Evaluation of the invasive techniques for diagnosing bacterial respiratory infections

Immunoreactivity of five monoclonal antibodies against the 37-kilodalton common cell wall protein (PsaA) of Streptococcus pneumoniae

Five monoclonal antibodies (MAbs) were produced against the Streptococcus pneumoniae pneumococcal surface adhesin A (PsaA) 37-kDa common cell wall protein. These antibodies were used in a dot immunoblot and Western blot study of clinical isolates of S. pneumoniae to detect the presence of the protein. By both assays, the MAbs reacted with clinical isolates representing the 23 type-specific serotypes present in the licensed pneumococcal polysaccharide vaccine. Western blot analysis confirmed the presence of a protein migrating in the gel with a molecular mass of 37 kDa. An extension of the study by using dot immunoblot analysis that included an analysis of the 90 serotypes of S. pneumoniae showed that all five MAbs reacted with 89 of the 90 serotypes tested. MAb 1B6, the exception, did not react with S. pneumoniae serotype 16F. Dot immunoblot analysis of the MAbs with Enterococcus faecalis and viridans streptococci showed varied reactivity patterns, depending on the species. The MAbs against the 37-kDa antigen did not react with Escherichia coli, respiratory pathogens, or nonpathogens representing 22 genera and 29 species of bacteria. All five MAbs also reacted with five multidrug-resistant strains of S. pneumoniae. In summary, these MAbs may be useful for detection of pneumococcal antigen and may lead to the development of diagnostic assays for pneumococcal disease.

Etiology and therapy of community-acquired pneumonia

The Authors report the data of a retrospective study performed on 520 patients admitted to the Institute of Respiratory Diseases, University of Sassari, Italy, for community acquired pneumonia (CAP) from 1980 to 1995. The aim of this study was to investigate: the frequency of risk factors and their impact on severity of pneumonia; the frequency of pathogens and their correlation with the severity of the illness; antibiotic treatments. One or more risk factors were found in 86% of patients, while 14% had none. In 286 patients (55%) no etiological diagnosis was possible, while in 234 patients (45%) the pathogen was identified. Of the latter, 73% suffered from pneumonia caused by Gram-negative bacilli, 24% by Gram-positive organisms, 0.8% by Mycoplasma pneumoniae and 1.7% by respiratory viruses and endemic fungi. The mortality rate found was 2.69%. In this study, pneumonia caused by Gram-negative bacilli showed a plurilobar and often bilateral involvement, frequent resistance to the most common antibiotics, which required longer hospitalization (> 30 days). The high prevalence of pneumonia caused by Gram-negative bacilli can be explained by the presence in most of the patients, of serious and numerous risk factors.