Critical illness from 2009 pandemic influenza A virus and bacterial coinfection in the United States

Diagnosis and treatment of community-acquired pneumonia in adults: 2016 clinical practice guidelines by the Chinese Thoracic Society, Chinese Medical Association

Community‐acquired pneumonia (CAP) in adults is an infectious disease with high morbidity in China and the rest of the world. With the changing pattern in the etiological profile of CAP and advances in medical techniques in diagnosis and treatment over time, Chinese Thoracic Society of Chinese Medical Association updated its CAP guideline in 2016 to address the standard management of CAP in Chinese adults. Extensive and comprehensive literature search was made to collect the data and evidence for experts to review and evaluate the level of evidence. Corresponding recommendations are provided appropriately based on the level of evidence. This updated guideline covers comprehensive topics on CAP, including aetiology, antimicrobial resistance profile, diagnosis, empirical and targeted treatments, adjunctive and supportive therapies, as well as prophylaxis. The recommendations may help clinicians manage CAP patients more effectively and efficiently. CAP in pediatric patients and immunocompromised adults is beyond the scope of this guideline. This guideline is only applicable for the immunocompetent CAP patients aged 18 years and older. The recommendations on selection of antimicrobial agents and the dosing regimens are not mandatory. The clinicians are recommended to prescribe and adjust antimicrobial therapies primarily based on their local etiological profile and results of susceptibility testing, with reference to this guideline.

Hospitalized Patients with Acute Pneumonia

Pneumonia is one of the leading causes of mortality and hospitalization among US adults. The decision to admit patients from the emergency department is a major one because of its impact on patients and the hospital. The diagnosis of pneumonia is often clinical and based on symptoms and signs combined with radiographic findings. There are multiple severity assessments available that can guide treatment, prognosis, and disposition. Viruses are an important cause of pneumonia and require early recognition and treatment. The recommended treatment for community-acquired pneumonia includes a beta lactam plus a macrolide or a respiratory fluoroquinolone.

Influenza

Influenza is an acute viral respiratory disease that affects persons of all ages and is associated with millions of medical visits, hundreds of thousands of hospitalizations, and thousands of deaths during annual winter epidemics of variable severity in the United States. Elderly persons have the highest influenza-associated hospitalization and mortality rates. The primary method of prevention is annual vaccination. Early antiviral treatment has the greatest clinical benefit; otherwise, management includes adherence to recommended infection prevention and control measures as well as supportive care of complications.

Elucidation of Bacterial Pneumonia-Causing Pathogens in Patients with Respiratory Viral Infection

Background

Bacterial pneumonia occurring after respiratory viral infection is common. However, the predominant bacterial species causing pneumonia secondary to respiratory viral infections other than influenza remain unknown. The purpose of this study was to know whether the pathogens causing post-viral bacterial pneumonia vary according to the type of respiratory virus.

Methods

Study subjects were 5,298 patients, who underwent multiplex real-time polymerase chain reaction for simultaneous detection of respiratory viruses, among who visited the emergency department or outpatient clinic with respiratory symptoms at Ulsan University Hospital between April 2013 and March 2016. The patients' medical records were retrospectively reviewed.

Results

A total of 251 clinically significant bacteria were identified in 233 patients with post-viral bacterial pneumonia. Mycoplasma pneumoniae was the most frequent bacterium in patients aged <16 years, regardless of the preceding virus type (p=0.630). In patients aged ≥16 years, the isolated bacteria varied according to the preceding virus type. The major results were as follows (p<0.001): pneumonia in patients with influenza virus (type A/B), rhinovirus, and human metapneumovirus infections was caused by similar bacteria, and the findings indicated that Staphylococcus aureus pneumonia was very common in these patients. In contrast, coronavirus, parainfluenza virus, and respiratory syncytial virus infections were associated with pneumonia caused by gram-negative bacteria.

Conclusion

The pathogens causing post-viral bacterial pneumonia vary according to the type of preceding respiratory virus. This information could help in selecting empirical antibiotics in patients with post-viral pneumonia.

Influenza virus infections among patients attending emergency department according to main reason to presenting to ED: A 3-year prospective observational study during seasonal epidemic periods

OBJECTIVE

The role of influenza virus in patients presenting at ED during seasonal-epidemic periods has not previously been specified. Our objective was to determine its frequency according to clinical presentation.

METHODS

This is a prospective observational study conducted during three-consecutive seasonal Influenza epidemics (2013-2015), including patients presenting i) community-acquired pneumonia (CAP); ii) severe acute symptoms (SAS): respiratory failure (RF), hemodynamic failure (HF), cardiac failure (CF), and miscellaneous symptoms (M); iii) symptoms suggesting influenza (PSSI). Patients were tested for influenza using specific PCR on naso-pharyngeal swabs.

RESULTS

Of 1,239 patients, virological samples were taken from 784 (63.3%), 213 (27.2%) of whom were positive for the influenza virus: CAP 52/177 (29.4%), SAS 115/447 (25.7%) and PSSI 46/160 (28.8%) (p = 0.6). In the SAS group positivity rates were: RF 76/263 (28.9%), HF 5/29 (17.2%), CF 15/68 (22.1%), and M 19/87 (21.8%) (p = 0.3). Among the major diagnostic categories, the influenza virus positivity rates were: asthma 60/231 (26%), acute exacerbation of chronic obstructive pulmonary disease 18/86 (20.9%), HIV 5/21 (23.8%) and cardiac failure 33/131 (25.2%). The positivity of the samples has not been associated (p>0.1) nor the presence of signs of severity or admission rate in medical ward nor intensive care unit.

CONCLUSIONS

Our results indicate that during seasonal influenza epidemics, Influenza virus-positivity rate is similar in patients attending ED for influenza-compatible clinical features, patients with acute symptoms including pneumonia, respiratory, hemodynamic and cardiac distress, and patients presenting for acute decompensation of chronic respiratory and cardiac diseases.

Legionnaire's Disease and Influenza

Legionella pneumophila and influenza types A and B viruses can cause either community-acquired pneumonia with respiratory failure, or Legionella infection could attribute to influenza infection with potentially fatal prognosis. Copathogenesis between pandemic influenza and bacteria is characterized by complex interactions between coinfecting pathogens and the host. Understanding the underlying reason of the emersion of the secondary bacterial infection during an influenza infection is challenging. The dual infection has an impact on viral control and may delay viral clearance. Effective vaccines and antiviral therapy are crucial to increase resistance toward influenza, decrease the prevalence of influenza, and possibly interrupt the potential secondary bacterial infections.

STAT1 Is Required for Suppression of Type 17 Immunity during Influenza and Bacterial Superinfection

Influenza is an annual, global health care concern. Secondary bacterial pneumonia is a severe complication associated with primary influenza virus infection, often resulting in critical morbidity and mortality. Our laboratory has identified influenza-induced suppression of anti-bacterial Type 17 immunity as a mechanism for enhanced susceptibility to bacterial super-infection. We have shown that influenza-induced type I interferon impairs Type 17 activation. STAT1 is a transcription factor involved in interferon signaling, shared by type I, II, and III interferon. In this work, we investigated the role of STAT1 signaling during influenza, methicillin-resistant Staphylococcus aureus (MRSA) super-infection. STAT1-/- mice had increased morbidity and airway inflammation compared to control mice during influenza mono-infection. Despite this worsened anti-viral response, STAT1-/- mice were protected from super-infection bacterial burden and mortality compared to controls. Type 17 immune activation was increased in lymphocytes in STAT1-/- mice during super-infection. The elevation in Type 17 immunity was not related to increased IL-23 production, as type I interferon could inhibit IL-23 expression in a STAT1 independent manner. STAT1-/- antigen presenting cells were inherently biased towards Type 17 polarization compared to control cells. Further, STAT1-/- dendritic cells produced attenuated IL-6 and TNFα upon heat-killed S. aureus stimulation compared to control. Overall, these data indicate that STAT1 signaling plays a detrimental role in influenza, MRSA super-infection by controlling the magnitude of Type 17 immune activation.

Contribution of innate immune cells to pathogenesis of severe influenza virus infection

Influenza A viruses (IAVs) cause respiratory illness of varying severity based on the virus strains, host predisposition and pre-existing immunity. Ultimately, outcome and recovery from infection rely on an effective immune response comprising both innate and adaptive components. The innate immune response provides the first line of defence and is crucial to the outcome of infection. Airway epithelial cells are the first cell type to encounter the virus in the lungs, providing antiviral and chemotactic molecules that shape the ensuing immune response by rapidly recruiting innate effector cells such as NK cells, monocytes and neutrophils. Each cell type has unique mechanisms to combat virus-infected cells and limit viral replication, however their actions may also lead to pathology. This review focuses how innate cells contribute to protection and pathology, and provides evidence for their involvement in immune pathology in IAV infections.

Secondary Bacterial Infections Associated with Influenza Pandemics

Lower and upper respiratory infections are the fourth highest cause of global mortality (Lozano et al., 2012). Epidemic and pandemic outbreaks of respiratory infection are a major medical concern, often causing considerable disease and a high death toll, typically over a relatively short period of time. Influenza is a major cause of epidemic and pandemic infection. Bacterial co/secondary infection further increases morbidity and mortality of influenza infection, with Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus reported as the most common causes. With increased antibiotic resistance and vaccine evasion it is important to monitor the epidemiology of pathogens in circulation to inform clinical treatment and development, particularly in the setting of an influenza epidemic/pandemic.

Higher mortality of severe influenza patients with probable aspergillosis than those with and without other coinfections

BACKGROUND/PURPOSE

Aspergillus-associated infection might comprise up to 23-29% of severe influenza patients from the community throughout stay in an intensive care unit (ICU). In Taiwan, cases of severe influenza with aspergillosis are increasingly reported. Therefore, we describe the relative risk of mortality among severe influenza patients with aspergillosis and other coinfections compared to severe influenza patients without Aspergillus coinfections.

METHODS

We retrospectively reviewed 124 adult patients with severe influenza in a tertiary medical center in southern Taiwan from January 2015 through March 2016. The definition of probable aspergillosis required abnormal radiological findings and positive Aspergillus galactomannan (GM) antigen and/or Aspergillus isolation.

RESULTS

Probable aspergillosis (detected throughout the whole course) and other coinfections (only community-acquired) were diagnosed in 21 (17%) and 38 (31%) of all patients respectively. Klebsiella pneumoniae (36.8%), Pseudomonas aeruginosa (31.6%) and Staphylococcus aureus (31.6%) were the most frequent isolates of other coinfections. In-ICU mortality of Aspergillus group (66.7%) was significantly higher than other coinfections (23.7%, p = 0.001) or control group without coinfections (15.4%, p < 0.001), with significant odds ratios after adjusting for important variables. The factor of GM index ≥0.6 had a 19.82 (95% CI, 4.91 to 80.07, p < 0.0001) odds of expiring in an ICU among the Aspergillus group.

CONCLUSION

Dual Aspergillus and influenza infection is emerging in southern Taiwan. Meanwhile, community-acquired P. aeruginosa should be listed in the common copathogens with severe influenza. The 67% mortality linked to aspergillosis highlights the need for physicians to focus attention on patients with GM ≥ 0.6.

Recognition of Viral RNA by Pattern Recognition Receptors in the Induction of Innate Immunity and Excessive Inflammation During Respiratory Viral Infections

The innate immune system is the first line of defense against virus infection that triggers the expression of type I interferon (IFN) and proinflammatory cytokines. Pattern recognition receptors (PRRs) recognize pathogen-associated molecular patterns, resulting in the induction of innate immune responses. Viral RNA in endosomes is recognized by Toll-like receptors, and cytoplasmic viral RNA is recognized by RIG-I-like receptors. The host innate immune response is critical for protection against virus infection. However, it has been postulated that an excessive inflammatory response in the lung caused by the innate immune response is harmful to the host and is a cause of lethality during influenza A virus infection. Although the deletion of genes encoding PRRs or proinflammatory cytokines does not improve the mortality of mice infected with influenza A virus, a partial block of the innate immune response is successful in decreasing the mortality rate of mice without a loss of protection against virus infection. In addition, morbidity and mortality rates are influenced by other factors. For example, secondary bacterial infection increases the mortality rate in patients with influenza A virus and in animal models of the disease, and environmental factors, such as cigarette smoke and fine particles, also affect the innate immune response. In this review, we summarize recent findings related to the role of PRRs in innate immune response during respiratory viral infection.

Impact of respiratory viruses in hospital-acquired pneumonia in the intensive care unit: A single-center retrospective study

BACKGROUND

Data on the frequency and role of respiratory viruses (RVs) in hospital-acquired pneumonia (HAP) are still scarce.

OBJECTIVES

We assessed the proportion of RVs and their impact on the outcome of hospital-acquired pneumonia (HAP) in the intensive care unit (ICU).

STUDY DESIGN

Cases of HAP were retrospectively selected among patients who underwent screening for RVs by multiplex PCR (mPCR) in the ICU of a French tertiary care hospital from May 2014 to April 2016. ICU length of stay and in-hospital mortality were compared between four groups defined according to the identified pathogens: virus only (V), virus/bacteria (V/B), bacteria only (B) and no pathogen (Neg). When available, previous mPCR was retrieved in order to assess possible chronic viral carriage.

RESULTS

Overall, 95/999 (10%) ICU patients who underwent mPCR had HAP (V(17,18%), V/B(13,14%), B(60,63%), Neg(5,5%)). Median age was 61 years and 45 (47%) were immunocompromised. Influenza (27%) and rhinovirus (27%) were the most common RVs. V/B group had higher mortality rate than B and V groups (62% vs. 40% and 35%, p=0.3) and a significantly longer length of stay (31days (18-48)) than V group (5days (3-11), p=0.0002)) and B group (14.5days (5.5-25.5), p=0.007)). Among the 15 patients with available mPCR tests before viral HAP, seven were negative and eight were positive corresponding to long-term carriage of community-acquired viruses.

DISCUSSION

RVs were detected in 32% of HAP patients who underwent mPCR. Two situations were encountered: (i) acute acquired viral infection; (ii) long-term viral carriage (mostly rhinovirus) especially in immunocompromised patients complicated by a virus/bacteria coinfection. The latter was associated with a longer length of stay and a trend toward a higher mortality.

Postviral Complications: Bacterial Pneumonia

Secondary bacterial pneumonia after viral respiratory infection remains a significant source of morbidity and mortality. Susceptibility is mediated by a variety of viral and bacterial factors, and complex interactions with the host immune system. Prevention and treatment strategies are limited to influenza vaccination and antibiotics/antivirals respectively. Novel approaches to identifying the individuals with influenza who are at increased risk for secondary bacterial pneumonias are urgently needed. Given the threat of further pandemics and the heightened prevalence of these viruses, more research into the immunologic mechanisms of this disease is warranted with the hope of discovering new potential therapies.

Impact of viral multiplex real-time PCR on management of respiratory tract infection: a retrospective cohort study

Background

Significance and clinical utility of multiple virus detection by multiplex real-time polymerase chain reaction (rtPCR) in respiratory tract infection remain unclear.

Methods

This retrospective cohort study analyzed how virus detection affected clinical management. During a 27-month period, clinical and laboratory information was collected from all children and adults in two Swiss tertiary centres whose respiratory samples were tested for respiratory viruses with a 16-plex rtPCR test.

Results

Pathogens were identified in 140 of 254 patients (55%); of those patients, there was ≥1 virus in 91 (65%), ≥ 1 bacterium in 53 (38%), and ≥1 virus and bacterium in 11 (8%). Of 80 patients with viral infection, 59 (74%) received antibiotics. Virus detection was associated with discontinuation of antibiotics in 2 of 20 adults (10%) and 6 of 14 children (43%). Overall 12 adults (34%) and 18 children (67%) were managed correctly without antibiotics after virus detection (p = 0.01). When taking biomarkers, radiologic presentations, and antibiotic pre-treatment into account, the impact of rtPCR and appropriateness of therapy for clinically viral infections increased to 100% in children and 62% in adults.

Conclusions

A substantial reduction of unnecessary antibiotic prescriptions seems possible. Appropriate application of rtPCR results in respiratory tract infections should be encouraged.

Impact of Type I and III Interferons on Respiratory Superinfections Due to Multidrug-Resistant Pathogens

The increased morbidity and mortality associated with bacterial pneumonias that are acquired following influenza infection are well appreciated by clinicians. One of the major components of the immune response to influenza is the induction of the types I and III interferon cascades, which encompasses the activation of over 300 genes. The immunological consequences of IFN activation, while important for viral clearance, modify the host proinflammatory responses through effects on the inflammasome, Th17 signaling and recruitment of phagocytic cells. IFN signaling affects both susceptibility to subsequent Streptococcus pneumoniae and Staphylococcus aureus infection as well as the intensity of the immune responses associated with pulmonary damage. Appreciation for the effects of IFN activation on anti-bacterial pulmonary defense mechanisms should help to inform therapeutic strategies in an ICU setting.

Potentiation and tolerance of toll-like receptor priming in human endothelial cells

Repeated challenge of lipopolysaccharide (LPS) alters the response to subsequent LPS exposures via modulation of toll-like receptor 4 (TLR4). Whether activation of other TLRs can modulate TLR4 responses, and vice versa, remains unclear. Specifically with regards to endothelial cells, a key component of innate immunity, the impact of TLR cross-modulation is unknown. We postulated that TLR2 priming (via Pam3Csk4) would inhibit TLR4-mediated responses while TLR3 priming (via Poly I:C) would enhance subsequent TLR4-inflammatory signaling. We studied human umbilical vein endothelial cells (HUVECs) and neonatal human dermal microvascular endothelial cells (HMVECs). Cells were primed with a combination of Poly I:C (10 μg/ml), Pam3Csk4 (10 μg/ml), or LPS (100 ng/ml), then washed and allowed to rest. They were then rechallenged with either Poly I:C, Pam3Csk4 or LPS. Endothelial cells showed significant tolerance to repeated LPS challenge. Priming with Pam3Csk4 also reduced the response to secondary LPS challenge in both cell types, despite a reduced proinflammatory response to Pam3Csk4 in HMVECs compared to HUVECs. Poly I:C priming enhanced inflammatory and interferon producing signals upon Poly I:C or LPS rechallenge, respectively. Poly I:C priming induced interferon regulatory factor 7, leading to enhancement of interferon production. Finally, both Poly I:C and LPS priming induced significant changes in receptor-interacting serine/threonine-protein kinase 1 activity. Pharmacological inhibition of receptor-interacting serine/threonine-protein kinase 1 or interferon regulatory factor 7 reduced the potentiated phenotype of TLR3 priming on TLR4 rechallenge. These results demonstrate that in human endothelial cells, prior activation of TLRs can have a significant impact on subsequent exposures and may contribute to the severity of the host response.

The pharmacological management of severe influenza infection - 'existing and emerging therapies'

INTRODUCTION

Over the last century several influenza outbreaks have traversed the globe, most recently the influenza A(H1N1) 2009 pandemic. On each occasion, a highly contagious, virulent pathogen has emerged, leading to significant morbidity and mortality amongst those affected. Areas covered: Early antiviral therapy and supportive care is the mainstay of treatment. Treatment should be started as soon as possible and not delayed for the results of diagnostic testing. Whilst oseltamivir is still the first choice, in case of treatment failure, oseltamivir resistance should be considered, particularly in immunosuppressed patients. Here we review the antivirals currently used for management of influenza and explore a number of investigational agents that may emerge as effective antivirals including parenteral agents, combination antiviral therapy and novel agents in order to adequately target influenza virulence. Expert Commentary: New tools for rapid diagnosis and susceptible strains will help if a patient is not improving because of a resistant strain or an inadequate immune response. Further randomized control trials will be conducted to investigate the use of new antivirals and co-adjuvant therapies that will help to elucidate the process of immune modulation, particularly in immunocompetent patients.

Microbial Etiology of Community-Acquired Pneumonia Among Infants and Children Admitted to the Pediatric Hospital, Ain Shams University

BACKGROUND

While recognizing the etiology of community-acquired pneumonia is necessary for formulating local antimicrobial guidelines, limited data is published about this etiology in Egyptian pediatric patients.

OBJECTIVES

To determine the frequency of bacterial and viral pathogens causing community-acquired pneumonia (CAP) among immunocompetent Egyptian infants and preschool children.

METHODS

Ninety infants and preschool-age children admitted to our hospital with CAP were prospectively included in the study. Etiological agents were identified using conventional bacteriological identification methods and IgM antibodies detection against common atypical respiratory bacteria and viruses.

RESULTS

An etiology was identified in 59 patients (65.5%). Bacterial pathogens were detected in 43 (47.8%) of the cases while viral pathogens were detected in 23 (25.5%). Coinfection with more than one etiologic agent was evident in seven patients (7.8%). The most common typical bacterial cause of pneumonia was Staphylococcus aureus (n = 12, 13.3%), followed by Streptococcus pneumoniae and Klebsiella pneumoniae (n = 7, 7.8%, each). The commonest atypical bacterium was Mycoplasma pneumoniae (n = 10, 11.1%), whereas the commonest viral etiology was influenza viruses (n = 11, 12.2%).

CONCLUSION

Although we could not determine the causative agent in some studied cases, this study provides preliminary data regarding the spectrum and frequency of microorganisms causing CAP in Egyptian infants and preschool children.

Host Physiologic Changes Induced by Influenza A Virus Lead to Staphylococcus aureus Biofilm Dispersion and Transition from Asymptomatic Colonization to Invasive Disease

Staphylococcus aureus is a ubiquitous opportunistic human pathogen and a major health concern worldwide, causing a wide variety of diseases from mild skin infections to systemic disease. S. aureus is a major source of severe secondary bacterial pneumonia after influenza A virus infection, which causes widespread morbidity and mortality. While the phenomenon of secondary bacterial pneumonia is well established, the mechanisms behind the transition from asymptomatic colonization to invasive staphylococcal disease following viral infection remains unknown. In this report, we have shown that S. aureus biofilms, grown on an upper respiratory epithelial substratum, disperse in response to host physiologic changes related to viral infection, such as febrile range temperatures, exogenous ATP, norepinephrine, and increased glucose. Mice that were colonized with S. aureus and subsequently exposed to these physiologic stimuli or influenza A virus coinfection developed pronounced pneumonia. This study provides novel insight into the transition from colonization to invasive disease, providing a better understanding of the events involved in the pathogenesis of secondary staphylococcal pneumonia.

In this study, we have determined that host physiologic changes related to influenza A virus infection causes S. aureus to disperse from a biofilm state. Additionally, we report that these same host physiologic changes promote S. aureus dissemination from the nasal tissue to the lungs in an animal model. Furthermore, this study identifies important aspects involved in the transition of S. aureus from asymptomatic colonization to pneumonia.

Global Variability in Reported Mortality for Critical Illness during the 2009-10 Influenza A(H1N1) Pandemic: A Systematic Review and Meta-Regression to Guide Reporting of Outcomes during Disease Outbreaks

Purpose

To determine how patient, healthcare system and study-specific factors influence reported mortality associated with critical illness during the 2009–2010 Influenza A (H1N1) pandemic.

Methods

Systematic review with meta-regression of studies reporting on mortality associated with critical illness during the 2009–2010 Influenza A (H1N1) pandemic.

Data Sources

Medline, Embase, LiLACs and African Index Medicus to June 2009-March 2016.

Results

226 studies from 50 countries met our inclusion criteria. Mortality associated with H1N1-related critical illness was 31% (95% CI 28–34). Reported mortality was highest in South Asia (61% [95% CI 50–71]) and Sub-Saharan Africa (53% [95% CI 29–75]), in comparison to Western Europe (25% [95% CI 22–30]), North America (25% [95% CI 22–27]) and Australia (15% [95% CI 13–18]) (P<0.0001). High income economies had significantly lower reported mortality compared to upper middle income economies and lower middle income economies respectively (P<0.0001). Mortality for the first wave was non-significantly higher than wave two (P = 0.66). There was substantial variability in reported mortality among the specific subgroups of patients: unselected critically ill adults (27% [95% CI 24–30]), acute respiratory distress syndrome (37% [95% CI 32–44]), acute kidney injury (44% [95% CI 26–64]), and critically ill pregnant patients (10% [95% CI 5–19]).

Conclusion

Reported mortality for outbreaks and pandemics may vary substantially depending upon selected patient characteristics, the number of patients described, and the region and economic status of the outbreak location. Outcomes from a relatively small number of patients from specific regions may lead to biased estimates of outcomes on a global scale.

Novel pandemic influenza A (H1N1) and community-associated methicillin-resistant Staphylococcus aureus pneumonia

Postinfluenza bacterial pneumonia is a leading cause of influenza-associated death, and Staphylococcus aureus and Streptococcus pneumoniae have been important pathogens that have caused pneumonia since the influenza pandemic in 1919. Emergence of novel influenza A (H1N1) pdm09 and the concomitant global spread of community-associated methicillin-resistant S. aureus (CA-MRSA) have led to increasing prevalence of CA-MRSA pneumonia following influenza infection. Such an epidemiologic change poses a therapeutic challenge due to a high risk of inappropriate empiric antimicrobial therapy and poor clinical outcomes. Early diagnosis and initiation of appropriate antimicrobial therapy for post-influenza bacterial pneumonia have become even more important in the era of CA-MRSA. Therefore, novel molecular diagnostic techniques should be applied to more readily diagnose MRSA pneumonia.

Influenza A and methicillin-resistant Staphylococcus aureus co-infection in rhesus macaques - A model of severe pneumonia

BACKGROUND

Influenza results in up to 500,000 deaths annually. Seasonal influenza vaccines have an estimated 60% effectiveness, but provide little or no protection against novel subtypes, and may be less protective in high-risk groups. Neuraminidase inhibitors are recommended for the treatment of severe influenza infection, but are not proven to reduce mortality in severe disease. Preclinical models of severe influenza infection that closely correlate to human disease are needed to assess efficacy of new vaccines and therapeutics.

METHODS

We developed a nonhuman primate model of influenza and bacterial co-infection that recapitulates severe pneumonia in humans. Animals were infected with influenza A virus via intra-bronchial or small-particle aerosol inoculation, methicillin-resistant Staphylococcus aureus, or co-infected with influenza and methicillin-resistant S. aureus combined. We assessed the severity of disease in animals over the course of our study using tools available to evaluate critically ill human patients including high-resolution computed tomography imaging of the lungs, arterial blood gas analyses, and bronchoalveolar lavage.

RESULTS

Using an intra-bronchial route of inoculation we successfully induced severe pneumonia following influenza infection alone and following influenza and bacterial co-infection. Peak illness was observed at day 6 post-influenza infection, manifested by bilateral pulmonary infiltrates and hypoxemia. The timing of radiographic and physiologic manifestations of disease in our model closely match those observed in severe human influenza infection.

DISCUSSION

This was the first nonhuman primate study of influenza and bacterial co-infection where high-resolution computed tomography scanning of the lungs was used to quantitatively assess pneumonia over the course of illness and where hypoxemia was correlated with pneumonia severity. With additional validation this model may serve as a pathway for regulatory approval of vaccines and therapeutics for the prevention and treatment of severe influenza pneumonia.

Bacterial and viral co-infections complicating severe influenza: Incidence and impact among 507 U.S. patients, 2013-14

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22.5% of adult patients with H1N1 developed bacterial co-infection.

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Staphylococcus aureus was the most common cause of co-infection.

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Bacterial and viral co-infections were associated with death in bivariate.

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Patients with a bacterial co-infection had greater use of resources.

Background

Influenza acts synergistically with bacterial co-pathogens. Few studies have described co-infection in a large cohort with severe influenza infection.

Objectives

To describe the spectrum and clinical impact of co-infections.

Study design

Retrospective cohort study of patients with severe influenza infection from September 2013 through April 2014 in intensive care units at 33 U.S. hospitals comparing characteristics of cases with and without co-infection in bivariable and multivariable analysis.

Results

Of 507 adult and pediatric patients, 114 (22.5%) developed bacterial co-infection and 23 (4.5%) developed viral co-infection. Staphylococcus aureus was the most common cause of co-infection, isolated in 47 (9.3%) patients. Characteristics independently associated with the development of bacterial co-infection of adult patients in a logistic regression model included the absence of cardiovascular disease (OR 0.41 [0.23–0.73], p = 0.003), leukocytosis (>11 K/μl, OR 3.7 [2.2–6.2], p < 0.001; reference: normal WBC 3.5–11 K/μl) at ICU admission and a higher ICU admission SOFA score (for each increase by 1 in SOFA score, OR 1.1 [1.0–1.2], p = 0.001). Bacterial co-infections (OR 2.2 [1.4–3.6], p = 0.001) and viral co-infections (OR 3.1 [1.3–7.4], p = 0.010) were both associated with death in bivariable analysis. Patients with a bacterial co-infection had a longer hospital stay, a longer ICU stay and were likely to have had a greater delay in the initiation of antiviral administration than patients without co-infection (p < 0.05) in bivariable analysis.

Conclusions

Bacterial co-infections were common, resulted in delay of antiviral therapy and were associated with increased resource allocation and higher mortality.

Relationship Between Upper Respiratory Tract Influenza Test Result and Clinical Outcomes Among Critically Ill Influenza Patients

Among critically ill patients with lower respiratory tract (LRT)-confirmed influenza, we retrospectively observed worse 28-day clinical outcomes in upper respiratory tract (URT)-negative versus URT-positive subjects. This finding may reflect disease progression and highlights the need for influenza testing of both URT and LRT specimens to improve diagnostic yield and possibly inform prognosis.

Development of a Core Clinical Dataset to Characterize Serious Illness, Injuries, and Resource Requirements for Acute Medical Responses to Public Health Emergencies

OBJECTIVES

In developed countries, public health systems have become adept at rapidly identifying the etiology and impact of public health emergencies. However, within the time course of clinical responses, shortfalls in readily analyzable patient-level data limit capabilities to understand clinical course, predict outcomes, ensure resource availability, and evaluate the effectiveness of diagnostic and therapeutic strategies for seriously ill and injured patients. To be useful in the timeline of a public health emergency, multi-institutional clinical investigation systems must be in place to rapidly collect, analyze, and disseminate detailed clinical information regarding patients across prehospital, emergency department, and acute care hospital settings, including ICUs. As an initial step to near real-time clinical learning during public health emergencies, we sought to develop an "all-hazards" core dataset to characterize serious illness and injuries and the resource requirements for acute medical response across the care continuum.

SUBJECTS

A multidisciplinary panel of clinicians, public health professionals, and researchers with expertise in public health emergencies.

DESIGN

Group consensus process.

INTERVENTIONS

The consensus process included regularly scheduled conference calls, electronic communications, and an in-person meeting to generate candidate variables. Candidate variables were then reviewed by the group to meet the competing criteria of utility and feasibility resulting in the core dataset.

MEASUREMENTS AND MAIN RESULTS

The 40-member panel generated 215 candidate variables for potential dataset inclusion. The final dataset includes 140 patient-level variables in the domains of demographics and anthropometrics (7), prehospital (11), emergency department (13), diagnosis (8), severity of illness (54), medications and interventions (38), and outcomes (9).

CONCLUSIONS

The resulting all-hazard core dataset for seriously ill and injured persons provides a foundation to facilitate rapid collection, analyses, and dissemination of information necessary for clinicians, public health officials, and policymakers to optimize public health emergency response. Further work is needed to validate the effectiveness of the dataset in a variety of emergency settings.

The administration of intranasal live attenuated influenza vaccine induces changes in the nasal microbiota and nasal epithelium gene expression profiles

BACKGROUND

Viral infections such as influenza have been shown to predispose hosts to increased colonization of the respiratory tract by pathogenic bacteria and secondary bacterial pneumonia. To examine how viral infections and host antiviral immune responses alter the upper respiratory microbiota, we analyzed nasal bacterial composition by 16S ribosomal RNA (rRNA) gene sequencing in healthy adults at baseline and at 1 to 2 weeks and 4 to 6 weeks following instillation of live attenuated influenza vaccine or intranasal sterile saline. A subset of these samples was submitted for microarray host gene expression profiling.

RESULTS

We found that live attenuated influenza vaccination led to significant changes in microbial community structure, diversity, and core taxonomic membership as well as increases in the relative abundances of Staphylococcus and Bacteroides genera (both p < 0.05). Hypergeometric testing for the enrichment of gene ontology terms in the vaccinated group reflected a robust up-regulation of type I and type II interferon-stimulated genes in the vaccinated group relative to controls. Translational murine studies showed that poly I:C administration did in fact permit greater nasal Staphylococcus aureus persistence, a response absent in interferon alpha/beta receptor deficient mice.

CONCLUSIONS

Collectively, our findings demonstrate that although the human nasal bacterial community is heterogeneous and typically individually robust, activation of a type I interferon (IFN)-mediated antiviral response may foster the disproportionate emergence of potentially pathogenic species such as S. aureus.

TRIAL REGISTRATION

This study was registered with Clinicaltrials.gov on 11/3/15, NCT02597647 .

Epidemiology, Co-Infections, and Outcomes of Viral Pneumonia in Adults: An Observational Cohort Study

Advanced technologies using polymerase-chain reaction have allowed for increased recognition of viral respiratory infections including pneumonia. Co-infections have been described for several respiratory viruses, especially with influenza. Outcomes of viral pneumonia, including cases with co-infections, have not been well described. This was observational cohort study conducted to describe hospitalized patients with viral pneumonia including co-infections, clinical outcomes, and predictors of mortality. Patients admitted from March 2013 to November 2014 with a positive respiratory virus panel (RVP) and radiographic findings of pneumonia within 48  h of the index RVP were included. Co-respiratory infection (CRI) was defined as any organism identification from a respiratory specimen within 3 days of the index RVP. Predictors of in-hospital mortality on univariate analysis were evaluated in a multivariate model. Of 284 patients with viral pneumonia, a majority (51.8%) were immunocompromised. A total of 84 patients (29.6%) were found to have a CRI with 48 (57.6%) having a bacterial CRI. Viral CRI with HSV, CMV, or both occurred in 28 patients (33.3%). Fungal (16.7%) and other CRIs (7.1%) were less common. Many patients required mechanical ventilation (54%) and vasopressor support (36%). Overall in-hospital mortality was high (23.2%) and readmissions were common with several patients re-hospitalized within 30 (21.1%) and 90 days (36.7%) of discharge. Predictors of in-hospital mortality on multivariate regression included severity of illness factors, stem-cell transplant, and identification of multiple respiratory viruses. In conclusion, hospital mortality is high among adult patients with viral pneumonia and patients with multiple respiratory viruses identified may be at a higher risk.

Impact of antibacterials on subsequent resistance and clinical outcomes in adult patients with viral pneumonia: an opportunity for stewardship

Introduction

Respiratory viruses are increasingly recognized as significant etiologies of pneumonia among hospitalized patients. Advanced technologies using multiplex molecular assays and polymerase-chain reaction increase the ability to identify viral pathogens and may ultimately impact antibacterial use.

Method

This was a single-center retrospective cohort study to evaluate the impact of antibacterials in viral pneumonia on clinical outcomes and subsequent multidrug-resistant organism (MDRO) infections/colonization. Patients admitted from March 2013 to November 2014 with positive respiratory viral panels (RVP) and radiographic findings of pneumonia were included. Patients transferred from an outside hospital or not still hospitalized 72 hours after the RVP report date were excluded. Patients were categorized based on exposure to systemic antibacterials: less than 3 days representing short-course therapy and 3 to 10 days being long-course therapy.

Results

A total of 174 patients (long-course, n = 67; short-course, n = 28; mixed bacterial-viral infection, n = 79) were included with most being immunocompromised (56.3 %) with active malignancy the primary etiology (69.4 %). Rhinovirus/Enterovirus (23 %), Influenza (19 %), and Parainfluenza (15.5 %) were the viruses most commonly identified. A total of 13 different systemic antibacterials were used as empiric therapy in the 95 patients with pure viral infection for a total of 466 days-of-therapy. Vancomycin (50.7 %), cefepime (40.3 %), azithromycin (40.3 %), meropenem (23.9 %), and linezolid (20.9 %) were most frequently used. In-hospital mortality did not differ between patients with viral pneumonia in the short-course and long-course groups. Subsequent infection/colonization with a MDRO was more frequent in the long-course group compared to the short-course group (53.2 vs 21.1 %; P = 0.027).

Conclusion

This study found that long-course antibacterial use in the setting of viral pneumonia had no impact on clinical outcomes but increased the incidence of subsequent MDRO infection/colonization.

Bacterial coinfection is associated with severity of avian influenza A (H7N9), and procalcitonin is a useful marker for early diagnosis

Patients contracting avian influenza A (H7N9) often develop severe disease. However, information on the contribution of bacterial coinfection to the severity of H7N9 is limited. We retrospectively studied 83 patients with confirmed H7N9 infection from April 2013 to February 2014. The severity of patients with bacterial coinfection and markers for early diagnosis of bacterial coinfection in H7N9 were analyzed. We found Staphylococcus aureus was the most prevalent pathogen. Higher Acute Physiology and Chronic Health Evaluation II score, shock, renal replacement treatment, mechanical ventilation, and extracorporeal membrane oxygenation treatment were more frequently observed in patients with bacterial coinfection. Procalcitonin is more sensitive than C-reactive protein in determining bacterial coinfection in H7N9 patients. In conclusion, H7N9 infection patients with bacterial coinfection had a more severe condition. Elevated procalcitonin is an accurate marker for diagnosing bacterial coinfection in H7N9 patients, thus enabling earlier antibiotic therapy.

Polymicrobial community-acquired pneumonia: An emerging entity

Polymicrobial aetiology in community-acquired pneumonia (CAP) is more common than previously recognized. This growing new entity can influence inflammation, host immunity and disease outcomes in CAP patients. However, the true incidence is complicated to determine and probably underestimated due mainly to many cases going undetected, particularly in the outpatient setting, as the diagnostic yield is restricted by the sensitivity of currently available microbiologic tests and the ability to get certain types of clinical specimens. The observed rate of polymicrobial cases may also lead to new antibiotic therapy considerations. In this review, we discuss the pathogenesis, microbial interactions in pneumonia, epidemiology, biomarkers and antibiotic therapy for polymicrobial CAP.

Nonsteroidal Anti-Inflammatory Drug and Aspirin Use, and Mortality among Critically Ill Pandemic H1N1 Influenza Patients: an Exploratory Analysis

We explored nonsteroidal anti-inflammatory drug (NSAID) and aspirin (ASA) use and mortality in the U.S. Department of Health and Human Services' registry of 683 adult and 838 pediatric critically ill pandemic 2009 H1N1 influenza (pH1N1) patients. Among adults, 88 (12.9%) and 101 (14.8%) reported pre-admission use of an NSAID and ASA, respectively; mortality was similar (23-24%) regardless of NSAID or ASA use. Mortality among 89 pediatric NSAID users and 749 nonusers did not differ significantly (10.1% and 8.8%, respectively). One of 16 pediatric ASA users died. Among pediatric patients, the adjusted relative risk estimate for NSAID use and 90-day mortality was higher when influenza vaccination was included in the model (risk ratio [RR] = 1.5; 95% confidence interval, 0.7-3.2), although not statistically significant. Among adults, RR estimates did not change appreciably after adjusting for age, sex, health status, or vaccine status. We found no compelling evidence that NSAID or ASA use influenced mortality in severe pH1N1.

Influenza and Bacterial Superinfection: Illuminating the Immunologic Mechanisms of Disease

Seasonal influenza virus infection presents a major strain on the health care system. Influenza virus infection has pandemic potential, which was repeatedly observed during the last century. Severe disease may occur in the young, in the elderly, in those with preexisting lung disease, and in previously healthy individuals. A common cause of severe influenza pathogenesis is superinfection with bacterial pathogens, namely, Staphylococcus aureus and Streptococcus pneumoniae. A great deal of recent research has focused on the immune pathways involved in influenza-induced susceptibility to secondary bacterial pneumonia. Both innate and adaptive antibacterial host defenses are impaired in the context of preceding influenza virus infection. The goal of this minireview is to highlight these findings and synthesize these data into a shared central theme of pathogenesis.

Influenza infection in the intensive care unit: Four years after the 2009 pandemic

The role of influenza viruses in severe acute respiratory infection (SARI) in Intensive Care Units (ICU) remains unknown. The post-pandemic influenza A(H1N1)pdm09 period, in particular, has been poorly studied.

OBJECTIVE

To identify influenza SARI patients in ICU, to assess the usefulness of the symptoms of influenza-like illness (ILI), and to compare the features of pandemic vs. post-pandemic influenza A(H1N1) pdm09 infection.

METHODS

A prospective observational study with SARI patients admitted to ICU during the first three post-pandemic seasons. Patient demographics, characteristics and outcomes were recorded. An influenza epidemic period (IEP) was defined as >100 cases/100,000 inhabitants per week.

RESULTS

One hundred sixty-three patients were diagnosed with SARI. ILI was present in 65 (39.9%) patients. Influenza infection was documented in 41 patients, 27 (41.5%) ILI patients, and 14 (14.3%) non-ILI patients, 27 of them during an IEP. Influenza A viruses were mainly responsible. Only five patients had influenza B virus infection, which were non-ILI during an IEP. SARI overall mortality was 22.1%, and 15% in influenza infection patients. Pandemic and post-pandemic influenza infection patients shared similar clinical features.

CONCLUSIONS

During influenza epidemic periods, influenza infection screening should be considered in all SARI patients. Influenza SARI was mainly caused by subtype A(H1N1)pdm09 and A(H3N2) in post-pandemic seasons, and no differences were observed in ILI and mortality rate compared with a pandemic season.

Plasma gelsolin improves lung host defense against pneumonia by enhancing macrophage NOS3 function

Plasma gelsolin (pGSN) functions as part of the "extracellular actin-scavenging system," but its potential to improve host defense against infection has not been studied. In a mouse model of primary pneumococcal pneumonia, recombinant human pGSN (rhu-pGSN) caused enhanced bacterial clearance, reduced acute inflammation, and improved survival. In vitro, rhu-pGSN rapidly improved lung macrophage uptake and killing of bacteria (Streptococcus pneumoniae, Escherichia coli, and Francisella tularensis). pGSN triggers activating phosphorylation (Ser(1177)) of macrophage nitric oxide synthase type III (NOS3), an enzyme with important bactericidal functions in lung macrophages. rhu-pGSN failed to enhance bacterial killing by NOS3(-/-) macrophages in vitro or bacterial clearance in NOS3(-/-) mice in vivo. Prophylaxis with immunomodulators may be especially relevant for patients at risk for secondary bacterial pneumonia, e.g., after influenza. Treatment of mice with pGSN challenged with pneumococci on postinfluenza day 7 (the peak of enhanced susceptibility to secondary infection) caused a ∼15-fold improvement in bacterial clearance, reduced acute neutrophilic inflammation, and markedly improved survival, even without antibiotic therapy. pGSN is a potential immunomodulator for improving lung host defense against primary and secondary bacterial pneumonia.

The immunology of influenza virus-associated bacterial pneumonia

Infection with influenza virus has been a significant cause of morbidity and mortality for more than a hundred years. Severe disease and increased mortality often results from bacterial super-infection of patients with influenza virus infection. Preceding influenza infection alters the host's innate and adaptive immune responses, allowing increased susceptibility to secondary bacterial pneumonia. Recent advances in the field have helped to define how influenza alters the immune response to bacteria through the dysregulation of phagocytes, antimicrobial peptides, and lymphocytes. Viral-induced interferons play a key role in altering the phenotype of the immune response. Potential genetic modifiers of disease will help to define additional immunologic mechanisms that predispose to viral, bacterial super-infection with the overarching goal of developing effective therapeutic strategies to prevent and treat disease.

Community-acquired pneumonia

PURPOSE OF REVIEW

This review examines the epidemiology, diagnosis, prognosis, treatment and prevention of community-acquired pneumonia (CAP) in adults.

RECENT FINDINGS

CAP is a significant cause of morbidity and mortality. Streptococcus pneumoniae is the most common CAP pathogen; however, microbial cause varies by geographic location and host factors. Identification of a microbial cause in CAP remains challenging - 30-65% of cases do not have a pathogen isolated. The use of molecular techniques in addition to culture, serology and urinary antigen testing has improved diagnostic yield. Scoring systems are useful for CAP prognostication and site of care decisions. Studies evaluating novel biomarkers including pro-B-type natriuretic peptide and procalcitonin suggest potential adjunctive roles in CAP prognosis. Guideline-based treatment for CAP has changed little in recent years. Effective and timely antimicrobial therapy is crucial in optimizing outcomes and should be based on local antimicrobial susceptibility patterns. Macrolides may have additional anti-inflammatory properties and a mortality benefit in severe CAP. Preventive strategies include immunization and modification of specific patient risk factors.

SUMMARY

CAP is common and causes considerable morbidity and mortality. A comprehensive approach including advanced diagnostic testing, effective and timely antimicrobial therapy and prevention is required to optimize CAP outcomes.

Clinical characteristics and outcomes of severe rhinovirus-associated pneumonia identified by bronchoscopic bronchoalveolar lavage in adults: comparison with severe influenza virus-associated pneumonia

BACKGROUND

Rhinoviruses (RVs) may cause pneumonia, but the characteristics of RV-associated pneumonia have not been adequately evaluated.

OBJECTIVE

We aimed to compare characteristics, complications, and outcomes between severe RV- and influenza virus (IFV)-associated pneumonia in adults.

STUDY DESIGN

We used prospective cohort data of adult patients with severe pneumonia who had been admitted to the medical intensive care unit of a tertiary care hospital over a 4-year period. The clinical features and outcomes of 27 patients with RV-positive bronchoscopic bronchoalveolar lavage (BAL) fluid were compared to those of 51 pneumonia patients with IFV-positive BAL fluid or IFV-positive nasopharyngeal specimens.

RESULTS

Of 356 patients who underwent bronchoscopic BAL and respiratory virus polymerase chain reaction (PCR), RV was the most commonly identified virus (8.1%) from BAL fluid. Patients with RV-associated pneumonia were more likely to be immunocompromised than patients with IFV-associated pneumonia (81.5% vs. 33.3%, p<0.001). Bacterial coinfection tended to be less common in the RV group (18.5% vs. 37.3%, p=0.09). Although septic shock was less common in the RV group (29.6% vs. 54.9%, p=0.03), other clinical manifestations, laboratory findings, and radiologic patterns were similar between the groups. The 28-day mortality of patients with severe RV- and IFV-associated pneumonia was similarly high (29.6% vs. 35.3% respectively, p=0.61).

CONCLUSIONS

Severe RV-associated pneumonia patients were more likely to be immunocompromised and less likely to present septic shock. Overall clinical features were similar and mortalities of both groups were comparably high. Studies of larger cohorts encompassing mild to moderate pneumonia patients are needed.

The burden of influenza-associated critical illness hospitalizations

OBJECTIVE

Influenza is the most common vaccine-preventable disease in the United States; however, little is known about the burden of critical illness due to influenza virus infection. Our primary objective was to estimate the proportion of all critical illness hospitalizations that are attributable to seasonal influenza.

DESIGN

Retrospective cohort study.

SETTING

Arizona, California, and Washington from January 2003 to March 2009.

PATIENTS

All adults hospitalized with critical illness, defined by International Classification of Diseases, 9th Edition, Clinical Modification diagnosis and procedure codes for acute respiratory failure, severe sepsis, or in-hospital death.

MEASUREMENTS AND MAIN RESULTS

We combined the complete hospitalization discharge databases for three U.S. states, regional influenza virus surveillance, and state census data. Using negative binomial regression models, we estimated the incidence rates of adult influenza-associated critical illness hospitalizations and compared them with all-cause event rates. We also compared modeled outcomes to International Classification of Diseases, 9th Edition, Clinical Modification-coded influenza hospitalizations to assess potential underrecognition of severe influenza disease. During the study period, we estimated that 26,760 influenza-associated critical illness hospitalizations (95% CI, 14,541, 47,464) occurred. The population-based incidence estimate for influenza-associated critical illness was 12.0 per 100,000 person-years (95% CI, 6.6, 21.6) or 1.3% of all critical illness hospitalizations (95% CI, 0.7%, 2.3%). During the influenza season, 3.4% of all critical illness hospitalizations (95% CI, 1.9%, 5.8%) were attributable to influenza. There were only 2,612 critical illness hospitalizations with International Classification of Diseases, 9th Edition, Clinical Modification-coded influenza diagnoses, suggesting influenza is either undiagnosed or undercoded in a substantial proportion of critical illness.

CONCLUSIONS

Extrapolating our data to the 2010 U.S. population, we estimate that about 28,000 adults are hospitalized for influenza-associated critical illness annually. Influenza in many of these critically ill patients may be undiagnosed. Critical care physicians should have a high index of suspicion for influenza in the ICU, particularly when influenza is known to be circulating in their communities.

Global burden of influenza as a cause of cardiopulmonary morbidity and mortality

Severe acute respiratory infections, including influenza, are a leading cause of cardiopulmonary morbidity and mortality worldwide. Until recently, the epidemiology of influenza was limited to resource-rich countries. Emerging epidemiological reports characterizing the 2009 H1N1 pandemic, however, suggest that influenza exerts an even greater toll in low-income, resource-constrained environments where it is the cause of 5% to 27% of all severe acute respiratory infections. The increased burden of disease in this setting is multifactorial and likely is the result of higher rates of comorbidities such as human immunodeficiency virus, decreased access to health care, including vaccinations and antiviral medications, and limited healthcare infrastructure, including oxygen therapy or critical care support. Improved global epidemiology of influenza is desperately needed to guide allocation of life-saving resources, including vaccines, antiviral medications, and direct the improvement of basic health care to mitigate the impact of influenza infection on the most vulnerable populations.

Recent advances in our understanding of Streptococcus pneumoniae infection

A number of significant challenges remain with regard to the diagnosis, treatment, and prevention of infections with Streptococcus pneumoniae (pneumococcus), which remains the most common bacterial cause of community-acquired pneumonia. Although this infection is documented to be extremely common in younger children and in older adults, the burden of pneumonia it causes is considerably underestimated, since the incidence statistics are derived largely from bacteremic infections, because they are easy to document, and yet the greater burden of pneumococcal pneumonias is non-invasive. It has been estimated that for every bacteremic pneumonia that is documented, three non-bacteremic infections occur. Management of these infections is potentially complicated by the increasing resistance of the isolates to the commonly used antibiotics. Furthermore, it is well recognized that despite advances in medical care, the mortality of bacteremic pneumococcal pneumonia has remained largely unchanged over the past 50 years and averages approximately 12%. Much recent research interest in the field of pneumococcal infections has focused on important virulence factors of the organism, on improved diagnostic and prognostication tools, on defining risk factors for death, on optimal treatment strategies involving both antibiotics and adjunctive therapies, and on disease prevention. It is hoped that through these endeavors the outlook of pneumococcal infections will be improved.

Outcomes of influenza A(H1N1)pdm09 virus infection: results from two international cohort studies

BACKGROUND

Data from prospectively planned cohort studies on risk of major clinical outcomes and prognostic factors for patients with influenza A(H1N1)pdm09 virus are limited. In 2009, in order to assess outcomes and evaluate risk factors for progression of illness, two cohort studies were initiated: FLU 002 in outpatients and FLU 003 in hospitalized patients.

METHODS AND FINDINGS

Between October 2009 and December 2012, adults with influenza-like illness (ILI) were enrolled; outpatients were followed for 14 days and inpatients for 60 days. Disease progression was defined as hospitalization and/or death for outpatients, and hospitalization for >28 days, transfer to intensive care unit (ICU) if enrolled from general ward, and/or death for inpatients. Infection was confirmed by RT-PCR. 590 FLU 002 and 392 FLU 003 patients with influenza A (H1N1)pdm09 were enrolled from 81 sites in 17 countries at 2 days (IQR 1-3) and 6 days (IQR 4-10) following ILI onset, respectively. Disease progression was experienced by 29 (1 death) outpatients (5.1%; 95% CI: 3.4-7.2%) and 80 inpatients [death (32), hospitalization >28 days (43) or ICU transfer (20)] (21.6%; 95% CI: 17.5-26.2%). Disease progression (death) for hospitalized patients was 53.1% (26.6%) and 12.8% (3.8%), respectively, for those enrolled in the ICU and general ward. In pooled analyses for both studies, predictors of disease progression were age, longer duration of symptoms at enrollment and immunosuppression. Patients hospitalized during the pandemic period had a poorer prognosis than in subsequent seasons.

CONCLUSIONS

Patients with influenza A(H1N1)pdm09, particularly when requiring hospital admission, are at high risk for disease progression, especially if they are older, immunodeficient, or admitted late in infection. These data reinforce the need for international trials of novel treatment strategies for influenza infection and serve as a reminder of the need to monitor the severity of seasonal and pandemic influenza epidemics globally.

TRIAL REGISTRATION

ClinicalTrials.gov Identifiers: FLU 002--NCT01056354, FLU 003--NCT01056185.