Frank Espersen

Taxonomic Application of Crossed Immunoelectrophoresis

We used crossed immunoelectrophoresis, crossed-line immunoelectrophoresis, tandem-crossed immunoelectrophoresis, and crossed immunoelectrophoresis with an intermediate gel (containing antibodies) in studies of bacterial taxonomy. By these quantitative immunoelectrophoretic methods, as many as 90 antigens from a bacterial species can easily and reproducibly be analyzed for immunological cross-reactivity with antigens from other bacterial species without prior purification of antigens. The immunological cross-reactivity between various bacterial species is expressed as the matching coefficient (MC), i.e., the ratio between the number of cross-reactive antigens with another bacterial species and the total number of antigens of the reference bacterial species. The MC has been found to be significantly correlated with phenotypic similarities (biochemical characteristics) and nucleic acid hybridization results obtained with the taxa investigated so far. In general, closely related strains (serotypes within a species) have a high MC (≥0.90), while different species of the same genus have a lower MC (0.90 to 0.70 or lower in some cases); genera within a family have an intermediate MC (0.70 to 0.15), and distantly related taxa have a very low MC (≤0.15).

Serological Assays against Staphylococcus aureus Peptidoglycan, Crude Staphylococcal Antigen and Staphylolysin in the Diagnosis of Serious S. aureus Infections

Immunoglobulin G antibody levels against Staphylococcus aureus peptidoglycan (PG) and crude staphylococcal antigen (SA) using enzyme-linked immunosorbent assay (ELISA) and antistaphylolysin (ASTA) antibody levels by gel diffusion were determined in 53 patients with S. aureus and 54 patients with non-S. aureus endocarditis and septicemia as compared with 63 febrile control patients. The two ELISAs were the most sensitive assays indicating S. aureus endocarditis in 83% and 88% in the PG- and SA-assays, respectively. 39% of non-S. aureus endocarditis patients were positive in the PG-assay due to antibodies cross-reacting with streptococci. A 100% specificity for S. aureus infections was obtained with the ASTA test, but this assay was less sensitive. A significant rise in anti-PG or anti-SA antibody levels was not only seen among S. aureus infections but also in some streptococcal and S. epidermidis infections as well as in 3 febrile control patients. When at least 2 of the 3 assays showed positive peak antibody levels 1-4 weeks after onset of infection together with a significant rise of both anti-PG and anti-SA antibody levels the S. aureus endocarditis diagnosis was highly suggestive. Thus, we recommend the combined use of these 3 assays using paired serum samples in diagnosing serious S. aureus infections.

Current Patterns of Bacterial Infection in Myelomatosis

Bacterial infections were registered in 39 patients with myelomatosis during 18 months in a prospective study. The infection incidence was 0.80 infections per patient year. 81% of a total of 32 isolates were gram-negative. Urinary tract infections due to Escherichia coli were the most frequent infections. Pneumonia due to Streptococcus pneumoniae were infrequently seen compared to previous studies. Hence, the etiologic spectrum has clearly shifted from gram-positive to gram-negative bacteria in these patients. 53% of all infections were hospital-acquired, and most of these were preceded by instrumentation of the urinary tract or indwelling venous catheters. The infections were nosocomial in 7/9 cases of septicemia registered. All 4 patients who died of infection, suffered from hospital-acquired infections. Patients who attracted infections had significantly higher serum creatinine levels and higher mortality compared to the rest of the patients.