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Capsular hyaluronic acid of equine isolates of S treptococcus zooepidemicus is upregulated at temperatures below 35°C
Author(s) -
Velineni S.,
Timoney J. F.
Publication year - 2015
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/evj.12272
Subject(s) - hyaluronidase , horse , streptococcus equi , microbiology and biotechnology , biology , population , phagocytosis , enzyme , hyaluronic acid , chemistry , bacteria , biochemistry , medicine , genetics , paleontology , environmental health
Summary Reasons for performing study S treptococcus zooepidemicus causes opportunist respiratory and other infections in the horse. Capsule expression is highly variable and known to affect resistance to phagocytosis. Most clinical isolates producing small, dry colonies at 37°C produce mucoid colonies at temperatures below 35°C. Objectives The aim was to understand the molecular basis of increased capsule expression by equine isolates of S . zooepidemicus at temperatures lower than 35°C. Study design Cross‐sectional observational study. Methods Capsule production by groups of equine S . zooepidemicus strains was determined at 23, 30, 35 and 37°C. Hyaluronidase ( HylC ) at 23 and 37°C was measured by quantitative enzyme‐linked immunosorbent assay. Expressions of has A and hyl C at 23 and 37°C were measured by quantitative reverse transcriptase ‐PCR . The covRS genes in representative S . zooepidemicus were sequenced and checked for mutations. Results Colonies of randomly selected S . zooepidemicus strains became mucoid or showed marked increase in colony mucoidy following the change in temperature to 23°C. Expression of hasA at 23°C was 45‐ to 700‐fold greater than at 37°C. Transcription of hylC at 23°C was 2.5‐ to 200‐fold greater than at 37°C, yet enzyme concentrations in cultures were significantly higher at 37°C (P<0.05), suggesting that production of HylC is regulated post transcriptionally. The covRS gene in S . zooepidemicus was not mutated as seen in isolates of S treptococcus pyogenes with increased capsule production at 25°C. Conclusions Sensitivity of capsule expression to temperature above 35°C but not HylC by the general population of equine S . zooepidemicus indicates that capsule is not required for extended colonisation nor for opportunist invasion. Instead, capsule production at lower than body temperature may reflect adaptation to life on skin and mucosal surfaces, where hyaluronic acid contributes to adhesion and resistance to desiccation. Pathogenicity of S . zooepidemicus following opportunist invasion is possibly dependent on factors other than capsule that may be co‐regulated with HylC. The Summary is available in Chinese – see Supporting information .