Diagnosis of pneumococcal pneumonia by polymerase chain reaction (PCR) in whole blood: a prospective clinical study

Recent advances in biosensors for diagnosis and detection of sepsis: A comprehensive review

Sepsis is one of the leading causes of mortality among critically ill patients globally. According to WHO report 2018, it is estimated to affect beyond 30 million people worldwide every year. It causes loss of human lives, which arise from infection and inflammation and long term stay in intensive care unit (ICU) in hospitals. Despite the availability of satisfactory prognostic markers contributing to the diagnosis of sepsis, millions of people die even after admission to the hospitals. Correct and early diagnosis of sepsis leads to rapid administration of appropriate antibiotics can thus potentially avert the attainment to critical stages of sepsis, thereby saving human lives. Conventional diagnostic practices are costly, time consuming and they lack adequate sensitivity and selectivity, provoking an urgent need for developing alternate sepsis diagnosis systems. Nevertheless, biosensors have the much-treasured scope for reasonable sepsis diagnosis. Advancement in nano-biotechnology has provided new paradigm for biosensor platforms with upgraded features. Here, we provide an overview of the recent advances in biosensors with a brief introduction to sepsis, followed by the conventional methods of diagnosis and bio-sensing. To conclude, a proactive role and an outlook on technologically advanced biosensor platforms are discoursed with possible biomedical applications.

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.

Laboratory diagnosis of pneumonia in the molecular age

Pneumonia remains a worldwide health problem with a high rate of morbidity and mortality. Identification of microbial pathogens which cause pneumonia is an important area for optimum clinical management of pneumonia patients and is a big challenge for conventional microbiological methods. The development and implementation of molecular diagnostic tests for pneumonia has been a major advance in the microbiological diagnosis of respiratory pathogens in recent years. However, with new knowledge regarding the microbiome, together with the recognition that the lungs are a dynamic microbiological ecosystem, our current concept of pneumonia is not totally realistic as this new concept of pneumonia involves a dysbiosis or alteration of the lung microbiome. A new challenge for microbiologists and clinicians has therefore arisen. There is much to learn regarding the information provided by this new diagnostic technology, which will lead to improvements in the time to antibiotic therapy, targeted antibiotic selection and more effective de-escalation and improved stewardship for pneumonia patients. This article provides an overview of current methods of laboratory diagnosis of pneumonia in the molecular age.

Sustained-release synthetic biomarkers for monitoring thrombosis and inflammation using point-of-care compatible readouts

Postoperative infection and thromboembolism represent significant sources of morbidity and mortality but cannot be easily tracked after hospital discharge. Therefore, a molecular test that could be performed at home would significantly impact disease management. Our lab has previously developed intravenously delivered 'synthetic biomarkers' that respond to dysregulated proteases to produce a urinary signal. These assays, however, have been limited to chronic diseases or acute diseases initiated at the time of diagnostic administration. Here, we formulate a subcutaneously administered sustained release system by using small PEG scaffolds (<10 nm) to promote diffusion into the bloodstream over a day. We demonstrate the utility of a thrombin sensor to identify thrombosis and an MMP sensor to measure inflammation. Finally, we developed a companion paper ELISA using printed wax barriers with nanomolar sensitivity for urinary reporters for point-of-care detection. Our approach for subcutaneous delivery of nanosensors combined with urinary paper analysis may enable facile monitoring of at-risk patients.

Standardisation and evaluation of a quantitative multiplex real-time PCR assay for the rapid identification of Streptococcus pneumoniae

Rapid diagnosis of Streptococcus pneumoniae can play a significant role in decreasing morbidity and mortality of infection. The accurate diagnosis of pneumococcal disease is hampered by the difficulties in growing the isolates from clinical specimens and also by misidentification. Molecular methods have gained popularity as they offer improvement in the detection of causative pathogens with speed and ease. The present study aims at validating and standardising the use of 4 oligonucleotide primer-probe sets (pneumolysin [ply], autolysin [lytA], pneumococcal surface adhesion A [psaA] and Spn9802 [DNA fragment]) in a single-reaction mixture for the detection and discrimination of S. pneumoniae. Here, we validate a quantitative multiplex real-time PCR (qmPCR) assay with a panel consisting of 43 S. pneumoniae and 29 non-pneumococcal isolates, 20 culture positive, 26 culture negative and 30 spiked serum samples. A standard curve was obtained using S. pneumoniae ATCC 49619 strain and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene was used as an endogenous internal control. The experiment showed high sensitivity with lower limit of detection equivalent to 4 genome copies/µl. The efficiency of the reaction was 100% for ply, lytA, Spn9802 and 97% for psaA. The test showed sensitivity and specificity of 100% with culture isolates and serum specimens. This study demonstrates that qmPCR analysis of sera using 4 oligonucleotide primers appears to be an appropriate method for the genotypic identification of S. pneumoniae infection.

Development of a rapid recombinase polymerase amplification assay for the detection of Streptococcus pneumoniae in whole blood

Background

Streptococcus pneumoniae is an important cause of microbial disease in humans. The introduction of multivalent vaccines has coincided with a dramatic decrease in the number of pneumococcal-related deaths. In spite of this, at a global level, pneumococcal infection remains an important cause of death among children under 5 years of age and in adults 65 years of age or older. In order to properly manage patients and control the spread of infection, a rapid and highly sensitive diagnostic method is needed for routine implementation, especially in resource-limited regions where pneumococcal disease is most prevalent.

Methods

Using the gene encoding leader peptidase A as a molecular diagnostics target, a real-time RPA assay was designed and optimised for the detection of S. pneumoniae in whole blood. The performance of the assay was compared to real-time PCR in terms of its analytical limit of detection and specificity. The inhibitory effect of human genomic DNA on amplification was investigated. The potential clinical utility of the assay was investigated using a small number of clinical samples.

Results

The RPA assay has a limit of detection equivalent to PCR (4.0 and 5.1 genome equivalents per reaction, respectively) and was capable of detecting the equivalent of <1 colony forming unit of S. pneumoniae when spiked into human whole blood. The RPA assay was 100 % inclusive (38/38 laboratory reference strains and 19/19 invasive clinical isolates) and 100 % exclusive; differentiating strains of S. pneumoniae species from other viridans group streptococci, including S. pseudopneumoniae. When applied to the analysis of a small number (n = 11) of clinical samples (blood culture positive for S. pneumoniae), the RPA assay was demonstrated to be both rapid and sensitive.

Conclusions

The RPA assay developed in this work is shown to be as sensitive and as specific as PCR. In terms of reaction kinetics, the RPA assay is shown to exceed those of the PCR, with the RPA running to completion in 20 minutes and capable generating a positive signal in as little as 6 minutes. This work represents a potentially suitable assay for application in point-of-care settings.

Use of an automated PCR assay, the GenomEra S. pneumoniae, for rapid detection of Streptococcus pneumoniae in blood cultures

BACKGROUND

Streptococcus pneumoniae is recognized as a major cause of pneumonia, meningitis, and bacteremia. Since the mortality rate for pneumococcal bacteremia remains high, the reliable detection of the bacterium in blood samples is important. In this study, the performance of a new automated PCR assay, the GenomEra(™) S. pneumoniae, for direct detection of S. pneumoniae in blood cultures was investigated.

METHODS

In total, 200 samples were analyzed, including 90 previously identified culture collection isolates and 110 blood culture specimens. The species identification was confirmed with routine diagnostic methods including MALDI-TOF or 16S rDNA sequencing.

RESULTS

From culture collection, the GenomEra S. pneumoniae assay correctly identified all 37 S. pneumoniae isolates consisting of 18 different serotypes, while all 53 non-S. pneumoniae isolates yielded negative test results. Of 110 blood culture specimens, 46 grew S. pneumoniae and all were positive by the GenomEra assay direct from bottle. The detection sensitivity and specificity of the GenomEra assay for direct analysis of S. pneumoniae in signal positive blood culture bottles was 100%, respectively. With a straightforward sample preparation protocol of blood cultures the results were available within 55 min, thus being significantly quicker than by the routinely used identification methods (18-48 h). The two-step, time-resolved fluorometric measurement mode employed by the GenomEra CDX(™) instrument showed no interference from blood or charcoal.

CONCLUSION

The GenomEra S. pneumoniae assay is a tool that performs well for the rapid and reliable detection of S. pneumoniae in blood cultures.

Monitoring infection: from blood culture to polymerase chain reaction (PCR)

In patients with sepsis, diagnosis of blood stream infection (BSI) is a key concern to the therapist. Direct verification of pathogens in the blood stream executed by blood cultures (BC) still is regarded as the gold standard up to date. The quickest possible initiation of an appropriate antimicrobial therapy is a cornerstone of an effective therapy. Moreover, in this view BC can also serve to identify antimicrobial agents to target the pathogen. However, when employing BC the time needed until microbiological results are available ranges from 24 up to 72 h. Moreover, infections caused by multiple pathogens often remain undetected and concurrent antibiotic therapy may lower the overall sensitivity. Alternative pathogen characterization can be performed by polymerase chain reaction (PCR) based amplification methods. Results using PCR can be obtained within 6-8 h. Therefore, the time delay until an appropriate therapy can be reduced enormously. Moreover, these methods have the potential to enhance the sensitivity in the diagnosis of blood stream infections. Therefore, PCR based methods might be a valuable adjunct to present procedures of diagnosing bacteraemia.

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.

Non-culture-based methods to diagnose bloodstream infection: Does it work?

Bloodstream infections are a major cause of morbidity and mortality worldwide. Molecular methods for the detection of pathogens in blood have been developed. The clinical utility of these methods and their integration into the clinical workflow is discussed.

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.

Screening of pneumococcal pneumonia by amplification of pneumolysin gene in children visiting hospitals in lahore, pakistan

OBJECTIVE

Streptococcus pneumoniae is a common worldwide potential pathogen causing pneumonia among children and the detection of pneumococcal infections by conventional culturing techniques is cumbersome. The present study describes a comparative analysis of sensitive nested-PCR and bacterial culture in pediatric patients with clinical and radiological indication of S. pneumoniae infection.

METHODS

PCR was performed using outer primers to amplify a 348-bp region and inner primers a 208-bp region of the pneumolysin gene. For pneumolysin PCR assay, DNA from peripheral blood and middle ear fluid (MEF) samples was extracted by salting out method. The sensitivity of the assay was evaluated with about 0.06 pg of purified S. pneumoniae genomic DNA.

FINDINGS

Among 90 MEF culture negative samples from acute otitis media pediatric patients, 8.8% pneumolysin-PCR positivity was detected, demonstrating the sensitivity and reliability of PCR for rapid pneumonia evaluation. Binomial test of proportionality performed on (SPSS 17) gives P< 0.05 indicating that PCR technique is statistically significant and sensitive in the diagnosis of S. pneumoniae infection.

CONCLUSION

The research work evaluated the effectiveness and efficacy of nested-PCR for detecting S. pneumoniae in pediatric patients with clinical and radiological confirmation of bacterial infection. This simplified method permitted quick selection of the patients and played a significant role in preliminary management of pneumococcal infections.

Guidelines for the management of adult lower respiratory tract infections--summary

This document is an update of Guidelines published in 2005 and now includes scientific publications through to May 2010. It provides evidence-based recommendations for the most common management questions occurring in routine clinical practice in the management of adult patients with LRTI. Topics include management outside hospital, management inside hospital (including community-acquired pneumonia (CAP), acute exacerbations of COPD (AECOPD), acute exacerbations of bronchiectasis) and prevention. The target audience for the Guideline is thus all those whose routine practice includes the management of adult LRTI.

Guidelines for the management of adult lower respiratory tract infections--full version

This document is an update of Guidelines published in 2005 and now includes scientific publications through to May 2010. It provides evidence-based recommendations for the most common management questions occurring in routine clinical practice in the management of adult patients with LRTI. Topics include management outside hospital, management inside hospital (including community-acquired pneumonia (CAP), acute exacerbations of COPD (AECOPD), acute exacerbations of bronchiectasis) and prevention. Background sections and graded evidence tables are also included. The target audience for the Guideline is thus all those whose routine practice includes the management of adult LRTI.

Conventional and molecular techniques for the early diagnosis of bacteraemia

Bloodstream infections account for 30-40% of all cases of severe sepsis and septic shock, and are major causes of morbidity and mortality. Diagnosis of bloodstream infections must be performed promptly so that adequate antimicrobial therapy can be started and patient outcome improved. An ideal diagnostic technology would identify the infecting organism(s) and their determinants of antibiotic resistance, in a timely manner, so that appropriate pathogen-driven therapy could begin promptly. Unfortunately, despite the essential information it provides, blood culture, the gold standard, largely fails in this purpose because time is lost waiting for bacterial or fungal growth. Several efforts have been made to optimise the performance of blood culture, such as the development of technologies to obtain rapid detection of microorganism(s) directly in blood samples or in a positive blood culture. The ideal molecular method would analyse a patient's blood sample and provide all the information needed to immediately direct optimal antimicrobial therapy for bacterial or fungal infections. Furthermore, it would provide data to assess the effectiveness of the therapy by measuring the clearance of microbial nucleic acids from the blood over time. None of the currently available molecular methods is sufficiently rapid, accurate or informative to achieve this. This review examines the principal advantages and limitations of some traditional and molecular methods commercially available to help the microbiologist and the clinician in the management of bloodstream infections.

Estimating the proportion of pneumonia attributable to pneumococcus in Kenyan adults: latent class analysis

BACKGROUND

Community-acquired pneumonia is a common cause of hospitalization among African adults, and Streptococcus pneumoniae is assumed to be a frequent cause. Pneumococcal conjugate vaccine is currently being introduced into childhood immunization programs in Africa. The case for adult vaccination is dependent on the contribution of the pneumococcus to the hospital pneumonia burden.

METHODS

Pneumococcal diagnosis is complex because there is no gold standard, and culture methods are invalidated by antibiotic use. We used latent class analysis to estimate the proportion of pneumonia episodes caused by pneumococcus. Furthermore, we extended this methodology to evaluate the effect of antimicrobial treatment on test accuracies and the prevalence of the disease. The study combined data from 5 validation studies of pneumococcal diagnostic tests performed on 281 Kenyan adults with pneumonia.

RESULTS

The proportion of pneumonia episodes attributable to pneumococcus was 0.46 (95% confidence interval = 0.36-0.57). Failure to account for the effect of antimicrobial exposure underestimates this proportion as 0.32. A history of antibiotic exposure was a poor predictor of antimicrobial activity in patients' urine. Blood culture sensitivity for pneumococcus was estimated at 0.24 among patients with antibiotic exposure, and 0.75 among those without.

CONCLUSIONS

The large contribution of pneumococcus to adult pneumonia provides a strong case for the investigation of pneumococcal vaccines in African adults.

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.

Development of a novel DNA microarray to detect bacterial pathogens in patients with chronic obstructive pulmonary disease (COPD)

A novel microarray was constructed with DNA PCR product probes targeting species specific functional genes of nine clinically significant respiratory pathogens, including the Gram-positive organisms (Streptococcus pneumoniae, Streptococcus pyogenes), the Gram-negative organisms (Chlamydia pneumoniae, Coxiella burnetii Haemophilus spp., Legionella pneumophila, Moraxella catarrhalis, and Pseudomonas aeruginosa), as well as the atypical bacterium, Mycoplasma pneumoniae. In a “proof-of-concept” evaluation of the developed microarray, the microarray was compared with real-time PCR from 14 sputum specimens from COPD patients. All of the samples positive for bacterial species in real-time PCR were also positive for the same bacterial species using the microarray. This study shows that a microarray using PCR probes is a potentially useful method to monitor the populations of bacteria in respiratory specimens and can be tailored to specific clinical needs such as respiratory infections of particular patient populations, including patients with cystic fibrosis and bronchiectasis.

PCR using blood for diagnosis of invasive pneumococcal disease: systematic review and meta-analysis

The use of molecular-based methods for the diagnosis of bacterial infections in blood is appealing, but they have not yet passed the threshold for clinical practice. A systematic review of prospective and case-control studies assessing the diagnostic utility of PCR directly with blood samples for the diagnosis of invasive pneumococcal disease (IPD) was performed. A broad search was conducted to identify published and unpublished studies. Two reviewers independently extracted the data. Summary estimates for sensitivity and specificity with 95% confidence intervals (CIs) were calculated by using the hierarchical summary receiver operating characteristic method. The effects of sample processing, PCR type, the gene-specific primer, study design, the participants' age, and the source of infection on the diagnostic odds ratios were assessed through meta-regression. Twenty-nine studies published between 1993 and 2009 were included. By using pneumococcal bacteremia for case definition and healthy people or patients with bacteremia caused by other bacteria as controls (22 studies), the summary estimates for sensitivity and specificity were 57.1% (95% CI, 45.7 to 67.8%) and 98.6% (95% CI, 96.4 to 99.5%), respectively. When the controls were patients suspected of having IPD without pneumococcal bacteremia (26 studies), the respective values were 66.4% (95% CI, 55.9 to 75.6%) and 87.8% (95% CI, 79.5 to 93.1%). With lower degrees of proof for IPD (any culture or serology result and the clinical impression), the sensitivity of PCR decreased and the specificity increased. All analyses were highly heterogeneous. The use of nested PCR and being a child were associated with low specificity, while the use of a cohort study design was associated with a low sensitivity. The lack of an appropriate reference standard might have caused underestimation of the performance of the PCR. Currently available methods for PCR with blood samples for the diagnosis of IPD lack the sensitivity and specificity necessary for clinical practice.

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.

Usefulness of real-time PCR for lytA, ply, and Spn9802 on plasma samples for the diagnosis of pneumococcal pneumonia

In the present study, we evaluated rapid real-time PCR assays for ply, Spn9802, and lytA applied to plasma samples for the detection of Streptococcus pneumoniae in patients with community-acquired pneumonia (CAP). In a prospective study of CAP aetiology, an EDTA plasma sample was collected together with blood culture in 92 adult CAP patients and 91 adult controls. Among the 92 CAP patients, lytA PCR was positive in eight (9%), Spn9802 PCR was positive in 11 (12%) and ply PCR was positive in 19 (21%) cases. Of 91 controls, the ply PCR was positive in eight cases (9%), but no positive cases were noted by Spn9802 or lytA PCRs. Ten CAP patients had pneumococcal bacteraemia. Compared to blood culture, PCR for lytA, Spn9802 and ply had sensitivities of 70% (7/10), 60% (6/10) and 70% (7/10), and specificities of 96% (79/82), 94% (77/82) and 85% (70/82) respectively. With blood culture and/or culture of representative sputum, and/or urinary antigen detection, S. pneumoniae was identified in 31 CAP patients. Compared to these tests in combination, PCR for lytA, Spn9802 and ply showed sensitivities of 26% (8/31), 32% (10/31) and 42% (13/31), and specificities of 100% (61/61), 98% (60/61) and 90% (55/61) respectively. We conclude that Spn9802 and lytA PCRs may be useful for the rapid detection of bacteraemic pneumococcal pneumonia, whereas ply PCR is not specific enough for routine use and blood PCR with small plasma volumes is not useful for the detection of nonbacteraemic pneumococcal pneumonia.

Streptococcus pneumoniae DNA load in blood as a marker of infection in patients with community-acquired pneumonia

Direct detection of Streptococcus pneumoniae DNA in blood adds to culture results in the etiological diagnosis of patients with community-acquired pneumonia (CAP). Quantification of the amount of DNA, the bacterial DNA load (BDL), provides a measurement of DNAemia that may increase the understanding of the clinical relevance of S. pneumoniae DNA in blood. We evaluated the S. pneumoniae BDL as a diagnostic tool in adult patients with CAP. The BDL was determined in whole-blood samples collected simultaneously with blood for culture from 45 adult patients with CAP. After DNA extraction, S. pneumoniae DNA was detected with specific real-time PCR amplification, and the BDL was calculated with a standard curve. PCR and microbiological results were compared, and the BDL was related to clinical and laboratory parameters. S. pneumoniae DNA was detected in 10/13 patients with positive blood cultures and in 67% of patients with microbiologically confirmed pneumococcal pneumonia. The positive predictive values of the receiver operating characteristic curves for the BDLs for pneumococcal infection (100%) and pneumococcal bacteremia (69%) were higher than those for the level of C-reactive protein (CRP; 43% and 23%, respectively) and the white blood cell count (WBC; 42% and 35%, respectively); the negative predictive values of these three parameters were in the same range (+/-90 and +/-97%, respectively). The BDL was higher in patients presenting with systemic inflammatory response syndrome and in patients with bacteremia. Positive correlations were observed for the BDL with WBC, CRP level, and length of stay. We conclude that the BDL supports the diagnosis of S. pneumoniae infection in patients with CAP and provides a putative marker of the severity of disease.

Diagnosis of Streptococcus pneumoniae infections in adults with bacteremia and community-acquired pneumonia: clinical comparison of pneumococcal PCR and urinary antigen detection

The diagnosis of severe Streptococcus pneumoniae infection relies heavily on insensitive culture techniques. To improve the usefulness of PCR assays, we developed a dual-PCR protocol (targeted at pneumolysin and autolysin) for EDTA blood samples. This was compared to the Binax NOW S. pneumoniae urine antigen test in patients with bacteremic pneumococcal infections. Patients with nonbacteremic community-acquired pneumonia also were tested by these methods to determine what proportion could be confirmed as pneumococcal infections. A direct comparison was made in a group of patients who each had both tests performed. The Binax NOW S. pneumoniae urine antigen test was positive in 51 of 58 bacteremic pneumococcal cases (sensitivity, 88%; 95% confidence interval [CI], 77 to 95%), whereas the dual PCR was positive in 31 cases (sensitivity, 53.5%; 95% CI, 40 to 67%; P < 0.0001), and all of these had detectable urinary antigens. Both tests gave positive results in 2 of 51 control patients (referred to as other-organism septicemia), giving a specificity of 96% (95% CI, 86.5 to 99.5%). In 77 patients with nonbacteremic community-acquired pneumonia, urinary antigen was detected significantly more often (in 21 patients [27%]) than a positive result by the dual-PCR protocol (6 [8%]) (P = 0.002). The development of a dual-PCR protocol enhanced the sensitivity compared to that of the individual assays, but it is still significantly less sensitive than the Binax NOW urine antigen test, as well as being more time-consuming and expensive. Urinary antigen detection is the nonculture diagnostic method of choice for patients with possible severe pneumococcal infection.

Detection of 11 common viral and bacterial pathogens causing community-acquired pneumonia or sepsis in asymptomatic patients by using a multiplex reverse transcription-PCR assay with manual (enzyme hybridization) or automated (electronic microarray) detection

Community-acquired pneumonia (CAP) and sepsis are important causes of morbidity and mortality. We describe the development of two molecular assays for the detection of 11 common viral and bacterial agents of CAP and sepsis: influenza virus A, influenza virus B, respiratory syncytial virus A (RSV A), RSV B, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, Legionella micdadei, Bordetella pertussis, Staphylococcus aureus, and Streptococcus pneumoniae. Further, we report the prevalence of carriage of these pathogens in respiratory, skin, and serum specimens from 243 asymptomatic children and adults. The detection of pathogens was done using both a manual enzyme hybridization assay and an automated electronic microarray following reverse transcription and PCR amplification. The analytical sensitivities ranged between 0.01 and 100 50% tissue culture infective doses, cells, or CFU per ml for both detection methods. Analytical specificity testing demonstrated no significant cross-reactivity among 19 other common respiratory organisms. One hundred spiked "surrogate" clinical specimens were all correctly identified with 100% specificity (95% confidence interval, 100%). Overall, 28 (21.7%) of 129 nasopharyngeal specimens, 11 of 100 skin specimens, and 2 of 100 serum specimens from asymptomatic subjects tested positive for one or more pathogens, with S. pneumoniae and S. aureus giving 89% of the positive results. Our data suggest that asymptomatic carriage makes the use of molecular assays problematic for the detection of S. pneumoniae or S. aureus in upper respiratory tract secretions; however, the specimens tested showed virtually no carriage of the other nine viral and bacterial pathogens, and the detection of these pathogens should not be a significant diagnostic problem. In addition, slightly less sensitive molecular assays may have better correlation with clinical disease in the case of CAP.

Characteristics of community-acquired pneumonia in patients with chronic obstructive pulmonary disease

STUDY OBJECTIVES

Community-acquired pneumonia is a frequent event in the course of chronic obstructive pulmonary disease (COPD). The aim of the present study was to provide information on clinical and microbiological characteristics and outcome of community-acquired pneumonia in these patients, in a comparative study with the non-COPD population.

DESIGN

Prospective study of cases.

SETTING

A university hospital in Lleida, Spain.

PATIENTS

During a 6 year-period, we prospectively studied the clinical and radiological manifestations, microbiological data and outcome of all patients with community-acquired pneumonia. A comparative analysis of characteristics of pneumonia between 132 patients with a definitive diagnosis of COPD and 575 patients who did not have this underlying disease was performed.

MEASUREMENTS AND RESULTS

COPD was associated with an older and predominantly male population. These patients frequently had concomitant comorbidities such as diabetes mellitus or chronic heart failure. Clinical presentation was more severe, manifested by septic shock, tachypnea, lower values of pH, pO(2) and oxygen saturation, and greater values of pCO(2). Purulent expectoration was also more frequent in this subset of patients. Admission was usually required for patients with COPD, and length of hospitalization was significantly increased; however, difference in the mortality rate was not observed. Although the spectrum of responsible microorganisms was very similar, the incidence of Pseudomonas aeruginosa and other Gram-negative bacilli was increased in COPD, particularly among patients with advanced situation and/or oral corticosteroid treatment.

CONCLUSIONS

Community-acquired pneumonia in patients with COPD was associated with epidemiological and clinical particularities mainly related to the underlying disease but showed only minor differences in outcome parameters. Gram-negative bacilli and P. aeruginosa are potential pathogens that need to be considered.

Evaluation of real-time PCR for the detection and quantification of bacteria in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) embraces a number of pathological processes including chronic bronchitis, chronic bronchiolitis and emphysema. The chronic and progressive course of COPD is often aggravated by short periods of increasing symptoms. Respiratory tract infections (RTIs) are the most common causes of COPD exacerbations. Detection and enumeration of respiratory bacteria are important techniques in diagnosing RTIs and in the validation of new treatment methods. We describe here the development and evaluation of real-time PCR assays for the simultaneous direct detection and quantification of a range of respiratory bacteria in individuals with COPD during stable periods and during acute exacerbations of the disease. Sputum samples from 30 subjects in a COPD study were analysed, and results compared with the current gold standard of culture. Real-time PCR assays proved highly sensitive, with no cross-reactivity with other species. The prevalence of bacteria detected by real-time PCR compared with that by culture was substantially higher for Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus spp. and Moraxella catarrhalis. Multiple pathogens were also found with real-time PCR but were not detected by culture. This study demonstrates the potential of such methods in the detection and enumeration of respiratory bacteria.

[Contribution of microbiological investigations to the diagnosis of lower respiratory tract infections]

The diagnosis of community-acquired pneumonia is usually based on clinical and radiological criteria. The identification of a causative organism is not required for the diagnosis. Although numerous microbiological techniques are available, their sensitivity and specificity are not high enough to guide first-line antimicrobial therapy. Consequently, this treatment remains most often empiric. If the causative organism is identified, the antimicrobial treatment is adapted. Sputum analysis may be proposed as a diagnostic tool for patients with an acute exacerbation of chronic obstructive pulmonary disease, in specific cases (prior antibiotherapy, hospitalization, failure of the empiric antimicrobial treatment).

Etiology and outcome of community-acquired pneumonia in patients with diabetes mellitus

STUDY OBJECTIVES

It has been suggested that diabetes mellitus is associated with an increased susceptibility to infection, the risk of using more aggressive therapeutic agents, and increased morbidity and mortality; however, current evidence supporting these events in the field of pneumonia is scarce. The aim of the present study was to provide information on clinical and microbiological characteristics and the outcome of community-acquired pneumonia in patients with diabetes mellitus.

DESIGN

Prospective study of cases.

SETTING

A university hospital in Lleida, Spain.

PATIENTS

During a 5-year period, we prospectively studied the clinical and radiologic characteristics, the spectrum of causative agents and other microbiological data, and the outcomes of 660 consecutive episodes of community-acquired pneumonia. Data derived from 106 patients with diabetes mellitus were analyzed and compared with data obtained from the remaining population.

MEASUREMENTS AND RESULTS

Patients with diabetes mellitus were significantly older (p = 0.001) and more frequently had other concomitant comorbid conditions (p = 0.018). Diabetes was also significantly associated with the development of pleural effusion (p = 0.015) and mortality (p = 0.002); for both events, diabetes remained as an independent predictive factor in multivariate analyses. By contrast, the incidence of the main etiologic agents, and the bacteremia or empyema rates did not show significant differences in relation to the remaining patients. In the subgroup of patients with diabetes, mortality was associated with the presence of multilobar infiltrates (p = 0.004), concomitant underlying diseases (p = 0.004), and some diabetes-related complications (nephropathy, p = 0.040; and vasculopathy, p = 0.002), although only multilobar infiltrates and comorbidities were selected as prognostic factors in the multivariate analysis.

CONCLUSIONS

In patients with community-acquired pneumonia, diabetes mellitus is associated with a poor prognosis, increasing the rate of pleural effusion and mortality. Our results suggest that this adverse outcome is more attributable to the underlying circumstances of patients than to uncommon microbiological findings.

Quantitative PCR assay using sputum samples for rapid diagnosis of pneumococcal pneumonia in adult emergency department patients

Accurate diagnosis of pneumococcal pneumonia in the acute-care setting remains a challenge due to the inadequate sensitivity of conventional diagnostic tests. Sputum cultures, which are likely to have the highest diagnostic yields of all specimen types, have been considered unreliable, due to their inability to differentiate colonization from infection. Our objective was to evaluate the potential clinical utility of a rapid quantitative real-time PCR assay using sputum samples for Streptococcus pneumoniae in adult patients with community-acquired pneumonia (CAP). A prospective clinical observational study of consecutively enrolled emergency department patients with CAP was performed; only those patients with excess good-quality sputum samples were included for evaluation. Sputum samples were tested for the presence of S. pneumoniae by using a quantitative PCR that targets the pneumolysin gene. PCR findings were compared with those of a composite reference standard comprising Gram staining of sputum samples and sputum/blood cultures. The area under the curve (AUC) and a log-transformed threshold, which provides the maximal sensitivity and specificity, were calculated. Of 487 subjects enrolled, 129 were evaluable. Receiver operating characteristic curve analysis demonstrated an AUC of 0.87. Sensitivity and specificity were 90.0 percent and 80.0 percent, respectively; positive and negative predictive values were 58.7 percent and 96.2 percent, respectively. We have demonstrated that a quantitative rapid pneumolysin PCR assay has favorable accuracy for diagnosis of pneumococcal pneumonia in adult patients with CAP; this assay may be a useful diagnostic adjunct for clinicians, particularly those practicing in the acute-care setting, where rapid pathogen identification may assist in selection of the most appropriate antibiotics.

Pneumococcal pneumonia in the UK--how herd immunity affects the cost-effectiveness of 7-valent pneumococcal conjugate vaccine (PCV)

This study examines the potential clinical and economic benefits for adults arising from paediatric pneumococcal vaccination in the UK. A UK birth cohort model with a 10-year horizon and using a primary 4-dose paediatric 7-valent pneumococcal conjugate vaccine (PCV) schedule was populated with 1999 morbidity and mortality data scaled up to the UK population. Herd immunity effects on adult pneumococcal hospital-treated pneumonia, meningitis and septicaemia, but not on community-treated pneumonia, were calculated using the lower end of the confidence intervals published for the effects in the US. Universal paediatric pneumococcal immunisation would prevent 1168 deaths (1141 adults) and 7147 cases (1791 adults constituted by 32 meningitis, 37 septicaemia and 1722 pneumonia) of serious pneumococcal infection (meningitis, septicaemia, pneumonia) with a resultant direct (payor) cost per life year gained of 4360 pounds. The 7-valent PCV appears to be highly cost effective.

Community-acquired pneumonia as the initial manifestation of serious underlying diseases

PURPOSE

Community-acquired pneumonia is common among patients with coexisting illnesses and it can be the initial manifestation of these comorbid diseases. The objectives of our study were to evaluate the frequency of this association and to analyze whether certain characteristics could predict the presence of unknown comorbid conditions.

SUBJECTS AND METHODS

Over a 5-year period, we prospectively studied 660 consecutive patients with community-acquired pneumonia seen at our institution. In a subgroup of these patients, diagnosis of previously unknown comorbid conditions was established during follow-up. Characteristics of these patients were compared with data from the remaining sample of patients.

RESULTS

Prior underlying diseases were present in 298 (45%) patients. One or more new comorbid conditions were found in 41 (6%), of which diabetes (14 cases), malignancies (12 cases), chronic obstructive pulmonary disease (8 cases), and human immunodeficiency virus (HIV) infection (5 cases) were the most common. In the comparative study, a bacterial etiology, positive blood cultures, and hospitalization were more frequently found (P < 0.05) in patients with new comorbid conditions than atypical microorganisms or viruses, negative blood cultures, or outpatient care.

CONCLUSION

In the initial diagnostic workup of patients with community-acquired pneumonia, the possibility of unknown comorbid conditions should be carefully evaluated.

Molecular genetic methods in the diagnosis of lower respiratory tract infections

Molecular diagnostic techniques, such as PCR, have become useful tools for the rapid etiological diagnosis of lower respiratory tract infections. Nucleic acid amplification tests (NAATs) have been evaluated for detecting most respiratory pathogens, and commercial assays are available for some pathogens. However, standardized protocols are needed before these assays are introduced into routine diagnostic use. For pneumonia, NAATs offer advantages over conventional tests for the detection of Mycoplasma pneumoniae, Legionella spp. and Chlamydia pneumoniae. For pneumococcal pneumonia in adults, PCR adds little to existing diagnostic tests, and is unable to distinguish pneumococcal colonization from infection when testing respiratory samples. Although less sensitive than culture-based methods, several commercial molecular diagnostic assays have been developed for tuberculosis and are useful rapid tests for selected patients. PCR can now be considered the rapid diagnostic test of choice for pertussis and some respiratory virus infections. Further work is required to better characterize the role of molecular diagnostic tests for diagnosing lower respiratory tract infections, and to develop standard assays that can be readily adopted by routine diagnostic laboratories.

[Guidelines for the management of community pneumonia in adult who needs hospitalization]

Community acquired pneumonia is still an important health problem. In Spain the year incidence is 162 cases per 100,000 inhabitants with 53,000 hospital admission costing 115 millions of euros per year. In the last years there have been significant advances in the knowledge of: aetiology, diagnostic tools, treatment alternatives and antibiotic resistance. The Spanish Societies of Intensive and Critical Care (SEMICYUC), Infectious Diseases and Clinical Microbiology (SEIMC) and Pulmonology and Thoracic Surgery (SEPAR) have produced these evidence-based Guidelines for the management of community acquired pneumonia in Adults. The main objective is to help physicians to make decisions about this disease. The different points that have been developed are: aetiology, diagnosis, treatment and prevention.

Comparison of four polymerase chain reaction assays for specificity in the identification of Streptococcus pneumoniae

We determined the usefulness of 4 conventional polymerase chain reaction (PCR) assays, lytA, psaA, and two primer sets from the ply gene, for accuracy in the discrimination of nontypeable (NT) Streptococcus pneumoniae from closely related atypical streptococci. The study used 100 strains. We compared the PCR results with laboratory tests that included optochin (ethylhydrocupreine hydrochloride) sensitivity, bile solubility, the Quellung reaction, and AccuProbe (Gen-Probe Inc., San Diego, CA). These latter tests did not discriminate the atypical streptococci from the NT pneumococci. All PCR primer sets amplified the NT pneumococcal isolates in agreement with the other laboratory tests. However, the IA and IB ply primers were positive for 8 of the 16 atypical streptococcal isolates, and the IIA and IIB ply primers amplified all atypical isolates. The psaA primers had only one discrepant result, a positive among the atypical streptococci. The lytA primers were the most specific with 100% specificity for all strains tested.

Autolysin-targeted LightCycler assay including internal process control for detection of Streptococcus pneumoniae DNA in clinical samples

The development and clinical evaluation of a LightCycler PCR assay, including an internal process control (IPC), to detect the Streptococcus pneumoniae autolysin gene in clinical samples is reported. The assay was developed to provide a second target for use in conjunction with existing pneumolysin PCR assays to increase the reliability of non-culture PCR diagnosis of pneumococcal infection. Primers amplify a 173 bp fragment of the autolysin gene (lytA), which is detected by fluorescence-labelled hybridization probes. An IPC was designed to check for the presence of PCR inhibitors and loss of assay sensitivity. The IPC product was amplified by the lytA primers and detected by a second set of hybridization probes. The analytical specificity of the autolysin PCR assay was 100% against 39 other bacterial species tested; these included related streptococci and other organisms. The assay, which could reliably detect 50 fg purified pneumococcal DNA per reaction, was capable of distinguishing between S. pneumoniae and atypical Streptococcus mitis and Streptococcus oralis strains known to contain the lytA gene. Using DNA extracts from a panel of EDTA bloods from patients with blood-culture-confirmed pneumococcal infection, the autolysin PCR had a sensitivity of 42.9%, which was similar to a previously reported TaqMan pneumolysin PCR (43.8%) run in parallel. Total agreement was shown between the autolysin assay and the pneumolysin TaqMan assay when used to test 23 culture-negative clinical samples, of which eight were positive by PCR, adding valuable clinical information. A specific autolysin-based LightCycler assay has been developed to complement pneumolysin PCR for the detection of S. pneumoniae in clinical samples. This should be a particularly useful tool for the rapid and sensitive diagnosis of pneumococcal meningitis, even after an antibiotic has been administered. However, poor sensitivity on blood samples limits its usefulness in other bacteraemic infections.

A quantitative LightCycler PCR to detect Streptococcus pneumoniae in blood and CSF

A quantitative real-time PCR targeting the Pneumolysin (ply) gene of Streptococcus pneumoniae was developed for the LightCycler instrument using Fluorescence Resonance Energy Transfer (FRET) probes. All common S. pneumoniae serotypes were detected while other bacteria and viruses were not. The sensitivity was determined to be between one and ten target copies per reaction. The PCR was applied to six CSF and 16 whole blood specimens from 17 patients with laboratory proven invasive pneumococcal disease. One hundred percent of CSF specimens and 69% of whole blood specimens were PCR positive. The bacterial loads were determined to be 7.6 to 6.01 x 10(5) copies/microL for the six CSF specimens, and 0.08 to 5.4 x 10(2) copies/microL for the 16 whole blood specimens. Ninety-seven percent of 30 culture and Gram's stain negative CSF specimens and 100% of 50 normal whole blood specimens were PCR negative. This highly sensitive and specific PCR assay has the potential to provide sufficiently rapid results to improve antibiotic treatment of S.pneumoniae infections, while bacterial load quantitation has opened up exciting possibilities for patient management.

Diagnosis of pneumococcal pneumonia by psaA PCR analysis of lung aspirates from adult patients in Kenya

psaA is the gene encoding pneumococcal surface adhesin A (PsaA), a 37-kDa protein expressed on the surface of Streptococcus pneumoniae. PCR primers for psaA have been shown to amplify the target DNA sequence in all 90 serotypes of S. pneumoniae and in none of 67 heterologous pathogens and colonizing bacteria of the upper respiratory tract. Pathogenic bacteria identified in lung aspirate specimens cannot normally be dismissed as contaminants or colonizers, which limit the assay specificity of other respiratory tract specimens. psaA PCR analysis was evaluated in 171 lung aspirates from Kenyan adults with acute pneumonia. The limit of detection was one genome equivalent. Sensitivity, estimated in 35 culture-positive lung aspirates, was 0.83 (95% confidence interval, 0.70 to 0.95). psaA PCR analysis extended the number of identifications of S. pneumoniae in lung aspirates from 35 on culture to 61 by both methods. Of 26 new pneumococcal diagnoses, 19 were corroborated by results of blood culture or urine antigen detection. Sequences of the PCR products from 12 positive samples were identical to the psaA target gene fragment. Using an internal control for the PCR, inhibition of psaA PCR was demonstrated in 17% (8 of 47) of false-negative specimens. The results of a control PCR for the human gene beta-actin suggested that false-negative psaA PCR results are attributable to problems of specimen collection, processing, or DNA extraction in 30% of cases (14 of 47). psaA PCR analysis is a sensitive tool for diagnosis of pneumococcal pneumonia in adults.

Nucleic acid amplification tests for the diagnosis of pneumonia

Molecular diagnostic techniques, such as polymerase chain reaction (PCR), are promising tools for the rapid etiological diagnosis of pneumonia. PCR offers potential advantages over conventional tests for the detection of Mycoplasma pneumoniae, Legionella species, and Chlamydia pneumoniae. For pneumococcal pneumonia in adults, PCR adds little to existing diagnostic tests and is unable to distinguish pneumococcal colonization from infection when testing respiratory samples. Although PCR is probably more sensitive than are conventional microscopy-based methods for diagnosing Pneumocystis carinii pneumonia, the specificity is uncertain, because P. carinii can occasionally be detected in the absence of clinical symptoms. PCR is useful for the diagnosis of viral pneumonia in immunocompromised patients. Further work is required to better characterize the role of PCR versus the role of other tests for diagnosing pneumonia and to develop standard PCR assays that can be readily adopted by routine diagnostic laboratories.

Evaluation of a PCR assay for detection of Streptococcus pneumoniae in respiratory and nonrespiratory samples from adults with community-acquired pneumonia

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia, but it is undoubtedly underdiagnosed. We used a nested PCR assay (targeting the pneumolysin gene) to detect S. pneumoniae DNA in multiple sample types from 474 adults with community-acquired pneumonia and 183 control patients who did not have pneumonia. Plasma or buffy coat samples were PCR positive in only 6 of the 21 patients with positive blood cultures for S. pneumoniae and in 12 other patients (4 of whom had no other laboratory evidence of S. pneumoniae infection). Buffy coat samples from two control patients (neither having evidence of S. pneumoniae infection), but no control plasma samples, were PCR positive. Although pneumococcal antigen was detected in the urine from 120 of 420 (29%) patients, only 4 of 227 (2%) urine samples tested were PCR positive. Overall, 256 of 318 (81%) patients had PCR-positive sputum samples, including 58 of 59 samples from which S. pneumoniae was cultured. Throat swab samples from 229 of 417 (55%) patients were PCR positive and, in those who produced sputum, 96% also had positive PCR results from sputum. Throat swabs from 73 of 126 (58%) control patients were also PCR positive. We conclude that the pneumolysin PCR assay adds little to existing diagnostic tests for S. pneumoniae and is unable to distinguish colonization from infection when respiratory samples are tested.

Evaluation of the polymerase chain reaction method for detection of Streptococcus pneumoniae DNA in pleural fluid samples

STUDY OBJECTIVE

Streptococcus pneumoniae is the most frequent causative agent of community-acquired pneumonia (CAP); however, an etiologic diagnosis by traditional techniques can be accomplished in only a small percentage of patients with CAP. Pleural fluid is present in approximately 40% of patients with CAP; therefore, we hypothesized that detection of S pneumoniae DNA in pleural fluid by polymerase chain reaction (PCR) may help to increase the rate of diagnosis of pneumococcal pneumonia.

DESIGN

A prospective study of cases.

SETTING

A university hospital in Lleida, Spain.

PATIENTS AND METHODS

One hundred two samples of pleural fluid (51 samples from consecutive adult patients with pneumonia and 51 samples from unselected control subjects) were tested by the nested-PCR method to detect selected pneumolysin gene of S pneumoniae, and the results were compared with those provided by alternative diagnostic methods.

RESULTS

PCR in pleural fluid had a diagnostic sensitivity of 78% in patients with pneumococcal pneumonia, with positive results in 2 of 2 patients (100%) and 5 of 7 patients (71%) who had positive or negative pleural fluid culture findings, respectively. PCR results were also positive in 3 of 24 patients (12%) with pneumonia of unknown etiology and negative in all patients with pneumonia due to microorganisms other than S pneumoniae. Thus, the calculated specificity was 93%. Among control subjects, PCR gave positive results in two cases (4%).

CONCLUSION

The nested-PCR test, applied to pleural fluid samples from patients with CAP, showed a sensitivity of 78% and a specificity of 93% in the diagnosis of pneumococcal pneumonia.

Culture-negative severe septic shock: indications for streptococcal aetiology based on plasma antibodies and superantigenic activity

We present a severe septic shock syndrome patient with negative blood cultures. Acute and convalescent plasma samples from the patient were analysed for anti-streptolysin O titres, superantigen-neutralizing activity and presence of superantigenic activity. The plasma analyses implicated superantigen-producing Streptococcus pyogenes as the causative agent.

A specific and ultrasensitive chemiluminescent sandwich ELISA test for the detection and quantitation of pneumolysin

A chemiluminescent sandwich ELISA test has been developed for the detection and quantitation of pneumolysin. The test is based on a mouse monoclonal as the capture antibody and on rabbit polyclonal IgGs as detection antibodies, in combination with an anti-rabbit IgG alkaline phosphatase conjugate. The estimated detection limit of the purified recombinant toxin in phosphate-buffered saline with 0.05% Triton X-100 is around 5 pg ml(-1), with averaged intra- and inter-assay variation coefficients of 7% and 13.5%, respectively. The assay has been applied to the quantitation of pneumolysin in pneumococcal isolates, providing, for the first time, a direct measurement of the amount of the toxin produced by different strains, a variation has been found in their pneumolysin content. The test is highly specific as no other purified toxins or human pneumonia- or meningitis-associated bacteria yielded false-positive results. This specific and highly sensitive method could help in the diagnosis of human infections.

Capsulate bacteria and the lung

Capsulate bacteria cause the majority of community-acquired pneumonia presenting to hospital world-wide, at all ages. They are united by the virulence factor of their differing capsular polysaccharides, enabling them to evade phagocytosis. All cause invasive disease beyond the respiratory tract, including septicaemia and central nervous system infection. Recent advances in vaccine development have made the capsular polysaccharide an achievable target for vaccine strategies across all ages, with impacts already seen upon Streptococcus pneumoniae and Haemophilus influenzae type b pneumonia in countries able to afford these new vaccines.

Diagnosis of Streptococcus pneumoniae lower respiratory infection in hospitalized children by culture, polymerase chain reaction, serological testing, and urinary antigen detection

A prospective study of 154 consecutive high-risk hospitalized children with lower respiratory infections was conducted to determine the clinical utility of a pneumolysin-based polymerase chain reaction (PCR) assay compared with blood and pleural fluid cultures and serological and urinary antigen tests to determine the incidence of Streptococcus pneumoniae. Whole blood, buffy coat, or plasma samples from 67 children (44%) tested positive by PCR. Sensitivity was 100% among 11 promptly tested culture-confirmed children and specificity was 95% among control subjects. Age, prior oral antibiotic therapy, and pneumococcal nasopharyngeal colonization did not influence PCR results, whereas several surrogates of disease severity were associated with positive tests. Although serological and urinary antigen tests had comparable sensitivity, specificity varied among infected children, and statistical agreement among all assays was limited. These findings support the use of PCR tests to evaluate the protective efficacy of pneumococcal conjugate vaccines and to identify promptly children with pretreated or nonbacteremic pneumococcal lower respiratory infections.