Streptococcaceae and Enterococcus species Flashcards
Based on hemolysis on 5% Sheep Blood Agar Medium
Smith and Brown’s Classification
denotes incomplete lysis of erythrocytes with reduction of hemoglobin and the formation of green pigment
α-hemolysis
Streptococci producing such pattern of hemolysis were later on described as “green streptococci”.
α-hemolysis
refers to the complete disruption of erythrocytes resulting to clearing of the blood around the bacterial growth.
β-hemolysis
signifies absence of hemolysis thereby no change is seen in the medium surrounding bacterial growth.
γ-hemolysis
Streptococci producing such pattern of hemolysis were later on described as “indifferent streptococci”.
γ-hemolysis
a small zone of intact erythrocytes immediately adjacent to bacterial colony is surrounded with a zone of complete erythrocyte hemolysis.
α’ (alpha prime)-hemolysis (wide zone of alpha hemolysis)
This type of hemolysis maybe confused with β-hemolysis.
α’ (alpha prime)-hemolysis (wide zone of alpha hemolysis)
Discovered by Rebecca Lancefield in the 1930s based on group-specific antigens which are either cell wall polysaccharides, AKA C-substance, (as in human group A, B, C, F, and G streptococci); or lipoteichoic acids as in the group D streptococci and Enterococcus species These antigens stimulated formation of antibodies with differing specificities.
Lancefield Classification
Typing with specific antiserum causing agglutination is generally done only for groups A, B, C, F, and G.
Lancefield Classification
Based on temperature for growth particularly at 10OC and 45OC.
Academic/ Bergey’s Classification
consists of streptococci that do not grow at both 10OC and 45OC.
Pyogenic group
includes streptococci which fail to grow at 10OC but can be recovered at temperatures up to 45OC.
Viridans group
are streptococci that grow at both 10OC and 45OC.
Enterococcus group
comprise of streptococci that are frequently recovered in dairy products, can grow at 10OC but fail to grow at 45OC.
Lactic group
Group A β-Hemolytic Streptococci (GAS): Streptococcus pyogenes: Habitat
human throat and skin
Group A β-Hemolytic Streptococci (GAS): Streptococcus pyogenes: Transmission
respiratory droplets or contact with cutaneous lesions.
The most common infection caused by S. pyogenes.
Pharyngitis or streptococcal sore throat
Although it may occur at any age, it occurs most frequently between the ages of 5 and 15 years.
Pharyngitis or streptococcal sore throat
Characterized by acute sore throat, malaise, fever, and headache
Pharyngitis or streptococcal sore throat
Typically involves the tonsillar pillars, uvula, and soft palate, which become red, swollen, and covered with a yellowwhite exudate. The cervical lymph nodes that drain this area may also become swollen and tender.
Pharyngitis or streptococcal sore throat
Usually self-limiting (illness resolves on its own even without medical intervention). Typically, the fever is gone by the third to fifth day, and other manifestations subside within 1 week.
Pharyngitis or streptococcal sore throat
Pharyngitis or streptococcal sore throat
Caused by lysogenized strains of S. pyogenes that produce pyrogenic exotoxins A - C
Scarlet Fever