[Legionella tests].
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Communicable Disease Control↗
Biomedical subjects
Johan A Maeland
Publications and source records attributed to Johan A Maeland.
Immunological markers of the R4 protein of Streptococcus agalactiae.
This study focuses on immunological markers of R4, an important Streptococcus group B (GBS) protein. The results obtained by using rabbit antisera and purified proteins for antigens in enzyme-linked immunosorbent assay-based experiments provided evidence that R4 possesses two antigenic determinants. One of the determinants is shared with the alpha-like protein 3 (Alp3) of GBS, was named R4/Alp3 common, and was expressed by GBS, which possessed the Alp3-encoding gene alp3 or the R4-encoding gene rib. The other antigenic determinant was detected only in rib-positive GBS organisms and was named R4 specific. This determinant probably is an immunological marker unique to the R4 protein. Neither of the antigenic R4 determinants showed serological cross-reactivity with the GBS proteins Calpha, Cbeta, and R3 or with alpha-like protein 2. Of 60 clinical serotype III GBS strains, 56 (93%) isolates possessed the rib gene and 50 (89%) of the rib-positive isolates expressed levels of R4 detectable by antibody-based tests, consistent with R4 expression failure or low-level expression in approximately 10% of rib-positive GBS. alp3 was not detected in type III GBS but was possessed by six of eight type V strains and six of six type VIII strains. All alp3-positive strains were recognized by the R4/Alp3 common antibodies, but none of them were recognized by the R4-specific antibodies. NCTC 9828, a reference strain for R3 and R4, expressed the determinant R4/Alp3 common but not R4 specific. A monoclonal R4 antibody, previously considered to be R4 specific and used in GBS serotyping, targeted R4/Alp3 common and is thus not R4 specific. The results show that failure to discriminate between R4 specific and R4/Alp3 common by antisera designed for GBS serotyping can result in the false identification of Alp3 as R4 or vice versa, whereas anti-R4 antibodies targeting only the determinant R4 specific will detect only R4. Both R4 and Alp3 need further evaluation with respect to the immunobiological function of each distinct antigenic determinant, for instance, with regard to their potential as GBS vaccine components.
Antibodies, Bacterial↗
Antigenic determinants of alpha-like proteins of Streptococcus agalactiae.
The majority of group B streptococcus (GBS) isolates express one or more of a family of surface-anchored proteins that vary by strain and that form ladder-like patterns on Western blotting due to large repeat units. These proteins, which are important as GBS serotype markers and as inducers of protective antibodies, include the alpha C (Calpha) and R4 proteins and the recently described alpha-like protein 2 (Alp2), encoded by alp2, and Alp3, encoded by alp3. In this study, we examined antigenic determinants possessed by Alp2 and Alp3 by testing of antibodies raised in rabbits, mainly by using enzyme-linked immunosorbent assays (ELISA) and an ELISA absorption test. The results showed that Alp2 and Alp3 shared an antigenic determinant, which may be a unique immunological marker of the Alp variants of GBS proteins. Alp2, in addition, possessed an antigenic determinant which showed specificity for Alp2 and a third determinant which showed serological cross-reactivity with Calpha. Alp3, in addition to the determinant common to Alp2 and Alp3, harbored an antigenic site which also was present in the R4 protein, whereas no Alp3-specific antigenic site was detected. These ELISA-based results were confirmed by Western blotting and a fluorescent-antibody test. The results are consistent with highly complex antigenic structures of the alpha-like proteins in a fashion which is in agreement with the recently described structural mosaicism of the alp2 and alp3 genes. The results are expected to influence GBS serotyping, immunoprotection studies, and GBS vaccine developments.
Animals↗
Recognition of different epitopes on the Ca & R4 proteins of group B streptococci by normal human & antibodies induced in animals.
BACKGROUND & OBJECTIVES: Levels of protective antibodies against Calpha and R4 proteins of the group B streptococci (GBS) have been measured in humans. The findings indicated that the human anti Calpha and anti-R4 antibodies may recognize targets which are different from those recognized by antibodies raised in animals. In the present study normal human serum antibodies which target the GBS proteins Calpha and R4 and immune anti-Calpha and anti -R4 antibodies raised in animals were compared. METHODS: The antigens were prepared by extraction of whole cells of GBS with trypsin and purified, and the testing was done by ELISA and Western blotting. RESULTS: The immune antibodies showed specificity for the corresponding protein and targeted proteins which had been denatured by hot sodium dodecyl sulphate (SDS) or by heating in a nearly neutral buffer. The human antibodies targeted a site(s) common to Calpha and R4 and failed to bind to the denatured proteins. The bulk of antibodies in sera from healthy pregnant women was directed against the SDS and heat labile determinant(s). INTERPRETATION & CONCLUSION: The present results indicated that the immune antibodies were directed against sequential epitopes and the normal human serum antibodies against epitopes determined by molecular conformation.
Antibodies↗
Susceptibility of skin and soft-tissue isolates of Staphylococcus aureus and Streptococcus pyogenes to topical antibiotics: indications of clonal spread of fusidic acid-resistant Staphylococcus aureus.
Staphylococcus aureus (SA) isolates (n = 255) from outpatients with skin and soft-tissue infections were collected in 3 different areas in Norway. Group A streptococci (GAS, n = 68) were isolated from skin or pharyngotonsillar specimens from outpatients. Minimum inhibitory concentrations (MIC) of bacitracin, fusidic acid and mupirocin were tested using the E-test. Pulsed field gel electrophoresis (PFGE) patterns of fusidic acid-sensitive (FusS) and -resistant (FusR) SA were compared. All GAS isolates showed MIC of bacitracin of < or = 1.0 mg/l, of mupirocin of < or = 0.125 mg/l and of fusidic acid 1.0-4.0 mg/l. All the SA showed MIC of mupirocin < or = 0.5 mg/l and of bacitracin of > or = 2.0 mg/l, 91% with MIC > or = 16 mg/l. FusR was shown by 32.5% of the SA strains with similar prevalence rates in 3 different geographical areas of Norway. One particular PFGE pattern (type 1) was shown by 76% of the FusR SA. SA of type 1 belonged to phage group II and produced exfoliative toxins. Thus, the results demonstrated a high prevalence of FusR among SA causing skin infections and that this was mainly due to dissemination of clonally related FusR SA.
Administration, Topical↗
Antibodies raised in animals against the Streptococcus agalactiae proteins c alpha and R4 and normal human serum antibodies target distinct epitopes.
The targets for normal human serum antibodies that react with proteins c(alpha) and R4 isolated from group B streptococci (GBS; Streptococcus agalactiae) have been studied and compared with the targets for murine monoclonal and rabbit polyclonal antibodies raised against these proteins. The proteins were extracted by trypsin digestion and purified by precipitations and gel filtration and testing was based on enzyme immunoassays. The immune antibodies showed specificity for the corresponding protein, targeted that protein in Western blotting and recognized their targets after heat treatment (100 degrees C) of the proteins. Human antibodies in a commercial gammaglobulin preparation targeted a site(s) common to c(alpha) and R4. This target failed to bind the antibodies in Western blotting and was destroyed by heating. c(alpha)- and R4-reactive antibodies in sera from healthy pregnant women recognized the common, heat-labile determinant(s), but contained little or no antibodies against the heat-stable c(alpha)- or R4-specific determinants. These results are consistent with the notions that (i) the normal human antibodies and the immunization-induced animal antibodies targeted different sites on the c(alpha) and R4 proteins and that (ii) the natural human antibodies targeted conformational epitopes and the immune antibodies targeted linear epitopes. These findings are important for further clarification of GBS immunology and immunoprotection in humans.
Animals↗
Typing of human isolates of Streptococcus agalactiae (group B streptococcus, GBS) strains from Zimbabwe.
Serotyping and genotyping are important tools in epidemiological studies of group B streptococcal (GBS) infections, which are important diseases in man, particularly in newborns. In the present study, 241 GBS isolates from Zimbabwe, comprising 124 carrier isolates from pregnant women and 117 isolates from patients hospitalised for various diseases, were serotyped. Antibodies specific for the capsular polysaccharide antigens (CPAs) Ia, Ib and II-V and antibodies specific for the surface-localised proteins, c(alpha), c(beta), R1, R3 and R4 were used for serotyping. Strains of the CPA types Ia (17%), III (47.7%) and V (23.2%) predominated. Of the various protein antigens, c(alpha) and R4 were expressed with highest frequency, c(alpha) by 100% of the CPA type Ia strains and R4 by 92% of the CPA type III strains. The R3 protein occurred frequently (24%), especially in type V strains (84%). A total of 25 serovariants was detected in the strain collection with the variants Ia/c(alpha) (16%), III/R4 (43.5%) and V/c(alpha), R3 (14.1%) occurring with the highest frequency. Serotype and subtype distribution of the carrier isolates were essentially similar to those of the disease-associated isolates. Genomic heterogeneity was demonstrated by pulsed-field gel electrophoresis of type III/R4 and type V/c(alpha), R3 isolates, but to a much lesser extent than recorded with Norwegian strains. These results demonstrate that many variants of GBS occur in the Zimbabwean population. The data obtained may assist in the formulation of a possible future GBS vaccine for Zimbabwe and perhaps for other African countries.
Adult↗