Rapid diagnosis of pneumococcal pneumonia among HIV-infected adults with urine antigen detection

Septic arthritis induced by Streptococcus pneumoniae occurring in rheumatoid arthritis treated with abatacept and methotrexate: A case report

Septic arthritis occurs more frequently in elderly patients with rheumatoid arthritis (RA), with Staphylococcus aureus being the most common aetiologic agent. Rarely, Streptococcus pneumoniae (pneumococcus) is the cause of septic arthritis. Biological disease-modifying antirheumatic drugs (bDMARDs) are widely used in RA, but it is unknown whether bDMARDs could be a risk factor for pneumococcal septic arthritis in such patients. Here, we report the case of a patient with RA treated with bDMARDs (abatacept) who developed pneumococcal septic arthritis. The patient is a 64-year-old female complicated with RA for >10 years. She was treated with abatacept and methotrexate and has been in remission for 2 years. She had not received any pneumococcal vaccination. She consulted at our hospital for left ankle arthralgia and fever. Blood culture and puncture of the left ankle joints detected pneumococcus, and the pneumococcal urine antigen test was positive. The patient was diagnosed with pneumococcal septic arthritis, and she recovered after the administration of antibiotics. This is the first case report discussing these circumstances, suggesting that bDMARDs may be a risk of pneumococcal septic arthritis in patients with RA. To prevent this, pneumococcal vaccination should be encouraged in such patients. Furthermore, if RA is in remission, we may consider the spacing or withdrawal of bDMARDs to avoid severe infection.

The Microbial Etiology of Community-Acquired Pneumonia in Adults: from Classical Bacteriology to Host Transcriptional Signatures

All modern advances notwithstanding, pneumonia remains a common infection with substantial morbidity and mortality. Understanding of the etiology of pneumonia continues to evolve as new techniques enable identification of already known organisms and as new organisms emerge. We now review the etiology of pneumonia (at present often called "community-acquired pneumonia") beginning with classic bacteriologic techniques, which identified Streptococcus pneumoniae as the overwhelmingly common cause, to more modern bacteriologic studies, which emphasize Haemophilus influenzae, Staphylococcus aureus, Moraxella catarrhalis, Enterobacteriaceae, Pseudomonas, and normal respiratory flora. Urine antigen detection is useful in identifying Legionella and pneumococcus. The low yield of bacteria in recent studies is due to the failure to obtain valid sputum samples before antibiotics are administered. The use of high-quality sputum specimens enables identification of recognized ("typical") bacterial pathogens as well as a role for commensal bacteria ("normal respiratory flora"). Nucleic acid amplification technology for viruses has revolutionized diagnosis, showing the importance of viral pneumonia leading to hospitalization with or without coinfecting bacterial organisms. Quantitative PCR study of sputum is in its early stages of application, but regular detection of high counts of bacterial DNA from organisms that are not seen on Gram stain or grown in quantitative culture presents a therapeutic dilemma. This finding may reflect the host microbiome of the respiratory tract, in which case treatment may not need to be given for them. Finally, host transcriptional signatures might enable clinicians to distinguish between viral and bacterial pneumonia, an important practical consideration.

Non-invasive pneumococcal pneumonia due to vaccine serotypes: A systematic review and meta-analysis

BACKGROUND

Non-invasive pneumococcal pneumonia causes significant morbidity and mortality in older adults. Understanding pneumococcal sero-epidemiology in adults ≥50 years is necessary to inform vaccination policies and the updating of pneumococcal vaccines.

METHODS

We conducted a systematic review and random-effects meta-analysis to determine the proportion of community-acquired pneumonia (CAP) in people ≥50 years due to pneumococcus and the proportion caused by pneumococcal vaccine serotypes. We searched MEDLINE, EMBASE and PubMed from 1 January 1990 to 30 March 2021. Heterogeneity was explored by subgroup analysis according to a) patient group (stratified versus age) and depth of testing, b) detection/serotyping method, and c) continent. The protocol is registered with PROSPERO (CRD42020192002).

FINDINGS

Twenty-eight studies were included (34,216 patients). In the period 1-5 years after introduction of childhood PCV10/13 immunisation, 18% of CAP cases (95% CI 13-24%) were attributable to pneumococcus, with 49% (43-54%) of pneumococcal CAP due to PCV13 serotypes. The estimated proportion of pneumococcal CAP was highest in one study that used 24-valent serotype-specific urinary-antigen detection (ss-UAD)(30% [28-31%]), followed by studies based on diagnostic serology (28% [24-33%]), PCR (26% [15-37%]), ss-UAD14 (17% [13-22%]), and culture alone (14% [10-19%]). A higher estimate was observed in Europe (26% [21-30%] than North America (11% [9-12%](p<0·001). PCV13-serotype estimates were also influenced by serotyping methods.

INTERPRETATION

Non-invasive pneumococcal CAP and vaccine-type pneumococcal CAP remains a burden in older adults despite widespread introduction of pneumococcal infant immunisation. Studies heavily reliant on ss-UADs restricted to vaccine-type serotypes may overestimate the proportion of potentially vaccine-preventable pneumococcal pneumonia. Sero-epidemiological data from low-income countries are lacking.

Time Trend of the Sensitivity of the Pneumococcal Urinary Antigen Test for Diagnosing Pneumococcal Community-Acquired Pneumonia: An Analysis of 15-Year, Prospective Cohort Data

Introduction

Whether the sensitivity of the BinaxNOW Streptococcus pneumoniae urinary antigen test kit (BinaxNOW), adjusted by some variables including vital signs, laboratory examinations and pneumonia severity, has been decreasing is unknown. The aim of the present study was to investigate whether BinaxNOW sensitivity has decreased recently and to identify the predictors of the BinaxNOW result, including the time trend.

Methods

This prospective cohort study enrolled consecutive patients with pneumococcal community-acquired pneumonia who were hospitalised at Kurashiki Central Hospital from January 2001 to December 2015. Pneumococcal community-acquired pneumonia was defined as positive blood or pleural effusion or sputum culture results. To evaluate the effect of the time trend for the sensitivity of BinaxNOW, time series regression analysis was performed. In addition, predictors of the BinaxNOW result were examined by multivariable analysis using variables such as sex, vital signs, blood tests such as C-reactive protein, albumin, blood urea nitrogen, creatinine, white blood cell count, haematocrit and platelets, antibiotic pre-treatment, bacteraemia, and pneumonia severity, in addition to time trend and seasonality.

Results

A total of 446 patients were included. BinaxNOW sensitivity showed a significant, gradual decrease from 2001 (81.3%) to 2015 (48.7%). On multivariable analysis [odds ratio (95% confidence interval)], bacteraemia [2.516 (1.387–4.561), P = 0.002] was a predictor of a positive BinaxNOW result, whereas male sex [0.467 (0.296–0.736), P = 0.001], white blood cell count [0.959 (0.930–0.989), P = 0.008] and the time trend per year [0.900 (0.859–0.943), P < 0.001] were predictors of a negative BinaxNOW result.

Conclusions

The sensitivity of BinaxNOW decreased over a 15-year period. We should be careful when interpreting BinaxNOW results in daily clinical practice, and the development of a new kit with good sensitivity is anticipated.

Trial registration number

UMIN000004353.

Community-acquired pneumonia: similarities and differences between European and American guidelines - A narrative review

Community-acquired pneumonia (CAP) is severe disease. Early prescription of an adequate treatment has a positive impact in the CAP outcome. Despite the evidence of existing relevant differences between CAP across geographical areas, general guidelines can be designed to be applied everywhere. Eight years have passed between the publication of the European (EG) and American (AG) CAP guidelines, thus the aim of this narrative review is to compare both guidelines and summarize their recommendations. The main similarity between both guidelines is the antibiotics recommendation with the exception that AG mention new antimicrobials that were not available at the time of EG publication. Both guidelines recommend against routinely adding steroids as an adjuvant treatment. Finally, both guidelines acknowledge that the decision to hospitalize a patient is clinical and should be complemented with an objective tool for risk assessment. EG recommend the CRB-65 while AG recommend the Pneumonia Severity Index (PSI). EG and AG share a similar core of recommendations and only differ in minor issues such as new antibiotics. Likewise, both guidelines recommend against the routine prescription of steroids as an adjuvant therapy.

Etiology of community-acquired pneumonia in adults: a systematic review

Background

The etiology of community-acquired pneumonia (CAP) has evolved since the beginning of the antibiotic era. Recent guidelines encourage immediate empiric antibiotic treatment once a diagnosis of CAP is made. Concerns about treatment recommendations, on the one hand, and antibiotic stewardship, on the other, motivated this review of the medical literature on the etiology of CAP.

Methods

We conducted a systematic review of English-language literature on the etiology of CAP using methods defined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched PubMed using a combination of the keywords ‘pneumonia’, ‘CAP’, ‘etiology’, ‘microbiology’, ‘bacteriology’, and ‘pathogen’. We examined articles on antibiotics that were develop to treat pneumonia. We reviewed all ‘related articles’ as well as studies referenced by those that came up in the search. After we excluded articles that did not give sufficient microbiological data or failed to meet other predetermined criteria, 146 studies remained. Data were stratified into diagnostic categories according to the microbiologic studies that were done; results are presented as the percentage in each category of all cases in which an etiology was established.

Results

Streptococcus pneumoniae remains the most common cause of CAP although declining in incidence; this decline has been greater in the US than elsewhere. Haemophilus influenzae is the second most common cause of CAP, followed by Staphylococcus aureus and Gram negative bacilli. The incidence of all bacteria as causes of CAP has declined because, with routine use of PCR for viruses, the denominator, cases with an established etiology, has increased. Viruses were reported on average in about 10% of cases, but recent PCR-based studies identified a respiratory virus in about 30% of cases of CAP, with substantial rates of viral/bacterial coinfection.

Conclusion

The results of this study justify current guidelines for initial empiric treatment of CAP. With pneumococcus and Haemophilus continuing to predominate, efforts at antibiotic stewardship might be enhanced by greater attention to the routine use of sputum Gram stain and culture. Because viral/bacterial coinfection is relatively common, the identification of a virus by PCR does not, by itself, allow for discontinuation of the antibiotic therapy.

Re-validation and update of an extended-specificity multiplex assay for detection of Streptococcus pneumoniae capsular serotype/serogroup-specific antigen and cell-wall polysaccharide in urine specimens

National surveillance of pneumococcal disease at the serotype level is essential to assess the effectiveness of vaccination programmes. We previously developed a highly sensitive extended-specificity multiplex immunoassay for detection of Streptococcus pneumoniae serotype-specific antigen in urine in the absence of isolates. The assay uses human mAbs that detect the 24 pneumococcal serotype/groups targeted by the pneumococcal conjugate vaccines (PCVs) and pneumococcal polysaccharide vaccine (PPV-23) plus some cross-reactive types and the pneumococcal cell-wall polysaccharide. However, the previous assay had some limitations, namely the reduced specificity of the serotype 7F, 20 and 22F assays, for which non-specific binding in urine samples was observed. Here we report on the further development and re-validation of a new version of the assay (version 2.1), which offers improved sensitivity towards serotypes 7F, 18C and 19F and increased specificity for serotypes 7F, 20 and 22F by replacement of some of the antibody clones with new clones. Using a panel of urine specimens from patients diagnosed with community-acquired pneumonia or pneumococcal disease, the overall clinical sensitivity of this version of the assay based on isolation of S. pneumoniae from a normally sterile site is 94.3 % and the clinical specificity is 93.6 %, in comparison with clinical sensitivity and specificity values of 96.2 % and 89.9 % in the previous assay.

A false-positive pneumococcal rapid urinary antigen test in Streptococcus intermedius infection

An 83-year-old woman was admitted with empyema. Pneumococcal rapid urinary antigen testing on admission showed a positive result, but culture of pleural effusion yielded only Streptococcus intermedius. S. intermedius is a member of the anginosus group and a component of the regular flora of the oral cavity and gastrointestinal tract. As a human pathogen, this species has gained notoriety for abscess formation in the liver and brain but has also been reported recently as a major agent causing pulmonary abscesses or empyema, and the number of affected patients is increasing with the aging of society. We present the first case of a false-positive pneumococcal rapid urinary antigen test in empyema caused by S. intermedius.

Evaluation of the Sofia S. pneumoniae FIA for Detection of Pneumococcal Antigen in Patients with Bloodstream Infection

The usefulness of pneumococcal urinary antigen tests (UATs) in severe pneumococcal infection relies heavily on the performance in bacteremic patients. Fluorescence technology and automatic reading of test results may improve UAT performance. We evaluated the automatically read Sofia S. pneumoniae FIA for diagnosing pneumococcal bloodstream infection (BSI) in hospitalized adult patients. First, the Sofia FIA was evaluated on 97 patients with pneumococcal (n = 47) and nonpneumococcal (n = 50) BSI and compared with results by the visually read BinaxNOW S. pneumoniae immunochromatographic test (ICT) and ImmuView S. pneumoniae and Legionella pneumophila ICT. In four cases (4.1%), the Sofia FIA showed invalid test results, three of which showed invalid results by the ImmuView ICT previously. Based on 93 valid cases, the Sofia FIA showed similar sensitivity (for both comparisons: 68% versus 62%; P = 0.45) and specificity (for both comparisons: 91% versus 93%; P = 1.00) as the visually read UATs. Second, the Sofia FIA was prospectively evaluated on 82 consecutive nonfrozen urine samples, detecting pneumococcal antigen in 10 of 14 (sensitivity, 71%) pneumococcal BSI patients, similarly to the visually and automatically read BinaxNOW ICT (both 12 of 14; sensitivity, 86%; P = 0.50). Of five nonpneumococcal BSI cases, the Sofia FIA showed an invalid test result in one case, but no positive UAT results were obtained. Thus, the sensitivity and specificity of the Sofia FIA were similar to the performance rates of other UATs in patients with BSI, but invalid test results are of concern for the usefulness in pneumococcal BSI.

Evaluation of pneumococcal urinary antigen testing for respiratory tract infection investigations

OBJECTIVE

The pneumococcal urinary antigen test enables rapid bacteriological diagnosis in respiratory tract infections. The objective was to identify factors associated with a positive pneumococcal urinary antigen test result.

PATIENTS AND METHODS

This seven-year retrospective monocentric study was performed on consecutive patients presenting with respiratory tract infections reported as pneumococcal-positive. Epidemiological, biological, and radiological factors were analyzed, and severity scores were calculated.

RESULTS

A total of 223 patients were included. Significant associations were observed between positive test results and age over 65years (P=0.01), positive test results and immunosuppression factors (blood disease [25% Ag+ group vs. 4% Ag- group, P=0.001], immunosuppressive therapy [10% Ag+ group vs. 0% Ag- group, P=0.02]). Clinically, fever (64% Ag+ group vs. 42% Ag- group, P=0.01) and cough (46% Ag+ group vs. 19% Ag- group, P<0.01) were associated with a positive result, as were radiological alveolar opacities (67% Ag+ group vs. 44% Ag- group, P=0.01). High PSI score was associated with the Ag+ group (79% vs. 56% Ag- group, P=0.001).

CONCLUSION

Age, immunosuppressive factors, typical pneumococcal symptoms, and PSI scores were associated with a positive pneumococcal urinary antigen result.

Treating bacterial pneumonia in people living with HIV

Introduction: Bacterial pneumonia remains an important cause of morbidity and mortality in people living with HIV (PLWH) in the antiretroviral therapy (ART) era. In addition to being immunocompromised, as reflected by low CD4 cell counts and elevated HIV viral loads, PLWH often have other behaviors associated with an increased risk of pneumonia including smoking and injected drug use. As PLWH are aging, comorbid conditions such as chronic obstructive pulmonary disease (COPD), cancers, and cardiovascular, renal and liver diseases are emerging as additional risk factors for pneumonia. Pathogens are often similar to those in HIV-uninfected individuals; however, PLWH are at risk for unusual and/or multi-drug resistant organisms causing bacterial pneumonia based, in part, on their CD4 cell counts and other exposures. Areas covered: In this review, we focus on the recognition and management of bacterial community-acquired pneumonia (CAP) in PLWH. Along with antimicrobial treatment, we discuss prevention strategies such as vaccination and smoking cessation. Expert opinion: Early initiation of ART after HIV infection can decrease the risk of pneumonia. Improved efforts at vaccination, smoking cessation, and reduction of other substance use are urgently needed in PLWH to decrease the risk for bacterial pneumonia. As PLWH are aging, comorbidities are additional risk factors for bacterial CAP.

Urinary antigen testing in community-acquired pneumonia in adults: an update

INTRODUCTION

Community-acquired pneumonia (CAP) continues to be a leading cause of hospitalization and mortality worldwide. Streptococcus pneumoniae and Legionella pneumophila remain the major etiological agents and are responsible for a significant proportion of CAP mortality. Among diagnostic tests for CAP, urine antigen detection of S. pneumoniae and L. pneumophila is widely accepted due to the simplicity of collection and the rapidity of the test results. Areas covered: This comprehensive review outlines the urinary antigen tests available, discusses their sensitivity and specificity, and assesses the usefulness of their results as the basis for targeted therapy. Expert commentary: There have been advances in urine antigen detection tests for patients with CAP. New methodologies show greater sensitivity, detect S. pneumoniae and L. pneumophila in a single test, and also detect pneumococcal serotypes. In addition, urine antigen detection tests have shown a high specificity, which means that a positive result practically indicates the causative pathogen of CAP. Therefore, a positive result can lead to a targeted therapy that is likely to improve patient outcomes and reduce the risk of resistance and adverse events. However, well-designed studies are needed to evaluate the usefulness of urine antigen detection tests with regard to clinical outcomes.

Evolving Understanding of the Causes of Pneumonia in Adults, With Special Attention to the Role of Pneumococcus

Before 1945, Streptococcus pneumoniae caused more than 90% of cases of pneumonia in adults. After 1950, the proportion of pneumonia caused by pneumococcus began to decline. Pneumococcus has continued to decline; at present, this organism is identified in fewer than fewer10%-15% of cases. This proportion is higher in Europe, a finding likely related to differences in vaccination practices and smoking. Gram-negative bacilli, Staphylococcus aureus, Chlamydia, Mycoplasma, and Legionella are each identified in 2%-5% of patients with pneumonia who require hospitalization. Viruses are found in 25% of patients, up to one-third of these have bacterial coinfection. Recent studies fail to identify a causative organism in more than 50% of cases, which remains the most important challenge to understanding lower respiratory infection. Our findings have important implications for antibiotic stewardship and should be considered as new policies for empiric pneumonia management are developed.

Lung Infections

A review of pulmonary infections of all types with diagnostic and morphological features.

Development of an Extended-Specificity Multiplex Immunoassay for Detection of Streptococcus pneumoniae Serotype-Specific Antigen in Urine by Use of Human Monoclonal Antibodies

Current pneumococcal vaccines cover the 10 to 23 most common serotypes of the 92 presently described. However, with the increased usage of pneumococcal-serotype-based vaccines, the risk of serotype replacement and an increase in disease caused by nonvaccine serotypes remains. Serotype surveillance of pneumococcal infections relies heavily on culture techniques, which are known to be insensitive, particularly in cases of noninvasive disease. Pneumococcal-serotype-specific urine assays offer an alternative method of serotyping for both invasive and noninvasive disease. However, the assays described previously cover mainly conjugate vaccine serotypes, give little information about circulating nonvaccine serotypes, and are currently available only in one or two specialist laboratories. Our laboratory has developed a Luminex-based extended-range antigen capture assay to detect pneumococcal-serotype-specific antigens in urine samples. The assay targets 24 distinct serotypes/serogroups plus the cell wall polysaccharide (CWP) and some cross-reactive serotypes. We report that the assay is capable of detecting all the targeted serotypes and the CWP at 0.1 ng/ml, while some serotypes are detected at concentrations as low as 0.3 pg/ml. The analytical serotype specificity was determined to be 98.4% using a panel of polysaccharide-negative urine specimens spiked with nonpneumococcal bacterial antigens. We also report clinical sensitivities of 96.2% and specificities of 89.9% established using a panel of urine specimens from patients diagnosed with community-acquired pneumonia or pneumococcal disease. This assay can be extended for testing other clinical samples and has the potential to greatly improve serotype-specific surveillance in the many cases of pneumococcal disease in which a culture is never obtained.

[Description and role of bacteriological techniques in the management of lung infections]

Les pneumopathies aiguës recouvrent des contextes cliniques variés et les étiologies bactériennes impliquées le sont tout autant. Aucun outil microbiologique n’est 100 % sensible ni 100 % spécifique et malgré les investigations, plus de 30 % des pneumopathies restent sans étiologie identifiée. Si aucun prélèvement n’est indiqué pour les patients traités en ambulatoire, les prélèvements respiratoires non invasifs sont à privilégier pour les pneumopathies aiguës hospitalisées (communautaires ou associées aux soins), tandis que les prélèvements invasifs sont indiqués en seconde ligne pour les pneumopathies aiguës communautaires en réanimation, et en première ligne pour les pneumopathies aiguës de l’immunodéprimé. La culture microbiologique garde une place importante, à condition que le malade soit prélevé avant instauration de l’antibiothérapie. Certains contextes peuvent justifier le recours aux hémocultures, à la recherche d’antigènes urinaires ou aux sérologies. Les PCR rendent déjà service au quotidien mais l’avenir à court terme appartient probablement aux panels moléculaires multiplex capables de détecter de nombreux micro-organismes en quelques heures, surtout dans les pneumopathies communautaires sévères de réanimation et les pneumopathies aiguës de l’immunodéprimé. Le séquençage nucléotidique haut débit révolutionnera bientôt le diagnostic microbiologique, en pneumologie comme dans les autres domaines de l’infectiologie.

Multiplex Urinary Antigen Detection for 13 Streptococcus pneumoniae Serotypes Improves Diagnosis of Pneumococcal Pneumonia in South African HIV-Infected Adults

A serotype-specific urinary antigen detection (UAD) assay for 13 serotypes included in the pneumococcal conjugate vaccine (PCV13) was recently reported as a useful diagnostic tool for pneumococcal pneumonia. We aimed to assess the diagnostic accuracy of the UAD in HIV-infected South African adults. Urine specimens from a well-defined cohort of HIV-infected South African adults with pneumonia were evaluated retrospectively in the UAD assay. Pneumonia was considered pneumococcal if either sputum Gram stain, sputum culture, blood culture, or the immunochromatographic (ICT) BinaxNow S. pneumoniae test (composite diagnostic) was positive. Among 235 enrolled pneumonia patients, the UAD assay was more frequently positive (104 [44.3%]) than the composite diagnostic (71 [30.2%]; P < 0.001) and increased the pneumococcal etiology from 30.2% by an additional 22.6% to 52.8%. The UAD assay detected more pneumococcal etiologies (45.0%) than the serotype-independent ICT (23.4%, P < 0.001). UAD identified 6/7 patients with PCV13 serotype bacteremia without misclassification of bacteremia episodes due to non-PCV13 serotypes. UAD was positive for 5.1% of asymptomatic HIV-infected persons, with higher rates among those with nasopharyngeal carriage. Concordance between serotypes identified by UAD and by Quellung reaction and PCR serotyping was 70/86 (81.4%). UAD identified the dominant serotype in multiple serotype carriage. This study confirms the utility of the UAD assay for HIV-infected adults comparing favorably with other diagnostic tests. A highly valent UAD may become a new standard for detection of pneumococcal pneumonia in adults. Prior to PCV introduction, at least 53% of pneumonia cases were due to pneumococci in HIV-infected South African adults.

Evaluation of urine pneumococcal antigen test performance among adults in Western Kenya

When used in an area of rural western Kenya, the BinaxNOW® urine antigen test had a sensitivity of 67% (95% Confidence Interval [CI]: 43-85%) among 21 adults ≥15 years old with acute respiratory illnesses and pneumococcal bacteremia and a specificity of 98% (95% CI: 96-99%) among 660 adults ≥15 years old without fever or cough. The specificity of the test was not significantly affected by pneumococcal colonization, regardless of patients' HIV status, age, or sex. Use of the pneumococcal urine antigen test in clinical assessments of adults in Africa with acute respiratory illness is a viable option regardless of whether a patient is colonized by pneumococci, even among HIV-infected adults, although the moderate sensitivity of the urine antigen test indicates that the test is probably best used clinically as part of a panel with other tests that can detect pneumococci.

[Urine antigen testing: Indication and contribution to the treatment of community-acquired pneumonia]

Urinary antigen tests are quick and simple tests helping to provide an etiological diagnosis in community-acquired pneumonia. However, their prescription is sometimes excessive and performed in unjustified situations. The therapeutic benefit is limited. Indeed, studies show that appropriate antibiotic therapy based on the result of urinary antigen tests does not improve the cost and the patient survival compared to empirical antibiotic therapy. One must be careful before antibiotic therapy reduction based on the sole negative result of urinary antigen test. Legionella urinary antigen test is the most commonly method used for the diagnosis of legionellosis but must be prescribed in a specific clinical context. Streptococcus pneumoniae urinary antigen test is especially interesting in the epidemiological surveillance of pneumococcal community-acquired pneumonia.

Clinical usefulness of pneumococcal urinary antigen test, stratified by disease severity and serotypes

Early diagnosis of pneumococcal pneumonia facilitates appropriate antibiotic therapy. The urinary antigen test (UAT) is known to be useful for the diagnosis of pneumococcal pneumonia. This study aimed to evaluate the usefulness of UAT in the 13-valent pneumococcal conjugated vaccine (PCV13) era. Community-acquired pneumonia (CAP) cases aged ≥19 years were reviewed retrospectively. This study evaluated the utility of Streptococcus pneumoniae UAT (BinaxNOW^® assay) for diagnosis of pneumococcal CAP, and the relation of the UAT positive rate to age, comorbidities, pneumonia severity, and pneumococcal serotypes. Among 752 microbiologically identified CAP cases, S. pneumoniae (36.7%) was the most common isolate, and of those cases, 56.4% were positive for UAT. UAT positivity varied by pneumococcal serotype (serotype 3, 50%; 9V/9A, 85%; 11A/11E, 54%; 14, 36.4%; 19A, 50%; and 23F, 37.5%), and was significantly increased since 2012, two years after introduction of PCV13. The positive rate of UAT was significantly related to CRP level (P = 0.007) and lobar pneumonia (P = 0.006), but not to age, co-morbidities or prior antibiotic therapy. In conclusion, urinary antigen detection varied depending on the S. pneumoniae serotype. In the PCV13 era, the serotype distribution of pneumococcal pneumonia may be changing, and the clinical usefulness of UAT needs to be monitored. The positive rate of UAT may be influenced by a localized bacterial burden and host reactions.

Sensitivity and specificity of the Streptococcus pneumoniae urinary antigen test for unconcentrated urine from adult patients with pneumonia: a meta-analysis

Studies on the sensitivity and specificity of the Binax Now Streptococcus pneumonia urinary antigen test (index test) show considerable variance of results. Those written in English provided sufficient original data to evaluate the sensitivity and specificity of the index test using unconcentrated urine to identify S. pneumoniae infection in adults with pneumonia. Reference tests were conducted with at least one culture and/or smear. We estimated sensitivity and two specificities. One was the specificity evaluated using only patients with pneumonia of identified other aetiologies ('specificity (other)'). The other was the specificity evaluated based on both patients with pneumonia of unknown aetiology and those with pneumonia of other aetiologies ('specificity (unknown and other)') using a fixed model for meta-analysis. We found 10 articles involving 2315 patients. The analysis of 10 studies involving 399 patients yielded a pooled sensitivity of 0.75 (95% confidence interval: 0.71-0.79) without heterogeneity or publication bias. The analysis of six studies involving 258 patients yielded a pooled specificity (other) of 0.95 (95% confidence interval: 0.92-0.98) without no heterogeneity or publication bias. We attempted to conduct a meta-analysis with the 10 studies involving 1916 patients to estimate specificity (unknown and other), but it remained unclear due to moderate heterogeneity and possible publication bias. In our meta-analysis, sensitivity of the index test was moderate and specificity (other) was high; however, the specificity (unknown and other) remained unclear.

The role of rapid diagnostic tests in managing adults with pneumonia in low-resource settings

In well-resourced settings the systematic use of rapid diagnostics tests (e.g. pneumococcal urinary antigen test) that define the causal pathogen to direct therapy has not resulted in significantly improved outcomes in adults withpneumonia. The management of pneumonia in many low-resource settings is complicated by a substantial burden of tuberculosis and HIV-associated opportunistic infections, in addition to the usual spectrum of pathogens seenin well-resourced settings. Clinical features alone do not reliably distinguish between these different aetiologiesand physicians often have to treat empirically. Given the limitations in diagnostic laboratory capability present inmost low-resource settings, rapid and point-of-care diagnostic tests could become valuable tools to guide treatment decisions. Pneumococcal and Legionella urinary antigen tests are specific and moderately sensitive, but their utilityin low-resource settings is uncertain. The Xpert MTB/RIF (Cepheid, USA) platform and rapid assays for urinary lipoarabinomannan can substantially speed up tuberculosis diagnosis; the current challenge is to translate this intoearlier treatment and hopefully improve patient outcome. In HIV-infected patients, 1-3-β-D-glucan is a serum marker of Pneumocystis jirovecii infection with excellent sensitivity. Further studies are needed to assess the clinical utilityand cost-effectiveness of these rapid diagnostic assays when they are incorporated into treatment algorithms.

Streptococcus pneumoniae antigen in urine: diagnostic usefulness and impact on outcome of bacteraemic pneumococcal pneumonia in a large series of adult patients

BACKGROUND AND OBJECTIVE

Urinary pneumococcal antigen detection provides good results in the diagnosis of pneumococcal pneumonia but has rarely been used in bacteraemic pneumococcal pneumonia and it is not known whether it is associated with outcome in this type of pneumonia. Our objectives were to assess the usefulness of an immunochromatographic technique for detecting the pneumococcal antigen in urine in a large prospective study of patients with bacteraemic pneumococcal pneumonia and explore any potential association with outcomes.

METHODS

This study, carried out over 8 years, included all adult immunocompetent patients admitted for bacteraemic pneumococcal pneumonia. An immunochromatographic test for the Streptococcus pneumoniae antigen in urine was performed in the first 24 h. The sensitivity of test was assessed and patients were divided into two groups according to test results to explore differences on admission and during the course of the illness using logistic regression models.

RESULTS

Of the 350 patients with bacteraemic pneumococcal pneumonia included, 261 (74.6%) were positive for the antigen. Patient characteristics were very similar on admission and differences in severity (Pneumonia Severity Index) were not statistically significant. In the adjusted analysis, antigen-positive patients had a higher risk of intensive care unit admission, treatment failure and adverse outcome.

CONCLUSIONS

The sensitivity of the immunochromatographic urinary antigen test was 74.6% and positive results were associated with poorer clinical outcome. We therefore recommend systematic use of this test when pneumonia is diagnosed in the emergency department.

Procalcitonin as a Biomarker of the Early Stage of Bacterial Infections in HIV/AIDS Patients

We observed that low concentrations of procalcitonin (PCT) in the early stages of bacterial infection among HIV/AIDS patients are not always associated with a good prognosis. Many of our patients developed sepsis despite a PCT level of <0.5 ng/ml on the first days of infection. The aim of our study was to assess whether laboratory standards for PCT in patients with HIV/AIDS correlate with their clinical condition. We analyzed the concentration of PCT and other inflammatory markers in the early stages of bacterial infection among 40 HIV-infected patients and 52 AIDS patients enrolled for the study. The control group consisted of 37 healthy individuals. In comparison with PCT and WBC, PCT proved to be the most reliable in the early stages of bacterial infection. To conclude, we suggest new PCT cut-off ranges for HIV/AIDS patients with bacterial infection.

Pneumomediastinum in patients with AIDS: a case report and literature review

OBJECTIVE

Pneumomediastinum is a rare complication of opportunistic infections in HIV-infected patients. However, the relationship between the causative pathogens and the prognosis is unclear. We report the case of a patient with AIDS presenting with community-acquired pneumonia complicated by pneumomediastinum. The cases of a further 10 HIV-infected patients with pneumomediastinum reported in the English language literature are reviewed.

METHODS

PubMed was searched for cases of HIV-infected patients with pneumomediastinum published in the English language literature.

RESULTS

Pneumocystis jirovecii is the most common pathogen causing pneumonia and concurrent pneumomediastinum in HIV-infected patients. Only one of the identified cases was caused by cytomegalovirus. Excluding the two cases with incomplete information, the overall mortality rate in the remaining nine cases was 55.5%.

CONCLUSION

In HIV-infected patients, Pneumocystis jirovecii pneumonia can occasionally present as pneumomediastinum. In such cases, adequate appropriate antimicrobial therapy is needed due to the high mortality rate.

Diagnosis of pneumococcal pneumonia: current pitfalls and the way forward

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia. However, it can also asymptomatically colonize the upper respiratory tract. Because of the need to distinguish between S. pneumoniae that is simply colonizing the upper respiratory tract and S. pneumoniae that is causing pneumonia, accurate diagnosis of pneumococcal pneumonia is a challenging issue that still needs to be solved. Sputum Gram stains and culture are the first diagnostic step for identifying pneumococcal pneumonia and provide information on antibiotic susceptibility. However, these conventional methods are relatively slow and insensitive and show limited specificity. In the past decade, new diagnostic tools have been developed, particularly antigen (teichoic acid and capsular polysaccharides) and nucleic acid (ply, lytA, and Spn9802) detection assays. Use of the pneumococcal antigen detection methods along with biomarkers (C-reactive protein and procalcitonin) may enhance the specificity of diagnosis for pneumococcal pneumonia. This article provides an overview of current methods of diagnosing pneumococcal pneumonia and discusses new and future test methods that may provide the way forward for improving its diagnosis.

Systematic review and meta-analysis of a urine-based pneumococcal antigen test for diagnosis of community-acquired pneumonia caused by Streptococcus pneumoniae

Standard culture methods for diagnosis of Streptococcus pneumoniae pneumonia take at least 24 h. The BinaxNOW urine-based test for S. pneumoniae (BinaxNOW-SP) takes only 15 min to conduct, potentially enabling earlier diagnosis and targeted treatment. This study was conducted to assess whether the use of BinaxNOW-SP at the time of hospital admission would provide adequate sensitivity and specificity for diagnosis of community-acquired pneumonia (CAP) in adult patients. We searched PubMed, EMBASE/OVID, Cochrane Collaboration, Centre for Reviews and Dissemination, INAHTA, and CADTH for diagnostic or etiologic studies of hospitalized predominately adult patients with clinically defined CAP that reported the diagnostic performance of BinaxNOW-SP versus cultures. Two authors independently extracted study details and diagnostic two-by-two tables. We found that 27 studies met our inclusion criteria, and three different reference standards were used between them. A bivariate meta-analysis of 12 studies using a composite of culture tests as the reference standard estimated the sensitivity of BinaxNOW-SP as 68.5% (95% credibility interval [CrI], 62.6% to 74.2%) and specificity as 84.2% (95% CrI, 77.5% to 89.3%). A meta-analysis of all 27 studies, adjusting for the imperfect and variable nature of the reference standard, gave a higher sensitivity of 74.0% (CrI, 66.6% to 82·3%) and specificity of 97.2% (CrI, 92.7% to 99.8%). The analysis showed substantial heterogeneity across studies, which did not decrease with adjustment for covariates. We concluded that the higher pooled sensitivity (compared to culture) and high specificity of BinaxNOW-SP suggest it would be a useful addition to the diagnostic workup for community-acquired pneumonia. More research is needed regarding the impact of BinaxNOW-SP on clinical practice.

Evaluation of respiratory disease

The spectrum of HIV-associated pulmonary diseases is broad. Opportunistic infections, neoplasms, and noninfectious complications are all major considerations. Clinicians caring for persons infected with HIV must have a systematic approach. The approach begins with a thorough history and physical examination and often involves selected laboratory tests and a chest radiograph. Frequently, the clinical, laboratory, and chest radiographic presentation suggests a specific diagnosis or a few diagnoses, which then prompts specific diagnostic testing and treatment. This article presents an overview of the evaluation of respiratory disease in persons with HIV/AIDS.

Evaluation of a rapid test for the diagnosis of pneumococcal pneumonia

We evaluated the usefulness of a rapid immunochromatographic pneumococcal urinary antigen test (UAT) for the diagnosis of pneumonia over a period of five years. The UAT was positive in 32 (2.3%) urine samples obtained from 1414 patients. In 46 of these 1414 patients results of UAT and/or sputum/pleural fluid culture and/or blood culture and/or procalcitonin levels were available and therefore the study was concentrated on these patients. A concordance between UAT positivity and the presence of Streptococcus pneumoniae in the sputum was observed in only 4 of 46 (8.7%) patients for which both urine and sputum samples were analyzed. A discordant result (UAT positive and absence of S. pneumoniae in sputum samples) was recorded in 8 of 46 (17.4 %) patients. UAT negative results with sputum culture positive for S. pneumoniae were recorded in 28.3% of patients. In 20 patients, UAT tested positive but sputum culture was not performed. A concordance between UAT positivity and the isolation of S. pneumoniae from blood was seen in 2 of 46 patients whereas a discordant result (UAT positive and blood culture negative) was seen in 12 (26.1%) patients. A concordance between the UAT and high levels (≥2ng/ml) of procalcitonin was observed in 4 out of 46 patients, whereas a positive UAT result and a procalcitonin negative result were observed in 2 patients. In our experience the UAT allows the detection of the etiological agent of pneumonia, and also when sputum and/or blood cultures are negative for S. pneumoniae, when the clinical picture is suggestive of alveolar pneumonia.

Invasive bacterial pathogens exploit TLR-mediated downregulation of tight junction components to facilitate translocation across the epithelium

Streptococcus pneumoniae and Haemophilus influenzae are members of the normal human nasal microbiota with the ability to cause invasive infections. Bacterial invasion requires translocation across the epithelium; however, mechanistic understanding of this process is limited. Examining the epithelial response to murine colonization by S. pneumoniae and H. influenzae, we observed the TLR-dependent downregulation of claudins 7 and 10, tight junction components key to the maintenance of epithelial barrier integrity. When modeled in vitro, claudin downregulation was preceded by upregulation of SNAIL1, a transcriptional repressor of tight junction components, and these phenomena required p38 MAPK and TGF-β signaling. Consequently, downregulation of SNAIL1 expression inhibited bacterial translocation across the epithelium. Furthermore, disruption of epithelial barrier integrity by claudin 7 inhibition in vitro or TLR stimulation in vivo promoted bacterial translocation. These data support a general mechanism for epithelial opening exploited by invasive pathogens to facilitate movement across the epithelium to initiate disease.

Is there any influence of immune deficit on procalcitonin results?

The role of procalcitonin (PCT) in immunocompromised patients is still under investigation. This study evaluated the influence of immune deficiency on the value of PCT concentrations in the diagnosis of early stages of bacterial infections in human immunodeficiency virus (HIV)-infected patients compared with other inflammatory markers, such as C-reactive protein and white blood cell count. We analyzed major immunologic markers including CD4, CD8, and HIV-1 viral load. PCT concentrations in the early stages of bacterial infections correlated negatively with CD4 count in HIV-infected patients. However, a similar relation was not seen in patients with acquired immune deficiency syndrome. We support the recommendation to change the cutoff value ranges of PCT in patients with immune deficiency. PCT concentrations can be influenced by various factors and hence should be carefully analyzed, especially in immunocompromised patients.

Pneumococcal antigen testing of blood culture broth to enhance the detection of Streptococcus pneumoniae bacteremia

The purpose of this investigation was to enhance the detection of pneumococcal bacteremia cases using the Binax NOW® immunochromatographic test (ICT) on blood culture broth as part of surveillance in two rural Thailand provinces. Blood cultures were collected as clinically indicated from hospitalized patients. ICT was performed on broth from culture bottles flagged as positive by BactT/ALERT® (alarm-positive) but which failed to grow organisms on subculture. During the period May 2005-June 2007, ICT was positive on 43 (24%) of 182 alarm-positive blood cultures with no growth on subculture. Compared to pneumococcal bacteremia cases confirmed by culture, cases detected only by ICT had a longer median time from culture collection to incubation and a longer median time from alarm positivity to subculture, and were more likely to be from patients pretreated with antibiotics. In a subsequent surveillance period (July 2007-December 2009), ICT continued to detect additional pneumococcal cases, but in a lower proportion of samples (7 of 221, 3.2%). Recently, as part of a separate study, ICT applied to uninoculated blood culture broth produced weak-positive results, mandating caution if testing broth from patient blood cultures. The antigen testing of blood culture broth appears to enhance the detection of pneumococcal bacteremia, but a controlled evaluation is needed.

A prospective study of urinary pneumococcal antigen detection in healthy Karen mothers with high rates of pneumococcal nasopharyngeal carriage

Background

Detection of Streptococcus pneumoniae C-polysaccharide in urine is a useful rapid diagnostic test for pneumococcal infections in adults. In young children, high rates of false positive results have been documented due to detection of concurrent nasopharyngeal pneumococcal carriage. The relationship between pneumococcal carriage and urinary antigen detection in adults from developing countries with high pneumococcal carriage prevalence has not been well established.

Methods

We nested an evaluation of the BinaxNOW S. pneumoniae test within a longitudinal mother-infant pneumococcal carriage study in Karen refugees on the Thailand-Myanmar border. Paired urine and nasopharyngeal swab specimens were collected from 98 asymptomatic women at a routine study follow-up visit. The urine specimens were analyzed with the BinaxNOW test and the nasopharyngeal swabs were semi-quantitatively cultured to identify pneumococcal colonization.

Results

24/98 (25%) women were colonized by S. pneumoniae but only three (3%) had a positive BinaxNOW urine test. The sensitivity of the BinaxNOW test for detection of pneumococcal colonization was 4.2% (95% CI: 0.1 - 21.1%) with a specificity of 97.3% (95% CI: 90.6 - 99.7%). Pneumococcal colonization was not associated with having a positive BinaxNOW test (odds ratio 1.6; 95% CI: 0.0 - 12.7; p = 0.7).

Conclusions

Significant numbers of false positive results are unlikely to be encountered when using the BinaxNOW test to diagnose pneumococcal infection in adults from countries with moderate to high rates of pneumococcal colonization.

Diagnosis of community-acquired pneumonia in adults

Community-acquired pneumonia (CAP) is a common presentation to both primary and secondary care, representing approximately 5% of the acute medical intake in the UK. Treatment is often based on an empirical approach, using broad-spectrum antibiotic regimens, with which the majority of patients will achieve clinical cure. However, in cases of severe CAP, initial treatment failure or severe comorbidity, a more rigorous diagnostic approach is required. This review assesses the evidence base behind the common diagnostic methods for CAP, and presents the case for a rapid and accurate microbiological and radiological diagnosis in improving management and outcomes of this common condition.

Community acquired bacterial pneumonia

IMPORTANCE OF THE FIELD

Community-acquired pneumonia (CAP) is a common and potentially life-threatening illness that continues to be a major medical problem. Among infectious diseases, CAP is the leading cause of death in the world and is associated with a substantial economic burden to health are systems around the globe.

AREAS COVERED IN THIS REVIEW

Recently identified clinical and biochemical tools promise to improve the assessment of CAP severity. Various prognostic scoring systems and predictive biomarkers have been proposed as tools to aid clinicians in key management decisions. This review provides a summary of current evidence about the use of prognostic scoring systems and biomarkers in the management of patients presenting with CAP. According to the existing guidelines, until more accurate and rapid diagnostic methods are available, the initial treatment for most patients with CAP will remain empirical. Some novel antibiotic and nonantibiotic therapies have recently been tested; some empirical antimicrobial regimens are still being debated. This review summarizes the recent advances in the field of therapy and novel approaches. We searched PubMed for English-language references published from 1997 to 2009 using combinations of the following terms: 'community acquired pneumonia', 'community acquired bacterial pneumonia', 'therapy', 'antibiotics', 'antimicrobials', 'prognostic scoring systems', 'biomarkers', 'diagnostic testing', 'guidelines' 'etiological diagnosis'.

WHAT THE READER WILL GAIN

A thorough description about recent advances in the field of therapy and novel approaches of CAP, as well as a summary of current evidence about the use of prognostic scoring systems and biomarkers in the management of patients presenting with CAP, is presented.

TAKE HOME MESSAGE

Recent developments have made significant contributions to the management of CAP patients. However, various hot topics remain open and urgently require prospective studies in order to optimize the outcomes of CAP.

Predicting bacteremic pneumonia in HIV-1-infected patients consulting the ED

INTRODUCTION

HIV-1-infected patients have higher incidence of community-acquired pneumonia (CAP) and risk of complications. Bacteremia has been associated with a higher risk of complications in such patients. We investigated factors associated with bacteremia in HIV-1-infected patients with CAP presenting at the emergency department.

METHODS

We included HIV-1-infected patients with CAP for 3 years (March 2005-February 2008). Only patients in whom blood cultures were performed were finally included. Clinical data (age; sex; CD4(+) count; serum HIV viral load; previous or current intravenous drug use and antiretroviral treatment; systolic blood pressure; and cardiac and respiratory rates), analytical data (leukocyte count, arterial oxygen content, C-reactive protein value, and urgent Streptococcus pneumoniae and Legionella spp antigen urine detection), and APACHE-II (Acute Physiology and Chronic Health Evaluation) score were compiled. The need for intensive care unit admission, mechanical ventilation, mortality, and for patients finally discharged, duration of admission were retrospectively obtained from the clinical history. A multivariate analysis using logistic regression was performed to find independent predictors of bacteremia.

RESULTS

We diagnosed 129 HIV-1-infected patients with CAP. Blood cultures were performed in 118 cases (91%). Bacteremia was present in 28 (24%). Independent predictors of bacteremia were the detection of S pneumoniae antigen in urine (odds ratio, 9.0; 95% confidence interval, 1.9-42.0) and the absence of current antiretroviral treatment (odds ratio, 7.1; 95% confidence interval, 1.4-33.3). In-hospital mortality was higher in patients with bacteremia (15% vs 0%).

CONCLUSION

HIV-1-infected patients with CAP who are not on current antiretroviral therapy and have positive S pneumoniae antigenuria are at increased risk of having bacteremia. Bacteremic patients have a poor outcome.

Performance measure of urinary antigen in patients with Streptococcus pneumoniae bacteremia

The Streptococcus pneumoniae (SP) urinary antigen (UAg) test is a commonly used assay. The purpose of this study was to evaluate the test's actual performance in the clinical setting and determine the effects of renal function, grade of bacteremia, and severity-of-illness scores on its outcome. Patients with pneumococcal bacteremia were retrospectively identified and stratified on the basis of glomerular filtration rates, number of positive blood cultures, and CURB-65 scores. Logistic regression was used to determine the effect that these 3 variables had on test outcomes. SP UAg testing was performed in 65 of 129 patients with pneumococcal bacteremia and was positive in 42 of 65 (64.5%). Impaired renal function was the only variable to have a significant effect on test outcome (P = 0.03). Test performance was less sensitive than prospective studies indicate. Patients with impaired renal function were significantly more likely to have positive UAg tests.

Pneumococcal pneumonia: potential for diagnosis through a urinary metabolic profile

Pneumonia, an infection of the lower respiratory tract, is caused by any of a number of different microbial organisms including bacteria, viruses, fungi, and parasites. Community-acquired pneumonia (CAP) causes a significant number of deaths worldwide, and is the sixth leading cause of death in the United States. However, the pathogen(s) responsible for CAP can be difficult to identify, often leading to delays in appropriate antimicrobial therapies. In the present study, we use nuclear magnetic resonance spectroscopy to quantitatively measure the profile of metabolites excreted in the urine of patients with pneumonia caused by Streptococcus pneumoniae and other microbes. We found that the urinary metabolomic profile for pneumococcal pneumonia was significantly different from the profiles for viral and other bacterial forms of pneumonia. These data demonstrate that urinary metabolomic profiles may be useful for the effective diagnosis of CAP.

Novel approaches to the identification of Streptococcus pneumoniae as the cause of community-acquired pneumonia

Current diagnostic tests lack sensitivity for the identification of the bacterial etiology of pneumonia. Attempts during the past 2 decades to improve sensitivity of detection of bacterial constituents in blood by use of antibody-antigen complexes and polymerase chain reaction have been disappointing. Recent data using pneumococcal conjugate vaccines as probes suggest that increased levels of both C-reactive protein and procalcitonin may be useful adjuncts to chest radiographs in the selection of patients with presumed bacterial pneumonia for inclusion in clinical trials. Among pneumococcal diagnostics currently under investigation, quantitative real-time polymerase chain reaction of respiratory secretions, as well as urinary antigen detection and pneumococcal surface adhesin A serological analysis for adults, are candidates for use in future clinical trials of antibiotics.

Serotype-specific immune unresponsiveness to pneumococcal conjugate vaccine following invasive pneumococcal disease

Following the introduction of the pneumococcal 7-valent conjugate vaccine (PCV7) into the routine infant immunization schedule in England, Wales, and Northern Ireland, pneumococcal serotype-specific immunoglobulin G (IgG) antibody testing was offered as a clinical service to all children within the program with invasive pneumococcal disease (IPD) to confirm an adequate antibody response to PCV7. As of March 2008, serum samples taken within 14 to 90 days of vaccination had been submitted from 107 children who had received one or more doses in the second year of life. Sera were assayed by a multiplexed microsphere assay incorporating both cell wall polysaccharide and serotype 22F adsorption. A protective serotype-specific antibody level was defined as a concentration of > or = 0.35 microg/ml. Eight children failed to develop a response to their infecting serotype (6B [n = 4], 18C [n = 2], 4 [n = 1], and 14 [n = 1]), despite receiving at least three doses of PCV7 in the second year of life or two doses in the second and two or three in the first year of life. A further two children were nonresponsive to a serotype (6B) different than that causing disease. None of the 10 children had a clinical risk factor for IPD. Two had marginally low levels of total serum IgG but mounted adequate responses to the other six PCV serotypes. This serotype-specific unresponsiveness may reflect immune paralysis due to large pneumococcal polysaccharide antigen loads and/or a potential genetic basis for nonresponse to individual pneumococcal serotypes.