From the Guidelines
Streptococcus intermedius should be treated with a combination of penicillin or ceftriaxone with gentamicin or netilmicin for 2 weeks in uncomplicated cases, as recommended by the 2015 ESC guidelines for the management of infective endocarditis 1. This bacterium is part of the normal flora of the human mouth, gastrointestinal tract, and urogenital tract, but can cause serious infections when it enters normally sterile sites. Key characteristics of Streptococcus intermedius include:
- Being a member of the Streptococcus anginosus group (also known as the "milleri group")
- Association with abscess formation in various parts of the body
- Requirement for both surgical drainage of abscesses and appropriate antibiotic therapy in treatment The first-line antibiotic treatment is usually high-dose penicillin G or ampicillin, often combined with metronidazole to cover potential anaerobic co-infection, as supported by the guidelines for treating susceptible streptococci 1. For penicillin-allergic patients, alternatives such as vancomycin or teicoplanin may be considered, with teicoplanin requiring loading doses and having limited retrospective studies assessing its efficacy in streptococcal and enterococcal IE 1. Treatment duration typically ranges from 2-6 weeks depending on infection severity and location, with longer courses needed for more complex infections. It's crucial to note that S. intermedius infections, especially those involving the Streptococcus anginosus group, may require adjunctive surgery due to their tendency to produce abscesses, as highlighted in the context of group B streptococci and S. anginosus 1.
From the Research
Streptococcus Intermedius Characteristics
- Streptococcus intermedius is a viridans Streptococcus belonging to the Anginosus group 2
- It is an oral commensal organism belonging to the Streptococcus anginosus group (SAG) 3
- S. intermedius is considered to be a low-virulence bacteria in immunocompetent patients but can be associated with significant morbidity and mortality 4
Infections Associated with Streptococcus Intermedius
- S. intermedius has been associated with abscesses in children, with 40% of cases being complicated and/or life-threatening 2
- It can cause invasive, pyogenic infection of the central nervous system, pleural space, or liver 3
- S. intermedius is also associated with subdural empyema, a collection of pus in the subdural space between the dura mater and the arachnoid 4
Antibiotic Susceptibility
- Penicillin-resistant isolates of S. intermedius also demonstrate decreased susceptibility to other antimicrobial agents 5
- High-level resistance to ceftriaxone has been found in some isolates of S. intermedius 5
- The susceptibility of S. intermedius to different antibiotics is not well studied, and more research is needed to determine the best treatment options 3, 4
Clinical Presentation and Diagnosis
- The clinical presentation of S. intermedius infections can range from indolent to fulminant 4
- Headache is the most common presenting symptom, but patients can also present with fever, nausea, seizure, or altered mental status 4
- Diagnosis can be obtained with CT and MRI scans of the brain, and prompt drainage of the abscess and lengthy antibiotics can improve the prognosis significantly 4