anginosus

Anginosus is a Latin-derived epithet used in the scientific naming of several bacteria, most notably Streptococcus anginosus. In microbiology, anginosus is most commonly encountered as part of the Streptococcus anginosus group (SAG), a cluster of closely related species that also includes Streptococcus constellatus and Streptococcus intermedius. These organisms are Gram-positive cocci, typically arranged in pairs or short chains, and are catalase-negative. They are part of the normal mucosal microbiota of the human oral cavity, upper respiratory tract, gastrointestinal tract, and genitourinary tract, and they are regarded as opportunistic pathogens.

Although commensal, SAG bacteria are well known for their ability to form abscesses in various tissues, especially the brain and liver, and they frequently participate in mixed infections with anaerobes or oral flora. Invasive disease is more common in individuals with dental infections, sinusitis, otitis, head and neck infection, or systemic immunosuppression.

Diagnosis and treatment involve standard culture methods, biochemical testing, and increasingly MALDI-TOF mass spectrometry or molecular methods for species-level identification, as differentiation within the group can be challenging. Antibiotic susceptibility is generally favorable to beta-lactams; however, some strains produce beta-lactamases, and therapy may require penicillin plus beta-lactamase inhibitors or broader agents. Abscesses typically require drainage in addition to antimicrobial therapy.

Epidemiology and notes: SAG strains are common human commensals and have emerged as important pathogens in clinical microbiology because of their propensity for abscess formation. Taxonomy has evolved, with S. anginosus, S. constellatus, and S. intermedius recognized as distinct species within the same group.