A bedside assay to detect streptococcus pneumoniae in children with empyema

Identifying pneumococci in parapneumonic pleural effusion: Is there a role for culture-independent methods?

OBJECTIVE

To evaluate culture-independent procedures (immunochromatography and quantitative polymerase chain reaction [qPCR]) in the detection and susceptibility of Streptococcus pneumoniae directly from culture-negative pleural fluid (PF) in children.

METHOD

Detection of S. pneumoniae in PF of children with parapneumonic effusion and/or empyema by using two culture-independent methods: an immunochromatographic membrane test (IMT) which identifies the pneumococcal C antigen, and a real-time PCR test to detect pneumococcal genes lytA and pbp2b, a marker of susceptibility of β-lactam agents, in PF samples.

RESULTS

We tested 36 PF specimens and recorded the previous use of antimicrobials. In the final analysis, 34 samples were included. IMT and qPCR presented positive results in 23 (67.6%) and 24 (70.6%) of the samples, respectively, showing a moderate agreement (k = 0.518) between the two methods. From the 36 children included, 34 (94.4%) had antibiotic data available by the time when PFs were collected. Thirty-four (100%) children had been given treatment before PF sampling, with 33 (97%) receiving β-lactam antibiotics administered empirically. Of the 24 lytA real-time positive samples, 21 (87.5%) were also positive for pbp2b, a marker of β-lactam susceptibility.

CONCLUSION

The reduced sensitivity of culture for pneumococcal detection can be improved through the addition of IMT and qPCR analysis. The utility of qPCR combining detection of lytA and a marker of β-lactam susceptibility should be explored further.

Microbiological Diagnosis of Respiratory Illness

A wide variety of microorganisms are potential respiratory pathogens, and the spectrum of known pathogens for each respiratory infection syndrome has not changed markers over recent years. Detection of likely etiologic agents of respiratory infections can help direct management and can also play an important role in disease surveillance. For this purpose, we are still reliant on many traditional diagnostic tools that have been used for decades in order to determine the microbial etiology of respiratory infections. However, these tools have been increasingly supplemented by newer methods, particular molecular diagnostic techniques, which have enabled the more rapid detection of many pathogens that were previously difficult to detect. These advances have particularly lead to improvements in the ability to detect respiratory viruses and also other microorganisms that do not normally colonize the respiratory tract. Recognition of the existence of the lung microbiome has challenged the traditional views of pneumonia pathogenesis and may provide the opportunity for new diagnostic tools that are focused on more than just detection of specific known pathogens. Continued liaison between clinicians and laboratory staff is vital in order to facilitate the most cost-effective use of laboratory diagnostics.

Pleural infection: past, present, and future directions

Pleural space infections are increasing in incidence and continue to have high associated morbidity, mortality, and need for invasive treatments such as thoracic surgery. The mechanisms of progression from a non-infected, pneumonia-related effusion to a confirmed pleural infection have been well described in the scientific literature, but the route by which pathogenic organisms access the pleural space is poorly understood. Data suggests that not all pleural infections can be related to lung parenchymal infection. Studies examining the microbiological profile of pleural infection inform antibiotic choice and can help to delineate the source and pathogenesis of infection. The development of radiological methods and use of clinical indices to predict which patients with pleural infection will have a poor outcome, as well as inform patient selection for more invasive treatments, is particularly important. Randomised clinical trial and case series data have shown that the combination of an intrapleural tissue plasminogen activator and deoxyribonuclease therapy can potentially improve outcomes, but the use of this treatment as compared with surgical options has not been precisely defined, particularly in terms of when and in which patients it should be used.

Etiology of Pneumonia in a Pediatric Population with High Pneumococcal Vaccine Coverage: A Prospective Study

BACKGROUND

Improved Childhood Immunizations Programs, especially the introduction of pneumococcal vaccination, better diagnostic methods and the importance of reduced antibiotic misuse, make this a critical time to increase knowledge on the etiology of pediatric pneumonia. Our main objective was to identify the contribution of various microbiological species that causes pneumonia in previously healthy children and adolescents in a population with high pneumococcal conjugate vaccine coverage.

METHODS

This prospective, observational study enrolled patients with clinical and radiological signs of pneumonia over a 2-year period. Both inpatients and outpatients were included. Paired sera, nasopharyngeal polymerase chain reaction and bacterial cultures from blood and pleura were analyzed to detect potential viral and bacterial causative pathogens.

RESULTS

TWO HUNDRED AND SIXTY-FIVE: cases of clinical and radiological verified pneumonia were identified. The pneumococcal vaccine coverage was 85%. We identified a causative pathogen in 84.2% of all cases; 63.4% with single viral etiology, 11.3% with pneumococcus and 7.5% with mycoplasma infection. Respiratory syncytial virus was the most common pathogen in children younger than 5 years, whereas mycoplasma was the most common in older children.

CONCLUSIONS

We identified the majority of 265 cases with radiology proven pneumonia as single viral infections, predominantly respiratory syncytial virus and a much lower proportion of bacterial causes. These findings may impact pneumonia management guidelines in areas where widespread pneumococcal vaccination is provided and contribute to reduced antibiotic overuse in pediatric pneumonia.

Improving diagnosis of pneumococcal disease by multiparameter testing and micro/nanotechnologies

The diagnosis and management of pneumococcal disease remains challenging, in particular in children who often are asymptomatic carriers, and in low-income countries with a high morbidity and mortality from febrile illnesses where the broad range of bacterial, viral and parasitic cases are in contrast to limited, diagnostic resources. Integration of multiple markers into a single, rapid test is desirable in such situations. Likewise, the development of multiparameter tests for relevant arrays of pathogens is important to avoid overtreatment of febrile syndromes with antibiotics. Miniaturization of tests through use of micro- and nanotechnologies combines several advantages: miniaturization reduces sample requirements, reduces the use of consumables and reagents leading to a reduction in costs, facilitates parallelization, enables point-of-care use of diagnostic equipment and even reduces the amount of potentially infectious disposables, characteristics that are highly desirable in most healthcare settings. This critical review emphasizes our vision on the importance of multiparametric testing for diagnosing pneumococcal infections in patients with fever and examines recent relevant developments in micro/nanotechnologies to achieve this goal.

Aetiology of paediatric pneumonia with effusion in the Dominican Republic and the potential impact of pneumococcal conjugate vaccines

Pleural effusion is a serious complication of pneumonia, and Streptococcus pneumoniae is a leading cause. We describe the aetiology of pneumonia with effusion among children in the Dominican Republic before the introduction of the 13-valent pneumococcal conjugate vaccine (PCV) in 2013 and the performance characteristics of a rapid immunochromatographic test (ICT) for detecting S. pneumoniae in pleural fluid. From July 2009 to June 2011, we enrolled children <15 years old admitted with pneumonia and pleural effusion to Robert Reid Cabral Children’s Hospital, Dominican Republic. Pleural fluid was tested by culture, polymerase chain reaction (PCR) for bacterial (S. pyogenes, S. pneumoniae) and viral (respiratory syncytial virus and human rhinovirus) pathogens, and by ICT for S. pneumoniae. We calculated the performance of ICT and culture compared with PCR. Among 121 cases, the median age was 31 months (range 1 week to 14 years). Pleural fluid culture (n = 121) and PCR testing (n = 112) identified an aetiology in 85 (70.2%) cases, including 62 S. pneumoniae (51.2%) and 19 Staphylococcus aureus (15.7%). The viruses tested were not detected. The most prevalent pneumococcal serotypes were 14 (n = 20), 1 (n = 13), and 3 (n = 12). Serotype coverage of the 10- and 13-valent PCVs would be 70.5% and 95.1%, respectively. The sensitivity of point-of-care ICT was 100% (95% confidence interval [CI] 94.1%–100%), while specificity was 86.3% (95% CI 73.7%–94.3%). S. pneumoniae caused more than half of paediatric pneumonia with effusion cases; introduction of PCV in the Dominican Republic could reduce the burden by 36–49%. ICT is a practical, valid diagnostic tool for clinical care and surveillance in settings with limited laboratory capacity.

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.

Rapid diagnosis of invasive pneumococcal disease in pediatric population

The aim of this study was to evaluate the Binax NOW immunochromatographic pneumococcal antigen test for the identification of Streptococcus pneumoniae in pleural and cerebrospinal fluids from children with suspected invasive pneumococcal disease. The results were compared with those obtained by PCR. Binax NOW was applied to these samples as recommended by the manufacturer for urine and cerebrospinal samples. Detection of pneumococcal DNA was performed by real-time PCR assay targeting the autolysin gene (lytA). Of the 199 samples analyzed, 131 were positive by both Binax NOW and lytA PCR, and 36 samples were negative by both techniques. Using the real-time PCR as a comparative method to the Binax for the detection of S. pneumoniae, the sensitivity and specificity of Binax NOW was 88% and 72.5%, respectively. Of the 145 positive samples analyzed by Binax NOW, 119 showed intense coloring of the sample line and 26 showed weak intensity. Conventional culture is the most common method in clinical settings, but Binax NOW is an easier and faster test for identifying S. pneumoniae in pleural and cerebrospinal fluids from children with suspected invasive pneumococcal disease.

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.

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.

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.