BACTERIOLOGY LEC - MIDTERMS: L2 - STREPTOCOCCI Flashcards
3 genera of family Streptococcaceae Bergey’s Manual of Determinative Bacteriology)
- Streptococcus
- Enterococcus (Note: previously from genus streptococcus)
- Lactococcus
T OR F
Streptococcaceae are gram positive cocci, and catalase positive, making them differ from Staph
False
Staph - catalase positive
Strep - catalase negative
T or F
Streptococcaceae are fastidious, facultative aerobes and needs 5-10% CO2 for growth
False
- Strep areFacultative anaerobes
MOTF
Patterns of Hemolysis
1. Beta hemolytic - complete hemolysis of RBC, clear or colorless zone
EX: S. pyogenes, S. agalactiae
- Gamma hemolytic - non-hemolytic, Enterococcus spp.
- Alpha hemolytic - incomplete or partial hemolysis of RBC, green discoloration
Ex: S. pneumoniae, S. viridans
ALL TRUE
MOTF
Physiological Division
- Viridans division - salt tolerant, grow at high pH, and Temp range of 10°C to 45°C.
- Pyogenic division - includes beta hemolytic strains (A,B,C,D,E,F,&G)
- Streptococcal organisms that are able to create diseases or infections associated with pus formation - Enterococcus division - not beta hemolytic, not salt tolerant, and grow at high pH.
- Lactic division - not clinically significant & associated with dairy industry
2,4 - TRUE
1,3 - FALSE
- Viridans division - not beta hemolytic, not salt tolerant, and grow at high pH.
- Enterococcus division - salt tolerant, grow at high pH, and Temp range of 10°C to 45°C.
MOTF
Lancefield Grouping
By Rebecca Lancefield 1993
- Divides the Streptococci into serologic groups - Based on antigenic properties of carbohydrate group antigens in their cell wall
- ABCDFG - clinically significant
- Mostly associated with human infection.
- ABCDE were the first five and cuurrently at almost 20 groups (A-H)(K-T)
All true
Beta Hemolytic Streptococcus
Enumerate all
Lancefield group A - S. pyogenes
Lancefield group B
- S. agalactiae
Lancefield group C & G - S. dysgalactiae &S. Equi
Lancefield group A, C, F & G - S. anginosus
MOTF
Group A: Streptococcus pyogenes (GAS)
- Normal flora
- Most virulent for humans
- Acquired only thru direct contact - person to person contact
1,3 - false
2 - true
1 - not normal flora
3 - also by inhalation of aerosol droplets
Cell surface antigens of GAS
- This structure is antiphagocytic; it prevents organisms from being phagocytized.
- Reason for mucoid colonies
Hyaluronic acid Capsule
Cell surface antigens of GAS
- Interferes with complement activity, Precipitates fibrinogen, Clumps platelet and wbc, Inhibits migration of WBC
- Can differentiate S pyogenes
M protein (about 80 types)
Group-specific cell wall antigen of GAS
Grp.A sugar: rhamnose-N-acetylglucosamine
Allow them to act like immune cells and attach to fc portion of IgG and IgA
IgG & IgA-binding proteins
- Cleaves C5a component of complement
- Inhibits neutrophil chemotaxis in vitro
C5a protease
(C5a - important anaphylatoxin, will attach to mast cells and basophils - initiating release of histamine and start inflammatory reaction)
MOTF
- F protein - allows binding to fibronectin in pharyngeal epithelium
- Lipoteichoic acid: - attached to M protein
- may allow binding to fibronectin
BOTH T
Fibronectin - binding sites for organism on membranes on host cells or structures.
MOTF
1. Streptokinase - fibrinolysin that lyses blood clots (just like staphylokinase)
- Hyaluronidase - hydrolyze or breakdown hyaluronic acid which is part of the connective tissue, important in spreading the infection
- Diphosphopyridine nucleotidase - degrades host DNA & RNA
- Streptodornase - Associated with the organism’s ability to
destroy WBCs
1,2 - true
3,4 - false
- Streptodornase - degrades host DNA & RNA
- Diphosphopyridine nucleotidase - Associated with the organism’s ability to
destroy WBCs
- Responsible for the increase in temperature and rashes (specially in Scarlet fever)
- Cause of Streptococcal TSS
Pyrogenic exotoxins/ erythrogenic toxins (A, B, C)
Most potent: Exotoxin A
NOTE: Staph TSS is more fatal
MOTF
- Streptolysin O - antigenic, oxygen labile
- Streptolysin S - oxygen stable, non-antigenic but toxic (surface hemolysin)
Both true
MOTF
Erysipelas
1. St. Anthony’s fire
2. Has pus production, but exotoxin A production
(increase temperature in the area) & rashes
3. Itchiness and hotness
1,3 - true
2 - false, has no pus production
- Inflammation of deep tissues including the skin
- Common in middle aged individuals
Cellulitis
- Begins as fluid-filled blisters that usually erupts creating weeping lesions
- Common in children
Impetigo
Red, swollen tonsils
Strep throat
- Streptococcal pharyngitis
- Made streptococcus pyogenes earn the name of “flesh-eating bacteria”
- Active component: Exotoxin A
- Destruction of tissue a rate of 2 inches per hour
Necrotizing fasciitis
- Cause Hypotension, multi-organ failure, fever,
erythema, swelling, tachycardia, acute respiratory distress, renal impairment and shock - Toxin mediated
Streptococcal toxic shock syndrome
- May occur after streptococcal pharyngitis or other infection
- Strawberry tongue, rashes, fever
Scarlet fever