Lancefield grouping of clinically relevant beta-hemolytic streptococci

Streptococcus as seen in Scanning electron microscope

Streptococci are Gram positive cocci either diplococci (lanceolate shaped; S. pneumoniae) or in chains. They are catalase negative (An important test which differentiate it from another cocci, Staphylococci). This fastidious gram positive cocci may give either alpha or beta or gamma hemolysis when cultured on Blood Agar.

β-hemolytic streptococci produce hemolysins that lyse the sheep RBCs (poorly lyse human RBCs too), resulting in a clearing of the Blood Agar plate surrounding the colonies. More intense β-hemolysis is noted in areas where the medium has been “stabbed,” pushing some of the bacteria under the surface of the medium. The β-hemolysis in these areas is due to the combined action of both hemolysins of Streptococci (Streptolysin O and Streptolysin S. The surface β-hemolysis is largely due to streptolysin S (oxygen stable hemolysin), as Streptolysin O which is oxygen-labile does not show maximal activity on the surface of the agar.

Beta Hemolysis in Sheep Blood Agar.

Serologic grouping of cell wall carbohydrates of Streptococci was classically been used to identify species of beta-hemolytic Streptococci, this grouping is known as  Lancefield grouping. Beta hemolytic streptococci are arranged into twenty (20) groups A-U without I and J (i.e. A through H and K through V). Rebecca Lancefield, a prominent American microbiologist, introduced Lancefield grouping.

Streptococcus as seen in Scanning electron microscope
Streptococcus as seen in Scanning electron microscope

The basis of grouping is the  antigenic differences in C carbohydrates, a group specific antigen.  C carbohydrate is located in the cell wall of streptococci

(Note: viridans streptococci and Streptococcus pneumoniae have no group-specific antigen).

The original Lancefield precipitin test is now rarely performed in clinical laboratories. Now, it has been replaced by either latex agglutination or coagglutination.

Group A Streptococci (GAS): Streptococcus pyogenes, it is one of the most important human pathogens which causes Streptococcal sore throat, skin infections and post streptococcal sequale such as Rheumatic fever and Post Streptococcal glomerulonephritis (PSGN). S. pyogenes is inhibited by the antibiotic bacitracin, an important diagnostic criterion.

Group B Streptococci: Streptococcus agalactiae  colonizes in the genital tract of some women and can cause neonatal meningitis and sepsis. It can cause septic abortion and puerperal or gynaecological sepsis and occasionally urinary tract infections. S. agalactiae gives CAMP test positive and can hydrolyze the hippurate.

Group C Streptococci: Group C beta hemolytic streptococci currently include S. dysgalactiae subsp. equisimilis and other related strains under same species or S. equi subspecies. S. dysgalactiae subsp. equisimilis has been recovered from pharyngitis and tonsillitis from the patients with underlying diseases such as cardiopulmonary disease, diabetes, immunosupression, HIV etc.

Group D Streptocci include enterococci (e.g., Enterococcus faecalis and Enterococcus faecium) and nonenterococci (S. bovis). Enterococci are members of normal flora of the colon. They can cause urinary, biliary and cardiovascular infections.

Note: By the mid 1980s, the enterococcal streptococci (Lancefield group D) had taken up residence in their own newly created Enterococcus genus and the “dairy” or “lactic” streptococci (Lancefield group N) were moved to new Lactococcus genus.

Group F Beta Hemolytic streptococci: Organisms of this group have been called S. milleri in the British taxonomic scheme and anginosus (S. anginosus) group in American taxonomic group.  Group F Beta-hemolytic streptococci are recognized as cause of severe suppurative infections including cellulitis, deep-tissue abscesses, bacteremia, osteomyelitis and endocarditis.

Group K-U contains streptococcal species of limited virulence which can cause infections in immunocompromised individuals.

Summary of Medically Important Streptococci 

Species Lancefield Group Typical Hemolysis Important Lab Characteristics
Streptococcus pyogenes A Beta Bacitracin sensitive
PYR Test positive
S. agalactiae  B Beta Bacitracin resistant
Hippurate utilized
CAMP test positive
Enterococcus faecalis D Alpha, Beta or None Growth in 6.5% NaCl
PYR Test positive
S. bovis D Alpha or none No growth in 6.5% NaCl
S. pneumoniae Not groupable Alpha Bile soluble
Inhibited by optochin
Viridans group Not groupable Alpha Not bile soluble
Not inhibited by optochin
About Acharya Tankeshwar 455 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.


    • Dear, Thank you so much for your remark. This is a clear guidance for me to focus on proof reading activity. That’s the blunder, I am amazed how i did such a typo. It has been corrected. Thank you once again.

    • Pyrrolidonyl Arylamidase (PYR) test is a rapid test which is used for the presumptive identification of group A beta-hemolytic Streptococci and Enterococci.

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