Co-detection of pandemic (H1N1) 2009 virus and other respiratory pathogens

Microbial and Immune Regulation of the Gut-Lung Axis during Viral-Bacterial Coinfection

Viral-bacterial coinfections of the respiratory tract have long been associated with worsened disease outcomes. Clinical and basic research studies demonstrate that these infections are driven via complex interactions between the infecting pathogens, microbiome, and host immune response, although how these interactions contribute to disease progression is still not fully understood. Research over the last decade shows that the gut has a significant role in mediating respiratory outcomes, in a phenomenon known as the "gut-lung axis." Emerging literature demonstrates that acute respiratory viruses can modulate the gut-lung axis, suggesting that dysregulation of gut-lung cross talk may be a contributing factor during respiratory coinfection. This review will summarize the current literature regarding modulation of the gut-lung axis during acute respiratory infection, with a focus on the role of the microbiome, secondary infections, and the host immune response.

Upper Respiratory Tract Co-detection of Human Endemic Coronaviruses and High-density Pneumococcus Associated With Increased Severity Among HIV-Uninfected Children Under 5 Years Old in the PERCH Study

BACKGROUND

Severity of viral respiratory illnesses can be increased with bacterial coinfection and can vary by sex, but influence of coinfection and sex on human endemic coronavirus (CoV) species, which generally cause mild to moderate respiratory illness, is unknown. We evaluated CoV and pneumococcal co-detection by sex in childhood pneumonia.

METHODS

In the 2011-2014 Pneumonia Etiology Research for Child Health study, nasopharyngeal and oropharyngeal (NP/OP) swabs and other samples were collected from 3981 children <5 years hospitalized with severe or very severe pneumonia in 7 countries. Severity by NP/OP detection status of CoV (NL63, 229E, OC43 or HKU1) and high-density (≥6.9 log10 copies/mL) pneumococcus (HDSpn) by real-time polymerase chain reaction was assessed by sex using logistic regression adjusted for age and site.

RESULTS

There were 43 (1.1%) CoV+/HDSpn+, 247 CoV+/HDSpn-, 449 CoV-/HDSpn+ and 3149 CoV-/HDSpn- cases with no significant difference in co-detection frequency by sex (range 51.2%-64.0% male, P = 0.06). More CoV+/HDSpn+ pneumonia was very severe compared with other groups for both males (13/22, 59.1% versus range 29.1%-34.7%, P = 0.04) and females (10/21, 47.6% versus 32.5%-43.5%, P = 0.009), but only male CoV+/HDSpn+ required supplemental oxygen more frequently (45.0% versus 20.6%-28.6%, P < 0.001) and had higher mortality (35.0% versus 5.3%-7.1%, P = 0.004) than other groups. For females with CoV+/HDSpn+, supplemental oxygen was 25.0% versus 24.8%-33.3% (P = 0.58) and mortality was 10.0% versus 9.2%-12.9% (P = 0.69).

CONCLUSIONS

Co-detection of endemic CoV and HDSpn was rare in children hospitalized with pneumonia, but associated with higher severity and mortality in males. Findings may warrant investigation of differences in severity by sex with co-detection of HDSpn and SARS-CoV-2.

Evaluation of Pneumococcal Surface Protein A as a Vaccine Antigen against Secondary Streptococcus pneumoniae Challenge during Influenza A Infection

Secondary bacterial pneumonia is responsible for significant morbidity and mortality during seasonal and pandemic influenza. Due to the unpredictability of influenza A virus evolution and the time-consuming process of manufacturing strain-specific influenza vaccines, recent efforts have been focused on developing anti-Streptococcus pneumoniae immunity to prevent influenza-related illness and death. Bacterial vaccination to prevent viral-bacterial synergistic interaction during co-infection is a promising concept that needs further investigation. Here, we show that immunization with pneumococcal surface protein A (PspA) fully protects mice against low-dose, but not high-dose, secondary bacterial challenge using a murine model of influenza A virus-S. pneumoniae co-infection. We further show that immunization with PspA is more broadly protective than the pneumococcal conjugate vaccine (Prevnar). These results demonstrate that PspA is a promising vaccine target that can provide protection against a physiologically relevant dose of S. pneumoniae following influenza infection.

Comparison of FTD® respiratory pathogens 33 and a singleplex CDC assay for the detection of respiratory viruses: A study from Cameroon

Introduction: This study compares the detection of 14 common respiratory viruses by two different real-time reverse transcription polymerase chain reaction (rRT-PCR) methods: in house singleplex tests developed by the Centers for Disease Control and Prevention and the commercially available Fast Track Diagnostic (FTD®) Respiratory Pathogens 33 multiplex test. Methods: A total of 217 nasopharyngeal swabs were analyzed using CDC singleplex rRT-PCR and FTD® Respiratory Pathogens 33 multiplex assays, for the detection of 14 respiratory viruses. Results: The results showed that 179/217 (82.5%) samples were positive with the singleplex method and 183/217 (84.3%) with the FTD® Respiratory Pathogens 33 multiplex test. Excellent or satisfactory agreement was obtained for all viruses (k > 0.6) except Parainfluenzavirus 4 (k = 0.24) and influenza B (k = 0.51). Conclusion: Although the multiplex FTD kits were more expensive than the singleplex assay, the FTD kits yielded rapid results in a shorter timeframe, increasing efficiency of diagnosis.

Quantitative detection of Staphylococcus aureus, Streptococcus pneumoniae and Haemophilus influenzae in patients with new influenza A (H1N1)/2009 and influenza A/2010 virus infection

INTRODUCTION

Viral influenza is a seasonal infection associated with significant morbidity and mortality. In the United States more than 35,000 deaths and 200,000 hospitalizations are recorded annually due to influenza. Secondary bacterial infections or co-infections associated with cases of influenza are a leading cause of severe morbidity and mortality, especially among high-risk groups such as the elderly and young children.

AIM

The aim of the present study was the quantitative detection of S. aureus, S. pneumoniae and H. influenzae in a group of patients with seasonal influenza A, influenza A (H1N1) pandemic 2009, and patients with symptoms of respiratory infection, but the negative for H1N1 serving as control group.

METHOD

In total, 625 patients suspected respiratory infection from April 2009 to April 2010 were studied. There were 58 patients with influenza A H1N1 and 567 patients negative for influenza A H1N1. From November 2010 to February 2011, 158 patients with respiratory symptoms were analyzed for seasonal influenza A. There were 25 patients with seasonal influenza A. To check the colonization status among the healthy individuals 62 healthy persons were further investigated. Individual were screened in parallel. The choices of special genes were amplified from clinical specimens using real-time PCR with a cutoff of 10(4) CFU/mL to differentiate colonization from infection in respiratory tract.

RESULTS

S. aureus, S. pneumoniae and H. influenzae were detected in 12%, 26% and 33% of patients with H1N1, while the corresponding figures were 9%, 19%, and 31% for H1N1 negative patients. Among patients with seasonal influenza A 12% S. aureus, 24% S. pneumoniae, and 32% H. influenzae co-infections were detected, while influenza negative control group yielded 5% S. aureus, 11% S. pneumoniae, and 10% H. influenzae, respectively.

CONCLUSION

The results of this study indicated that the serotype of pandemic H1N1 2009 did not increase incidence of secondary infection with S. aureus, S. pneumoniae and H. influenzae. Quantitative detection of secondary bacterial infection by QR-PCR can help us for distinguishing colonization from infection and controlling misuse of antibiotics and bacterial drug resistances.

Non-rhinovirus enteroviruses associated with respiratory infections in Peru (2005-2010)

Background

Enteroviruses (EVs) are a common cause of respiratory tract infections and are classified into seven species (EVA-D and rhinoviruses [RHVs] A-C) with more than 200 different serotypes. Little is known about the role of non-RHV EVs in respiratory infections in South America. The aim of this study was to describe the epidemiology of non-RHV EVs detected in patients with influenza-like illness enrolled in a passive surveillance network in Peru.

Methods

Throat swabs and epidemiological data were collected from participants after obtaining verbal consent. Viral isolation was performed in cell culture and identified by immunofluorescence assay. Serotype identification of EV isolates was performed using commercial monoclonal antibodies. Identification of non-serotypeable isolations was carried out by reverse transcriptase-PCR, followed by sequencing.

Results

Between 2005 and 2010, 24,239 samples were analyzed, and 9,973 (41.1%) possessed at least one respiratory virus. EVs were found in 175 samples (0.7%). Our results revealed a clear predominance of EVB species, 90.9% (159/175). No EVDs were isolated. The mean and median ages of EV-positive subjects were 9.1 and 4.0 years, respectively, much younger than the population sampled, 17.6 and 12.0 years. Sixteen serotypes were identified, four EVA, 11 EVB, and one EVC species. The most common serotypes were coxsackievirus B1, coxsackievirus B2, coxsackievirus B5, and coxsackievirus B3.

Conclusion

This study provides data about the serotypes of EVs circulating in Peru and sets the need for further studies.

Early therapy with neuraminidase inhibitors for influenza A (H1N1) pdm 2009 infection

BACKGROUND

Neuraminidase inhibitors have been reported to decrease mortality in patients infected with influenza A (H1N1) pdm 2009 (H1N1 pdm09), but it is not clear whether they are effective against H1N1pdm09 in apparently healthy children.

METHODS

The effect of early treatment with neuraminidase inhibitors on 70 otherwise healthy children with possible H1N1 pdm09 (pH1N1pdm09) infection was investigated. The children were simultaneously treated with a neuraminidase inhibitor (oseltamivir or zanamivir) and maoto, a Japanese traditional herbal medicine, which had been reported to be effective against seasonal influenza. Clinical severity was assessed using patient history, namely the worst values for clinical vital signs and laboratory data on admission. After refining these parameters with univariate, decision tree and multiple regression analysis, mean covariance structure equation analysis was used to investigate the association of estimated clinical severity to the selected parameters.

RESULTS

Total path analysis using a Bayesian method indicated that the estimated clinical severity of pH1N1pdm09 was positively associated with maximum body temperature, pulse rate, respiration rate, duration necessary for defervescence, admission duration and log urinary β2-microglobulin/creatinine level, and negatively associated with age and the presence and duration of treatment with the neuraminidase inhibitor in the outpatient clinic.

CONCLUSIONS

This study provides the first clinical evidence that early treatment with neuraminidase inhibitors in outpatient clinic decreased the estimated clinical severity of pH1N1pdm09 in apparently otherwise healthy pediatric inpatients.

Benefit of conjugate pneumococcal vaccination in preventing influenza hospitalization in children: a case-control study

BACKGROUND

The pneumococcal conjugate vaccine (PCV) might prevent hospitalizations in children because of the role of Streptococcus pneumoniae in the complications of influenza infection. We investigated the benefit of PCV vaccination in preventing influenza hospitalization in children <5 years of age during the 2009 to 2010 pandemic wave and the 2010 to 2011 influenza epidemic in Spain.

METHODS

A multicenter matched case-control study was undertaken in 27 hospitals from 7 Spanish regions between July 2009 and April 2011. A case was defined as a hospitalized patient between 6 months and 5 years of age with influenza virus infection confirmed by real-time reverse-transcription polymerase chain reaction. We selected 2 matched controls for each case from patients with unplanned hospital admission for reasons other than acute respiratory infection or influenza-like illness. Cases and controls were matched according to age, date of hospitalization and province of residence. Crude and adjusted odds ratios were calculated for associations between influenza hospitalization and PCV vaccination.

RESULTS

One hundred ninety-four cases and 342 controls were included in the study. In the 2009 to 2010 pandemic wave, the adjusted benefit in preventing hospitalization was 48% (95% confidence interval: 1 to 76) in fully vaccinated children compared with -79% (95% confidence interval: -341 to 27) in the 2010 to 2011 influenza season.

CONCLUSIONS

The results obtained suggest that, in children <5 years of age, PCV vaccination reduced hospitalization during the 2009 to 2010 pandemic wave. By contrast, there was no observed benefit of vaccination in the 2010 to 2011 influenza season.

Effectiveness of vaccination with 23-valent pneumococcal polysaccharide vaccine in preventing hospitalization with laboratory confirmed influenza during the 2009-2010 and 2010-2011 seasons

BACKGROUND

Since influenza predisposes to bacterial pneumonia caused by Streptococcus pneumoniae, studies have suggested that pneumococcal vaccination might reduce its occurrence during pandemics. We assessed the effectiveness of pneumococcal polysaccharide vaccination alone and in combination with influenza vaccination in preventing influenza hospitalization during the 2009-2010 pandemic wave and 2010-2011 influenza epidemic.

RESULTS

1187 cases and 2328 controls were included. The adjusted estimate of effectiveness of pneumococcal vaccination in preventing influenza hospitalization was 41% (95% CI 8-62) in all patients and 43% (95% CI 2-78) in patients aged ≥ 65 y. The adjusted effectiveness of dual PPV23 and influenza vaccination was 81% (95% CI 65-90) in all patients and 76% (95% CI 46-90) in patients aged ≥ 65 y. The adjusted effectiveness of influenza vaccination alone was 58% (95% CI 38-72).

METHODS

We conducted a multicenter case-control study in 36 Spanish hospitals. We selected patients aged ≥ 18 y hospitalized with confirmed influenza and two hospitalized controls per case, matched according to age, date of hospitalization and province of residence. Multivariate analysis was performed using conditional logistic regression. Subjects were considered vaccinated if they had received the pneumococcal or seasonal influenza vaccine>14 d (or>7 d for pandemic influenza vaccine) before the onset of symptoms (cases) or the onset of symptoms in matched cases (controls).

CONCLUSIONS

In elderly people and adults with chronic illness, pneumococcal vaccination may reduce hospitalizations during the influenza season. In people vaccinated with both the influenza and pneumococcal vaccines, the benefit in hospitalizations avoided was greater than in those vaccinated only against influenza.

Nasopharyngeal microbial interactions in the era of pneumococcal conjugate vaccination

The nasopharynx of children is often colonised by microorganisms such as Streptococcus pneumoniae (the pneumococcus) that can cause infections including pneumonia and otitis media. In this complex environment, bacteria and viruses may impact each other through antagonistic as well as synergistic interactions. Vaccination may alter colonisation dynamics, evidenced by the rise in non-vaccine serotypes following pneumococcal conjugate vaccination. Discovery of an inverse relationship between S. pneumoniae and Staphylococcus aureus carriage generated concern that pneumococcal vaccination could increase S. aureus carriage and disease. Here we review data on co-colonisation of pathogens in the nasopharynx, focusing on S. pneumoniae and the impact of pneumococcal vaccination. Thus far, pneumococcal vaccination has not had a sustained impact on S. aureus carriage but it is associated with an increase in non-typeable Haemophilus influenzae in acute otitis media aetiology. Advances in bacterial and viral detection methodologies have facilitated research in nasopharyngeal microbiology and will aid investigation of potential vaccine-induced changes, particularly when baseline studies can be conducted prior to pneumococcal vaccine introduction.

Serum immunoglobulin G subclass levels and estimated clinical severity caused by possible influenza A (H1N1) pdm 2009 infection

The clinical severity of the 2009 pandemic H1N1 influenza (H1N1 pdm09) was thought to be related to the difference between the amount of viral load and condition of the host immune response. We investigated the role of serum levels of IgG and its subclasses in clinical severity using the data from 45 child inpatients suffering from bronchitis or mild pneumonia caused by possible H1N1 pdm09 (pH1N1 pdm09) infection. After selecting parameters for serum IgG subclasses and logarithmically transformed urinary beta-2 microglobulin/creatinine (b2MG/Cr) values and admission duration, we performed path analysis using a mean covariance structure equation analysis to investigate the relationship between the clinical severity and the foregoing selected parameters. Total path analyses using a Bayesian method revealed that the estimated clinical severity caused by pH1N1 pdm09 was positively associated with maximal respiration rates, admission duration, and log urinary b2MG/Cr levels, whereas negatively associated with serum IgG, IgG1, IgG2, and IgG3 levels, duration of neuraminidase inhibitor therapy in outpatient clinics, and age. Serum IgG and its subclasses (IgG1-IgG3) reduced estimated clinical severity in children with pH1N1 pdm09 infection.

Severe acute respiratory infections in the postpandemic era of H1N1

PURPOSE OF REVIEW

Shortly after the advent of severe acute respiratory syndrome and the avian influenza, the emergence of the influenza A(H1N1)2009 pandemic caused significant vibrations to the public health authorities and stressed the health systems worldwide. We sought to investigate whether this experience has altered our knowledge and our current and future practice on the management of severe acute respiratory infections (SARI) and community-acquired pneumonia.

RECENT FINDINGS

A changing epidemiology was demonstrated, with obesity and pregnancy beyond established risk groups for influenza A, other clinical syndromes beyond primary viral pneumonia, possible coinfections by other viral beyond bacterial pathogens and a disappointing performance of all available severity assessment tools. On the treatment topic, accumulating evidence suggesting worse outcomes argues against the use of corticosteroids, but some noninvasive ventilating modalities require further assessment.

SUMMARY

The recent influenza A(H1N1)2009 pandemic has highlighted our weaknesses relating to the diagnosis and assessment of severity of SARI, compromising early treatment and ultimate outcomes; further research based on this experience will help to improve prognosis and boost our future preparedness. An important message is the necessity of international collaboration for the rapid dissemination of locally acquired knowledge.

Incidence and epidemiology of hospitalized influenza cases in rural Thailand during the influenza A (H1N1)pdm09 pandemic, 2009-2010

Background

Data on the burden of the 2009 influenza pandemic in Asia are limited. Influenza A(H1N1)pdm09 was first reported in Thailand in May 2009. We assessed incidence and epidemiology of influenza-associated hospitalizations during 2009–2010.

Methods

We conducted active, population-based surveillance for hospitalized cases of acute lower respiratory infection (ALRI) in all 20 hospitals in two rural provinces. ALRI patients were sampled 1∶2 for participation in an etiology study in which nasopharyngeal swabs were collected for influenza virus testing by PCR.

Results

Of 7,207 patients tested, 902 (12.5%) were influenza-positive, including 190 (7.8%) of 2,436 children aged <5 years; 86% were influenza A virus (46% A(H1N1)pdm09, 30% H3N2, 6.5% H1N1, 3.5% not subtyped) and 13% were influenza B virus. Cases of influenza A(H1N1)pdm09 first peaked in August 2009 when 17% of tested patients were positive. Subsequent peaks during 2009 and 2010 represented a mix of influenza A(H1N1)pdm09, H3N2, and influenza B viruses. The estimated annual incidence of hospitalized influenza cases was 136 per 100,000, highest in ages <5 years (477 per 100,000) and >75 years (407 per 100,000). The incidence of influenza A(H1N1)pdm09 was 62 per 100,000 (214 per 100,000 in children <5 years). Eleven influenza-infected patients required mechanical ventilation, and four patients died, all adults with influenza A(H1N1)pdm09 (1) or H3N2 (3).

Conclusions

Influenza-associated hospitalization rates in Thailand during 2009–10 were substantial and exceeded rates described in western countries. Influenza A(H1N1)pdm09 predominated, but H3N2 also caused notable morbidity. Expanded influenza vaccination coverage could have considerable public health impact, especially in young children.

Associations between pathogens in the upper respiratory tract of young children: interplay between viruses and bacteria

Background

High rates of potentially pathogenic bacteria and respiratory viruses can be detected in the upper respiratory tract of healthy children. Investigating presence of and associations between these pathogens in healthy individuals is still a rather unexplored field of research, but may have implications for interpreting findings during disease.

Methodology/Principal Findings

We selected 986 nasopharyngeal samples from 433 6- to 24-month-old healthy children that had participated in a randomized controlled trial. We determined the presence of 20 common respiratory viruses using real-time PCR. Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus were identified by conventional culture methods. Information on risk factors was obtained by questionnaires. We performed multivariate logistic regression analyses followed by partial correlation analysis to identify the overall pattern of associations. S. pneumoniae colonization was positively associated with the presence of H. influenzae (adjusted odds ratio 1.60, 95% confidence interval 1.18–2.16), M. catarrhalis (1.78, 1.29–2.47), human rhinoviruses (1.63, 1.19–2.22) and enteroviruses (1.97, 1.26–3.10), and negatively associated with S. aureus presence (0.59, 0.35–0.98). H. influenzae was positively associated with human rhinoviruses (1.63, 1.22–2.18) and respiratory syncytial viruses (2.78, 1.06–7.28). M. catarrhalis colonization was positively associated with coronaviruses (1.99, 1.01–3.93) and adenoviruses (3.69, 1.29–10.56), and negatively with S. aureus carriage (0.42, 0.25–0.69). We observed a strong positive association between S. aureus and influenza viruses (4.87, 1.59–14.89). In addition, human rhinoviruses and enteroviruses were positively correlated (2.40, 1.66–3.47), as were enteroviruses and human bocavirus, WU polyomavirus, parainfluenza viruses, and human parechovirus. A negative association was observed between human rhinoviruses and coronaviruses.

Conclusions/Significance

Our data revealed high viral and bacterial prevalence rates and distinct bacterial-bacterial, viral-bacterial and viral-viral associations in healthy children, hinting towards the complexity and potential dynamics of microbial communities in the upper respiratory tract. This warrants careful consideration when associating microbial presence with specific respiratory diseases.

Severity of influenza A 2009 (H1N1) pneumonia is underestimated by routine prediction rules. Results from a prospective, population-based study

BACKGROUND

Characteristics of patients with community-acquired pneumonia (CAP) due to pandemic influenza A 2009 (H1N1) have been inadequately compared to CAP caused by other respiratory pathogens. The performance of prediction rules for CAP during an epidemic with a new infectious agent are unknown.

METHODS

Prospective, population-based study from November 2008-November 2009, in centers representing 70% of hospital beds in Iceland. Patients admitted with CAP underwent evaluation and etiologic testing, including polymerase chain reaction (PCR) for influenza. Data on influenza-like illness in the community and overall hospital admissions were collected. Clinical and laboratory data, including pneumonia severity index (PSI) and CURB-65 of patients with CAP due to H1N1 were compared to those caused by other agents.

RESULTS

Of 338 consecutive and eligible patients 313 (93%) were enrolled. During the pandemic peak, influenza A 2009 (H1N1) patients constituted 38% of admissions due to CAP. These patients were younger, more dyspnoeic and more frequently reported hemoptysis. They had significantly lower severity scores than other patients with CAP (1.23 vs. 1.61, P= .02 for CURB-65, 2.05 vs. 2.87 for PSI, P<.001) and were more likely to require intensive care admission (41% vs. 5%, P<.001) and receive mechanical ventilation (14% vs. 2%, P= .01). Bacterial co-infection was detected in 23% of influenza A 2009 (H1N1) patients with CAP.

CONCLUSIONS

Clinical characteristics of CAP caused by influenza A 2009 (H1N1) differ markedly from CAP caused by other etiologic agents. Commonly used CAP prediction rules often failed to predict admissions to intensive care or need for assisted ventilation in CAP caused by the influenza A 2009 (H1N1) virus, underscoring the importance of clinical acumen under these circumstances.

The impact of the H1N1 influenza pandemic on clinical presentations and viral epidemiology of acute respiratory infection in preschool children in Brazil

We assessed the impact of the H1N1 influenza pandemic on acute respiratory infection in young children from low-income families in Brazil. Influenza (specifically H1N1) detection in acute respiratory infection quintupled during the pandemic and, during its peak, it was associated with 30% of all acute respiratory infection visits to the emergency department. H1N1 was also associated with increased risk of hospitalization and coinfection.

Benefits and effectiveness of administering pneumococcal polysaccharide vaccine with seasonal influenza vaccine: an approach for policymakers

For the influenza pandemic of 2009-2010, countries responded to the direct threat of influenza but may have missed opportunities and strategies to limit secondary pneumococcal infections. Delivering both vaccines together can potentially increase pneumococcal polysaccharide vaccine (PPV23) immunization rates and prevent additional hospitalizations and mortality in the elderly and other high-risk groups. We used PubMed to review the literature on the concomitant use of PPV23 with seasonal influenza vaccines. Eight of 9 clinical studies found that a concomitant program conferred clinical benefits. The 2 studies that compared the cost-effectiveness of different strategies found concomitant immunization to be more cost-effective than either vaccine given alone. Policymakers should consider a stepwise strategy to reduce the burden of secondary pneumococcal infections during seasonal and pandemic influenza outbreaks.

Epidemiology and clinical characteristics of hospitalized patients with pandemic influenza A (H1N1) 2009 infections: the effects of bacterial coinfection

Background

Numerous reports have described the epidemiological and clinical characteristics of influenza A (H1N1) 2009 infected patients. However, data on the effects of bacterial coinfection on these patients are very scarce. Therefore, this study explores the impact of bacterial coinfection on the clinical and laboratory parameters amongst H1N1 hospitalized patients.

Findings

This retrospective study involved hospitalized patients with laboratory-confirmed H1N1 infections (September 2009 to May 2010). Relevant clinical data and the detection of bacterial coinfection from respiratory or sterile site samples were obtained. Multiplex PCR was used to determine the co-existence of other respiratory viruses. Comparison was made between patients with and without bacterial coinfection. The occurrence of coinfection was 34%; 14 (28%) bacterial and only 3 (6%) viral. Mycoplasma pneumoniae (n = 5) was the commonest bacteria followed by Staphylococcus aureus (n = 3). In univariate analysis, clinical factors associated with bacterial coinfection were age > 50 years (p = 0.02), presence of comorbidity (p = 0.04), liver impairment (p = 0.02), development of complications (p = 0.004) and supplemental oxygen requirement (p = 0.02). Leukocytosis (p = 0.02) and neutrophilia (p = 0.004) were higher in bacterial coinfected patients. Multivariate logistic regression analysis revealed that age > 50 years and combined complications were predictive of bacterial coinfection.

Conclusions

Bacterial coinfection is not uncommon in H1N1 infected patients and is more frequently noted in the older aged patients and is associated with higher rates of complications. Also, as adjunct to clinical findings, clinicians need to have a higher index of suspicion if neutrophilia was identified at admission as it may denote bacterial coinfection.

Risk factors of A/H1N1 etiology in pneumonia and its impact on mortality

OBJECTIVE

Pandemic flu has changed the epidemiology of pneumonia, thus challenging the prediction of etiology and outcome. We analyze the risk factors to predict influenza A/H1N1 infection in patients with pneumonia, and the impact of this etiology on mortality during a pandemic period. Differences between pneumonia with or without A/H1N1 coinfection are described.

METHODS

Retrospective observational study in 364 consecutive patients hospitalized with pneumonia during the A/H1N1 pandemic flu, April-December 2009.

RESULTS

294 patients (80.5%) had A/H1N1(-) pneumonia, 47 (13.2%) A/H1N1(+) pneumonia, and 23 (6.3%) coinfection. Mortality during hospitalization was 24/294 (8.2%), 8/47 (16.7%), 2/23 (8.7%) respectively. A regression logistic analysis (Area under curve, AUC 0.81) to predict A/H1N1(+) pneumonia identified four independent variables: age < 60 years (Odds ratio, OR 5.9), multilobar infiltrates (OR 7.7), C-reactive protein (CRP) < 10 mg/dL (OR 2.8), and leukopenia < 5000/mm(3) (OR 3.4). Risk factors for in-hospital mortality in the whole group were A/H1N1 (+) etiology and LDH > 600 IU/L (OR 4.1) when adjusting for PSI, and hypoxemia (OR 4.2) when adjusting for CURB 65 (AUC 0.81). Heart disease (OR 27.4) and LDH > 600 IU/L (OR 10.5) were risk factors for in-hospital mortality in A/H1N1(+) patients (AUC 0.81)

CONCLUSION

Leukopenia, multilobar infiltrates, CRP<10 mg/dl and age < 60 years were independently associated with A/H1N1(+) etiology. Pandemic A/H1N1(+) increased mortality pneumonia. Heart disease and LDH > 600 were independently associated with mortality in A/H1N1(+) pneumonia.