Properties of high and low density subpopulations of group B streptococci: enhanced virulence of the low density variant |
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| Authors: | S H?kansson A M Bergholm S E Holm B Wagner M Wagner |
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| Affiliation: | 1. Department of Clinical Microbiology, University of Umeå, S-901 85 Umeå, Sweden;2. Department of Pediatrics, University of Umeå, S-901 85 Umeå, Sweden;3. Research Center for Molecular Biology and Medicine, Central Institute of Microbiology and Experimental Therapy, Jena, GDR;1. School of Nutrition Sciences, University of Ottawa, Ottawa, Ontario, Canada;2. Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada;3. The Royal''s Institute of Mental Health Research, Ottawa, Ontario, Canada;3. College of Fisheries, Huazhong Agricultural University, Wuhan 430070, China;4. Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China;5. College of Animal Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China;6. College of Animal Science and Technology, Huazhong Agricultural University, Wuhan 430070, China;1. ICBAS – Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Porto, Portugal;2. i3S – Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal;3. IBMC – Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal;4. Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal;5. ICVS/3B''s, PT Government Associate Laboratory, Braga/Guimarães, Portugal;6. Health Data Science Unit, Medical Faculty University Heidelberg and BioQuant, Heidelberg, Germany;7. UMIB – Unit for Multidisciplinary Investigation in Biomedicine (Endocrine, Cardiovascular & Metabolic Research), University of Porto, Portugal;8. Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram-positif, Centre National de la Recherche Scientifique (CNRS UMR 60647), Paris 75015, France |
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| Abstract: | ![]()
From the group B streptococcus (GBS) reference strain 090 la Colindale two subpopulations, which differed markedly regarding their capacities for biosynthesis of type-specific polysaccharide, were obtained by separation on a hypotonic Percoll density gradient. In the original strain and the high and low density variants, there was a negative correlation between buoyant density and bio-synthesis of type-specific polysaccharide as determined by ultrastructure and quantitative assays. The invasiveness of these variants was investigated by infecting rabbits via subcutaneously implanted tissue cages. In the animals infected with highly encapsulated bacteria, heavy bacteremia was detected 8 h post-infection, whereas in the animals which received high density bacteria with small amount of capsule, heavy bacteremia was not detected until after five days. All isolates recovered from the blood or organs of these rabbits were of the capsule rich phenotype, indicating a phenotypic shift in the subpopulation of high density bacteria. An apparently similar phenotypic shift was noted in an isolate from a baby with early onset septicemia. There was a dominance of low density bacteria in the isolate obtained from the baby as compared with the colonizing population of bacteria isolated from the cervix of the mother. From these type III isolates, subpopulations with different density maxima were obtained. A reversed shifting towards dominance of less encapsulated, high density bacteria was observed during in vitro passage of these subpopulations. |
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