Abstract
IntroductionStreptococcus dysgalactiae can cause severe recurrent infections. This study aimed to investigate antibody responses following S. dysgalactiae bacteraemia and possible development of protective immunity.Materials and MethodsPatients with S. dysgalactiae bacteraemia in the county of Skåne between 2017 and 2018 were prospectively included. Acute and convalescent sera were obtained. All isolates were emm typed and enzyme-linked immunosorbent assay (ELISA) was utilised to analyse specific antibody responses to bacteria and antigens. Bactericidal- and phagocytosis assays were applied to further establish antibody function.ResultsSixteen patients with S. dysgalactiae bacteraemia were included of whom one had recurrent episodes of bacteraemia. Using ELISA with S. dysgalactiae isolates and mutants, development of IgG antibodies was demonstrated in few patients. Type-specific antibodies were demonstrated in one patient when recombinant M proteins as antigens, were applied. The type-specific serum mediated a small increase in phagocytosis but did not facilitate increased killing of the S. dysgalactiae isolate, carrying that M protein, in blood or by phagocytic cells.ConclusionS. dysgalactiae bacteraemia sometimes results in increased levels of antibodies to the infecting pathogen. We did not find evidence that these antibodies are effectively opsonising. Apparent failure to produce opsonising antibodies might partially explain why S. dysgalactiae can cause recurrent invasive infections in the same host.
Highlights
Streptococcus dysgalactiae can cause severe recurrent infections
In S. pyogenes, protective immunity has been attributed to antibodies against the hypervariable NH2-terminal part of the M protein to which Rebecca Lancefield described the development of M-type specific antibodies following S. pyogenes bacteraemia (Lancefield, 1959)
This study aimed to investigate the antibody response in patients with S. dysgalactiae bacteraemia since a lack of such a response would explain the propensity of S. dysgalactiae to cause recurrent infections
Summary
Streptococcus dysgalactiae can cause severe recurrent infections. This study aimed to investigate antibody responses following S. dysgalactiae bacteraemia and possible development of protective immunity. S. dysgalactiae in the perianal tract in many patients with erysipelas, even after antibiotic treatment (Eriksson, 1999; Eriksson et al, 2019) This may indicate a host-specific colonisation and a potential risk for recurrent bacteraemia. In S. pyogenes, protective immunity has been attributed to antibodies against the hypervariable NH2-terminal part of the M protein to which Rebecca Lancefield described the development of M-type specific antibodies following S. pyogenes bacteraemia (Lancefield, 1959). This finding has been confirmed in later studies (Bencivenga et al, 2009). This was interpreted as a lack of development of protective immunity
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