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Micro > Gram + Cocci > Flashcards

Gram + Cocci Flashcards

1
Q

Describe the morphology of cocci

A 
Spherical cells
Purple beadies - grape like clusters due to pattern of cell division
Gram positive
Non motile
Non spore forming
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2
Q

Describe the metabolic characteristics of cocci

A 
Facultative anaerobes (can use oxygen or not)
Catalase positive (make catalysts... It bubbles! Not really doing anything...)
Ferment sugars
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3
Q

Describe characteristics of staphylococcus aureus in micro lab

A 
Golden pigment (Aureus = gold)
Coagulase positive (unique to staph aureus!)
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4
Q

Virulence factors of staph. Aureus

A

Protein A - binding antibodies the WRONG way which coats the bacterial cell in immunoglobulin making it hard to identify (Master in Disguise!)
Exotoxins - don’t memorize all 4 (alpha, beta, delta, gamma)
Leukocidins
TSST**
Enterotoxin - if present on consumed food (heat-stable)
Exfoliatin - scalded skin syndrome

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5
Q

What is toxic shock syndrome toxin?

A

A super antigen causing massive release of cytokines (cytokine Storm) causing drastic drop in blood pressure and kidney failure!

Powerful exotoxin that stimulates tumor necrosis factor leading to necrosis

Stimulates interleukin leading to fever, rash

Originally associated with tampon use BUT also affect men and non-menstruating women

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6
Q

Name the Extracellular enzymes utilized by staphylococcus aureus

A

Coagulase

Catalase

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7
Q

Where is Staphylococci found?

A

Found as part of the normal flora and are the leading cause of wound infection (surgical and accidental)

Skin
Upper respiratory tract
Gastrointestinal tract

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8
Q

What is osteomyelitis?

A

Bone infection from staph. Aureus and commonly follows trauma

Most common in boys under 12

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9
Q

What is MRSA?

A

Staph aureus that is methicillin resistant

Hospital Acquired - pt had surgery and got wound infection or admitted for something else and since they had a weakened immune system, acquired this bacteria

Community Acquired - acquire at gym, supermarket, etc. No medical record of MRSA infection or surgeries

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10
Q

What are skin pathologies that can be caused by staph aureus?

A

Furuncles (boils) and carbuncles
Impetigo
Folliculitis
Scalded skin syndrome

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11
Q

What are characteristics of staphylococcus epidermis?

A

Coagulase negative
Opportunistic pathogen
Catheters, prosthetic joints and artificial heart valves can cause it
Frequent contaminant in blood draws because it lives on the skin

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12
Q

How do you tell the difference between staphylococcus and streptococcus?

A

Staphylococcus is catalase positive (bubbles under hydrogen peroxide) and strep will not

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13
Q

How can you isolate staphylococcus aureus?

A

Mannitol fermentation agar will ferment in the presence of staphylococcus aureus which will change the colour of the agar from red to yellow

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14
Q

What would you see with alpha hemolysis?

A

Partial hemolysis with greenish cast around colonies

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15
Q

What would you see with Beta hemolysis on an agar plate?

A

Complete lysis of blood cells creating a clear area around colonies

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16
Q

What would gamma hemolysis look like on a agar plate?

A

No lysis of blood cells

17
Q

What was Rebecca Lancefield for?

A

Lancefield Groups that divide strep by serological testing of extractable carbohydrate

18
Q

Characteristics of lactic streptococci

A

Non pathogenic
No hemolysis (gamma)
Found in milk!

19
Q

What are characteristics of enterococcus

A

Lancefield group D
Normal flora of intestinal tract (in our poop)
Different hemolysis patterns
Clinically commonly cause urinary tract infections

20
Q

Non beta-hemolytic streptococci characteristics

A

Large group of heterogenous group
No Lancefield antigen
Alpha hemolysis
May cause tooth decay
May enter bloodstream and infect a weakened heart during dental cleaning
Normal flora of the mouth and resp. Tract

21
Q

Beta hemolytic cocci characteristics

A

Lancefield groups A and B

22
Q

What are virulence factors of Lancefield Group A (streptococcus pyogenes or beta hemolytic streptococci)

A

M proteins
Hyaluronic acid capsule (sneaky)
Progenitor exotoxins - fever
Extracellular products (hyaluronidase, streptokinase, leukocidin, proteinase)

23
Q

What are pathologies that can be caused by Group A?

A

Streptococcal pharyngitis (can lead to middle ear infections and meningitis)
Streptococcal impetigo (co-infection w/staph. Aureus)
Cellulitis
Erysipelas (St. Anthony’s Fire)
Scarlet fever

24
Q

List 2 post stretococcal diseases

A

Rheumatic fever

Glomerulonephritis

25
Q

How would you treat Group A infections?

A

Penicillin for 8-10 days

Benzylpenicillin

26
Q

What are pathologies from Lancefield Group B (beta-hemolytic streptococci, s. Agalactiae)

A

Neonatal meningitis, pneumonia, sepsis in first week of life

27
Q

How would you diagnose Lancefield a group B? What would it look like on an agar plate?

A

CAMP test: weak beta hemolysis of Group B strep combines and grows with beta hemolysis of staph aureus strain
Positive test products arrow shape of strong beta hemolysis

28
Q

Where is Lancefield Group B found normally?

A

Normal flora of the female genital tract

29
Q

What makes the streptococcus pneumoniae so virulent?

A

Polysaccharide capsule

30
Q

Where does s. Pneumoniae live normally?

A

It’s part of the normal body flora

31
Q

How does infection of s. Pneumoniae begin?

A

When an invasive strain moves to the lower lungs

(Follows viral flu often and is Common in alcoholics and elderly)

Also causes meningitis in adults and osteomyelitis in children

32
Q

How would you diagnose s. Pneumoniae?

A

Gram stain sputum sample

33
Q

How would you treat s. Pneumoniae?

A

Early treatment = rapid recovery!

Penicillin
Vancomycin

34
Q

Your patient is a teacher and requires vaccinations to protect herself and her students. She asks you how to avoid getting pneumonia. What do you suggest for her?

A

PCV13 vaccination which contains 7 capsular polysaccharide antigens that account for most of the disease

35
Q

Describe the morphology of streptococci

A 
Spherical cells
Found in chains
Gram positive
Non-motile
Non-endospore forming

Micro (13 decks)

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