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Ann Lab Med. 2019 Sep;39(5):488-492. doi: 10.3343/alm.2019.39.5.488.

Comparison of Characteristics of Streptococcus dysgalactiae subsp. equisimilis Isolates Causing Repetitive vs Single Infections.

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Department of Clinical Laboratory, Kitasato University Medical Center, Saitama, Japan.
Laboratory of Infectious Diseases, Kitasato Institute for Life Sciences, Kitasato University, Tokyo, Japan.
Department of Health and Medical Sciences, Shinshu University Graduate School of Medicine, Nagano, Japan.
Laboratory of Infectious Diseases, Kitasato Institute for Life Sciences, Kitasato University, Tokyo, Japan.
Contributed equally


No study has described Streptococcus dysgalactiae subsp. equisimilis (SDSE) isolates that cause repetitive infections (recurrence and reinfection). We compared the microbiological characteristics of SDSE causing repetitive infections with those causing single infections. Three patients with invasive infections were identified based on their medical records, and multiple SDSE isolates were collected at intervals over three weeks, using a laboratory repository. Isolates from 12 patients with single-episode infections served as controls. Six isolates were collected from three patients with first and second episodes of infection. All isolates causing either repetitive or single-episode infection were subjected to emm typing, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and random amplified polymorphic DNA (RAPD) analyses. Amplification of five virulence genes (sicG, prtF1, prtF2, lmb, and cbp), biofilm formation (BF), and cell invasion abilities (CIAs) were measured as virulent phenotypes. We observed close genetic similarities in the data obtained by emm typing, MLST, PFGE, and RAPD in four isolates from two patients, suggesting recurrence, whereas two isolates from one patient indicated genetic differences in these data, suggesting re-infection. The presence of the five virulence genes and the BF and CIA measurements appeared not to contribute to repetitive infections, compared with isolates causing single-episode infection. In conclusion, clinicians encountering patients with repetitive infections should be aware of both possibilities: recurrence with closely related strains and reinfection with different strains.


Recurrence; Reinfection; Streptococcus dysgalactiae subsp. equisimilis

[Available on 2019-09-01]
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Conflict of interest statement

No potential conflicts of interest relevant to this article were reported.

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