MICRO EXAM 2 CH14 Flashcards
When do you see arrangement morphology on media?
Direct smear
When do you not see arrangement morphology on media?
Indirect smear
Which Staphylococcus spp. is coagulase pos?
S. aureus
Which Staphylococcus spp. is coagulase neg?
S. epidermidis
S. saprophyticus
S. haemolyticus
S. legdunesis
Characteristics of Staphylococcus spp.?
Non-motile
Non-spore forming
Non-encapsulated
Aerobic
Oxidase Neg
Bacitracin R (Taxo A)
Primary reservoir of S. aureus?
Nares; also vagina, pharynx and skin surfaces
Mode of transmission of S. aureus?
Traumatic introduction
Direct Contact
Inanimate objects
Indueling devices
Immune response defects
What are the 6 virulence factors of S. aureus?
Enterotoxins
Toxic Shock Syndrome
Toxin 1 (TSST)
Exfoliatin toxin
Cytolytic toxins
Extracellular enzymes
Protein A
Enterotoxins
Vomiting and diarrhea/food poisoning
TSST
Superantigen stimulating T-cell proliferation and cytokines.
Seen in nearly all menstruation associated TSS.
Exfoliatin toxin
Epidermolytic toxin
Scalded skin syndrome
Cytolytic toxins
4 hemolysis (alpha beta, gamma, delta)
1 Leukocidin
What is the toxin for leukocidin called?
Panton-Valentine Leukocidin (PVL)
Causes cutaneous infections, necrotizing pneumonia.
Extracellular eznymes
Hyaluronidase
Lipase
Staphylocoagulase
Protein A
Cell wall component
Binds to Fc on IgG
Inhibits phagocytosis
How is S. epidermidis predominantly aquired?
HAI via catheters, shunts, and heart valves.
Types of skin/wound infections caused by S. aureus?
Folliculitis
Furuncles (boils)
Carbuncles
Impetigo
Scalded skin
syndrome/Ritter disease
Abscess
What does S. epidermidis need to become pathogenic?
Biofilm
What source does S. saprophyticus come from?
Urine
Significance of S. lugdunensis?
Contains mecA gene that makes it resistant to methicillin.
Mocks S. aureus
What media does Staphylococci grow easily on?
BAP or thioglycollate
What other medias can you grow Staphylococci on?
MSA, CNA, PEA and chromagar
Pos thioglycollate in broth result?
Cloudy with streamers
Direct gram stain results?
GPC in clusters and WBC
Colony morphology of S. aureus?
Round
White to golden creamy
Beta-hemolysis
Colony morphology of S. epidermidis?
Small-medium sized
Gray to white
Non-hemolytic
Colony morphology of S. saprophyticus?
Medium sized
White to slight yellow
What biochemical test is used to differentiate Staph from Strep?
Catalase
How many seconds after beginning catalase test do you read results?
20 sec
What would give you a false pos catalase test?
Gouging the BAP media onto slide when performing catalase test. RBC react with H2O2.
What are the 3 types of coagulase tests?
Slide Coagulase
Tube Coagulase
Rapid Coagulase
What does slide coagulase test detect?
Cell-bound clumping
What does tube coagulase test detect?
Free coagulase/staphylocoagulase
What does rapid coagulase test detect?
Clumping factor and protein A
What Staph sp. is coagulase pos?
S. aureus
What test can differentiate S. saprophyticus from other Staph spp.?
Novobiocin susceptibility test
What is the result on novobiocin test for S. saprophyticus?
If zone of inhibition is less than 16mm (resistant)
Related genus to Staphylococcus?
Micrococcus
Biochemical test results for micrococcus?
Catalase Pos
Coagulase Neg
What biochemical test is used to detect Micrococcus?
Microdase disc
What antibiotic is resistant to S. aureus?
Penicillin (MRSA)
Why is S. aureus resistant to penicillin (methicillin)?
Beta lactamase enzyme
What virulence factor causes oxacillin resistance?
MecA gene
Review If erythro R and clinda S, what do you do?
Perform D-test
Review Pos D-test results for erythro and clinda?
No ZOI for erythro, D shape ZOI for clinda
Review Neg D-test results for erythro and clinda?
No ZOI for erythro, circular ZOI for clinda
Rapid methods for detecting MRSA and MSSA?
RT-PCR and/or MALDI-TOF
