Determination of avidity of IgG against protein antigens from Streptococcus pneumoniae: assay development and preliminary application in clinical settings.

The measurement of antibody levels is a common test for the diagnosis of Streptococcus pneumoniae infection in research. However, the quality of antibody response, reflected by avidity, has not been adequately evaluated. We aimed to evaluate the role of avidity of IgG against eight pneumococcal proteins in etiologic diagnosis. Eight pneumococcal proteins (Ply, CbpA, PspA1 and 2, PcpA, PhtD, StkP-C, and PcsB-N) were used to develop a multiplex bead-based avidity immunoassay. The assay was tested for effects of the chaotropic agent, multiplexing, and repeatability. The developed assay was applied to paired samples from children with or without pneumococcal disease (n = 38 for each group), determined by either serology, polymerase chain reaction (PCR), or blood culture. We found a good correlation between singleplex and multiplex assays, with r ≥ 0.94.The assay was reproducible, with mean inter-assay variation ≤ 9% and intra-assay variation < 6%. Children with pneumococcal disease had lower median avidity indexes in the acute phase of disease for PspA1 and 2 (p = 0.042), PcpA (p = 0.002), PhtD (p = 0.014), and StkP-C (p < 0.001). When the use of IgG avidity as a diagnostic tool for pneumococcal infection was evaluated, the highest discriminative power was found for StkP-C, followed by PcpA (area under the curve [95% confidence interval, CI]: 0.868 [0.759-0.977] and 0.743 [0.607-879], respectively). The developed assay was robust and had no deleterious influence from multiplexing. Children with pneumococcal disease had lower median avidity against five pneumococcal proteins in the acute phase of disease compared to children without disease.

Detection of antibody responses against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis proteins in children with community-acquired pneumonia: effects of combining pneumococcal antigens, pre-existing antibody levels, sampling interval, age, and duration of illness.

We evaluated the effects of combining different numbers of pneumococcal antigens, pre-existing antibody levels, sampling interval, age, and duration of illness on the detection of IgG responses against eight Streptococcus pneumoniae proteins, three Haemophilus influenzae proteins, and five Moraxella catarrhalis proteins in 690 children aged <5 years with pneumonia. Serological tests were performed on acute and convalescent serum samples with a multiplexed bead-based immunoassay. The median sampling interval was 19 days, the median age was 26.7 months, and the median duration of illness was 5 days. The rate of antibody responses was 15.4 % for at least one pneumococcal antigen, 5.8 % for H. influenzae, and 2.3 % for M. catarrhalis. The rate of antibody responses against each pneumococcal antigen varied from 3.5 to 7.1 %. By multivariate analysis, pre-existing antibody levels showed a negative association with the detection of antibody responses against pneumococcal and H. influenzae antigens; the sampling interval was positively associated with the detection of antibody responses against pneumococcal and H. influenzae antigens. A sampling interval of 3 weeks was the optimal cut-off for the detection of antibody responses against pneumococcal and H. influenzae proteins. Duration of illness was negatively associated with antibody responses against PspA. Age did not influence antibody responses against the investigated antigens. In conclusion, serological assays using combinations of different pneumococcal proteins detect a higher rate of antibody responses against S. pneumoniae compared to assays using a single pneumococcal protein. Pre-existing antibody levels and sampling interval influence the detection of antibody responses against pneumococcal and H. influenzae proteins. These factors should be considered when determining pneumonia etiology by serological methods in children.

Distinct regulation of tonsillar immune response in virus infection.

BACKGROUND: The relationships between tonsillar immune responses, and viral infection and allergy are incompletely known. OBJECTIVE: To study intratonsillar/nasopharyngeal virus detections and in vivo expressions of T-cell- and innate immune response-specific cytokines, transcription factors, and type I/II/III interferons in human tonsils. METHODS: Palatine tonsil samples were obtained from 143 elective tonsillectomy patients. Adenovirus, bocavirus-1, coronavirus, enteroviruses, influenza virus, metapneumovirus, parainfluenza virus, rhinovirus, and respiratory syncytial virus were detected using PCR. The mRNA expression levels of IFN-α, IFN-ß, IFN-γ, IL-10, IL-13, IL-17, IL-28, IL-29, IL-37, TGF-ß, FOXP3, GATA3, RORC2, and Tbet were directly analyzed by quantitative RT-PCR. RESULTS: Fifty percentage of subjects reported allergy, 59% had ≥1 nasopharyngeal viruses, and 24% had ≥1 intratonsillar viruses. Tonsillar virus detection showed a strong negative association with age; especially rhinovirus or parainfluenza virus detection showed positive association with IFN-γ and Tbet expressions. IL-37 expression was positively associated with atopic dermatitis, whereas IFN-α, IL-13, IL-28, and Tbet expressions were negatively associated with allergic diseases. Network analyses demonstrated strongly polarized clusters of immune regulatory (IL-10, IL-17, TGF-ß, FOXP3, GATA3, RORC2, Tbet) and antiviral (IFN-α, IFN-ß, IL-28, IL-29) genes. These two clusters became more distinctive in the presence of viral infection or allergy. A negative correlation between antiviral cytokines and IL-10, IL-17, IL-37, FOXP3, and RORC2 was observed only in the presence of viruses, and interestingly, IL-13 strongly correlated with antiviral cytokines. CONCLUSIONS: Tonsillar cytokine expression is closely related to existing viral infections, age, and allergic illnesses and shows distinct clusters between antiviral and immune regulatory genes.

Normal behavior of plasma procalcitonin in adolescents undergoing surgery for scoliosis.

BACKGROUND AND AIMS: Surgical site infections are relatively common after spinal deformity surgery. Early detection of deep wound infections is important, since it may allow retention of spinal instrumentation. However, serum C-reactive protein and erythrocyte sedimentation rate may remain elevated for almost 6 weeks, making differential diagnosis of systemic inflammatory response and acute deep bacterial wound infection difficult. Plasma procalcitonin has been suggested to be a useful indicator for bacterial infection. However, there are no studies evaluating behavior of procalcitonin in patients undergoing major spine surgery with instrumentation. MATERIALS AND METHODS: A total of 50 consecutive adolescents (37 idiopathic scoliosis and 13 neuromuscular scoliosis, mean age = 15 years at surgery and follow-up time = 21 months (range = 12-29 months)) undergoing scoliosis surgery participated in this prospective follow-up study. White blood cell count, serum C-reactive protein, and plasma procalcitonin levels were measured on the day before surgery, on the day of surgery, and daily thereafter for 1 week. None of the patients developed signs of acute or delayed wound infection during the follow-up period; however, two neuromuscular scoliosis patients developed severe postoperative pneumonia, and their inflammatory parameter data will be reported separately. RESULTS: Plasma procalcitonin levels peaked on the first postoperative day (mean = 0.19 ng/mL, range = 0.04-1.29 ng/mL), and mean values were less than 0.5 ng/mL during the whole first postoperative week, while C-reactive protein remained elevated during the whole first postoperative week (highest mean value = 63.8 mg/L (range = 5-248 mg/L) on third postoperative day). Patients with idiopathic scoliosis had lower C-reactive protein levels (p < 0.05 from first to sixth postoperative day) and lower procalcitonin levels (p < 0.05 from third to seventh postoperative day) than neuromuscular scoliosis patients. Two patients with postoperative pneumonia showed elevated procalcitonin values over the whole postoperative week (22.34 ng/mL and 0.72 ng/mL highest values, respectively). CONCLUSIONS: Elevated plasma procalcitonin levels seem useful when excluding acute deep wound infection from systemic inflammatory response.

Human parvoviruses B19, PARV4 and bocavirus in pediatric patients with allogeneic hematopoietic SCT.

Among the immunocompetent, infections with parvovirus B19 (B19V) and human bocavirus (HBoV) 1 range clinically from asymptomatic to severe, while following allogeneic hematopoietic SCT (HSCT) B19V can cause a persistent severe illness. The epidemiology and clinical impact of HBoV1 and the other emerging parvovirus 4 (PARV4) among immunocompromised patients have not been established. To determine the occurrence and clinical spectrum of B19V, PARV4 and HBoV1 infections, we performed a longitudinal molecular surveillance among 53 allogeneic HSCT recipients for pre- and post-HSCT DNAemias of these parvoviruses. Quantitative real-time PCR showed B19V DNA in sera of 16 (30%) patients, at mean levels of 4.6 × 10(3), 9.9 × 10(7), 1.1 × 10(10) and 1.6 × 10(2) B19V DNA copies/mL pre-HSCT (9/53), and at 1 (6/53), 2 (4/53) and 3 months (1/25) post HSCT, respectively. However, no clinical manifestation correlated with the presence of B19V viremia. All B19V sequences were of genotype 1. None of the sera investigated contained PARV4 or HBoV1 DNAs. Our data demonstrate B19V viremia to be frequent among pediatric allogeneic HSCT recipients, yet without apparent clinical correlates. PARV4 or HBoV1 viremias were not seen in these immunocompromised patients.

Specific antibody deficiency in children with recurrent respiratory infections: a controlled study with follow-up.

Specific antibody deficiency (SAD) to unconjugated pneumococcal vaccine (PPV) is an established primary B cell immunodeficiency. The occurrence and natural history of SAD in children is unclear. We conducted an observational study to identify SAD in children with recurrent respiratory infections. Ninety-nine children, mean age 5·9 (range 2-16) years, with recurrent or severe infections were vaccinated with PPV; serum antibody concentrations for serotypes 4, 6B, 9V, 14, 18C, 19F and 23F were measured before and 2 weeks after vaccination with enzyme immunoassay. The retrospective control group consisted of 89 healthy children matched for age and gender. No children had received previous conjugated pneumococcal vaccine (PCV) or PPV. The structured history of infectious diseases of all participants was collected. Ten of 91 (11%) children (eight excluded due to immunoglobulin G subclass deficiency) with recurrent respiratory infections had SAD. In the control group, three children (3%) responded inadequately to PPV (P = 0·05). Most children with SAD also had many other minor immune defects. After 0·5-5 years (medium 3·8), eight children with SAD were revaccinated with PPV; five responded adequately and three inadequately. Two SAD children were revaccinated with PCV, one developed an adequate and one an inadequate response. Two children with SAD received treatment with intravenous immunoglobulin; the remaining eight children recovered without replacement therapy during the follow-up. SAD is common in young children with recurrent respiratory infections, but it is often transient and resolves itself within a few years without specific treatment.

Virus shedding after human rhinovirus infection in children, adults and patients with hypogammaglobulinaemia.

The shedding of human rhinovirus (HRV) after an acute, naturally acquired infection has not been described in detail. We determined the duration of HRV shedding in immunocompetent children and adults, and in patients with primary hypogammaglobulinaemia. Subjects with symptoms of respiratory tract infection, and their household contacts, were screened for HRV by reverse transcription PCR. They were followed by serial, self-collected nasal swab specimens until negative for HRV or infected by another HRV type. We followed 62 HRV infections in 54 subjects. The mean (95% CI) duration of HRV shedding was 11.4 (8.2-14.7) days in children, 10.1 (7.4-12.9) days in adults, and 40.9 (26.4-55.4) days in patients with hypogammaglobulinaemia (p <0.001). The duration of respiratory tract symptoms correlated with the duration of virus shedding (p 0.002). A new infection by another HRV type soon after the first episode was common. We conclude that the shedding times of HRV are relatively short in otherwise healthy individuals. In contrast, prolonged shedding over 28 days is frequent in patients with hypogammaglobulinaemia despite immunoglobulin replacement therapy.

Viruses and bacteria in sputum samples of children with community-acquired pneumonia.

Few comprehensive studies have searched for viruses and bacteria in children with community-acquired pneumonia (CAP). We identified 76 children hospitalized for pneumonia. Induced sputum samples were analysed for 18 viruses by antigen detection and PCR, and for six bacteria by culture and PCR. Viruses were found in 72% of samples, bacteria in 91%, and both in 66%. Rhinovirus (30%), human bocavirus (18%) and human metapneumovirus (14%) were the most commonly detected viruses. Two viruses were found in 22% of samples and three in 8%. The most common bacteria found were Streptococcus pneumoniae (50%), Haemophilus influenzae (38%), and Moraxella catarrhalis (28%). Rhinovirus-S. pneumoniae was the most commonly found combination of virus and bacterium (16%). All six children with treatment failure had both viruses and bacteria detected in the sputum. Otherwise, we found no special clinical characteristics in those with mixed viral-bacterial detections. With modern molecular diagnostic techniques, there are high rates of both viral and bacterial identification in childhood CAP. The clinical significance of mixed viral-bacterial infections remains unclear, although we found a potential association between them and treatment failure.

Admission diagnoses of children 0-16 years of age hospitalized with influenza.

The prompt diagnosis of influenza enables the institution of antiviral therapy and adequate cohorting of patients, but scarce data are available to help clinicians correctly suspect influenza in children at the time of admission. This 16-year retrospective study assessed the main admission diagnoses of 401 children aged ≤16 years hospitalized with virologically confirmed influenza. The clinical data were derived from a systematic review of the medical records of the children. Sepsis-like illness was the main reason for admission in 52% of infants aged <6 months and in 7-16% of the older children. Respiratory symptoms accounted for 38% of admissions, and 15% of children were hospitalized due to acute neurologic conditions, primarily febrile convulsions. Wheezing or exacerbation of asthma was the primary reason for admission in 14% of children aged <3 years. No differences were observed in the admission diagnoses between children with influenza A and B infections. The main admission diagnoses vary widely in different age groups of children with influenza, and only a minority of children are hospitalized for respiratory symptoms. The leading role of sepsis-like illness in infants aged <6 months calls for increased efforts to find protective measures against influenza in this age group.

Nasopharyngeal bacterial colonization during the first wheezing episode is associated with longer duration of hospitalization and higher risk of relapse in young children.

The purpose of this study was to examine the association between bacterial colonization/infection and respiratory outcomes in children younger than 3 years old who were hospitalized for their first wheezing episode. This was an observational study. The primary outcome was hospitalization time and the secondary outcomes included relapses within 2 months and time to recurrent wheezing (i.e. three physician confirmed wheezing episodes) within 12 months. Bacterial antibody assays for Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Mycoplasma pneumoniae and Chlamydia pneumoniae were studied as well as nasopharyngeal bacterial culture for the three former and urine pneumococcal antigen. Nasopharyngeal bacterial culture was positive in 31/52 (60%) children, serologic evidence of bacterial infection was found in 17/96 (18%) children, urine pneumococcal antigen was positive in 24/101 (24%), and any bacterial detection method was positive in 53/106 (50%) children. The children with positive nasopharyngeal bacterial culture had longer duration of hospitalization (hazard ratio 2.4) and more often relapsed within two months than those with negative culture (odds ratio 7.3). In this study, half of the first time wheezing children had bacterial colonization or symptomatic or asymptomatic bacterial infection. The bacterial colonization (i.e. positive nasopharyngeal bacterial culture) was associated with longer duration of hospitalization and higher risk of recurrent wheezing.

Allergic sensitization is associated with rhinovirus-, but not other virus-, induced wheezing in children.

BACKGROUND: Data on the link between atopy and viral wheeze are limited. AIM: To evaluate the association between IgE sensitization and viral infection in wheezing children. METHODS: This is an observational study in hospitalized wheezing children (n = 247; median age 1.6 ; interquartile range 1.1, 2.9). Eighteen respiratory viral infections were studied using all available methods. A specific immunoglobulin E (IgE) sensitization for common food and aeroallergens and other atopy-related variables including total IgE, blood and nasal eosinophils, exhaled nitric oxide, eczema and atopic eczema, parental allergy and asthma, number of wheezing episodes, positive asthma predictive index or asthma and use of inhaled corticosteroid were correlated with specific viral etiology. RESULTS: Atopy was closely associated with sole rhinovirus etiology (n = 58) but not with sole respiratory syncytial virus, sole enterovirus, sole human bocavirus, sole other virus, mixed viral, or virus negative etiology. The number of sensitizations was particularly associated with sole rhinovirus etiology (odds ratio 4.59; 95% confidence interval 1.78, 11.8; adjusted to age and sex), followed by aeroallergen sensitization (respectively; 4.18; 2.00, 8.72), total IgE level (2.06; 1.32, 3.21), food allergen sensitization (2.02; 1.08, 3.78), and nasal eosinophil count (1.52; 1.08, 2.13). CONCLUSIONS: According to our data, allergic sensitization is positively linked to rhinovirus-, but not other virus-, associated wheezing and calls attention for studies to test rhinovirus-associated wheezing as a part of asthma risk indices.

Recurrent wheezing after respiratory syncytial virus or non-respiratory syncytial virus bronchiolitis in infancy: a 3-year follow-up.

BACKGROUND: Recent studies have suggested that rhinovirus-associated early wheezing is a greater risk factor for development of recurrent wheezing in children than is early wheezing associated with respiratory syncytial virus (RSV). We determined the development of recurrent wheezing in young children within 3 years after hospitalization for RSV or non-RSV bronchiolitis. METHODS: We identified retrospectively all children <2 years of age who were admitted to Turku University Hospital because of bronchiolitis in the months of August-December during 1988-2001. The primary outcome was recurrent wheezing that required long-term asthma medication. Data on asthma medications of the individual children were derived from the Social Insurance Institution of Finland. RESULTS: Within the first year after hospitalization, 36 of 217 (16.6%) children with non-RSV bronchiolitis developed recurrent wheezing, compared with five of 199 (2.5%) children with RSV bronchiolitis [relative risk (RR) 6.6; 95% confidence interval (CI) 2.6-16.5]. The rates of recurrent wheezing were significantly increased in the non-RSV group also within 2 years (RR 2.9; 95% CI 1.7-5.1) and 3 years (RR 3.4; 95% CI 2.0-5.7) after hospitalization. The increased risk of recurrent wheezing in children with non-RSV-associated bronchiolitis was observed both in boys and girls at all time points of the 3-year follow-up, and it was not explained by the age difference between the RSV and non-RSV groups or any confounding seasonal factors. CONCLUSION: Children hospitalized with bronchiolitis caused by other viruses than RSV develop recurrent wheezing at substantially higher rates during a 3-year follow-up period than do children with RSV-induced bronchiolitis.

Induced sputum in the diagnosis of childhood community-acquired pneumonia.

BACKGROUND: The usefulness of induced sputum in searching for causative agents of pneumonia in children has not been studied. METHODS: The study involved 101 children, aged 6 months to 15 years, treated for community-acquired pneumonia at Turku University Hospital (Turku, Finland) from January 2006 to April 2007. Nasopharyngeal aspirate samples were first collected through both nostrils. Sputum production was then induced by inhalation of 5.0% hypertonic saline for 5-10 min and a sputum sample was either aspirated or expectorated. The presence and amount of bacteria and viruses in paired nasopharyngeal aspirate and sputum specimens was analysed and compared using semiquantitative bacterial culture and quantitative PCR techniques. RESULTS: A good quality sputum specimen was obtained from 76 children. The possible causative agent was found in 90% of cases. Streptococcus pneumoniae (46%) and rhinovirus (29%) were the most common microbes detected. Newly discovered viruses human bocavirus and human metapneumovirus were detected in 18% and 13% of the children, respectively. One-quarter of all bacterial findings were only detected in sputum, and the amount of bacteria in the remainder of the sputum specimens compared with nasopharyngeal aspirate was higher in 14% and equal in 70%. The amount of rhinovirus in sputum was higher than in nasopharyngeal aspirate in 82%. CONCLUSIONS: Sputum induction provides good quality sputum specimens with high microbiological yield in children with community-acquired pneumonia. Induced sputum analysis can be useful in the microbiological diagnosis of childhood community-acquired pneumonia.

Pneumococcal serology in children's respiratory infections.

The role of Streptococcus pneumoniae in the etiology of respiratory tract infections has been studied serologically using microbe-specific antibody and immune complex assays. Serological methods are sensitive in the bacteremic pneumococcal pneumonia of adults. In children, however, pneumococcal pneumonia is seldom bacteremic, and, thus, in the absence of a gold standard for the detection of pneumococcal infection, serological methods are still insufficiently validated. We report here indirect evidence for the sensitivity and specificity of pneumococcal serology in children. Serological evidence of pneumococcal infection has been found in 27% to 38% of children with radiologically confirmed pneumonia, in 7% to 8% of children with viral wheezy bronchitis, and in <1% to 5% of children and young adults with viral upper respiratory infection. Serological findings for pneumococcal infection have been dependent on the study venue, whether in hospital or ambulatory subjects, and on the test panel used. Where both antibody and immune complex assays have been available, the proportion of children with pneumococcal infection has been 32% to 37% in inpatients and 27% to 28% in outpatients. The respective rates have been 10% to 18% by antibody assays alone. Pneumococcal acute otitis media, when present with pneumonia, may confound findings in pneumococcal serology, but pure nasopharyngeal carriage of S. pneumoniae has little effect. In contrast, carriage acquisition of a new serotype may induce significant antibody production. Thus, understandably, significant rises between paired sera in antibodies to pneumococcal capsular polysaccharides and pneumococcal pneumolysin have been found in <1% to 3% of non-symptomatic children and young adults. Findings from the last 20 years indirectly suggest that pneumococcal antibody and immune complex assays are sensitive and specific enough for the detection of pneumococcal infection in children. However, the methods are too complex for routine clinical practice, and, so far, serological methods for S. pneumoniae infections have only been used for research purposes.

A randomized, controlled trial of tonsillectomy in periodic fever, aphthous stomatitis, pharyngitis, and adenitis syndrome.

OBJECTIVE: We carried out a prospective, randomized, controlled trial to clarify the effect of tonsillectomy on the clinical course of periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) syndrome. STUDY DESIGN: Twenty-six consecutive children (mean age 4.1 years) with at least 5 PFAPA attacks were recruited from 3 tertiary care pediatric hospitals during 1999-2003 and randomly allocated to tonsillectomy or follow-up alone. They were all followed up with symptom diaries for 12 months. Tonsillectomy was allowed after 6 months in the control group if the attacks recurred. RESULTS: Six months after randomization all 14 children in the tonsillectomy group and 6/12 children in the control group (50%) were free of symptoms (difference 50%, 95% confidence interval 23% to 75%, P < .001). Tonsillectomy was performed on 5/6 of the patients in the control group who still had symptoms after 6 months. The remaining unoperated child in the control group had recurrences of the fever episodes throughout the follow-up, but the symptoms became less severe, and the parents did not choose tonsillectomy. CONCLUSION: Tonsillectomy appeared to be effective for treating PFAPA syndrome. The fever episodes ceased without any intervention in half of the control subjects. We conclude that although the mechanisms behind this syndrome are unknown, tonsillectomy can be offered as an effective intervention for children with PFAPA.

Pneumolysin polymerase chain reaction for diagnosis of pneumococcal pneumonia and empyema in children.

Streptococcus pneumoniae is the most important cause of childhood pneumonia and empyema, yet the diagnosis of pneumococcal infections by conventional methods is challenging. In this study, the clinical value of the pneumolysin-targeted real-time polymerase chain reaction (PCR) method for the diagnosis of pneumococcal pneumonia and empyema was evaluated with 33 whole blood samples and 12 pleural fluid samples. The analytical sensitivity of the PCR assay was 4 fg of pneumococcal DNA, corresponding to two genome equivalents of pneumococcal DNA per reaction. The PCR assay correctly detected all clinical isolates of S. pneumoniae tested, whereas all nonpneumococcal bacterial organisms tested were negative by PCR. In a clinical trial, S. pneumoniae was detected by PCR in the pleural fluid of 75% of children with empyema, increasing the detection rate of pneumococcus almost tenfold that of pleural fluid culture. However, in whole blood samples, PCR detected S. pneumoniae in only one child with pneumonia and one child with pneumococcal empyema and failed to detect S. pneumoniae in three children with blood cultures positive for S. pneumoniae. The present data indicate that pneumolysin-targeted real-time PCR of pleural fluid is a valuable method for the etiologic diagnosis of pneumococcal empyema in children. The ease and rapidity of the LightCycler technology (Roche Diagnostics, Mannheim, Germany) make real-time PCR an applicable tool for routine diagnostics. In the evaluation of blood samples, blood culture remains the superior method for the diagnosis of bacteremic pneumococcal disease.

Bacterial coinfections in children with viral wheezing.

Bacterial coinfections occur in respiratory viral infections, but the attack rates and the clinical profile are not clear. The aim of this study was to determine bacterial coinfections in children hospitalized for acute expiratory wheezing with defined viral etiology. A total of 220 children aged 3 months to 16 years were investigated. The viral etiology of wheezing was confirmed by viral culture, antigen detection, serologic investigation, and/or PCR. Specific antibodies to common respiratory bacteria were measured from acute and convalescent serum samples. All children were examined clinically for acute otitis media, and subgroups of children were examined radiologically for sinusitis and pneumonia. Rhinovirus (32%), respiratory syncytial virus (31%), and enteroviruses (31%) were the most common causative viruses. Serologic evidence of bacterial coinfection was found in 18% of the children. Streptococcus pneumoniae (8%) and Mycoplasma pneumoniae (5%) were the most common causative bacteria. Acute otitis media was diagnosed in 44% of the children. Chest radiographs showed alveolar infiltrates in 10%, and paranasal radiographs and clinical signs showed sinusitis in 17% of the older children studied. Leukocyte counts and serum C-reactive protein levels were low in a great majority of patients. Viral lower respiratory tract infection in children is often associated with bacterial-type upper respiratory tract infections. However, coexisting bacterial lower respiratory tract infections that induce systemic inflammatory response are seldom detected.