Micro 19: Streptococcus and Enterococcus

Описание: This episode explores the Gram-positive cocci that grow in chains or pairs - Streptococcus and Enterococcus. Drawing from Murray’s chapter, it introduces their classification by haemolysis patterns and Lancefield grouping, linking laboratory identity with clinical consequence.


The narrative moves through the major streptococcal groups:


Streptococcus pyogenes (Group A) and its role in pharyngitis, cellulitis, necrotising fasciitis, and post-infectious sequelae such as rheumatic fever and glomerulonephritis.


Streptococcus pneumoniae as a leading cause of pneumonia, meningitis, and otitis media, distinguished by its capsule and alpha-haemolysis.


Viridans streptococci in dental flora and subacute endocarditis.


Enterococcus species as resilient colonisers capable of causing urinary tract infection, bacteraemia, and endocarditis, often with notable antimicrobial resistance.


Virulence mechanisms such as M protein, capsule formation, pneumolysin, and intrinsic antibiotic tolerance are framed as adaptive tools that shape clinical patterns.


Clinically, this chapter emphasises pattern recognition - sore throat with rash, lobar pneumonia, dental source bacteraemia - and the importance of recognising immune-mediated complications.


Key Takeaways


Streptococci are classified by haemolysis and Lancefield grouping


Group A streptococci cause both acute infection and immune sequelae


S. pneumoniae relies heavily on its capsule for virulence


Viridans streptococci are linked to dental flora and endocarditis


Enterococci are notable for resilience and antibiotic resistance


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