Enterococcus, Streptococcus Flashcards
Commensal organisms of human gastrointestinal tract that cause opportunistic infections
Enterococcus
Most common species of enterococcus in human
infections
E. faecalis, E. faecium
Primary sites of infection and transmissions of S. pyogenes
UPPER RESPIRATORY TRACT and SKIN LESIONS
Normal flora of upper respiratory; leading cause of acute otitis in children (0-3); major cause of bacterial meningitis
S. pneumoniae
One of S. pyogenes’ virulence factors which destroys complement chemotactic factors
C5a peptidase
Can be transmitted person to person from mother in utero or during delivery; Nosocomial transmissio
n by unwashed hands of mother or health care personnel
Streptococcus agalactiae
Virulence factor of S. agalactiae which interferes with phagocytic activity and complement cascade activation
Capsular material
Primary virulence factor of S. pneumoniae which inhibits phagocytosis
Polysaccharide capsule
Colonizer of nasopharynx
S. pneumoniae
Virulence factors of S. pneumoniae
Polysaccharide capsule, pneumolysin, secretory IgA
Normal flora of the oral cavity, GI tract, genital tract
Viridans
Endogenous strain
• Gain access to sterile site
• From dental manipulations
Viridans
Production of extracellular complex polysaccharides (glucans; dextrans)
Enhance attachment to host cell surfaces such as cardiac endothelial cells or tooth surfaces in case of dental caries
Viridans
Infections are health-care related; Mixed infections of
abdomen and pelvis
Enterococcus
Used to detect S. pneumoniae C-polysaccharide
Urine antigen test
Used to diagnose meningitis using CSF
S. pneumoniae & S. agalactiae (grp. B) antigen kits
Lancet-shaped and evident by clear halo in gram stain
S. pneumoniae
Odor of beta- hemolytic strep
Buttery odor
Odor of Viridans strep
Butterscotch odor
Complete or true lysis of RBC; Clear zone approaching the color and transparency of base medium around colony
Beta hemolysis
Reduction of RBC hemoglobin to methemoglobin; Green or brown discoloration; Partial hemolysis
Alpha hemolysis
No reaction surrounding medium; lack of hemolysis
Gamma hemolysis
Alpha hemolytic, optochin sensitive, bile soluble, capsule (+), quellung (+)
S. pneumoniae
Optochin resistant, not bile soluble, no capsule
Viridans
Reacts with iron salt to form dark brown precipitate. Differentiate group D Enterococci
Bile esculin agar
Detect genital carriage of Grp. B during pregnancy using vaginal or rectal swab
Todd-Hewitt broth with CNA (LIM)