Case Report: Streptococcus dysgalactiae ssp. dysgalactiae bloodstream infections in patients with breast cancer after radiotherapy and chemotherapy

Abstract

Bloodstream infections are life-threatening conditions in patients with breast cancer, especially among older individuals. Although the most common risk factor in these patients with tumors is the use of severe neutropenia secondary to myelosuppressive chemotherapy and radiotherapy, other factors are possibly associated with the invasive pathogenicity of microorganisms, including Streptococcus dysgalactiae. Streptococcus dysgalactiae ssp. dysgalactiae (SDSD) has been considered both an environmental pathogen and a contagious pathogen. However, there have been few reports of bloodstream infections with SDSD in patients with breast cancer after radiotherapy and chemotherapy. In this study, we report an interesting case of bloodstream infection caused by SDSD in an older patient with breast cancer after radiotherapy and chemotherapy. A 60-year-old Chinese woman had a history of breast cancer for 2 years. She developed chills and fever after puncturing blood blisters in the mouth, accompanied by fatigue and poor appetite. After 6 days of antimicrobial therapy, the patient showed gradual recovery. Bloodstream infections with SDSD in patients with breast cancer are rare. Therefore, accurate diagnosis and timely treatment can be lifesaving.

Keywords: Streptococcus dysgalactiae; Streptococcus dysgalactiae ssp. dysgalactiae; bloodstream infections; breast cancer; whole genome sequencing analysis.

Figure 1

Patient was diagnosed with breast cancer by B-ultrasound. B-ultrasound examination showed that the size of the tumor in the left breast was 0.984 cm*0.455 cm. The patient had a history of breast cancer for 2 years.

Figure 2

(A) Streptococcus dysgalactiae ssp. dysgalactiae obtained from the patient’s blood sample was cultured on a blood agar plate. (B) The microscopic examination of the colonies of Streptococcus dysgalactiae ssp. dysgalactiae showed purple round spheroids by Gram staining (100×).

Figure 3

Phylogenetic analysis of 20 Streptococcus dysgalactiae ssp. dysgalactiae strains. The tree was built with Snippy v4.4.5 and FastTree using RAxML under the GTRGAMMA model with GCA 009650235.1 as the reference strain and visualized with iTOL v5. Isolate names, isolation date, and collection locations are shown for each strain. The TRL strain was used in this study and was labeled as red.