Streptococcus and Enterococcus Flashcards
What does Streptococcus and Enterococcus look like on gram stain?
gram positive, chaining cocci - can be square or lemon-shaped
Where do Streptococcus and Enterococcus tend to live?
they are widely distributed in nature - skin and mucous membranes
Typically when can hemolysis be seen in Streptococcus and Enterococcus species?
18-24 hours
What are the growth requirements for Streptococci?
some require serum or blood for growth, 35-37 C, faculative anaerobes, decreaased O2 and increased CO2 helps on primary isolation
What are the growth requirements for Enterococcus?
less fastidious than Streptococcus, resistant to esculin, tolerate higher temperatures, and highly resistant to antimicrobials
How do Streptococci respond to catalase tests?
they are catalase negative
What is a useful test in determining what type of streptococcus species is present?
carbohydrate fermentation tests
What do Streptococci colonies look like?
they are smaller than staphylococcal colonies and are usually clear
What type of hemolysis can Streptococci species have?
alpha, beta, or no hemolysis
What type of hemolysis is shown here?
beta
What types of antigens are associated with Streptococci?
group-specific antigens and type-specific antigens
How are the cell wall carbohydrates in streptococci grouped?
into Lancefield groups (A, B, C, etc.)
How is the Lancefield test carried out?
boiling an unknown streptococcus or treating it with acid to destroy the protein antigens
What Lancefield group are capsules important in?
Group A streps
What toxins are associated with Streptococci?
streptolysin-O, streptolysin-S, streptokinase, streptodornase, and hyaluronidase
What type of toxin is streptolysin-O?
it is cholesterol-binding
When are streptolysin-O best seen?
under anaerobic growth conditions
What does streptolysin-O do?
attacks leukocytes, platelets, RBC’s,and fibroblasts
Describe streptolysin-S?
less toxic, non-antigenic, and stable to oxygen
What does streptokinase do?
lyse fibrin
What does streptodornase do?
liquefaction of pus
What lancefield group is streptodornase associated with?
A
What does hyaluronidase do?
break down hyaluronic acid in tissues
What group of strep is Streptococcus pyogenes?
Group A - it is the only species in this group