Streptococcaceae Flashcards
Genuses of Family Streptococcaceae (3):
Streptococcus (mostly pathogenic)
Enterococcus (facultative pathogens)
Lactococcus (milk streptococci)
Where can Streptococci be found?
Commensals of mucus membranes of upper respiratory tract and lower urogenital tract
What does commensals mean?
Microorganism that lives continuously on, or in certain parts of the body without causing disease
What does Streptococci cause?
Pyogenic infections such as mastitis, metritis, polyarhritis, meningitis and septicaemia
Which type of haemolysis does the more pathogenic Streptococci have?
beta-hemolysis
Streptococci can be differentiated based on:
Type of hemolysis
Lancefield groups (based on group specific C substance in the cell wall-polysaccharide)
Clinical signs
Biochemical reactions
Types of hemolysis of streptococci
alpha- (viridans), beta-, and non-haemolytic
Division of Streptococci according to clinical signs (2):
Oral - mostly viridans
Enteric - enterococcus
b-hemolytic species of Streptococcus (7):
Str. pyogenes
Str. agalactia
Str. equi subsp. zooepidemicus
Str. dysgalactie subsp. equisimilis
Str. equi
Str. canis
Str. porcinus
a-hemolytic species of Streptococcus (7)
Str. pneumoniae
Str. dysgalactiae
Str. uberis
Str. sanguis
Str. mutans
Str. salivarius
Enterococcus facialis
What causes chronic mastitis in ruminants?
Streptococci agalactia
What does Str. Equi cause?
mastitis, pneumonia and navel infections in horses
What does Str. dysgalactie cause?
Endometritis, mastitis and abscesses in horses
What causes acute mastitis in cattle?
Str. dysgalactie
What causes polyarthritis in lamb?
Str. dysgalactie
Virulence factors of Streptococci
Toxins: haemolysins a, b-streptolysin O, S and y. Phage-coded pyrogenic toxin.
Enzymes: streptokinase, hyaluronidase, DNase, NADase and protease.
Cell structures: capsule and cell wall M protein are antiphagocytic.
Which Streptococci produce capsule?
Str. pyogenes and Str. pneumoniae
Microscopical examination of Streptococci
Gram +
Non-motile
(Enterococci are motile)
Chains of different length
Str. Pneumoniae - diplococci
Material for cultivation of Streptococci
exudate, pus, milk, skin swabs, urine, tissue, cerebrospinal fluid
Cultivation properties for Streptococci
S form (Str. equi and Str. pneumoniae have M form)
Small colonies
Facultative anaerobes
37 degrees celsius (10-40C), Enterococcus 45C
24 hours
Streptococci on meat-peptone-broth
Sediment
Weak turbidity
Streptococci on blood agar
S form
Small colonies
Different types of haemolysis
Special media for detection of Enterococci
Bile aesculin agar
Bile salts suppress the growth of other bacteria - change colour from yellow to brown-black
Streptococci reaction to catalse and oxidase
Catalase -, oxidase -
Which tests can be used for serological examination of Streptococci (3)?
Ring precipitation test
Latex-agglutination test
CAMP test (special examination)
Describe ring precipitation test for Streptococcus
C-substance is extracted by acid or heat, and layered over antisera of different specificities.
Positive reaction = formation of white ring of precipitate close to interface of two fluids within 30 minutes.
Describe latex-agglutination test for Streptococcus
A drop Ag is mixed with suspensions of latex particles coated with group-specific antibodies. Positive = agglutination
What is CAMP test?
- Phenonemon of enhanced haemolysis.
Str. agalactiae (group B) secret CAMP factor that completes the lysis of red blood cells, only partially haemolysed by St. aureus. They are streaked with right angles to each other without touching.
How do we distinguish b-haemolytic Streptococci of group A (S pyogenes) from other b-haemolytic Streptococci?
Susceptibility test to bacitracin
How to differentiate Streptococcus Pneumoniae from other a-haemolytic streptococci?
Susceptibility test to optochin
