). For the 333 cases included in the survival analysis, the overall mortality was 15.92% (53/333) during a median 27-month follow-up. The risk factors, including age older than 60 years (HR: 3.18; 95% CI: 1.66–6.10), complication with bacterial pneumonia (HR: 2.64; 95% CI: 1.30–5.35), diagnosis delay (HR: 2.60; 95% CI: 1.42–4.78), CD4+ T cell count less than 50/mm3 (HR: 2.38; 95% CI: 1.27–4.43) and pulmonary atelectasis (HR: 2.20; 95% CI: 1.05–4.60), might independently contribute to poor survival. Among patients without cART before anti-TB treatment, the later initiation of cART (more than 8 weeks after starting anti-TB treatment) was found to increase the mortality rate (OR: 4.33; 95% CI: 1.22–15.36), while the initiation of cART within 4–8 weeks after starting anti-TB treatment was associated with the fewest deaths (0/14).ConclusionsThe subjects in this study conducted in the cART era were still characterized by depressed immunological competence and low rates of cART administration, revealing possible intervention targets for preventing TB reactivation in HIV-infected individuals under current circumstances. Furthermore, our study indicated that the timely diagnosis of PTB, prevention of secondary bacterial pneumonia by prophylactic management and optimization of the timing of cART initiation could have significant impacts on decreasing mortality among HIV/PTB co-infected populations. These findings deserve further prospective investigations to optimize the management of HIV/PTB-co-infected patients.Trial registrationNCT01344148, Registered September 14, 2010.

Streptococcus pneumoniae Modulates Staphylococcus aureus Biofilm Dispersion and the Transition from Colonization to Invasive Disease.

ABSTRACTStreptococcus pneumoniae and Staphylococcus aureus are ubiquitous upper respiratory opportunistic pathogens. Individually, these Gram-positive microbes are two of the most common causative agents of secondary bacterial pneumonia following influenza A virus infection, and they constitute a significant source of morbidity and mortality. Since the introduction of the pneumococcal conjugate vaccine, rates of cocolonization with both of these bacterial species have increased, despite the traditional view that they are antagonistic and mutually exclusive. The interactions between S. pneumoniae and S. aureus in the context of colonization and the transition to invasive disease have not been characterized. In this report, we show that S. pneumoniae and S. aureus form stable dual-species biofilms on epithelial cells in vitro. When these biofilms are exposed to physiological changes associated with viral infection, S. pneumoniae disperses from the biofilm, whereas S. aureus dispersal is inhibited. These findings were supported by results of an in vivo study in which we used a novel mouse cocolonization model. In these experiments, mice cocolonized in the nares with both bacterial species were subsequently infected with influenza A virus. The coinfected mice almost exclusively developed pneumococcal pneumonia. These results indicate that despite our previous report that S. aureus disseminates into the lungs of mice stably colonized with these bacteria following influenza A virus infection, cocolonization with S. pneumoniae in vitro and in vivo inhibits S. aureus dispersal and transition to disease. This study provides novel insight into both the interactions between S. pneumoniae and S. aureus during carriage and the transition from colonization to secondary bacterial pneumonia.

Effect of triazavirine on the outcome of a lethal influenza infection and secondary bacterial pneumonia following influenza in mice

ABSTRACT Pneumonia often occurs as secondary infection post influenza disease and accounts for a large proportion of the morbidity and mortality associated with seasonal and pandemic influenza outbreaks. The antiviral drug triazavirine is licensed in Russia for the treatment and prophylaxis of acute respiratory infections, including influenza A and B viruses. In the present study, we investigated the efficacy of triazavirine in a mouse model of secondary Staphylococcus aureus pneumonia following A/California/04/2009 (H1N1)pdm09 influenza virus infection. We also performed a study of the efficacy of triazavirine against the A/California/04/2009 (H1N1)pdm09 lethal influenza infection in mice. In this model, triazavirine at the dose of 25 mg/kg/day significantly enhanced the survival of animals (60% compared to 20%) and the mean survival time to death, prevented weight loss, and reduced viral titer in the lungs of mice infected with influenza virus. At doses of 50 and 100 mg/kg/day, triazavirine was highly effective in the treatment of the secondary bacterial pneumonia following influenza infection in mice. At these doses, triazavirine protected 67-75% of animals against death, increased the mean survival time to death by twofold, and reduced the virus titer by 2.2-3.0 log10TCID50/ml compared to the mice in the control group. These findings suggest the possible benefit of triazavirine treatment in reducing post influenza pneumonia incidence in humans.

The problem of bacterial complications post respiratory viral infections

ABSTRACT Every person over the course of their lifetime is repeatedly infected by a variety of respiratory viruses that represent risk factors for the development of bacterial complications. The most dangerous among the etiological factors of acute respiratory viral diseases is the influenza A virus. This virus is capable of causing catastrophic pandemics with high mortality mainly due to secondary bacterial pneumonia. As has been shown in numerous recent studies, the main mechanism of provoking bacterial infections irrespective of the type of respiratory virus is the imbalanced response of the antiviral innate immunity – excessive interferon response and uncontrolled inflammation. The probability of severe bacterial complications in the course of acute respiratory viral infections is determined by both the virulence of the virus itself and by the composition of the respiratory microbiota at the time of the viral infection as well as by the genetic characteristics of the organism. The occurrence of severe bacterial complications is also affected by the chronic diseases that have an impact on the regulation of the innate immune response. This review summarizes the current concept of the mechanisms of the development of post viral bacterial complications as well as the potential prevention strategies for these complications.

Проблема бактериальных осложнений при респираторных вирусных инфекциях

Разнообразные респираторные вирусы многократно поражают каждого человека в течение жизни и являются фактором риска развития бактериальных осложнений. Наиболее опасным среди возбудителей острых респираторных вирусных заболеваний является вирус гриппа А, способный вызывать катастрофические пандемии, высокая смертность при которых в значительной степени обусловлена вторичной бактериальной пневмонией. В многочисленных исследованиях последних лет показано, что независимо от типа респираторного вируса основным механизмом провоцирования бактериальных инфекций является несбалансированный ответ системы врожденного противовирусного иммунитета – избыточный интерфероновый ответ и неконтролируемое воспаление. Вероятность тяжелых бактериальных осложнений при острых респираторных вирусных инфекциях определяется как вирулентностью самого вируса, так и составом респираторной микробиоты в момент вирусного заражения, а также генетическими особенностями организма и наличием хронических заболеваний, влияющих на регуляцию системы врожденного иммунного ответа. В данном обзоре суммированы современные представления о механизмах развития бактериальных осложнений, следующих за вирусной инфекцией, и возможностях их предотвращения.