Pneumococcal antigen detection in bronchoalveolar lavage fluid from patients with pneumonia

Enhancing the etiologic diagnosis of community-acquired pneumonia in adults using the urinary antigen assay (Binax NOW)

OBJECTIVES

Approximately 40% of community-acquired pneumonia (CAP) remains of unknown etiology. To improve the rate of detection of the causative microbiologic agent, the Binax NOW Streptococcus pneumoniae urinary antigen test (UAT) was evaluated.

DESIGN

In this prospective study, 67 adults with CAP were compared with 81 healthy patients to determine sensitivity and specificity of the UAT and its role in improving the etiologic diagnosis of CAP.

RESULTS

An etiology could be found for 22 patients (33%) using conventional methods (14 S. pneumoniae, sensitivity 64.3%, 1/81 positive UAT control urine samples, specificity 98.8%). This proportion increased to 33 patients (49%) with the addition of the urinary antigen test (p = 0.039). Pneumococcal infection was diagnosed by the UAT in 24% of our patients without an etiologic identification by conventional methods.

CONCLUSIONS

Given its excellent specificity, this test can be considered an important tool for detecting S. pneumoniae in CAP of unknown etiology, enabling the diagnosis of pneumococcal pneumonia in a quarter of cases.

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.

Necrotizing pneumococcal pneumonia in childhood

We describe the rare complication of necrotizing pneumonia and invasive pneumococcal infection in 3 previously healthy pediatric patients. Lobar consolidation and pleural effusions appeared initially, followed within several days by the appearance of multiple small lucencies in the area of consolidation. In one case, necrosis progressed to a large abscess cavity. Surgical intervention was limited to treatment of pleural space complications. There were no deaths. Pulmonary parenchymal residual was limited to a thin-walled cavity in one case.

Is Streptococcus pneumoniae the leading cause of pneumonia of unknown etiology? A microbiologic study of lung aspirates in consecutive patients with community-acquired pneumonia

PURPOSE

Although a wide variety of recognized pathogens can cause community-acquired pneumonia, in many patients the etiology remains unknown after routine diagnostic workup. The aim of this study was to identify the causal agent in these patients by obtaining lung aspirates with transthoracic needle aspiration.

SUBJECTS AND METHODS

During a 15-month period, all consecutive patients with community-acquired pneumonia who were eligible for transthoracic needle aspiration were enrolled in the study. In addition to conventional microbial methods (culture of blood and sputum, serologic studies), we performed cultures and genetic and antigen tests for common respiratory pathogens in lung aspirates.

RESULTS

The study group consisted of 109 patients. Conventional microbial studies identified an etiology in 54 patients (50%), including Mycoplasma pneumoniae in 19 patients, Chlamydia pneumoniae in 9 patients, and Streptococcus pneumoniae in 9 patients. Among the remaining 55 patients, study of the lung aspiration provided evidence of the causal agent in 36 (65%). In 4 additional patients with a single microbial diagnosis by conventional methods, the lung sample provided evidence of an additional microorganism. The new pathogens detected by lung aspiration were S. pneumoniae in 18 patients, Haemophilus influenzae in 6 patients, Pneumocystis carinii in 4 patients, and C. pneumoniae in 3 patients; other organisms were identified in 4 patients.

CONCLUSIONS

In our study, S. pneumoniae was the leading cause of community-acquired pneumonia, accounting for 25% of all cases, including about one-third of the cases the cause of which could not be ascertained with routine diagnostic methods.

Rapid detection of pneumococcal antigen in lung aspirates: comparison with culture and PCR technique

Detection of pneumococcal antigen has been used to increase the rate of diagnosis of pneumococcal pneumonia. The present study was designed to determine the value of rapid detection of pneumococcal antigen in samples obtained by transthoracic needle aspiration (TNA) from patients with community-acquired pneumonia (CAP) in a comparative analysis with culture and polymerase chain reaction (PCR). Pneumococcal antigen was detected by latex agglutination. One hundred and ten consecutive patients diagnosed with CAP underwent TNA. Patients were grouped, according to PCR, culture and serological results, into pneumococcal pneumonia (n = 18), other known aetiology (n = 67) and unknown aetiology (n = 25). In patients with pneumococcal pneumonia, antigen was detected in 17 (94.4%) cases. Antigen was detected in one and nine patients with pneumonia of other known or unknown aetiologies, respectively, yielding a specificity of 89.1%. In conclusion, detection of pneumococcal antigen on samples obtained by TNA from patients with CAP provides a sensitive and specific diagnosis of Streptococcus pneumoniae infection. Furthermore, its rapid results would reduce the dependence on empirical treatments.