Streptococcus constellatus (S. constellatus) is a Gram-positive commensal bacterium that is commonly found in the oral, nasal, pharyngeal, gastrointestinal, and urogenital tracts. It can be further consisted by three subspecies: subsp, constellatus, subsp. pharynges, and subsp. viborgensis. As an opportunistic pathogen, S. constellatus can cause abscesses and bacteremia, so infection requires timely and accurate identification in clinical practice. There are a few case reports describing the range of infections caused by S. constellatus, which include intracardiac, thoracic, intracranial, and abdominal infections. Here we report the first case of thigh abscess caused by S. constellatus subsp. constellatus which was rarely insensitive to penicillin in a patient with exacerbation of bronchiectasis. The patient improved significantly after receiving antibiotic therapy with ceftriaxone and vancomycin, as well as percutaneous catheter drainage guided by color ultrasonography.The thigh abscess did not recur during follow-up. This case report demonstrates that although S. constellatus is a rare infectious pathogen, it is important to gain a better understanding of the range of possible infections to ensure timely diagnosis. Furthermore, although the prognosis of most patients with such infections is relatively good, the timely identify the resistant strains and administration of sensitive antibiotics along with abscess drainage may ensure effective treatment.

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