Exam 3 Streptococcus sp. Flashcards
What is the catalase test
the most important test to differentiate Gram positive Cocci: Staph from Strep
What is indicative of a positive catalase test and a negative catalase test
positive=bubbles
negative=no bubbles
What are the results for a catalase of streptococcus and enterococcus species
they are catalase negative
What are the characteristics of streptococcus and enterococcus species
they are gram positive cocci (in pains and chains) and have varying hemolytic patterns such as gamma, alpha, and beta
What is streptococcus’ drug of choice
penicillin, works by inhibiting bacterial cell wall synthesis
What are latex antigen detection
commercially available kits that allow for the rapid detection of the Lancefield classification in B-hemolytic streps
Where are streptococcus normally found
in the pharynx, mouth, lower Gi tract, and vagina
Streptococcus can cause life-threatening infections when identified in sterile sites such as
blood, csf, other body fluids (pleural, pericardial, joint, and vitreous), bone, and vascular tissue
What is the Lancefield classification of strep pyogenes
group A streptococcus
When Strep A is plated on SBA, what type of hemolysis can be seen
a large well-defined area of b-hemolysis
Sensitivity to bacitracin is
‘A’ disk positive
Resistance to bacitracin is
‘A’ disk negative
Is Strep A sensitive or resistant to bacitracin
Strep A is sensitive to bacitracin making it ‘A’ disk positive
Is group A strep pyr+ or -
pyr +
Which proteins give group A strep a virulence factor
M proteins blocks the binding of C3b (opsonization), and F protein both help with the adherence and invasion of the epithelial cells
What is Streptolysin O
streptolysin O is a hemolysin virulence factor of Group A strep that destroys WBCs, platelets, RBCs, and other tissues (oxygen labile- destroyed by oxygen)
How is Streptolysin O detected on SBA
to detect streptolysin O SBA should be stabbed to force some of the organism to grow in a reduced oxygen content
What is Streptolysin S
streptolysin S is another hemolysin virulence factor of Group A strep that can lyse RBCs and WBCs (oxygen stabile-can grow in the presence of oxygen)
What are some other virulence factors of Group A strep
hyaluronidase- a spreading factor that causes the breakdown of connective tissue
Streptokinase- lysis fibrin clots
Streptococcal pyrogenic exotoxins (SPEs)- causes a red spreading rash and acts as superantigens (SPE A,B,C, and F exotoxins)
What are infections caused by Group A strep
pharyngitis (strep throat THE MOST COMMON CAUSED BY A STREP), pyoderma (skin infections), sepsis (blood infections), and necrotizing fasciitis (streptococcal gangrene)
What are some pyoderma infections
impetigo (in very young children), erysipelas (spreading red rash), and cellulitis (deep invasion of GAS leading to necrosis and gangrene)
What are some complications that can happen post Group A infection
Rheumatic fever (occurs after pharyngitis), scarlet fever, and acute glomerulonephritis
What is the Lancefield classification of streptococcus agalactiae
Group B strep
What are some virulence factors of group B strep
capsule, hemolysin, CAMP factor
Who are group B strep often associated with
neonates, 80% of cases are caused by vertical transmission from mother during birth
premature birth, membrane rupture, pneumonia, and meningitis with bacterium can all be caused by Group B strep if mother is not treated during pregnancy
How is Group B strep detected
by a collection of a vaginal swab of pregnant women between 35 and 37 weeks
What type of media can Strep B be grown in
Todd Hewitt (LIM) broth with antimicrobials
What is the result of Group B catalase test
negative
What type of hemolysis does group B strep have
pin-point colonies with narrow zone of Beta Hemolysis
Is Group B strep sensitive or resistant to bacitracin
Group B is resistant to bacitracin- ‘A’ disk negative
Is Group B Camp test negative or positive
Camp test positive
Is Group B strep Hipp test positive or negative
Hipp test positive
What is the CAMP test
the Christie-Atkins-Munch-Petersen test is used to identify group B strep and differentiate it from other streptococci
What are some virulence factors of Streptococcus pneumoniae
a polysaccharide capsule, toxins such as hemolysins, IgA protease, neuraminidase, and hyaluronidase
What type of hemolysis does Strep pneumo have and what do the colonies look like
Strep Pneumo has a large well-defined area of alpha hemolysis, the colonies are umblicate with highly mucoid =, glistening colonies, older colonies have a collapsed center giving it the appearance of a penny/coin with a raised rim “water drop” colony
What type of infections do strep pnuemo cause
MOPS Meningitis, Otitis, Pneumonia (THE MOST COMMON), and Sinusitis
Where is strep pnuemo located
Strep Pnuemo is common as normal flora in the upper respiratory tract
What other infections can step pneumo be involved in
Endocarditis, Peritonitis, and Hemolytic uremic syndrome
What type of cocci is Strep pneumo
Gram positive diplococci
Is strep pneumonia Optochin resistant or sensitive
It is optochin sensitive making it ‘P’ disk positive
Is strep pnuemo Bile + or -
It is bile +
How can the strep pneumo capsule be seen
with a quelling reaction
What is a common occurrence of Strep Pneumo
Rust colored sputum
How is strep pneumo screened for penicllin
an oxacillin disc is used to screen for penicillin sensitivity >20mm=sensitive
Is there a vaccine for strep pneumo
there is a vaccine for strep pneumo called a polyvalent vaccine & it is recommended for children under 2 years old
What is Group D streptococcus
Group D is strep Bovis and equinus and it is known as the SBSE complex
What type of hemolysis does Group D strep have
Alpha, beta, and gamma hemolysis
Is Group D strep resistant or sensitive to optochin
Group D strep is resistant to optochin making it ‘P’ disk negative
Is Group D strep bile esculin + or -
it is BE +
Is Group D strep 6.5% NaCl - or +
no growth at 6.5% making it 6.5% NaCl negative
Is Group D resistant or sensitive to penicillin
sensitive to penicillin which makes it different from enterococcus species
