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Microbiology > Staphylococci > Flashcards

Staphylococci Flashcards

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Biology 101 flashcards
1
Q

S. Aureus

A
  • Catalase +
  • Coagulase +
  • Beta- hemolytic
  • Found on Skin & Mucous
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2
Q

Beta- hemolytic

A

Organism causes hemolysis of RBC on agar plate

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3
Q

S. Aureus Virulence Factors (Protective proteins)

A
  • Protein A
  • Coagulase
  • Hemolysins
  • Leukocidins
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4
Q

S. Aureus Tissue Destroying Proteins

A
  • Hyaluronidase
  • Staphylokinase
  • Lipase
  • Protease
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5
Q

Protein A

A

Binds Fc of IgG and prevents opsonization

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6
Q

Coagulase

A

Leads to fibrin formation protecting from phagocytosis

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7
Q

Hemolysins

A

Alpha- lyses RBC and neutrophils

Beta- “hot-cold” lysis. Sphingomelinase

Delta- surfactant that disrupts cell membranes

gamma- lysis of various cells

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8
Q

Leukocidins

A

Destroys WBC’s

PVL-alters cation permeability resulting in WBC destruction, eventually caues increase in abscess formation

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9
Q

S. Aureus Treatment

A

Penicillinase-resistant Penicillins: Nafcillin (V) and dicloxacillin (Oral)

First generation cephalosporins: Cefazolin (IV) cephalexin (oral)

Clindamycin

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10
Q

S. Aureus Treatment if MRSA

A

Vancomycin
Daptomycin
Clindamycin
Linezolid

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11
Q

Hyaluronidase

A

Spreading factor

Breaks down proteoglycans in connective tissue

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12
Q

Staphylokinase

A

Lyses formed fibrin clots

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13
Q

Lipase

A

Degrades fats and oils which often accumulate on surface of our body. Facilitates colonization of sebaceous glands

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14
Q

Protease

A

Destroys tissue proteins

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15
Q

S. Aureus Exotoxin Assault Weapon: Exfoliatin

A

Diffusible exotoxin that causes the skin to slough off (scalded skin syndrome)

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16
Q

S. Aureus Exotoxin Assault Weapon: Enterotoxins

A

Heat stable exotoxins that cause food poisoning, result in vomiting and diarrhea

17
Q

S. Aureus Exotoxin Assault Weapon: Toxic Shock Syndrome toxin (TSST-1)

A

Causes Toxic Shock syndrome

Superantigen that binds to MHC class II molecules on APC (macrophages). This causes a massive T- cell response and outpouring of cytokines that results in toxic shock syndrome

18
Q

Toxic Shock Syndrome

A

Tampons when left too long stimulate S. Aureus to release TSST-1 that penetrates the vaginal mucosa and is a stimulator of TNF and IL-1.

*Can also be caused by infected sutures in surgical wounds, cutaneous and subcutaneous infections, infections following childbirth or abortion

Symptoms:

  • Septic Shock
  • Fever
  • Diffuse Erythematous Rash
  • Vomiting + Diarrhea
  • Peeling of Palms and Soles
19
Q

Gastroenteritis

A

Disease caused by Exotoxin release

Staph can grow in food and produce an exotoxin. Eating the food that contains a pre-formed toxin simulates peristalsis of the intestine and causes nausea, vomiting, diarrhea, abdominal pain (Lasts 12 to 24 hours)

20
Q

Scalded Skin Syndrome

A

neonates and children under age four

Exfoliative Toxin A & B establishes localized infection and releases a diffusible toxin that exerts distant effects.

Causes cleavage of middle epidermis with sheets of skin peeling off to reveal moist red skin beneath.

21
Q

Pyoderma

A

Skin disease that is pyogenic

Causes pus filled pustules in the back of the baby.

22
Q

Furuncle (boil)

A

Skin disease caused by infection of hair follicles resulting in localized accumulation of pus and dead tissue

  • Red, pus-filled lumps that are tender, warm, and extremely painful
  • Yellow or white point at center can be seen when the boil is ready to drain
23
Q

Carbuncle

A

Abscess larger than boil with more openings draining pus onto the skin

Can develop anywhere but more common on the nape of the neck

24
Q

Diseases caused by direct organ invasion by S. Aureus

A
  • Pneumonia (Effusions & Empyema)
  • Meningitis, Cerebritis, Brain Abscess
  • Osteomyelitis
  • Acute Endocarditis (Destructive infection of hear valves with onset of high fever, chills and myalgias- causes valvular destruction and embolism to the brain or lung)
  • Septic Arthritis (closed infection of joint cavity. Patients complain of acute painful swollen going with decrease range of motion)
  • Skin Infections
    • Impetigo
    • Cellulitis
    • Furuncles and Carbuncles
    • Wound infections
25
Q

Impetigo

A

Contagious

Occurs on face especially around mouth

Small vesicles lead to pustules that crust over and beome honey-colored, wet and flakey

26
Q

Cellulitis

A

Deeper infection of the cells, tissue becomes hot, red shiny and swollen

27
Q

Methicillin-Resistant Staph. Aureus (MRSA)

A

Most Staph are penicillin resistant because they secrete penicillinase.

Methicillin, Nafcillin and other penicillinase-resistant penicillins are not broken down by penicillinase so they enable you to kill most strains of S. Aureus.

MRSA is a strain that has multi-drug resistance even against methicillin and nafcillin. Resistance is mediated by mecA. Can be treated with Vancomycin

28
Q

mecA

A

Encodes for penicillin binding protein 2A that can take over the job of peptidoglycan cell wall assembly when the normal PBP is inhibited.

29
Q

CA- MRSA

A

Community Acquired MRSA

Common among:

  • Sports Teams
  • Correctional Facilities
  • Daycares
  • Dorms
  • Men who have sex with Men

Presents as: Spider bites, cellulitis, skin infections since associated with PCL toxin that has a propensity to form skin absecess

30
Q

S. Epidermidis

A

Catalase +

Coagulase -

Novobiocin Susceptible

Virulence Factor: Adheres to prosthetic devices. Forms a biofilm (protects organisms from antimicrobial agents, removal of foreign bodies necessary)

HIGHLY RESISTANT TO ANTIBIOTICS

Treatment: Vancomycin (since multiple Resistance)

Clinical: Infections of prosthetics, IV lines, UTI’s

31
Q

S. Saprophyticus

A

Catalase +

Coagulase -

Resistant to Novobiocin

Clinical: UTI’s in young women

Treatment: Penicillin

32
Q

S. Lugdunesis

A

Colonizes in inguinal area

PYR and Ornithine positive

Microbiology (2 decks)

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