Mixed infection is common in children with respiratory adenovirus infection

A preliminary nomogram constructed for early diagnosis of bronchitis obliterans in children with severe pneumonia

BACKGROUND

To establish and internally validate a nomogram for early diagnosis of bronchitis obliterans in children with severe pneumonia.

METHODS

The diagnostic model was established using a dataset of 147 pediatric patients with severe pneumonia. The clinical characteristics of bronchitis obliterans were determined using the least absolute shrinkage and selection operator method. According to the results of the multivariate logistic regression analysis, an individual nomogram was established, the C-index, calibration plot, and decision curve analysis were used to evaluate the performance of the nomogram.

RESULTS

Adenovirus infection, length of symptoms, percentage of macrophages in bronchial alveolar lavage fluid, and mucosal abnormalities were all important clinical characteristics included in the nomogram. According to internal validation, the C-index of nomogram was 0.91 (C-index, 0.878 to 0.942), suggesting that the nomogram has excellent discrimination. The nomogram showed good calibration with the Hosmer-Lemeshow test demonstrating no statistical significance. The net reclassification index was 0.2022 (95% CI, 0.008 to 0.3968; P=0.042), and the integrated discrimination improvement was 0.0975 (95% CI, 0.026 to 0.169; P=0.008). Decision curve analysis showed that the nomogram is clinically useful.

CONCLUSIONS

This nomogram can help clinicians make early diagnoses of bronchitis obliterans in children for whom membranous tissue has not yet formed.

Bacterial co-infections with SARS-CoV-2

The pandemic coronavirus disease 2019 (COVID‐19), caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS‐CoV‐2), has affected millions of people worldwide. To date, there are no proven effective therapies for this virus. Efforts made to develop antiviral strategies for the treatment of COVID‐19 are underway. Respiratory viral infections, such as influenza, predispose patients to co‐infections and these lead to increased disease severity and mortality. Numerous types of antibiotics such as azithromycin have been employed for the prevention and treatment of bacterial co‐infection and secondary bacterial infections in patients with a viral respiratory infection (e.g., SARS‐CoV‐2). Although antibiotics do not directly affect SARS‐CoV‐2, viral respiratory infections often result in bacterial pneumonia. It is possible that some patients die from bacterial co‐infection rather than virus itself. To date, a considerable number of bacterial strains have been resistant to various antibiotics such as azithromycin, and the overuse could render those or other antibiotics even less effective. Therefore, bacterial co‐infection and secondary bacterial infection are considered critical risk factors for the severity and mortality rates of COVID‐19. Also, the antibiotic‐resistant as a result of overusing must be considered. In this review, we will summarize the bacterial co‐infection and secondary bacterial infection in some featured respiratory viral infections, especially COVID‐19.

Serum Inflammatory Markers in Patients with Adenovirus Respiratory Infection

Background

The aim of this study was to characterize adenovirus-associated acute respiratory infection (ARI) and observe correlations between inflammatory markers and severity of human adenovirus type 7 (HAdV-7) infection, and to evaluate the potential of inflammatory markers to predict progression from upper-respiratory infection (URI) to adenovirus pneumonia (AdP).

Material/Methods

A total of 81 patients with adenovirus-associated ARI and confirmed HAdV-7 infection were enrolled. Cases were classified according to severity, as AdP and URI. Demographic and clinical data were collected retrospectively. Clinical features and serum inflammatory markers were evaluated and compared according to the severity of adenoviral infection.

Results

We observed high-grade fever and strong inflammatory response in patients with HAdV-7–associated ARI. Procalcitonin (PCT), interleukin 6 (IL-6), and C-reactive protein concentrations were higher in patients with AdP than in those with URI. The mean erythrocyte sedimentation rate (ESR) was significantly higher in patients with AdP (p=0.008). Reduced serum prealbumin levels were observed in patients with HAdV-7 infection. In the analysis of URI to AdP prediction ability, areas under the curve (AUCs) for all inflammatory markers were <0.9. We found that 35.9% of pneumonia had ≥2 lobars of lung infiltrate and bilateral lung infiltrate, and 20% of patients with SP had pleural effusion and atelectasis.

Conclusions

IL-6 and ESR were associated with the severity of HAdV-7 respiratory infection. No inflammatory marker in our study predicted URI-to-AdP progression accurately. Lung infiltration and consolidation are common in HRCT in AdP. Multiple- or single-lobar/segment consolidation was most common in SP. SP progressed very quickly after onset.

Chlamydia trachomatis infection influences the clinical course of acute bronchiolitis

The frequency of Chlamydia trachomatis infection among young infants admitted with acute bronchiolitis was analysed to determine whether the former affects the clinical course of the latter. A total of 92 infants aged <6 months admitted with acute bronchiolitis were tested for C. trachomatis by a cell culture technique, obtaining nasal smears from each infant's nostrils. A second nasal sampling was taken for respiratory viruses from the study group and tested with real-time polymerase chain reaction. Clinical characteristics of C. trachomatis-positive and -negative cases were compared. C. trachomatis was detected in 22.8% of the infants, mostly as coinfection with respiratory viral agents. Infection with C. trachomatis affected the clinical outcome in acute bronchiolitis and such infants tended to have severe bronchiolitis.

Etiology, Seasonality, and Clinical Features of Viral Respiratory Tract Infections in Children Hospitalized With Acute Bronchiolitis: A Single-Center Study

The purpose of this study was to evaluate the viral frequency, seasonality, and clinical and demographic features of patients hospitalized with acute bronchiolitis. A cross-sectional, descriptive study was performed in 316 infants younger than 2 years of age who were hospitalized for acute viral bronchiolitis. Respiratory tract infection agents were investigated with polymerase chain reaction (PCR). A total of 316 infants were included in this study. Of the 316 infants, at least one respiratory tract pathogen was detected in 75% (237/316). Respiratory syncytial virus (RSV) was the most common virus identified in 127 infants (40.1%) followed by rhinovirus (n = 78, 24.6%). In this study, where viral agents were determined via PCR in patients who were followed-up due to the diagnosis of acute bronchiolitis, RSV was detected as the most common agent, as in other studies. In almost half of the RSV-positive patients, RSV was accompanied by a second or third agent.

Clinical differences between respiratory viral and bacterial mono- and dual pathogen detected among Singapore military servicemen with febrile respiratory illness

Background

Although it is known that febrile respiratory illnesses (FRI) may be caused by multiple respiratory pathogens, there are no population-level studies describing its impact on clinical disease.

Methods

Between May 2009 and October 2012, 7733 FRI patients and controls in the Singapore military had clinical data and nasal wash samples collected prospectively and sent for PCR testing. Patients with one pathogen detected (mono-pathogen) were compared with those with two pathogens (dual pathogen) for differences in basic demographics and clinical presentation.

Results

In total, 45.8% had one pathogen detected, 20.2% had two pathogens detected, 30.9% had no pathogens detected, and 3.1% had more than two pathogens. Multiple pathogens were associated with recruits, those with asthma and non-smokers. Influenza A (80.0%), influenza B (73.0%) and mycoplasma (70.6%) were most commonly associated with mono-infections, while adenovirus was most commonly associated with dual infections (62.9%). Influenza A paired with S. pneumoniae had higher proportions of chills and rigors than their respective mono-pathogens (P = 0.03, P = 0.009). H. influenzae paired with either enterovirus or parainfluenzae had higher proportions of cough with phlegm than their respective mono-pathogens. Although there were observed differences in mean proportions of body temperature, nasal symptoms, sore throat, body aches and joint pains between viral and bacterial mono-pathogens, there were few differences between distinct dual-pathogen pairs and their respective mono-pathogen counterparts.

Conclusion

A substantial number of FRI patients have multiple pathogens detected. Observed clinical differences between patients of dual pathogen and mono-pathogen indicate the likely presence of complex microbial interactions between the various pathogens.

Wet cough in children: infective and inflammatory characteristics in broncho-alveolar lavage fluid

Wet cough is a common feature of many disease processes affecting children. Our aim was to examine the relationships between cough nature, lower airway infection (bacterial, viral, and viral-bacterial) and severity of neutrophilic airway inflammation. We hypothesized that viral-bacterial co-infection of the lower airway would be associated with wet cough and heightened neutrophilic airway inflammation. We prospectively recruited 232 children undergoing elective flexible bronchoscopy. Participants were grouped using a cough nature symptom-based approach, into wet, dry or no cough groups. Broncho-alveolar lavage (BAL) and clinical data, including presence, nature, and duration of cough and key demographic factors, were collected. Children with wet cough (n = 143) were more likely to have lower airway bacterial infection (OR 2.6, P = 0.001), viral infection (OR 2.04, P = 0.045) and viral-bacterial co-infection (OR 2.65, P = 0.042) compared to those without wet cough. Wet cough was associated with heightened airway neutrophilia (median 19%) as compared to dry or no cough. Viral-bacterial co-infection was associated with the highest median %neutrophils (33.5%) compared to bacteria only, virus/es only and no infection (20%, 18%, and 6%, respectively, P < 0.0001). Children with wet cough had higher rates of lower airway infection with bacteria and viruses. Maximal neutrophilic airway inflammation was seen in those with viral-bacterial co-infection. Cough nature may be a useful indicator of infection and inflammation of the lower airways in children.

Clinical manifestations of respiratory adenoviral infection among hospitalized children in Korea

BACKGROUND

The objective of our study was to understand the epidemiological and clinical features of respiratory adenoviral infections among children at a single institution over the course of several years.

METHODS

From January 2005 to April 2009, 1836 children (≤15 years old) who had been admitted to Korea University Ansan Hospital were tested for acute respiratory infection. The patients who were positive for an adenovirus infection were enrolled in this study, and their medical records were retrospectively reviewed.

RESULTS

Adenoviruses were isolated from 310 patients. The male to female ratio was 1.6:1 and mean age was 32 ± 24 months. Children under 5 years of age had the highest prevalence. In 2007, adenovirus infections occurred endemically throughout the year. The clinical diagnoses were primarily upper respiratory tract infections (45.4%), lower respiratory tract infections (48.1%), and neurologic disease (5.2%). Associated symptoms, signs and laboratory findings included fever (91.9%), cough (83.9%), pharyngeal injection (62.3%), rale (32.6%) and elevated C-reactive protein (93.9%). The most common radiologic findings were perihilar and peribronchial infiltrates (42.6%). Co-infections were observed in 29 cases. The mean durations of hospitalization and fever were 6.2 ± 6.5 and 4.8 ± 3.1 days, respectively. The lengths of hospitalization were similar for patients admitted for upper respiratory tract infections with severe morbidity and those admitted for lower respiratory tract infections. No children in the study died.

CONCLUSION

Our study demonstrates that respiratory adenovirus infections are an important cause of hospitalization in young children, and contribute to a significant morbidity.

Atypical bacterial pathogen infection in children with acute bronchiolitis in northeast Thailand

BACKGROUND

Atypical bacterial pathogens--including Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Chlamydia trachomatis--are important infectious agents of the respiratory system. Most current information pertains to adults and little is known about the role of these organisms in lower respiratory tract infections among young children with acute bronchiolitis.

METHODS

This study detected these pathogens in the nasopharyngeal secretions of children between 1 month and 2 years of age admitted with acute bronchiolitis to hospitals in Khon Kaen, northeast Thailand. The M pneumoniae and C pneumoniae in the nasopharyngeal secretions were detected using multiplex and nested-polymerase chain reaction (PCR), whereas PCR and restriction fragment length polymorphism were used to investigate C trachomatis. These samples were also tested by multiplex reverse transcriptase PCR for respiratory viruses, including respiratory syncytial virus (RSV), influenza A, influenza B, and human metapneumovirus.

RESULTS

Of the 170 samples taken from hospitalized children with acute bronchiolitis, 12.9% were infected with atypical bacteria and 85.3% with respiratory viruses. RSV was the most common causative viral agents found in 64.7% of the samples. M pneumoniae was the most common atypical bacterial pathogen (14/170, 8.2%) and most of the patients infected with it were between 6 and less than 12 months of age (71 cases). Of the infected cases in this age group, 7 of 14 were infected with M pneumoniae and 4 of 4 with C pneumoniae. Both M pneumoniae (13/14) and C pneumoniae (4/4) had etiologies indicating viral coinfections. Four (2.4%) of all of the cases had C trachomatis infections and all of these were infected with RSV, including three patients less than 6 months of age.

CONCLUSION

These results suggest that in children with virus-induced acute bronchiolitis coinfection with M pneumoniae, C pneumoniae, or C trachomatis can be expressed differently in each age group. These atypical bacteria may be the important infectious agents that induce severe illness of acute bronchiolitis.

Comparison of commercial systems for extraction of nucleic acids from DNA/RNA respiratory pathogens

This study compared six automated nucleic acid extraction systems and one manual kit for their ability to recover nucleic acids from human nasal wash specimens spiked with five respiratory pathogens, representing Gram-positive bacteria (Streptococcus pyogenes), Gram-negative bacteria (Legionella pneumophila), DNA viruses (adenovirus), segmented RNA viruses (human influenza virus A), and non-segmented RNA viruses (respiratory syncytial virus). The robots and kit evaluated represent major commercially available methods that are capable of simultaneous extraction of DNA and RNA from respiratory specimens, and included platforms based on magnetic-bead technology (KingFisher mL, Biorobot EZ1, easyMAG, KingFisher Flex, and MagNA Pure Compact) or glass fiber filter technology (Biorobot MDX and the manual kit Allprep). All methods yielded extracts free of cross-contamination and RT-PCR inhibition. All automated systems recovered L. pneumophila and adenovirus DNA equivalently. However, the MagNA Pure protocol demonstrated more than 4-fold higher DNA recovery from the S. pyogenes than other methods. The KingFisher mL and easyMAG protocols provided 1- to 3-log wider linearity and extracted 3- to 4-fold more RNA from the human influenza virus and respiratory syncytial virus. These findings suggest that systems differed in nucleic acid recovery, reproducibility, and linearity in a pathogen specific manner.

Adenovirus Infection Dramatically Augments Lipopolysaccharide-Induced TNF Production and Sensitizes to Lethal Shock

We observed a remarkable synergism of adenoviruses and LPS in triggering the production of TNF in intact animals. We found that in mice pre-exposed to adenoviruses, LPS injections generated extremely high levels of TNF with altered kinetics. The elevated TNF synthesis stemmed mostly from posttranscriptional up-regulation of TNF production, although transcription of the TNF gene was also induced. Adenoviruses and LPS exhibited a significant but less dramatic synergism in the induction of IL-6, IFN-gamma, and NO. Only marginal changes were detected in the synthesis of a panel of other cytokines. Different serotypes of the virus showed practically identical effects. As deletion mutants lacking indispensable viral genes or UV inactivated virions exhibited similar activities as the infectious, wild-type virus, it seems unlikely that the viral genome plays any significant role in the phenomenon. Published data indicate that other viruses also show some kind of synergism with LPS, although by different cellular mechanisms. T cells and their IFN-gamma production--crucial in the synergism of influenza viruses and LPS--were dispensable in our experiments. We suggest that the phenomenon is probably a general one: an overlap between different molecular mechanisms detecting bacterial and viral pathogens and inducing mediators of nonspecific cell-mediated host defense. The synergism of viruses and LPS (bacteria) could be a concern in medical practice as well as in gene therapy experiments with high doses of recombinant adenoviruses.

Increased sensitivity to staphylococcal enterotoxin B following adenoviral infection

Staphylococcal enterotoxin B induces toxic shock and is a major virulence factor of staphylococcal diseases. We examined the effects of systemic adenoviral infection on responses to staphylococcal enterotoxin B in a murine model. We found that adenoviral infection markedly increases the severity of liver injury following exposure to staphylococcal enterotoxin B without d-galactosamine sensitization. In adenovirus-infected mice, staphylococcal enterotoxin B triggered a more profound hypothermia and increased apoptosis in the liver. Consistent with these observations, we also found that adenoviral infection primed for an increased production of gamma interferon in vivo and in vitro following stimulation with staphylococcal enterotoxin B. Gamma-interferon-knockout mice did not show increased sensitivity to staphylococcal enterotoxin B following adenoviral infection. These data suggest that a preexisting viral infection primes mice for subsequent staphylococcal enterotoxin B exposure, possibly via a gamma-interferon-mediated mechanism.

Chinchilla and murine models of upper respiratory tract infections with respiratory syncytial virus

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infections in infants and the elderly. While the primary infection is the most serious, reinfection of the upper airway throughout life is the rule. Although relatively little is known about either RSV infection of the upper respiratory tract or host mucosal immunity to RSV, recent literature suggests that RSV is the predominant viral pathogen predisposing to bacterial otitis media (OM). Herein, we describe mouse and chinchilla models of RSV infection of the nasopharynx and Eustachian tube. Both rodent hosts were susceptible to RSV infection of the upper airway following intranasal challenge; however, the chinchilla proved to be more permissive than the mouse. The chinchilla model will likely be extremely useful to test the role of RSV in bacterial OM and the efficacy of RSV vaccine candidates designed to provide mucosal and cytotoxic T-lymphocyte immunity. Ultimately, we hope to investigate the relative ability of these candidates to potentially protect against viral predisposal to bacterial OM.

Adenoviral infection decreases mortality from lipopolysaccharide-induced liver failure via induction of TNF-alpha tolerance

Effects of adenoviral infection on in vivo responses to LPS mediated by TNF-alpha were evaluated in a murine model. Adenovirus-infected mice showed decreased mortality from fulminant hepatitis induced by administration of LPS or staphylococcal enterotoxin B in the presence of D-galactosamine. Importantly, TNF-alpha resistance genes within adenoviral E3 region were not required, because E1,E3-deleted vectors showed similar effects. Adenovirus-infected mice exhibited higher TNF-alpha levels after LPS stimulation, no difference in TNFR1 expression, and similar mortality from Fas-induced fulminant hepatitis. Decreased production of IL-6 and KC in response to exogenous TNF-alpha, in addition to protection from TNF-alpha, suggested that adenoviral infection results in TNF-alpha tolerance.

Mixed microbial aetiology of community-acquired pneumonia in children

Seven paediatric studies on community-acquired pneumonia with serological methods for both viruses and bacteria have been published, allowing the evaluation of concomitant multiple etiological findings. In these studies, dual viral infection has been present in 0-14%, dual bacterial infection likewise in 0-14%, and mixed viral-bacterial infection in 3-30% of the pneumonia cases. The results confirm former clinical observations that respiratory viruses often pave the way for airway-colonising bacteria. The measured frequency of multiple infections has been dependent on the available test panel, mainly on the tests used for pneumococcal aetiology. Mixed viral-bacterial infections have been especially common in young children under 2 years of age, reflecting the high frequency of respiratory syncytial virus infections and their tendency to induce bacterial co-infections. No microbe-specific viral-bacterial associations have been demonstrated. The clinical implications of mixed viral-bacterial infections, compared with viral infections alone or bacterial infections alone, have so far remained unresolved. Current guidelines recommend antibiotic therapy for all community-acquired pneumonia cases in children.

A comparison of nested polymerase chain reaction and immunofluorescence for the diagnosis of respiratory infections in children with bronchiolitis, and the implications for a cohorting strategy

Cohorting bronchiolitis patients infected with respiratory syncytial virus (RSV) and/or influenza viruses is paramount in preventing cross-infection of these viruses in hospital. Nested polymerase chain reaction (nPCR) was compared with immunofluorescence (IF) for the detection of RSV subtypes A and B in children with suspected bronchiolitis. Co-infection with influenza A(H3N2), Chlamydia spp. and picornavirus/rhinovirus was also investigated using molecular techniques.A total of 50 nasopharyngeal secretions collected from babies admitted with bronchiolitis in the month of January 2000, comprising IF RSV positive (N= 27) and RSV negative (N= 23) specimens, were tested for both RSV subtypes, influenza A(H3N2), Chlamydia spp. and picornavirus/rhinovirus by nPCR. Nested PCR detected 28 specimens positive for RSV (RSV A = 20, RSV B = 8), which was two more than detected by IF. Influenza A(H3N2) was detected in three specimens, Chlamydia trachomatis in one, and picornavirus in 11, of which nine were confirmed to be rhinovirus by nPCR. Dual infection was detected in five cases using nPCR. Nested PCR proved useful in detecting RSV and influenza A(H3N2) infections missed by IF, and also other respiratory tract pathogens not routinely investigated. The clinical implications and risk of cross-infection with potentially virulent viruses due to inaccurate results from insensitive techniques, highlights the need for molecular assays such as nPCR to be employed as a routine method of investigation, provided as part of the laboratory service. Cohorting of patients with clinical bronchiolitis should continue, whilst awaiting laboratory confirmation.

[Epidemiology of community-acquired pneumonia in children. Current data]

Viruses, particularly syncitial respiratory virus, are the main aetiology of community-acquired lower respiratory tract infections in infants, while bacterial agents are more frequently responsible in children older than 3 years. Antimicrobial therapy must take into account the development of reduced susceptibility of penicillin to strains of Streptoccocus pneumoniae and Haemophilus influenzae with beta-lactamase, and high frequency of Mycoplasma pneumoniae and Chlamydia pneumoniae infections. Although the mortality rate has remained low in France, the morbidity appeared to increase in recent years.

Aerobic bacteria, Chlamydia trachomatis, Pneumocystis carinii and Cytomegalovirus as agents of severe pneumonia in small infants

The authors studied 58 infants hospitalized for pneumonia in a semi-intensive care unit. Age ranged from 1 complete to 6 incomplete months. The infants were sent from another hospital in 20 cases and from home in a further 38. Pulmonary involvement, which was alveolar in 46 cases and interstitial in 12, was bilateral in 31 children. The investigation was carried out prospectively on the etiological agents associated with respiratory infection to look for evidence of aerobic bacteria (blood cultures), Chlamydia trachomatis and Cytomegalovirus (serology), and Pneumocystis carinii (direct microscopy of tracheal aspirated material). The following infectious agents were diagnosed in 21 children (36.2%): Aerobic bacteria (8), Chlamydia trachomatis (5), Pneumocystis carinii (3), Cytomegalovirus (3), Cytomegalovirus and Chlamydia trachomatis (1), Aerobic bacteria and Cytomegalovirus (1). Seven cases of infection by Chlamydia trachomatis and/or Cytomegalovirus were diagnosed out of the 12 cases with pulmonary interstitial involvement.

Adenovirus pneumonia in lung transplant recipients

Although Adenovirus (ADV) pneumonia has been documented in bone marrow, kidney, and liver transplantation recipients, it has only been sporadically reported in lung transplantation recipients. Among our 308 lung transplantation recipients, we identified four who developed ADV pneumonia. Formalin-fixed paraffin-embedded biopsy and autopsy specimens on all cases were studied by routine histology, immunohistochemistry (IHC), and by in situ hybridization (ISH) for evidence of ADV, and the results were correlated with the patients' clinical progression. Three of the four patients were children, and all four had a progressive and rapidly fatal course within 45 days posttransplantation. The lungs showed necrotizing bronchocentric pneumonia with tendency to spread diffusely to produce alveolar damage and organizing pneumonia. The occurrence of this rapidly fatal ADV pneumonia mainly affecting the pediatric population, early in the posttransplantation course, suggests that the infection is primary to the recipient with ADV either originating and reactivating in the donor lung or acquired from the upper respiratory tract of the recipient. The characteristic smudgy intranuclear inclusions of ADV, as well as IHC and ISH positivity, were observed in the lungs of all autopsies. Antemortem biopsy demonstration of ADV by inclusion formation, IHC, and ISH was observed in two patients. In another patient, antemortem ADV was shown only by ISH, and the recognition of inclusions was made difficult by coexistent CMV infection. Although IHC and ISH may have the potential for detecting early infection, recognition of the characteristic clinical setting with necrotizing bronchocentric pneumonia and smudgy intranuclear inclusions should alert one to the diagnosis of ADV pneumonia.

Comparison of radiological findings and microbial aetiology of childhood pneumonia

Sixty-one children were treated in hospital from 1981 to 1982 because of both radiologically and microbiologically verified viral or bacterial pneumonia. The chest radiographs were interpreted by two radiologists, not familiar with the clinical data, on two occasions three years apart, and only those patients with a definite alveolar (n = 27) or interstitial (n = 34) pneumonia at both evaluations were included in the present analysis. In addition, all patients had viral (n = 20), mixed viral-bacterial (n = 21) or bacterial (n = 20) infections diagnosed by viral or bacterial antibody or antigen assays. Viral infection alone was seen in 7 (26%), mixed viral-bacterial infection in 8 (30%) and bacterial infection alone in 12 (44%) of the 27 patients with alveolar pneumonia. The respective figures were 13 (38%), 13 (38%) and 8 (24%) for the 34 patients with interstitial pneumonia. C-reactive protein concentration was greater than 40 mg/l (a screening limit for viral and bacterial infections) in 15 (56%) of the patients with alveolar and in 11 (32%) of the patients with interstitial pneumonia. Thus 74% of the patients with alveolar and 62% with interstitial pneumonia had bacterial infection, either alone or as a mixed viral-bacterial infection. Our results suggest that the presence of an alveolar infiltrate in a chest radiograph is a specific but insensitive indicator of bacterial pneumonia. We conclude that patients with alveolar pneumonia should be treated with antibiotics. In patients with interstitial pneumonia, however, both viral and bacterial aetiology are possible. In those, the decision concerning antibiotic treatment should be based on clinical and laboratory findings.

Fever and neutropenia: bacterial etiology revealed by serological methods

In a prospective study, 91 episodes of fever in neutropenic children with cancer were evaluated. Fifteen episodes were septicemias, verified by a positive blood culture, 62 were fevers of unknown origin, 6 were focal infections and 8 were of other etiologies (i.e. drug fevers and viral infections). Serum antibody responses to bacteria were measured in paired sera by an enzyme immunoassay method. Bacterial infection was demonstrated serologically in 20% of documented septicemias, in 35% of fevers of unknown origin and occasionally in the other groups. Tests were available and found positive in the fever of unknown origin group for Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella (Branhamella) catarrhalis and enterobacteria. Some had multiple etiology. In conclusion, bacterial serology is a promising method of identifying bacterial etiology in fever of otherwise unknown origin in neutropenic children with cancer.

Antigen and antibody assays in the aetiological diagnosis of respiratory infection in children

The diagnostic efficacy of two methods--demonstration of seroconversion in paired sera and detection of antigen in clinical specimens--was evaluated in 183 children with respiratory syncytial, parainfluenza or adenoviral, or pneumococcal respiratory tract infection. Viral infection was diagnosed in 46 (37%) of the 125 cases by antigen assay alone, in 36 (29%) by antibody assay alone and in 43 (34%) by both methods. In respiratory syncytial viral infections, antigen assays were more often positive than antibody assays; 80% of the cases were antigen positive and 63% solely antigen positive. In parainfluenza and adenoviral infections, antigen assays were not as useful; a positive result was seen in 59% and 44% of cases, respectively. Pneumococcal infection was diagnosed in 25 (30%) of the 84 cases by antigen assay alone, in 54 (64%) by antibody assay alone and in only 5 (6%) by both methods. Thus nearly all pneumococcal infections were diagnosed by only one method. The efficacy of antigen and antibody assay was clearly dependent on the age of the patients. In infants less than six months of age, nearly all (27 (90%)) of the 30 infections were diagnosed by antigen detection; 25 solely by antigen detection. In older patients, antigen and antibody assays supplemented each other. We conclude that antigen detection should be used as the primary method for the diagnosis of viral or pneumococcal respiratory tract infection. In infants, antigen detection is the only reliable method of microbial diagnosis. In addition, antigen detection is the method of rapid microbial diagnosis. In pneumococcal infections, the sensitivities of antigen detection methods are not sufficient; this is an important area for further research.

Aetiology of community-acquired pneumonia in children treated in hospital

Viral and bacterial antigen and antibody assays were prospectively applied to study the microbial aetiology of community-acquired pneumonia in 195 hospitalised children during a surveillance period of 12 months. A viral infection alone was indicated in 37 (19%), a bacterial infection alone in 30 (15%) and a mixed viral-bacterial infection in 32 (16%) patients. Thus, 46% of the 69 patients with viral infection and 52% of the 62 patients with bacterial infection had a mixed viral and bacterial aetiology. Respiratory syncytial virus (RSV) was identified in 52 patients and Streptococcus pneumoniae in 41 patients. The next common agents in order were non-classified Haemophilus influenzae (17 cases), adenoviruses (10 cases) and Chlamydia species (8 cases). The diagnosis of an RSV infection was based on detecting viral antigen in nasopharyngeal secretions in 79% of the cases. Pneumococcal infections were in most cases identified by antibody assays; in 39% they were indicated by demonstrating pneumococcal antigen in acute phase serum. An alveolar infiltrate was present in 53 (27%) and an interstitial infiltrate in 108 (55%) of the 195 patients. The remaining 34 patients had probable pneumonia. C-reactive protein (CRP), erythrocyte sedimentation rate and total white blood cell count were elevated in 25%, 40% and 36% of the patients, respectively. CRP was more often elevated in patients with bacterial infection alone than in those with viral or mixed viral-bacterial infections. No other correlation was seen between the radiological or laboratory findings and serologically identified viral, bacterial or mixed viral-bacterial infections.(ABSTRACT TRUNCATED AT 250 WORDS)

C-reactive protein in viral and bacterial respiratory infection in children

C-reactive protein (CRP) was studied in 209 children treated in hospital due to middle or lower respiratory tract infection with serologically demonstrated viral or bacterial aetiology. Of the 110 patients with serological evidence of bacterial infection, either alone or in association with viral infection, 52% had CRP > 20 mg/l, 35% > 40 mg/l and 15% > 80 mg/l. Of the 99 patients with serological evidence of viral infection alone, 35% had CRP > 20 mg/l, but only 12% > 40 mg/l and 5% > 80 mg/l. Nearly all, 88%, of the 25 patients with CRP > 40 mg/l in association with viral infection had either an infectious focus, specific microbial or non-specific laboratory evidence suggestive of bacterial infection. By calculating diagnostic parameters at 3 cut-off levels of CRP, the level 40 mg/l seemed more useful than 20 mg/l or 80 mg/l for differentiation between viral and bacterial infections. By using a CRP value of 40 mg/l as a screening limit sensitivity was 0.55, specificity 0.88, positive predictive value 0.76, negative predictive value 0.55, and likelihood ratios of a positive and negative test result 2.9 and 0.74, respectively. It is concluded that low CRP values do not rule out bacterial aetiology of respiratory infection in children. On the other hand viral infection without bacterial involvement is very improbable if CRP is > 40 mg/l. Our results suggest that high CRP values rule out viral infection as a sole aetiology of infection; bacterial infection and antibiotic treatment should be considered in these cases.

Role of non-capsulated Haemophilus influenzae as a respiratory pathogen in children

During a 12-month surveillance period from 1981-1982, non-capsulated Haemophilus influenzae was detected in nasopharyngeal aspirates from 64 (14%) of the 449 children hospitalized for middle or lower respiratory infection. An antibody response to H. influenzae was indicated in 15(23%) of the 64 patients with H. influenzae present in nasopharyngeal aspirate and in 10 (3%) of the 385 patients with a negative finding. Thus, serological evidence of H. influenzae infection was demonstrated in 25 (6%) of all the 449 children with respiratory infection. Of 13 patients with cultures positive for H. influenzae acute otitis media, an antibody response was seen in only 4 (30%) patients. H. influenzae infection was associated with infections caused by other microbes in 20 children (80%), with viral infections in 60% and with pneumococcal infections in 24% of cases. An infection focus was present in 15 (79%) of the 25 patients with H. influenzae infection; pneumonia was present in 10 cases and acute otitis media in 9 cases. Non-specific laboratory evidence of bacterial infection was seen in 11 patients (58%); C-reactive protein was increased in 7 and erythrocyte sedimentation rate in 9 patients. It is concluded that non-capsulated H. influenzae is a genuine respiratory pathogen in children. H. influenzae infections appear to be secondary to preceding viral or other bacterial infections in children who are carriers of this strain.

Role of Moraxella (Branhamella) catarrhalis as a respiratory pathogen in children

During a 12-month surveillance period in 1981-1982, Moraxella catarrhalis was detected in cultures from nasopharyngeal aspirates from 76 (17%) of 449 children hospitalized with middle or lower respiratory tract infection. Seroconversion to M. catarrhalis was positive in 4 (5%) of the 76 patients with M. catarrhalis present in nasopharyngeal aspirates and in 4 (1%) of 373 patients with a negative finding. Although children with respiratory tract infections were often colonized by the organism, this was rarely the infective agent of the middle or lower airways. Four of 8 patients with seroconversion to M. catarrhalis exhibited a concomitant RSV infection. The carriage of this species was more closely associated with parainfluenza virus infections. Serological responses to M. catarrhalis were not associated with acute otitis media, and were also rare in children with pneumonia. It is concluded that bronchopulmonary infections caused by M. catarrhalis are rare in children, and that M. catarrhalis aetiology need not be considered in the selection of antibiotics in cases of community-acquired pneumonia or other infections of the middle or lower respiratory tract affecting primarily healthy children.

Pneumococcal finding in a sample from upper airways does not indicate pneumococcal infection of lower airways

The presence of pneumococcus (Pnc) by antigen detection and culture was examined in nasopharyngeal aspirates (NPA) of 315 children hospitalized with middle or lower respiratory tract infection. Pnc was found in NPA from 115 (37%) patients, being demonstrated by antigen detection alone in 34 (30%), by culture alone in 26 (23%) and by both methods in 55 (48%) of Pnc-positive samples. Pnc findings in NPA were most common, 45-46%, in patients aged 1-4 years. Serological evidence of Pnc infection, based either on detection of Pnc antigen in serum or urine, or on demonstration of an antibody response to these antigens, was present in 31 (27%) of the 115 patients with and in 28 (14%) of the 200 patients without Pnc in NPA samples. In the 48 patients positive for Pnc in NPA samples both by antigen detection and culture the isolated Pnc strains were serotyped. In 45 (94%) of these the type/group of Pnc was the same by both methods indicating that the specificity of the antigen detection tests, latex particle agglutination and counterimmunoelectrophoresis, was high. To evaluate the diagnostic significance of Pnc antigen detection and culture in NPA, sensitivity, specificity and likelihood ratios were calculated; serological evidence of Pnc aetiology was used as a reference. For both methods, sensitivity was poor, less than 0.3, but specificity was good, greater than 0.8. It is concluded that the finding of Pnc by culture or antigen detection in NPA is no indication of Pnc respiratory infection. On the other hand, Pnc etiology is unprobable, if Pnc is not present in NPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Serologically indicated pneumococcal respiratory infection in children

Streptococcus pneumoniae infection was indicated serologically in 84 (19%) of 449 children hospitalized with middle or lower respiratory tract infection. Pneumococcal antigen was detected in acute serum in 28 patients, but in acute urine in only 2. An antibody response to type-specific capsular polysaccharides of S. pneumoniae was indicated in 27 patients and to a protein antigen, pneumolysin, in 25 patients, but to C-polysaccharide in only 10 patients. The observations mentioned above suggest that each serological test for pneumococcal etiology is insensitive, and to get an optimal result, a large panel of pneumococcal antigen and antibody assays must be used. Pneumococcal infection could be indicated serologically although no focus of infection, such as pneumonia or acute otitis media, or no laboratory evidence of bacterial infection as elevated values of C-reactive protein concentration, erythrocyte sedimentation rate or white blood cell count was present. Particularly antibody responses to pneumococcal pneumolysin were present in children without pneumonia or acute otitis media. Our results point out that no nonspecific parameter can be used for the selection of patients with probable pneumococcal etiology among children with respiratory tract infection. Concomitant viral infection, in most cases RSV infection, was present in a third of the children with pneumococcal infection. It is concluded that pneumococcal etiology should be actively sought for also in patients with viral respiratory infection, especially in young children with RSV infection.

Bacterial infection in under school age children with expiratory difficulty

Serological evidence of bacterial infection was prospectively studied in less than 6 years old patients during 188 acute episodes of expiratory difficulty requiring hospital treatment. Such evidence indicated by antibody or antigen assays was found in 40 patients (21%). Streptococcus pneumoniae was identified in 25 cases; antigenemia was found in 10, antigenuria in 2 and seroconversion in 14 cases. Seroconversion to nontypable Haemophilus influenzae was found in 9 and to Branhamella catarrhalis in 2 cases. Seroconversion to Chlamydia spp. was demonstrated in 8 patients, but specific tests for C. trachomatis were negative. C-reactive protein was over 40 mg/L in 35 patients (19%); serological evidence of bacterial infection was present in 14 and absent in 21 of them. Thus, either serological evidence of bacterial infection or an elevated C-reactive protein was found in 61 of the 188 cases (32%). We conclude that bacterial infection is commonly associated with acute wheezing in children under school age. We suggest that bacterial, as well as viral, infections may trigger an acute obstructive attack in children with reactive airways.