No abstract

The predictive value of cord blood IgE (cIgE) for atopy and related disorders was investigated. Samples were collected from 792 infants delivered consecutively at the National University Hospital in Reykjavík in 1987. The concentration of IgE, but not that of IgA, was found to increase with increasing gestational age at birth. There was no correlation between IgE and IgA levels in individual samples. At the age of 18-23 months 180 of these children were studied for manifestations of allergy and related disorders. Included were all available infants with detectable (> or = 0.23 kU/L) cIgE. However, infants born by Cesarean section or with IgA exceeding 10 mg/L were excluded because of potential contamination with maternal blood. The clinical evaluation was made without knowledge of the IgE levels. Sixty-six of the 180 participants (36.6%) were judged to have had definite allergic manifestations. However, no striking correlation was found between allergic symptoms and cIgE levels in this study, nor did high levels of IgE add significantly to the predictive value of family history. Children with atopic features had more frequently been affected by otitis media. Unexpectedly, infants with intermediate cIgE levels (0.2-0.6 kU/L) were significantly less affected by otitis media than children with unmeasurable (< 0.2 kU/L) or high (> or = 0.7 kU/L) cIgE levels. It is concluded that cord blood IgE can not be used to predict allergic manifestations in children under the age of 2 years.

Studies relating opsonization and IgG antibodies to Streptococcus pneumoniae have yielded contradictory results. This study compared changes in opsonization with IgG subclass response after vaccinating healthy subjects with a 23-valent pneumococcal vaccine. Total IgG and IgG subclass antibodies to pneumococcal polysaccharide types 8, 9, and 19 were measured by ELISA. Opsonic activity was assayed using 3H-labeled bacteria and polymorphonuclear leukocytes in different serum concentrations (5%-40%). A substantial postvaccination increase in total and subclass IgG antibody was observed in most subjects, although variations were seen. Postvaccination sera generally gave rise to enhanced opsonization, and a correlation was found between increases in antibody levels and opsonization. This correlation was closest for IgG1 and IgG4 and generally strongest at the lowest serum concentration, but weak or absent at the highest concentration. Thus, vaccination against S. pneumoniae stimulates a variable increase in specific opsonic activity in health persons that is best demonstrated when serum is a limiting factor in the opsonin assay.

Changes in bacterial ultrastructure after antibiotic exposure and during the postantibiotic effect (PAE) have been demonstrated by electron microscopy (EM). However, EM is qualitative and subject to individual interpretation. In contrast, flow cytometry gives qualitative and quantitative information. The sizes and nucleic acid contents of Escherichia coli and Pseudomonas aeruginosa were studied during antimicrobial exposure as well as during the PAE period by staining the organisms with propidium iodide and analyzing them with flow cytometry and fluorescence microscopy. The effects of ampicillin, ceftriaxone, ciprofloxacin, gentamicin, and rifampin were studied for E. coli, whereas for P. aeruginosa imipenem and ciprofloxacin were investigated. After exposure of E. coli to ampicillin, ceftriaxone, and ciprofloxacin, filamentous organisms were observed by fluorescence microscopy. These changes in morphology were reflected by increased forward light scatter (FSC) and nucleic acid content as measured by flow cytometry. For the β-lactams the extent of filamentation increased in a dose-dependent manner after drug removal, resulting in formation of distinct subpopulations of bacteria. These changes peaked at 20 to 35 min, and bacteria returned to normal after 90 min after drug removal. In contrast, the subpopulations induced by ciprofloxacin did not return to normal until >180 min after the end of the classically defined PAE. Rifampin resulted in formation of small organisms with low FSC, whereas no distinctive characteristics were noted after gentamicin exposure. For P. aeruginosa an identifiable subpopulation of large globoid cells and increased nucleic acid content was detected after exposure to imipenem. These changes persisted past the PAE, as defined by viability counting. Swollen organisms with increased FSC were detected after ciprofloxacin exposure, even persisting during bacterial growth. In summary, for β-lactam antibiotics and ciprofloxacin, the PAE is characterized by dynamic formation of enlarged cell populations of increased nucleic acid content, whereas rifampin induces a decrease in size and nucleic acid content in the organisms. Flow cytometry is an ideal method for future studies of bacterial phenotypic characteristics during the PAE.