Human pathogens staph vs strep Flashcards
Staphaurex Kit (Latex Agglutination Test)
purpose?
What does it consist of?
Positive rxn?
*Identifies Staphylococcus using the plasma coagulase kit
*Consists of polystyrene latex particles coated with fibrinogen and IgG. If Staphylococcus is present, free coagulase will react with the latex particles, causing strong agglutination (clumping)
Staphaurex procedure
1.Shake latex bottle and dispense on drop onto reaction card for each culture being tested
2.Pick up a large amount of culture (about 6 colonies)
3.Carefully mix culture with latex reagent
4.Gently rock card for about 20 seconds and examine for agglutination
Name the 3 major species in humans (for staphylococcus
S.aureus, S.epidermis, S.saprophytics
Effects of S.aureus
*Pathogenic
*Often causes skin lesions and abscesses, causing issues such as boils and acne
*Can also infect internal organs, causing issues such as pneumonia and inflammation of internal organs
Effects of S.epidermis
*Generally harmless, but can be an opportunistic pathogen that causes skin lesions and endocartitis
Effects of s.saprophyticus
*Generally harmless, but has been found in some urinary tract infections
What is the purpose of the coagulase test? Which enzyme is used and it convert what into what? What indicates a positive reaction? What is the general process? What tube does it occur in?
*Used to identify S. aureus
*Enzyme which converts fibrinogen to fibrin, which bacteria can use to prevent degradation from non-specific immune responses
*Sample is inoculated into a tube with citrated plasma. Formation of a clot is positive.
DNase test, which microbe produces this, what does this enzyme break down, where is it grown in, what indicates a positive sample?
*Coagulase positive staph. generally also produce DNase
*DNase is an enzyme that breaks down foreign DNA
*Sample is grown on media containing DNA. 0.1% toluidine blue is added to identify DNase activity.
*Positive samples will produce a pink halo
What is Novobiocin used to distinguish? What plate is used, what is positive reaction?
*Used to distinguish between S. epidermis and S. saprophyticus
*Mueller-Hinton agar plate is seeded with test organism, then a 30 μg novobiovin antibiotic disk is applied
*S. aureus and S. epidermis are highly sensitive to the antibiotic, but S. saprophyiticus is not.
MSA
7.5% Nacl
Turns yellow, looks for microbes that can ferment mannitol
Streptococcus
Responsible for?
All members are gram posiive/negative? Require which media?
*Responsible for a wide variety of diseases
*All members are gram-positive and require enriched media to grow
Streptococcus
Classified by?
Extremely virulent due to?
*Classified by:
1.hemolytic activity
2.serologic classification of Lancefield
*20 serogroups A-V, omitting I and J
*Based on the presence of an antigen called the C substance
*Extremely virulent due to the wide variety of extracellular metabolites produced, such as hemolysins, leukocidins, hyaluronidase, and nucleases
Streptococcus= Groups A, B, C, and D are usually implicated in human infections
Group A is what species of microbes? What problems is t responsible for
*collectively Streptococcus pyogenes.
*Responsible for a variety of respiratory infections and skin disorders
Streptococcus= Groups A, B, C, and D are usually implicated in human infections
Group B is what species of microbes? Found where
*Group B consists of β-hemolytic streptococci found in the vaginal mucosa
Streptococcus= Groups A, B, C, and D are usually implicated in human infections
Group C is what species of microbes? Found where?
*Group C are β-hemolytic and commonly causes throat infections among other diseases
