Usefulness of urinary antigen detection by an immunochromatographic test for diagnosis of pneumococcal pneumonia in children

Efficient Method for Rapid Diagnosis of Streptococcal Pneumoniae in the Context of Co-Infection in Children-Case Report

Background

Bacterial pneumonia caused by Streptococcus pneumoniae continues to be one of the most common medical conditions in the pediatric population under 5 years of age, sometimes requiring prolonged hospitalizations and high costs. The time period (3 to 7 days) from the collection of biological samples (ie nasal exudate, pharyngeal exudate, sputum, blood culture and various secretions) to the arrival of the results has been a much discussed issue. Thus, the use of a rapid diagnostic test for Streptococcus pneumoniae urinary antigen, which is easy to use, may lead after the result is known to a targeted therapeutic management and thus to a favorable prognosis of the disease for the patient.

Methods

This case report presents the case of a 4 years and 5 months old patient diagnosed with invasive pneumococcal-associated pneumococcal infection in the context of SARS-COV2 infection.

Results

The clinical course was slowly favorable with complications that required a long hospitalization.

Conclusion

In conclusion, some rapid diagnostic techniques, clinician judgment and some prevention methods, such as vaccination, can improve a patient's quality of life. One prospect for the future would be the development of new vaccines covering other aggressive Streptococcus pneumoniae serotypes.

Advancing Access to Diagnostic Tools Essential for Universal Health Coverage and Antimicrobial Resistance Prevention: An Overview of Trials in Sub-Saharan Africa

We introduce the Antimicrobial Resistance Diagnostic Use Accelerator program, and the articles in this Supplement, which cover the program in 3 sub-Saharan Africa countries.

A case report of disseminated Streptococcus pneumoniae infection complicated by infective endocarditis, septic arthritis and epidural abscess in an immunocompetent patient

Streptococcus pneumoniae is a highly virulent, vaccine-preventable pathogen which can cause disease on a spectrum from benign to fatal. Apart from pneumonia, it commonly causes septicaemia and meningitis. This case report describes an unusual range of complications in a 53-year-old Caucasian female presenting to a regional hospital, without any risk known factors for severe disease (such as extremes of age, immunodeficiency or co-morbidities). Progressing from an episode of otitis media, her condition rapidly progressed to mastoid sinusitis, septic arthritis, infective endocarditis, epidural abscesses and multiple subcutaneous abscesses. Following quick identification of S. pneumoniae from a positive blood culture, the patient was treated with high-dose benzylpenicillin and ceftriaxone and aggressive source control by surgery, enabling a good clinical recovery.

Acute Kidney Injury and Hemolytic Uremic Syndrome in Severe Pneumococcal Pneumonia—A Retrospective Analysis in Pediatric Intensive Care Unit

Objectives: This study aimed to evaluate the prevalence of acute kidney injury (AKI) and hemolytic uremic syndrome (HUS) in severe pediatric pneumonia due to Streptococcus pneumoniae and to identify factors associated with AKI and HUS in these patients.

Methods: We retrospectively analyzed pediatric patients who were admitted to our pediatric intensive care unit due to severe pneumococcal pneumonia between 2013 and 2019.

Results: Forty-two patients with a median age of 4.3 years were included. Among these patients, 14 (33.3%) developed AKI, including seven (16.7%) stage 1, two (4.8%) stage 2, and five (11.9%) stage 3 AKI. Features of HUS were present in all of the patients with stage 3 AKI, and four required renal replacement therapy (RRT), with a median duration of 10.5 days (range 3 to 16 days). All patients with HUS required mechanical ventilation and inotropic supports. Patients with lower leukocyte and platelet counts, serum sodium and bicarbonate levels, positive urine dipstick (heme or protein ≥ 2 + ), and presence of bacteremia were associated with stage 2 and 3 AKI.

Conclusions: Pediatricians should be aware of the relatively high prevalence of kidney involvement in severe pneumococcal pneumonia, with one-third having AKI and 11.9% developing HUS. Majority (80%) of HUS patients required RRT. Positive urine dipstick, serum sodium, and bicarbonate at presentation, which can be measured in point-of-care tests, may potentially be useful as quick tests to stratify the risks of moderate-to-severe AKI.

Rapid Diagnostic Tests to Guide Case Management of and Improve Antibiotic Stewardship for Pediatric Acute Respiratory Illnesses in Resource-Constrained Settings: a Prospective Cohort Study in Southwestern Uganda

Pediatric acute respiratory illness (ARI) is one of the most common reasons for evaluation at peripheral health centers in sub-Saharan Africa and is frequently managed based on clinical syndrome alone. Although most ARI episodes are likely caused by self-limited viral infections, the majority are treated with antibiotics. This overuse contributes to the development of antimicrobial resistance. To evaluate the preliminary feasibility and potential impact of adding pathogen-specific and clinical biomarker diagnostic testing to existing clinical management algorithms, we conducted a prospective, observational cohort study of 225 children presenting with malaria-negative, febrile ARI to the outpatient department of a semi-urban peripheral health facility in southwestern Uganda from October 2019 to January 2020. In addition to routine clinical evaluation, we performed influenza and Streptococcus pneumoniae antigen testing and measured levels of C-reactive protein, procalcitonin, and lactate in the clinic's laboratory, and conducted a follow-up assessment by phone 7 days later. Almost one-fifth of participants (40/225) tested positive for influenza. Clinical biomarker measurements were low with C-reactive protein of >40 mg/L in only 11% (13/222) of participants and procalcitonin >0.25 ng/mL in only 13% (16/125). All but two children received antibiotic treatment; only 3% (7/225) were admitted. At follow-up, 59% (118/201) of caregivers reported at least one persistent symptom, but fever had resolved for all children. Positive influenza testing was associated with persistent symptoms. In summary, we demonstrate that simple, rapid pathogen-specific testing and biomarker measurement are possible in resource-limited settings and could improve syndromic management and, in turn, antibiotic stewardship. IMPORTANCE Globally, respiratory illness is one of the most common reasons that children seek care. It is often treated inappropriately with antibiotics, which can drive the development of antibiotic resistance. In resource-rich settings, testing for specific pathogens or measurement of clinical biomarkers, such as procalcitonin and C-reactive protein, is often employed to help determine which children should receive antibiotics. However, there are limited data on the use of these tests in resource-constrained, outpatient contexts in sub-Saharan Africa. We enrolled children with respiratory illness presenting to a clinic in southwestern Uganda and performed testing for influenza, Streptococcus pneumoniae, C-reactive protein, and procalcitonin on-site. Almost all children received antibiotics. We demonstrate that employing clinical algorithms that include influenza and clinical biomarker testing could significantly decrease antibiotic prescriptions. Our study therefore provides preliminary data to support the feasibility and potential utility of diagnostics to improve management of respiratory illness in resource-constrained settings.

Decrease of Pneumococcal Community-Acquired Pneumonia Hospitalization and Associated Complications in Children after the Implementation of the 13-Valent Pneumococcal Conjugate Vaccine (PCV13) in Taiwan

The impact of the 13-valent pneumococcal conjugate vaccine (PCV13) on overall community-acquired pneumonia (CAP) and disease severity still needs thorough evaluation. In this study, we retrieve both pneumococcal CAP (P-CAP) and unspecific CAP (U-CAP) inpatient data from the Taiwan National Health Insurance Database (NHID) between 2005 and 2016. The interrupted time-series (ITS) analysis was performed to compare the incidence trend before and after the implementation of PCV13. After PCV13 implementation, there is a significant decreasing trend of P-CAP hospitalization, especially in children <1 year, 2-5 years, adults aged 19-65 years, 66 years, or older (all p value < 0.05). This corresponds to a 59% reduction in children <1 year, 47% in children aged 2-5 years, 39% in adult aged 19-65 years, and 41% in elderly aged 66 years or older. The intensive care rate (6.8% to 3.9%), severe pneumonia cases (21.7 to 14.5 episodes per 100,000 children-years), and the need for invasive procedures (4.3% to 2.0%) decreased in children aged 2-5 years (p value < 0.0001) with P-CAP. This PCV13 implementation program in Taiwan not only reduced the incidence of P-CAP, but also attenuated disease severity, especially in children aged 2-5 years.

Approach to Identifying Causative Pathogens of Community-Acquired Pneumonia in Children Using Culture, Molecular, and Serology Tests

Determining the causative pathogen(s) of community-acquired pneumonia (CAP) in children remains a challenge despite advances in diagnostic methods. Currently available guidelines generally recommend empiric antimicrobial therapy when the specific etiology is unknown. However, shifts in epidemiology, emergence of new pathogens, and increasing antimicrobial resistance underscore the importance of identifying causative pathogen(s). Although viral CAP among children is increasingly recognized, distinguishing viral from bacterial etiologies remains difficult. Obtaining high quality samples from infected lung tissue is typically the limiting factor. Additionally, interpretation of results from routinely collected specimens (blood, sputum, and nasopharyngeal swabs) is complicated by bacterial colonization and prolonged shedding of incidental respiratory viruses. Using current literature on assessment of CAP causes in children, we developed an approach for identifying the most likely causative pathogen(s) using blood and sputum culture, polymerase chain reaction (PCR), and paired serology. Our proposed rules do not rely on carriage prevalence data from controls. We herein share our perspective in order to help clinicians and researchers classify and manage childhood pneumonia.

Detection of Streptococcus pneumoniae in Urine by Loop-Mediated Isothermal Amplification

Objective To assess the loop-mediated isothermal amplification (LAMP) to detect cell-free DNA from Streptococcus pneumoniae in urine samples from children with pneumococcal pneumonia.

Methods LAMP reactions using four primers (backward inner primer, forward inner primer, B3, and F3) targeting conserved regions of the S. pneumoniae ply gene and DNA from the recombinant plasmid pTrc99A-ply were optimized for temperature (65°C) and MgSO4 concentration (8 mM) conditions. Urine samples from 71 patients with symptoms of pneumonia and from 17 healthy children were tested side by side using the isothermal methodology LAMP and the commercial urinary antigen test, BinaxNOW S. pneumoniae assay. Percentages of sensitivity, specificity, positive predictive value (PPV), negative predictive value, and positive (LR) were calculated to compare both tests.

Results The specificity of the LAMP reaction was confirmed against several species of bacteria and yeast that can cause pneumonia or urine infections. The suitability of the LAMP assay was evaluated in urine samples from 71 patients and 17 healthy children. All patients (100%) with confirmed pneumococcal pneumonia were positive for the LAMP assay. Among patients with possible/probable pneumonia, 74.1% were identified as positive using the LAMP test. Notably, a higher specificity (95.4%), PPV (94.1%) and positive LR (21.7) were found compared with the urinary antigen test.

Conclusion The presence of S. pneumoniae cell-free DNA in urine samples of pediatric patients can be used as a specific diagnostic biomarker for community-acquired pneumonia by using the LAMP methodology.

Consensus Document on Community-Acquired Pneumonia in Children. SENP-SEPAR-SEIP

Community-acquired pneumonia (CAP) is a prevalent disease among children and is frequently associated with both diagnostic and therapeutic uncertainties. Consensus has been reached between SEPAR, SENP and SEIP, and their conclusions are as follows.

Detection of Streptococcus pneumoniae antigen in pleural fluid: usefulness of an immunofluorescence-based lateral flow assay for the diagnosis of pneumococcal pneumonia

The performance of an immunofluorescence-based Streptococcus pneumoniae antigen detection test in pleural fluid (IF-PF) was evaluated. For proven and possible pneumococcal pneumonias global sensitivity and specificity were 92.6 (95 CI 76.6-97.9) and 80 (95 CI 62.7-90.5), respectively, with no significant differences between children and adults. Global diagnostic accuracy of IF-PF was 86% (74.2-93.7), and a substantial k index of concordance with culture/RT-PCR of 0.716 (0.535-0.896). IF-PF might be useful as a rapid complementary test for the etiologic diagnosis of pneumococcal pneumonia.

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.

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.

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.

Bacteria in the respiratory tract-how to treat? Or do not treat?

BACKGROUND

Acute and chronic respiratory tract infections are a common cause of inappropriate antimicrobial prescription. Antimicrobial therapy leads to the development of resistance and the emergence of opportunistic pathogens that substitute the indigenous microbiota.

METHODS

This review explores the major challenges and lines of research to adequately establish the clinical role of bacteria and the indications for antimicrobial treatment, and reviews novel therapeutic approaches.

RESULTS

In patients with chronic pulmonary diseases and structural disturbances of the bronchial tree or the lung parenchyma, clinical and radiographic signs and symptoms are almost constantly present, including a basal inflammatory response. Bacterial adaptative changes and differential phenotypes are described, depending on the clinical role and niche occupied. The respiratory tract has areas that are potentially inaccessible to antimicrobials. Novel therapeutic approaches include new ways of administering antimicrobials that may allow intracellular delivery or delivery across biofilms, targeting the functions essential for infection, such as regulatory systems, or the virulence factors required to cause host damage and disease. Alternatives to antibiotics and antimicrobial adjuvants are under development.

CONCLUSIONS

Prudent treatment, novel targets, and improved drug delivery systems will contribute to reduce the emergence of antimicrobial resistance in lower respiratory tract infections.

Au@Ag SERRS tags coupled to a lateral flow immunoassay for the sensitive detection of pneumolysin

Establishing a definitive diagnosis of pneumonia using conventional tests is difficult and expensive. Lateral flow immunoassays (LFIAs) are an advantageous point of care (POC) test option, but they have some limitations in terms of detection and quantification. In this work we have developed a lateral flow immunoassay for the ultrasensitive detection of penumolysin employing plasmonic Surface-Enhanced Resonance Raman Scattering (SERRS) tag as labelled probe. The combination of Au@Ag core-shell nanoparticles as plasmonic platform and Rhodamine B Isothiocyanate as Raman reporter has allowed us to fabricate a SERRS tag with high efficiency and reliability. The limit of detection of the SERRS-based LFIA was 1 pg mL^-1. This could be a strong foundation for a pneumonia diagnosis test based on pneumolysin detection.

A three-step diagnosis of pediatric pneumonia at the emergency department using clinical predictors, C-reactive protein, and pneumococcal PCR

Recommendations for the management of community-acquired pneumonia (CAP) advocate that, in the absence of the clinical and laboratory findings typical of bacterial CAP, antibiotics are not required. However, the true value of the clinical and laboratory predictors of pediatric CAP still needs to be assessed. This prospective cohort study in three emergency departments enrolled 142 children with radiological pneumonia. Pneumonia with lung consolidation was the primary endpoint; complicated pneumonia (bacteremia, empyema, or pleural effusion) was the secondary endpoint. We showed that three clinical signs (unilateral hypoventilation, grunting, and absence of wheezing), elevated procalcitonin (PCT), C-reactive protein (CRP), negative nasopharyngeal viral PCR, or positive blood pneumococcal PCR (P-PCR) were significantly associated with both pneumonia with consolidation and complicated pneumonia. Children with negative clinical signs and low CRP values had a low probability of having pneumonia with consolidation (13%) or complicated pneumonia (6%). Associating the three clinical signs, CRP >80 mg/L and a positive P-PCR ruled in the diagnosis of complicated pneumonia with a positive predictive value of 75%.

CONCLUSION

A model incorporating clinical signs and laboratory markers can effectively assess the risk of having pneumonia. Children with negative clinical signs and low CRP are at a low risk of having pneumonia. For children with positive clinical signs and high CRP, a positive blood pneumococcal PCR can more accurately confirm the diagnosis of pneumonia. What is Known: • Distinguishing between bacterial and viral pneumonia in children is challenging. • Reducing the inappropriate use of antibiotics is a priority. What is New: • Children with negative clinical signs and low C-reactive protein (CRP) values have a low probability of having pneumonia. • Children with high CRP values can be tested using a pneumococcal PCR to rule in the diagnosis of pneumonia with a high positive predictive value.

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.

Enhanced Diagnosis of Pneumococcal Bacteremia Using Antigen- and Molecular-Based Tools on Blood Specimens in Mali and Thailand: A Prospective Surveillance Study

Prior antibiotic use, contamination, limited blood volume, and processing delays reduce yield of blood cultures for detection of Streptococcus pneumoniae. We performed immunochromatographic testing (ICT) on broth from incubated blood culture bottles and real-time lytA polymerase chain reaction (PCR) on broth and whole blood and compared findings to blood culture in patients with suspected bacteremia. We selected 383 patients in Mali and 586 patients in Thailand based on their blood culture results: 75 and 31 were positive for pneumococcus, 100 and 162 were positive for other pathogens, and 208 and 403 were blood culture negative, respectively. ICT and PCR of blood culture broth were at least 87% sensitive and 97% specific compared with blood culture; whole blood PCR was 75–88% sensitive and 96–100% specific. Pneumococcal yields in children < 5 years of age increased from 2.9% to 10.7% in Mali with > 99% of additional cases detected by whole blood PCR, and from 0.07% to 5.1% in Thailand with two-thirds of additional cases identified by ICT. Compared with blood culture, ICT and lytA PCR on cultured broth were highly sensitive and specific but their ability to improve pneumococcal identification varied by site. Further studies of these tools are needed before widespread implementation.

A novel quantitative PCR assay for the detection of Streptococcus pneumoniae using the competence regulator gene target comX

Streptococcus pneumoniae is responsible for an estimated 1.6 million deaths worldwide every year. While rapid detection and timely treatment with appropriate antibiotics is preferred, this is often difficult due to the amount of time that detection with blood cultures takes. In this study, a novel quantitative PCR assay for the detection of Streptococcus pneumoniae was developed. To identify novel targets, we analysed the pneumococcal genome for unique, repetitive DNA sequences. This approach identified comX, which is conserved and present in duplicate copies in Streptococcus pneumoniae but not in other bacterial species. Comparison with lytA, the current 'gold standard' for detection by quantitative PCR, demonstrated an analytic specificity of 100% for both assays on a panel of 10 pneumococcal and 18 non-pneumococcal isolates, but a reduction of 3.5 quantitation cycle values (± 0.23 sem), resulting in an increased analytical detection rate of comX. We validated our assay on DNA extracted from the serum of 30 bacteraemic patients who were blood culture positive for Streptococcus pneumoniae and 51 serum samples that were culture positive for other bacteria. This resulted in a similar clinical sensitivity between the comX and lytA assays (47%) and in a diagnostic specificity of 98.2 and 100% for the lytA and comX assays, respectively. In conclusion, we have developed a novel quantitative PCR assay with increased analytical sensitivity for the detection of Streptococcus pneumoniae, which may be used to develop a rapid bedside test for the direct detection of Streptococcus pneumoniae in clinical specimens.

Comparison of Binax NOW urine antigen test and pneumococcal DNA assay using qPCR before and after nasopharyngeal swabbing in healthy Malawian children

Diagnosis of invasive pneumococcal disease is challenging. We compared Binax NOW pneumococcal urinary antigen test with blood pneumococcal PCR in healthy Malawian children with and without pneumococcal carriage, and we found a high false-positive rate with Binax NOW. Blood pneumococcal PCR positivity was 66/88 (75%) compared to 5/27 (18%) when nasopharyngeal swabbing was performed first compared to after blood sampling for pneumococcal blood PCR. We speculate that nasopharyngeal swabbing may be causing a breach of mucosal integrity, leading to invasion into the bloodstream. These findings need to be confirmed with autolysin-based PCR assays.

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.

Pneumococcal urinary antigen positivity in healthy colonized children: is it age dependent?

BACKGROUND

Pneumococcal urinary antigen test is a valuable tool for diagnosing pneumococcal pneumonia and meningitis in adults. Its use in children is generally not accepted because of nonspecificity at this age. It is frequently positive in asymptomatic nasopharyngeal carriers. The aim of our study was to assess the age limit from which the test is no longer positive in asymptomatic healthy carriers.

METHODS

A total of 197 children aged 36-83 months attending 9 day care centers in Prague were enrolled during February and March 2010. Nasopharyngeal swab specimens were collected from each participant and selectively cultivated. The presence of pneumococcal antigen in urine was detected by BinaxNOW® S. pneumoniae kit.

RESULTS

Streptococcus pneumoniae was cultivated in 53.3 % of healthy children with the highest colonization rate (59.3 %) in children aged 48-59 months. The most frequently colonizing serotypes were: 19F, 23F, 3, 19A, 6B and 4. The presence of pneumococcal antigen in urine decreased with age from 39.0 % in 36-47 months to 17.9 % in 72-83 months old (p = 0.031). The antigen positivity was serotype-dependent and more frequent in nonvaccinated children.

CONCLUSION

We demonstrated age-dependent linear decrease of pneumococcal antigen excretion into urine in healthy children. The positivity rate of the test in children aged 72-83 months was similar to that referred in healthy adults, irrespective of colonization. To confirm this age limit for use of this test in diagnostics of pneumococcal diseases, further study in school-age children is justified.

Diagnostics for community-acquired and atypical pneumonia

PURPOSE OF REVIEW

After decades of neglect, the importance of establishing an aetiological diagnosis for community-acquired and atypical pneumonias has increased dramatically in recent years--driven by the movement towards more rational use of antibiotics, the further spread of antimicrobial resistance, and advances in point-of-care assays that circumvent the diagnostic delays that result from the centralization of laboratories.

RECENT FINDINGS

There have been very few developments in patient sampling, or the direct visualization, culture, and serological detection of respiratory pathogens. There has, however, been significant interest in the development of improved and more clinically useful assays for the detection of pathogen nucleic acids and proteins, and also in the potential utility of the assessment of host response for tailoring therapy.

SUMMARY

The majority of patients have yet to benefit from any advances. However, nucleic acid, newer protein, and possibly host-response assays have significant potential to influence patient care in the near future.

Microbiological diagnosis of community-acquired respiratory tract infections by nucleic acid detection

BACKGROUND

Microbiological diagnostic procedures have changed significantly over the last decade. Initially the implementation of the polymerase chain reaction (PCR) resulted in improved detection tests for microbes that were difficult or even impossible to detect by conventional methods such as culture and serology, especially in community-acquired respiratory tract infections (CA-RTI). A further improvement was the development of real-time PCR, which allows end point detection and quantification, and many diagnostic laboratories have now implemented this powerful method.

OBJECTIVE

At present, new performant and convenient molecular tests have emerged targeting in parallel many viruses and bacteria responsible for lower and/or upper respiratory tract infections. The range of test formats and microbial agents detected is evolving very quickly and the added value of these new tests needs to be studied in terms of better use of antibiotics, better patient management, duration of hospitalization and overall costs.

CONCLUSIONS

Molecular tools for a better microbial documentation of CA-RTI are now available. Controlled studies are now required to address the relevance issue of these new methods, such as, for example, the role of some newly detected respiratory viruses or of the microbial DNA load in a particular patient at a particular time. The future challenge for molecular diagnosis will be to become easy to handle, highly efficient and cost-effective, delivering rapid results with a direct impact on clinical management.

Validation of an immunodiagnostic assay for detection of 13 Streptococcus pneumoniae serotype-specific polysaccharides in human urine

To improve the clinical diagnosis of pneumococcal infection in bacteremic and nonbacteremic community-acquired pneumonia (CAP), a Luminex technology-based multiplex urinary antigen detection (UAD) diagnostic assay was developed and validated. The UAD assay can simultaneously detect 13 different serotypes of Streptococcus pneumoniae by capturing serotype-specific S. pneumoniae polysaccharides (PnPSs) secreted in human urine. Assay specificity is achieved by capturing the polysaccharides with serotype-specific monoclonal antibodies (MAbs) on spectrally unique microspheres. Positivity for each serotype was based on positivity cutoff values calculated from a standard curve run on each assay plate together with positive- and negative-control urine samples. The assay is highly specific, since significant signals are detected only when each PnPS was paired with its homologous MAb-coated microspheres. Validation experiments demonstrated excellent accuracy and precision. The UAD assay and corresponding positivity cutoff values were clinically validated by assessing 776 urine specimens obtained from patients with X-ray-confirmed CAP. The UAD assay demonstrated 97% sensitivity and 100% specificity using samples obtained from patients with bacteremic, blood culture-positive CAP. Importantly, the UAD assay identified Streptococcus pneumoniae (13 serotypes) in a proportion of individuals with nonbacteremic CAP, a patient population for which the pneumococcal etiology of CAP was previously difficult to assess. Therefore, the UAD assay provides a specific, noninvasive, sensitive, and reproducible tool to support vaccine efficacy as well as epidemiological evaluation of pneumococcal disease, including CAP, in adults.

Laboratory methods for determining pneumonia etiology in children

Laboratory diagnostics are a core component of any pneumonia etiology study. Recent advances in diagnostic technology have introduced newer methods that have greatly improved the ability to identify respiratory pathogens. However, determining the microbial etiology of pneumonia remains a challenge, especially in children. This is largely because of the inconsistent use of assays between studies, difficulties in specimen collection, and problems in interpreting the presence of pathogens as being causally related to the pneumonia event. The laboratory testing strategy for the Pneumonia Etiology Research for Child Health (PERCH) study aims to incorporate a broad range of diagnostic testing that will be standardized across the 7 participating sites. We describe the current status of laboratory diagnostics for pneumonia and the PERCH approach for specimen testing. Pneumonia diagnostics are evolving, and it is also a priority of PERCH to collect and archive specimens for future testing by promising diagnostic methods that are currently under development.

Usefulness of consecutive biomarkers measurement in the management of community-acquired pneumonia

The aim of this study was to investigate whether procalcitonin (PCT), neopterin, C-reactive protein (CRP), and mid regional pro-atrial natriuretic peptide (MR-proANP) levels at admission and during the clinical course can be useful for the management of patients with pneumonia. The study population consisted of 75 patients with clinical and radiological diagnosis of pneumonia. Serum samples were collected at admission and during hospitalization. Complications were defined as intensive care unit (ICU) admission or death. The levels of PCT were significantly higher in pneumonia of definite bacterial origin in comparison to probable bacterial or unknown origin. The PCT levels were higher in pneumococcal pneumonia. The PCT and MR-proANP levels increased significantly according to the Pneumonia Severity Index (PSI). All biomarkers levels are higher in patients developing complications and who were dying. The serial levels of MR-proANP remain significantly elevated in patients developing complications and in patients classified in PSI and CURB-65 risk groups. In patients not developing complications, there is a significant decrease in the PCT levels. PCT can be useful for identifying pneumonia etiology. PCT and MR-proANP levels correlate with pneumonia severity rules. PCT and MR-proANP serial measurements can be useful for predicting short-term prognosis. Systemic biomarkers can provide additional information regarding clinical evolution, because these are dynamic and can be measured daily.

[Relationships with microbiology: the view from other specialties]

The major advances produced in infectious diseases, partly favored by technological development in the last few years, together with current changes in healthcare, have led to a new scenario in which, far from the control of infectious diseases, clinical microbiology has acquired an undoubted leading role. This new panorama implies collaboration among distinct health professionals within the same healthcare setting, with common and occasionally conflicting interests. Setting aside the individual differences that can be produced in the daily life of our hospitals, all health professionals should understand one another, not only because such cooperation is required for optimal patient care but also because synergistic collaboration among professions would improve professional development. Based on this principle of a multidisciplinary approach, collaboration and mutual respect, the moment seems opportune for the various professionals involved in infectious diseases (infectologists, internists, pediatricians and intensivists) to express their view of the specialty of clinical microbiology. The present article includes reflections, from a highly liberal and personal point of view, on how mutual relationships can be approached and on how greater knowledge of infectious diseases can continue to be gained in Spain. In all these reflections, the questions of where we come from and where we are going are explicit or implicit.

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.

Pneumococcal DNA is not detectable in the blood of healthy carrier children by real-time PCR targeting the lytA gene

The diagnosis of invasive pneumococcal disease (IPD) is currently based on culture methods, which lack sensitivity, especially after antibiotic therapy. Molecular methods have improved sensitivity and do not require viable bacteria; however, their use is complicated by reports of low specificity with some assays. The present study investigated the specificity of a real-time PCR targeting lytA for the detection of IPD. A group of 147 healthy children, aged 6 months to 16 years (mean 6.4 years, median 4.9 years, interquartile range 6.4 years), who were in hospital for routine examinations, were tested for pneumococcal carrier status and for the presence of detectable pneumococcal DNA in their blood by real-time PCR targeting the pneumococcal lytA gene. In addition, 35 culture-positive biological samples were analysed. Urine was examined for the presence of pneumococcal DNA and C-polysaccharide antigen. Carriage was detected in 77 of the 147 subjects (52.4 %); however, regardless of carrier status, none of the subjects had a positive result from blood. Analysis of the culture-positive biological samples yielded positive results in 100 % (15/15) of cerebrospinal fluid samples and 95 % (19/20) of blood samples. All urine samples from healthy carriers were negative for DNA, whilst antigenuria was detected in 44/77 carriers (57.1 %). In conclusion, real-time PCR is both sensitive and specific and can be a useful tool in the routine diagnosis of IPD. Its sensitivity, which surpasses that of other methods for this purpose, does not come at the cost of reduced specificity.

PneumoniaCheck: A Device for Sampling Lower Airway Aerosols

The pathogens causing pneumonia are difficult to identify because a high quality specimen from the lower lung is difficult to obtain. A new specimen collection device is designed to collect aerosol specimens selectively from the lower lung generated during deep coughing. The PneumoniaCheck device utilizes a separation reservoir and Venturi valve to segregate contents from the upper and lower airways. The device also includes several specially designed features to exclude oral contaminants from the sample and a filter to collect the aerosolized pathogens. Verification testing of PneumoniaCheck demonstrates effective separation of upper airway gas from the lower airway gas (p<0.0001) and exclusion of both liquid and viscous oral material (p<0.0001) from the collection chamber. The filters can collect 99.9997% of virus and bacteria sized particles from the sampled lower lung aerosols. The selective collection of specimens from the lower airway may aid in the diagnosis of specific pathogens causing pneumonia.

Identification of bacterial pathogens in pediatric community-acquired lower respiratory tract infection using a simplified procedure of sputum sampling and examination: comparison between hospitalized children with and without underlying diseases

The aim of this study is to confirm the usefulness of sputum sampling from the hypopharynx through the nose to identify causative bacteria of pediatric community-acquired lower respiratory tract infection (CA-LRTI) and compare its features between the patients with and without underlying diseases. A retrospective study was performed on 244 pediatric patients hospitalized for CA-LRTI of suspected bacterial etiology. Sputum sample was obtained from these patients by aspirating airway secretion through the nose or the tracheostomy orifice, or coughing up by themselves. Sputum samples were assessed as suitable in 119 (74.4%) of 160 patients with CA-LRTI of suspected pure bacterial etiology. Ninety-six (70.1%) of 137 samples suctioned from the hypopharynx through the nose were suitable for bacterial examination. Seventy-eight (73.6%) of 106 patients identified with causative bacteria had some underlying diseases, and the other 28 patients did not have any underlying diseases. Proportions and antibiotics susceptibility profiles of the identified causative bacteria were almost similar in the patients with and without underlying diseases. Sputum sampling from the hypopharynx through the nose might be significant in pediatric CA-LRTI of suspected bacterial etiology. The initial treatment for patients without underlying diseases would be applicable to those with underlying diseases in the CA-LRTI of children.

Pediatric parapneumonic pleural effusion: epidemiology, clinical characteristics, and microbiological diagnosis

BACKGROUND

In recent years an increase in the incidence and severity of parapneumonic pleural effusion (PPE) in pediatric populations has been observed. Streptococcus pneumoniae remains the main causal agent. New molecular and antigen techniques have increased the microbiological diagnosis of this pathology.

OBJECTIVES

To describe the epidemiology and clinical characteristics of PPE in our population.

PATIENTS AND METHODS

Prospective study of patients under the age of 18 years admitted for PPE in a tertiary-care pediatric hospital in Barcelona (Spain) between September 2003 and December 2006.

RESULTS

One hundred ninety cases of PPE were diagnosed. The annual incidence of PPE in the population under 18 years of age increased from 19.9 cases per 100,000 in 2004 to 35.2 per 100,000 in 2006. S. pneumoniae was the main causal agent identified: 82.9% of the 21.6% patients with positive culture. Non-vaccine serotypes (NVS) predominated (81.5%), and serotype 1 was responsible for 38.5% of cases. The use of polymerase chain reaction (PCR) test to detect S. pneumoniae increased etiological diagnosis from 21.6% to 42.1%. Antigen assays used to detect pneumococcus in pleural fluid demonstrated 87.9% sensitivity and 100% specificity when PCR was used as the gold standard.

CONCLUSIONS

There has been an increase in the incidence of PPE that parallels the increase in CAP. S. pneumoniae remains the principal causal agent, and NVS clearly predominate. The use of PCR to detect S. pneumoniae substantially increases etiologic diagnosis. The use of antigen assays to detect pneumococcus in pleural fluid is a quick and sensitive diagnostic method, and thus a valid alternative to PCR.

Diagnostic detection of Streptococcus pneumoniae PpmA in urine

Streptococcus pneumoniae infections are often difficult to diagnose accurately, as it is not uncommon for clinical samples to be culture-negative, particularly after antibiotic administration. The rapid Binax NOW S. pneumoniae urinary antigen test lacks specificity in children, owing to pneumococcal antigen reactions in children who are nasopharyngeal carriers of S. pneumoniae. A western blot assay with a specific polyclonal antibody was developed for direct detection of the putative proteinase maturation protein A (PpmA) in urine samples from children with pneumococcal infections. The sensitivity and specificity of the assay were 66.7% and 100%, respectively. Previous antibiotic treatment or S. pneumoniae nasopharyngeal colonization did not affect PpmA antigenuria. Results also demonstrated the presence of PpmA cross-reactive epitopes in commensal bacteria that co-colonize the nasopharyngeal niche, although the non-pneumococcal cross-reactive protein(s) did not interfere with the detection assay. S. pneumoniae PpmA in the urine of children with pneumococcal infections may be a marker that has the potential to be used in the clinical diagnosis of pneumococcal infection.

Competitive inhibition flow analysis assay for the non-culture-based detection and serotyping of pneumococcal capsular polysaccharide

Traditional confirmation procedures for the identification of a pneumococcal serotype require an isolate. Non-culture-based confirmation protocols are available. Some of these confirm only the presence of pneumococci, and others are capable of identifying a limited number of serotypes. The increased use of pneumococcal polysaccharide and conjugate vaccines, especially in high-risk patient groups, and the likely increase in the number of serotypes included in future versions of the conjugate vaccines have necessitated the need for improved enhanced surveillance in order to assess their impact on public health. Since 2006, a multiplexed assay has been used at the Health Protection Agency of the United Kingdom for the detection of 14 pneumococcal serotypes which requires pneumococcal serotype-specific monoclonal antibodies (MAbs). We have developed a microsphere competitive inhibition method capable of detecting 23 pneumococcal capsular polysaccharide serotypes in cerebrospinal fluid (CSF) and urine and serotyping pneumococcal suspensions, utilizing an international reference serum, 89-SF. The assay was shown to be reproducible and specific for homologous polysaccharide. Validation of the assay was performed with a selection of MAbs specific for pneumococcal capsular polysaccharide serotypes, which confirmed the specificity of the assay. Analysis of pneumolysin PCR-positive CSF samples in the competitive inhibition assay determined a serotype for 89% of the samples. The assay developed here is well suited to large-scale epidemiologic studies because the assay is simple, robust, and rapid and utilizes readily available resources.

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.

Midregional pro-atrial natriuretic peptide as a prognostic marker in pneumonia

OBJECTIVE

To evaluate the usefulness of midregional pro-atrial natriuretic peptide (MR-proANP) measurement in the stratification of severity in community-acquired pneumonia.

METHODS

The population studied was three hundred patients admitted to Emergency Department of a tertiary university hospital presenting clinical signs of lower respiratory tract infection, a new infiltrate on the chest radiograph and a confirmed pneumonia by clinical evolution. Patients were stratified by the Pneumonia Severity Index (PSI), by CURB-65 score and by the development of complications. Serum samples were obtained at the moment of admission and prior to antibiotic therapy, and stored until analysis. MR-proANP was measured by B.R.A.H.M.S MR-proANP KRYPTOR.

RESULTS

Serum levels of MR-proANP increased with the severity of pneumonia, according to PSI score and CURB-65 score. Median MR-proANP levels were significantly higher (p<0.0001) in patients with high PSI risk class (IV-V) than in those with low PSI risk class (I-III). MR-proANP levels were also significantly higher (p=0.029) in those patients that developed complications or died. There was no association between MR-proANP and etiology of pneumonia and the radiographic extent.

CONCLUSION

We can conclude that MR-proANP measurement was helpful for individual risk assessment in patients with pneumonia admitted to the emergency department.

Microbiological aspects of bacterial lower respiratory tract illness in children: typical pathogens

Whilst childhood immunization programmes have had an impact on the spectrum of pneumonic diseases seen in children, bacteria remain an important cause of lower respiratory tract infection (LRTI), particularly in younger and debilitated children. Because of the difficulty in obtaining lower respiratory tract specimens in children, specific diagnosis has often been difficult, although advances in diagnostic techniques have provided a much greater range of tools for the clinician. The challenge is to understand the application and limitation of these tests in the diagnosis of LRTI. This review examines the microbiological and diagnostic issues around Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis, Neisseria meningitidis and enteric Gram negative pathogens.