Streptococcus agalactiae and Tonsillitis Etiology

Introduction to Tonsillitis Causes

The American College of Physicians and Infectious Diseases Society of America recommend that Group A beta-hemolytic streptococcus (Streptococcus pyogenes) is the most common bacterial cause of tonsillitis, with a prevalence of 5-15% in adults and 15-30% in children aged 5-15 years, although the exact percentage is not specified in this context 1, 2
Group B streptococcus (S. agalactiae) is not typically identified as a significant cause of tonsillitis in the medical literature, according to the Clinical Microbiology and Infection guidelines 1, 3

The Centers for Disease Control and Prevention (CDC) state that Streptococcus agalactiae (Group B streptococcus) is primarily known for causing invasive disease in newborns, pregnant women, and adults with underlying medical conditions such as diabetes mellitus, with a high level of evidence 4
The primary clinical significance of Group B streptococcus is related to neonatal infections (bacteremia, pneumonia, meningitis), maternal infections (urinary tract infection, amnionitis, endometritis), and infections in non-pregnant adults with comorbidities, as recommended by the CDC 4

Besides Group A streptococcus, other less common bacterial causes of pharyngitis/tonsillitis include Groups C and G beta-hemolytic streptococci, Arcanobacterium haemolyticum, Neisseria gonorrhoeae (in sexually active individuals), Mycoplasma pneumoniae and Chlamydia pneumoniae (uncommon), and mixed anaerobic infections (Vincent's angina, rare), according to the Clinical Infectious Diseases guidelines 1, 2, 3

Group C streptococci have been documented to cause severe or recurrent pharyngitis/tonsillitis, with a moderate level of evidence 3
A case-control study found that patients with Group C streptococci had exudative tonsillitis and anterior cervical adenopathy more frequently than subjects negative for this infection, as reported in the Clinical Microbiology and Infection journal 3
There is insufficient evidence for a significant role of Group G streptococci in severe/recurrent pharyngitis and other adverse outcomes, according to the Clinical Microbiology and Infection guidelines 3

Throat culture on sheep blood agar remains the standard for documenting the presence of streptococci in the upper respiratory tract, as recommended by the Clinical Infectious Diseases guidelines 5
Rapid antigen detection tests are useful for quick identification of Group A streptococcus but are not typically designed to detect Group B streptococcus, although this information is not directly relevant to the current context 2