The genera Streptococcus and Enterococcus both consist of Gram-positive cocci that are typically arranged in pairs or chains during growth.5 These bacteria are non-spore forming, facultative anaerobes.1, 5,6 While some are important members of the normal human microbiota, others are pathogenic and cause human diseases.1, 6 Thus far, the classification of these bacteria into major categories has been based on:
1. Serologic specificity of the cell wall group antigens (Lancefield antigens) and other cell wall or capsular antigens
2. Hemolytic reactions on blood agar
3. Biochemical reactions and resistance to physical and chemical factors 1,4,5-8
However, the genera Streptococcus and Enterococcus (which is an extension of the Streptococcus genus) are widely heterogeneous group and no one method suffices to classify them.1 In practice, many species of streptococci and enterococci are characterized using a combination of methods previously stated.1, 6
Serological Specificity of Lancefield Antigens
Typically, the most definitive identification of streptococci and enterococci is the serologic specificity of the cell wall (Lancefield) …show more content…
Different streptococcal and enterococcal species can also be identified in a laboratory setting using biochemical tests such as tests for susceptibility or resistance to various chemical agents.1,6 For example, Bacitracin disks are typically used in susceptibility tests to identify Group A streptococci.1 Trimethoprim sulfamethoxazole (SXT) inhibits β-hemolytic streptococcal groups other than group A and B; thus Group A streptococcus would grow in the presence of SXT.1 L-pyrrolidonyl-β-napthlyamide (PYR) is hydrolyzed by Group A streptococci and enterococci.1,3 The ability to hydrolyze sodium hippurate differentiates Group B streptococci from other β-hemolytic streptococci.1 Growth in 6.5% NaCl differentiates Group D streptococci from enterococci because enterococci grow well in 6.5% NaCl while non-enterococcal group D streptococci do
1. Serologic specificity of the cell wall group antigens (Lancefield antigens) and other cell wall or capsular antigens
2. Hemolytic reactions on blood agar
3. Biochemical reactions and resistance to physical and chemical factors 1,4,5-8
However, the genera Streptococcus and Enterococcus (which is an extension of the Streptococcus genus) are widely heterogeneous group and no one method suffices to classify them.1 In practice, many species of streptococci and enterococci are characterized using a combination of methods previously stated.1, 6
Serological Specificity of Lancefield Antigens
Typically, the most definitive identification of streptococci and enterococci is the serologic specificity of the cell wall (Lancefield) …show more content…
Different streptococcal and enterococcal species can also be identified in a laboratory setting using biochemical tests such as tests for susceptibility or resistance to various chemical agents.1,6 For example, Bacitracin disks are typically used in susceptibility tests to identify Group A streptococci.1 Trimethoprim sulfamethoxazole (SXT) inhibits β-hemolytic streptococcal groups other than group A and B; thus Group A streptococcus would grow in the presence of SXT.1 L-pyrrolidonyl-β-napthlyamide (PYR) is hydrolyzed by Group A streptococci and enterococci.1,3 The ability to hydrolyze sodium hippurate differentiates Group B streptococci from other β-hemolytic streptococci.1 Growth in 6.5% NaCl differentiates Group D streptococci from enterococci because enterococci grow well in 6.5% NaCl while non-enterococcal group D streptococci do