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Microbiology II > Gram Positive Cocci > Flashcards

Gram Positive Cocci Flashcards

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Biology 101 flashcards
1
Q

Catalase Positive Genera

A
  • Micrococcus and related genera
  • Staphylococcus
  • Rothia (Stomatococcus) mucilaginosus

Staphylococcus genera are primary clinical significance

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2
Q

Micrococcus, Rothia, and related Genera Characteristics

Morph, habitat, transmission, clinical

A

G+ cocci in tetrads
Grow on routine media
Colonies may be pigmented
Habitat: skin, mucosa, oropharynx
Transmission: endogenous
Clinical significance: rarely complicated, low virulence

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3
Q

Staphylococcus General Characteristics

Morph, atmosphere, habitat, transmission, clinical

A

G+ cocci in clusters
Grow on routine media
Type: facultative anaerobe
Habitat: nares, axillae, vagina, pharynx, skin surfaces
Transmission: spread of endogenous flora, person to person
Clinical significance: virulence factors, species variation

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4
Q

S. Epidermidis

Predisposing factors? virulence?

A

Most frequently encountered staph. - moist body surfaces

Predisposing factors: catheters, medical implants, prosthetics, immune status

Major virulence factor: biofilm

Other: a lot are healthcare-acquired, bloodstream, endocarditis

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5
Q

Biofilm

What problems?

A
  • Biofilm cells are more resistant to antibiotics
  • More resilient to phagocytosis than free floating bacteria
  • Many diseases associated with biofilms
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6
Q

Catheter Associated Infection

A
  • Microbe moves from catheter skin entry side to catheter tip within bloodstream
  • Inside the catheter hub into the body
  • Hematogenous spread
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7
Q

Staphylococcus lugdunensis

Where, problems, virulence, special test?

A
  • Lower body, axillae
  • Community and healthcare infections
  • Skin, soft tissue
  • Endocarditis, bacteremia, prosthetic devices

Major virulence factor: biofilm
Extracellular clumping factor positive

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8
Q

Staphylococcus saprophyticus

Where, clinical, virulence

A

GI tract - age season dependent
- UTIs in young, sexually active women
Major virulence factor: adhere to epithelial cells in urogenital tract

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9
Q

Staphylococcus hominis, Staphylococcus haemolyticus

where,what is special about this? Virulence?

A

Colonize axillae and pubic areas
S. haemolyticus second most common coag- associated with infections: most virulent coag- staphs

Major virulence factor: biofilm or adhesion

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10
Q

Staphylococcus capitis

Where, virulence

A

Colonize scalp, forehead after puberty
Major virulence factor: biofilm or adhesion

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11
Q

Staphylococcus aureus General

The apex! Raaagh

A

Most significant staph species
- Mild to life-threatening infections
- Can be on almost any specimen
- Healthcare associated infection
- Increasing antimicrobial resistance problem

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12
Q

S. aureus: Virulence Factors

A
  • Structural components
  • Exotoxins
  • Enzymes
  • Biofilm
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13
Q

S. aureus: Structural Components

Virulence factors, 4 things

A

Capsule: slime layer, resists chemotaxis, phagocytosis, and facilitates adherence to other bodies
Peptidoglycan: resists phagocytosis
Teichoic acid/lipoteichoic acid: binds to fibronectin, ahesion to human cells
Protein A: binds IgG, inhibits antibody mediated clearance

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14
Q

S. aureus: Exotoxins

Virulence factor, 4 of them

A

Enterotoxins: superantigens that stimulate T cells and release cytokines, heat stable, involved in food poisoning
- interfere with adaptive immune system, not processed by antigen presenting cell, activates T cell directly, cytokine storm = fever and shock
- Cytolytic toxins: lyses different human cells (RBCS, WBCs, tissue damage)
- Exfoliative toxins: epidermolytic, epidermal cells slough off
- Toxic shock syndrome toxin: superantigen, penetrate mucosal barriers, systemic effects

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15
Q

S. aureus: Enzymes

A

Hyaluronidase: digest hyaluronic acids in host tissue, spreads microbes
Staphylokinase (fibrinolysin): dissolves fibrin clots, spreads microbes
Lipases: hydrolyzes lipids, microbe can survive in sebaceous areas, spread more

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16
Q

S. aureus Infection: Impetigo

A
  • Intraepidermal vesicles with exudate, leaking and crusting lesion
  • Common in children
  • Moist areas, warm, highly contagious
  • Clears on its own or with antibiotics
17
Q

S. aureus Infection: Folliculitis

A
  • Inflammation/infection of hair follicles
  • Small papule lesions, pustulates with white/yellow centers
  • At points of friction like thighs, groin
18
Q

S. aureus Infection: Furuncles

Boils

A
  • Spreads from follicle to follicle, tissue around it too
  • Redness, firm, painful with drainage
  • Neck, face, breasts, buttocks, friction and sweat
19
Q

S. aureus Infection: Carbuncle

Multiple boils

A
  • Infection a lot deeper, into fat, has multiple drainage sites
  • Fever and chills maybe
  • Don’t really heal by itself, drain and antibiotic treatments
20
Q

S. aureus Infection: Cellulitis

A
  • Acute inflammatory, subcutaneous tissue, redness, heat, tenderness
  • Lower body, legs, skin
  • Over 90% of cases are because of S. aureus
  • Develop rapidly (24-48 hours) from minor injury to severe septicemia
21
Q

S. aureus Infection: Scalded Skin Syndrome

Toxin mediated!!

A

“Ritter disease”
- Abrupt onset, redness, inflammation around mouth and spreads over whole body in 2 days
- Blisters soon after
- Young children, 5% mortality
- Spontaneous recovery, 7 day period of infection

22
Q

S. aureus Infection: Toxic Shock Syndrome

Toxin mediated!!!

A
  • Rare, may be fatal
  • Localized growth in vagina or wound, then releases toxins
  • Fever, chills, rash
  • 5-65% fatality if incorrect antibiotic is given
23
Q

S. aureus Infection: Food Poisoning

Toxin mediated!!!!

A
  • Quick onset, 1-6 hours
  • Heat stable: reheating food won’t get rid of toxin even after bacteria dies
  • Poor food handling
  • Vomiting, nausea, cramps, diarrhea
24
Q

Antibiotic Resistance in S. Aureus

A
  • Methicillin-resistant S. aureus (MRSA)
  • Vancomycin-intermediate S. aureus (VISA)
  • Vancomycin-resistant S. aureus (VRSA)
  • Coag- staphs can be resistant to a variety of antimicrobials
25
Q

Community Acquired Methicillin Resistant S. aureus (CA-MRSA)

How do you get it?

A
  • Person who hasn’t been recently hospitalized or had a procedure
  • Skin infections, otherwise healthy people
  • Athletes, military, children, MLM, prisoners
  • Skin contact, crowded conditions, openings in skin, bad hygiene
  • Contaminated surfaces
  • Drug injections
26
Q

Distinguishing CA-MRSA from Healthcare MRSA

A
  • Location during/before diagnosis (hospital or outpatient?)
  • No history of MRSA or colonization
  • No medical history recently
  • No catheters or things breaking skin
27
Q

Strain Characteristics of CA-MRSA

A

Virulence factors:
- susceptible to wider range of antibiotics than HA-MRSA
- Exotoxin Pantone-Valentine leucocidin (PVL) = skin and soft tissue infection and necrotizing pneumonia

28
Q

Treatment and Prevention

A
  • Antibiotics for Staphylococcs
  • Surgical removal
  • Good hygiene
  • Food safety
  • Healthcare precautions
29
Q

Laboratory Diagnosis

Methods

A
  • Microscopy
  • Culture, biochemical
  • Instrumentation
30
Q

Bloodstream Infections: Diagnosis and Results

What to do, diff between contaminant and pathogen?

A

Collection
- Collection appropriate amount for age
- Prior to antibiotics/at fever spikes
Results
Contaminant: normal skin flora, multiple organisms, blood culture organism not the same as infection site
Pathogen: same organism growing at differen collections, S. aureus, S. pyogenes, S. agalactiae, A. pneumoniae, E. coli, Candida

Microbiology II (16 decks)

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