Streptococcus Flashcards
Appears as lancet – shape or diplococci)
Streptococcus pneumoniae
Streptococcus O2 and CO2 requirement
Facultative anaerobe
NOTE‼️: Genus streptococcus are commonly found as part of normal flora; encountered in clinical specimens as contaminants or as components of mixed cultures with minimal or unknown clinical significance.
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BROWN and SMITH: ALPHA hemolytic (partial hemolysis)
*Viridans streptococci
*Streptococcus pneumoniae
BROWN and SMITH: BETA hemolytic (complete hemolysis)
Streptococcus pyogenes (Group A)
Streptococcus agalactiae
(Group B)
Streptococcus equisimilis, zoopedemicus, equi
(Group C)
BROWN and SMITH: GAMMA hemolytic (Non-hemolytic)
Enterococcus faecalis
LANCEFIELD CLASSIFICATION is based on what carbohydrate?
Based on the C – carbohydrate antigen found in the cell wall
DO NOT have carbohydrate cell wall antigen
Streptococcus pneumoniae
Viridans streptococci
Group C strep
S. equisimilis,
S. zooepidemicus
S. equi
Group G strep
S. arginosus
STREPTOCOCCUS OF MEDICAL IMPORTANCE
- pyogenes (A)
- agalactiae (B)
- pneumoniae
- viridans
- faecalis (D)
Main human pathogen associated with local or systemic invasion and post – streptococcal immunologic disorders
Streptococcus pyogenes
produces large (1cm in diameter) zones of β hemolysis around colonies greater that 0.5 mm in diameter
Group A β Hemolytic Streptococcus
Its habitat skin and Upper Respiratory tract of humans, carried on nasal,
pharyngeal, sometimes anal mucosa
Streptococcus pyogenes
Characteristic that has earned the designation ‘’flesh – eating bacteria”
Streptococcus pyogenes (Group A strep)
Most strains of S. pyogenes produces capsules composed of____
hyaluronic acid
S. pyogenes Fastidious, requires enriched media for primary isolation incubated with ______.
5% – 10% CO2
Catalase negative (- )
PYR - positive (+)
Bacitracin: Sensitive
Streptococcus pyogenes
Appears as circular, translucent, grayish to
opalescent colonies, matte or glossy large zone beta hemolysis
S. pyogenes
test for Group A Streptococcus
demonstrate presence of pyrrolidonyl arylamidase
(+): development of a deep cherry red color
within a minute addition of reagent
PYR Hydrolysis Test (POSITIVE)
Presumptive test for S. pyogenes
Used to differentiate Streptococcus pyogenes and Streptococcus agalactiae
RESULT:
S. pyogenes (sensitive)
S. agalactiae (resistant
Bacitracin Susceptibility Test
use as basis for serological classification using Lancefield method
C - carbohydrate
major virulence factor of group A S pyogenes. (most important virulence factor)
M – Protein
obtained from streptococci by proteolytic digestion, which rapidly destroys M proteins.
permits differentiation of certain types of streptococci by agglutination with specific antisera,
T – Protein
allows organism to cling to epithelial surfaces
Cytotoxic; destroys rbc and wbc
Lipoteichoic Acid (LTA)
depolymerizes DNA; facilitate removal of purulent exudate/ discharges
Streptodornase (Streptococcal Deoxyribonuclease)
transforms the plasminogen of human plasma into plasmin, an active proteolytic enzyme that digests fibrin and other proteins
Streptokinase (Fibrinolysin)
An enzyme elaborated into the environment and is related to the organism’s ability to kill leukocytes, PMN’s and macrophages.
Diphosphopyridine nucleotidase
(oxygen stable; non antigenic : surface BAP hemolysis during aerobic condition)
Streptolysin S
oxygen labile; antigenic) Immunogenic;
responsible for some of the hemolysis seen when
growth is in cuts deep into the medium in blood agar plates.
Streptolysin O
ASO serum titer in excess of ________ is considered abnormally high and suggests either recent infection with S. pyogenes
160–200 units
associated with streptococcal toxic shock syndrome and scarlet fever.
– act as superantigens
Erythrogenic Toxin
Most common cause of bacterial sore throat
PHARYNGITIS (Streptococcal sore throat)
Characterized by massive brawny edema and a rapidly advancing marin of infection
Erysipelas
surface is covered with pus and later is encrusted.
honey colored crust
Impetigo (Sreptococcal pyoderma)
Follows infection associated with mild trauma, burns, wounds, or surgical incisions; pain, tenderness, swelling, and erythema occur.
lesion is NOT raised, and the line between the involved and uninvolved tissue is indistinct.
caused by Hyaluridinase
Cellulitis