Clinical and microbiological features of Streptococcus anginosus group infections: a 7-year retrospective study in...

The Streptococcus anginosus group (SAG) is emerging as a significant cause of invasive infections, yet data from Vietnam remain scarce. This study characterized the clinical features and outcomes of SAG infections in Ho Chi Minh City.

We retrospectively reviewed patients with culture-confirmed SAG infections at the Hospital for Tropical Diseases (January 2017-August 2023). Demographics, clinical, and microbiological data were analyzed.

A total of 82 patients (mean age 50.6 ± 16.8 years; 64.6% male) with culture-confirmed SAG infections were included. Comorbidities were present in 56.1% of patients, with diabetes mellitus being the most common (23.2%). S. anginosus was the most frequently isolated species (43.9%), followed by S. constellatus (34.1%) and S. intermedius (22.0%). Bacteremia (35.4%) and intra-abdominal infections (31.7%, mainly hepatic abscesses) were the predominant clinical presentations. Polymicrobial infections occurred in 14.6% of cases, primarily among patients with bacteremia and skin or soft tissue infections. All isolates remained susceptible to ceftriaxone and vancomycin, and 94.3% to ampicillin, but susceptibilities were lower to penicillin (84.3%), erythromycin (65.7%), clindamycin (54.3%), and tetracycline (54.3%). Despite a 92.7% cure rate, 19.5% required drainage procedures, and the 28-day mortality rate was 6.1%.

In this cohort, SAG infection most often present as occult bacteremia or hepatobiliary abscess, frequently in patients with comorbidities, but not restricted to immunocompromised hosts. Empirical β-lactam therapy (ampicillin or ceftriaxone) remains appropriate, although rising penicillin and macrolide resistance and the 15% polymicrobial rate, may warrant broader initial coverage when deep soft-tissue foci are suspected.