2.1 Flashcards
Clinically significant species under catalase-neg gram-pos cocci
Streptococcus pyogenes
Streptococcus agalactiae
Streptococcus pneumoniae
Viridans streptococci
Enterococcus faecalis
Enterococcus faecium
Beta hemolytic streptococci species
Streptococcus pyogenes
Streptococcus agalactiae
Groups C, F, and G betahemolytic Streptococci
Streptococcus pneumoniae
Viridans streptococci
Streptococcus mutans
Streptococcus salivarius
Streptococcus mitis
Streptococcus bovis
Streptococcus urinalis
Streptococcus anginosus
(Streptococcus milleri )
Nutritionally variant streptococci
Abiotrophia defective
Granulicatella adiacens
Granulicatella balaenopterae
Granulicatella elegans
Enterococci
Enterococcus faecalis
Enterococcus faecium
E. durans
E. mundtii
E. dispar
E. gallinarum
E. avium
E. hirae
E. raffinosus
E. casseliflavus
Other Catalase-Negative, Gram-Positive Cocci
Leuconostoc spp.
Lactococcus spp.
Globicatella sp.
Pediococcus spp.
Aerococcus spp.
Gemella spp.
Helcococcus sp.
Alloiococcous otitidis
Dolosicoccus paucivorans
Facklamia
Dolosigranulum pigrum
Ignavigranum ruoffiae
Tetragenococcus
Considered as true pathogen under catalase-neg gram-pos cocci
Streptococcus pyogenes
Considered as colonizer under cat-neg gram-pos cocci
Streptococcus pneumoniae
Shows a positive result in catalase test when cultured in a blood agar plate and shows a negative result when cultured in chocolate agar plate
Alloicoccus paucivorans
What family do catalase-negative, gram-positive cocci belong to?
Streptococcaceae
What is the shape and Gram reaction of catalase-negative, gram-positive cocci?
Spherical to ovoid, catalase-negative, gram-positive cocci
How are catalase-negative, gram-positive cocci arranged when grown in liquid media?
They are arranged in pairs or chains.
Are catalase-negative, gram-positive cocci spore-forming?
No, they are non-spore-forming.
Do catalase-negative, gram-positive cocci exhibit motility?
They are generally non-motile, except for rare motile strains of group D streptococci
What oxygen conditions do catalase-negative, gram-positive cocci prefer?
They are facultative anaerobes, but some strains require added CO₂ and are considered microaerophilic
Which strain of catalase-negative, gram-positive cocci is microaerophilic?
Viridans streptococci
Are catalase-negative, gram-positive cocci encapsulated
They are generally non-encapsulated, except for some strains of groups A, B, C, and D.
Where are catalase-negative, gram-positive cocci commonly found in humans?
They are commonly found as part of the normal human flora.
What enhances the growth of catalase-negative, gram-positive cocci?
Their growth is enhanced by blood (blood agar plate - BAP), serum, or glucose
Describe the appearance of catalase-negative, gram-positive cocci colonies on a blood agar plate (BAP).
Colonies are grayish, pinpoint, circular, and translucent to slightly opaque; some colonies may appear mucoid
What are the biochemical test results for catalase-negative, gram-positive cocci?
They are negative for catalase, oxidase, and gas production.
What are the three main classifications of Streptococci?
Academic or Bergey’s Classification, Smith & Brown’s Classification, and Lancefield Classification.
On what basis is Academic or Bergey’s Classification performed?
Based on temperature requirements
Which group of Streptococci grows only at 37°C and is mostly β-hemolytic?
Pyogenic Group.
Name the Streptococcal species in the Pyogenic Group
Streptococcus pyogenes,
group C and G Streptococci (large-colony-forming isolates)
Which group of Streptococci grows at 45°C and 37°C but not at 10°C, and resists the Lancefield Precipitation Test?
Viridans Group.
Name the Streptococcal species in the Viridans Group
Streptococcus salivarius,
S. mutans (dental plaque),
S. mitis,
S. sanguis,
S. anginosus
Which group of Streptococci grows at 10°C and 37°C but not at 45°C and is non-hemolytic with Lancefield N antigen
Lactic Group
Name the Streptococcal species in the Lactic Group
Streptococcus lactis (involved in milk coagulation and souring).
Which group of Streptococci grows at 10°C, 45°C, and 37°C, and can withstand temperatures above 60°C?
Enterococcus Group.
Name the Streptococcal species in the Enterococcus Group.
Enterococcus faecalis (part of normal fecal flora).
On what basis is Smith & Brown’s Classification performed?
Based on hemolytic patterns on blood agar plates (BAP).
What type of hemolysis does alpha-hemolytic Streptococci exhibit?
Partial or incomplete hemolysis of red blood cells around colonies, causing greenish or brownish discoloration.
Name species in the alpha-hemolytic group
Streptococcus pneumoniae,
some Enterococci species,
and Streptococcus bovis complex species
What type of hemolysis does beta-hemolytic Streptococci exhibit
Complete hemolysis of red blood cells, forming clear zones around colonies
Name species in the beta-hemolytic group
Streptococcus pyogenes,
S. agalactiae,
S. dysgalactiae subsp. equisimilis,
S. anginosus group, and
some Enterococci species.
What type of hemolysis does gamma-hemolytic Streptococci exhibit?
No hemolysis of red blood cells; no change around colonies
Name species in the gamma-hemolytic group
Enterococci species and Streptococcus bovis complex species.
A small area of intact red blood cells around the colony surrounded by a wider zone of complete hemolysis.
alpha-prime (α’) or wide-zone hemolysis
How can hemolysis be enhanced on blood agar?
By stabbing the inoculating loop into the agar several times
How should plates be examined for hemolysis
By holding them in front of a light source.
Who developed the Lancefield Classification system?
Rebecca Lancefield.
On what basis is Lancefield Classification performed?
Based on the antigenic characteristics of group-specific C substance, a cell wall polysaccharide.
How is the C carbohydrate extracted in Lancefield Classification?
By using dilute acid and heating the suspension for 10 minutes
For which type of Streptococci is Lancefield Classification most significant?
Beta-hemolytic Streptococci
