Identification, antimicrobial resistance and molecular characterization of the human emerging pathogen Streptococcus gallolyticus subsp. pasteurianus

- Phenotypic, MALDI, and 16S rRNA gene sequencing were used for S. bovis group members identification.
- The combination of these methods identified strains as S. gallolyticus subsp. Pasteurianus (SGSP).
- SGSP isolation was most frequently associated with diabetes, among women, and from urinary tract.
- Approximately 30% of the SGSP were both erythromycin- and clindamycin-resistant, with erm(B).
- PFGE analysis revealed a high genetic variability among SGSP isolates.

This study aimed to retrospectively identify 22 Streptococcus bovis clinical strains based on the new taxonomy, as well as to investigate their antibiotic-resistance and clonality. Strains were identified by Phoenix100 system, 16S rRNA sequencing, and two MALDI-TOF MS platforms (Bruker Biotyper, Vitek MS). Antibiotic resistance was determined both phenotypically and genotypically, and clonality was assessed by PFGE. Most of strains (63.6%) were isolated from urine, and diabetes was the most common underlying disease (31.8%). Phoenix100 system revealed all strains belonged to biotype II, and 16S rRNA sequencing identified all strains as S. gallolyticus subsp pasteurianus (SGSP). Although both MALDI-TOF MS systems correctly identified isolates to the species level, only Bruker Biotyper accurately identified to the subspecies level. Erythromycin-resistant strains (31.8%) were also clindamycin-resistant and positive for erm(B). Strains resistant to tetracycline (68.2%) were also resistant to erythromycin. PFGE showed high genetic variability identifying 17 different pulsotypes, most of which single.