Exercise 2 Sreptococci are gram-positive cocci which typically occur in chains,clusters,and pairs. The that fo in nt hac the mout orm the dom ial flora of gastrointestinal tract Streptococcus pyogenes (Lancefield's GroupA,beta-hemolytic streptococci)is the most reknown pathogen in this genus.It causes infections such as acute pharyngitis(strep sore throat),impetigo,post-operative wound infections,cellulitis,erysipelas,post-streptococcal glomerulonephritis,and acute rheumatic fever.Asymptomatic colonization of S.pyogenes in the pharynx and on skin surfaces as well as anal carriage is not uncommon and may serve as a source of infection. Streptococcus agalactiae(Lancefield's Group B,beta-hemolytic streptococci)can be vered from the g nital and intestinal t arently healthy adults and children.It is primarily i ated i natal infectio s pn ia and/or he it ha Enterococcus faecalis(Lancefield's Group D,nonhemolytic streptococci)is normally found in the intestinal tract along with other enterococci(E.faecium and E.durans).It causes infections such as subacute bacterial endocarditis(20%),urinary tract infections(10%), wound infections,and some other opportunistic infections.The resistance of enterococcal species to penicillin is an important fact to remember in treating patients infected with these streptococci. eumoniae can be isolated from the pharynx of 30-70%of apparently healthy rimarily causes a bacterial r monia ially in the debilitated or compr atients with conjunctivitis meningitis,otitis,pericarditis,empyemaendocarditis,and septicemia Viridans streptococci includes about 10 species(S.mutans.S.sanguis.S.salivarius)which are normally found in the mouth and pharynx.These streptococci are usually alpha or non-hemolytic on blood agar and cause about 50-70%of all subacute bacterial endocarditis They have also been implicated in causing dental caries,bacteremia,and sepsis. Blood agar plate cultures of each of the following microorganisms will be available for student examination a Streptococcus(Group A Streptococci) b.Streptococcus agalactiae (Group B Streptococci) c.Streptococcus pneumoniae(Pneumococci) d.Enterococcus faecalis(Group D Streptococci) >>> Each student should use one of these cultures to perform the following tests. 1.Describe the cultural characteristics of the various streptococci on blood agar medium Note the type.size.and color of the colonies and describe the various types of hemolysis observed with these microorganisms. Streptococcus pyogenes Streptococcus agalactiae Streptococcus pneumoniae Enterococcus faecalis file://CWIND n/Microb Lab Web 2001/Exercise2/exercise2.htm(2 of 10)[8/31/2002 4:30:02 PM]Streptococci are gram-positive cocci which typically occur in chains, clusters, and pairs. There are many members of the genus Streptococcus that form the dominant bacterial flora of the mouth and the pharynx. Some streptococcal species are normally found in the gastrointestinal tract. Streptococcus pyogenes (Lancefield's GroupA, beta-hemolytic streptococci) is the most reknown pathogen in this genus. It causes infections such as acute pharyngitis (strep sore throat), impetigo, post-operative wound infections, cellulitis, erysipelas, post-streptococcal glomerulonephritis, and acute rheumatic fever. Asymptomatic colonization of S. pyogenes in the pharynx and on skin surfaces as well as anal carriage is not uncommon and may serve as a source of infection. Streptococcus agalactiae (Lancefield's Group B, beta-hemolytic streptococci) can be recovered from the genital and intestinal tract of apparently healthy adults and children. It is primarily implicated in causing neonatal infections such as pneumonia, septicemia and/or meningitis. Nevertheless, it has been isolated from patients with urinary tract infections, wound infections and otitis media. Enterococcus faecalis (Lancefield's Group D, nonhemolytic streptococci) is normally found in the intestinal tract along with other enterococci (E. faecium and E. durans). It causes infections such as subacute bacterial endocarditis (20%), urinary tract infections (10%), wound infections, and some other opportunistic infections. The resistance of enterococcal species to penicillin is an important fact to remember in treating patients infected with these streptococci. Streptococcus pneumoniae can be isolated from the pharynx of 30-70% of apparently healthy individuals. It primarily causes a bacterial pneumonia especially in the debilitated or compromised patient. This diplococcus has also been isolated in patients with conjunctivitis, meningitis, otitis, pericarditis, empyema, endocarditis, and septicemia. Viridans streptococci includes about 10 species (S. mutans, S. sanguis, S. salivarius) which are normally found in the mouth and pharynx. These streptococci are usually alpha or non-hemolytic on blood agar and cause about 50-70% of all subacute bacterial endocarditis. They have also been implicated in causing dental caries, bacteremia, and sepsis. Blood agar plate cultures of each of the following microorganisms will be available for student examination: a. Streptococcus (Group A Streptococci) b. Streptococcus agalactiae (Group B Streptococci) c. Streptococcus pneumoniae (Pneumococci) d. Enterococcus faecalis (Group D Streptococci) >>>>> Each student should use one of these cultures to perform the following tests. 1. Describe the cultural characteristics of the various streptococci on blood agar medium. Note the type, size, and color of the colonies and describe the various types of hemolysis observed with these microorganisms. Streptococcus pyogenes Streptococcus agalactiae Streptococcus pneumoniae Enterococcus faecalis Exercise 2 file:///C|/WINDOWS/Desktop/clown/Microb Lab Web 2001/Exercise2/exercise2.htm (2 of 10) [8/31/2002 4:30:02 PM]