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M2 Classes > Immunology and Infections > Flashcards

Immunology and Infections Flashcards

1
Q

Organism that causes:

Toxin-mediated (food poisoning, toxic shock syndrome); cutaneous (carbuncles, folliculitis, furuncles, impetigo, wound infections); other (bacteremia, endocarditis, pneumonia, empyema, osteomyelitis, septic arthritis)

A

S. aureus

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2
Q

Organism that causes:

Bacteremia; endocarditis; surgical wounds; urinary tract infections; opportunistic infections of catheters, shunts, prosthetics devices, and peritoneal dialysates

A

S. epidermidis “outer skin”

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3
Q

Organism that causes:

Endocarditis; arthritis; bacteremia; opportunistic infections; and urinary tract infections

A

S. lugdunensis

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4
Q

Organism that causes:

Urinary tract infections; opportunistic infections

A

S. saprophyticus

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5
Q

Organism that cause:

Bacteremia; endocarditis; bone and joint infections; urinary tract
infections; wound infections; and opportunistic infections

A

S. hemolyticus

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6
Q

Mechanism of the coagulase enzyme:

A

n plasma binds to serum factor which converts fibrinogen to fibrin clot

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7
Q

Describe the blood agar test for S. aureus.

A

Golden colonies due to carotenoid pigments formed in growth. Coagulase binds to prothrombin and promotes the conversion of fibrinogen to the fibrin clot.

Versus
Coagulase negative staphylococcus

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8
Q

What virulence factor of S. aureus: Inhibits chemotaxis and phagocytosis by PMNs; inhibits
proliferation of mononuclear cells

A

Capsule

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9
Q

What virulence factor of S. aureus : Facilitates adherence to foreign bodies e.g. catheters, grafts, prosthetic valves and shunts

A

Slime Layer

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10
Q

What virulence factor of S. aureus: Provides osmotic stability; stimulates production of endogenous pyrogen (endotoxin-like activity); leukocyte chemoattractant (abscess formation by aggregation of PMNs); inhibits phagocytosis

A

Peptidoglycan

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11
Q

Enzymes that catalaze contruction of peptidoglycan layer Targets of beta-lactam antibiotics

A

PBP: Penicillin -Binding Proteins

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12
Q

Describe the peptidoglycan layer

A

Many cross-linked layers of glycan chains with 10-12 alternating subunits of N- acetylmuramic acid (NAM) and N-acetylglucosamine (NAG)
Unlike gram negatives Makes cell more rigid

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13
Q

What is MRSA?

A

Methicillin-resistant S. aureus (MRSA)

Bacterial resistance to methicillin through acquisition of mecA that codes for novel penicillin-binding protein PBP2’

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14
Q

What virulence factor of S. Aureus: Binds to fibronectin

A

Techoic Acid

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15
Q

What virulence factor of S. aureus: Inhibits antibody-mediated clearance by binding IgG1, IgG2, and IgG4 Fc receptors; leukocyte chemoattractant; anticomplementary

A

Protein A

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16
Q

What virlence factor of S. aureus: Binds fibrinogen and converts to insoluble fibrin causing staphylococci to clump or agglutinate

A

Clumping Factor (bound coagulase)

MSCRAMM (microbial surface components recognizing adhesive matrix molecules)

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17
Q

Describe how the toxic virulence factor S. aureus that are categorized as toxins.

A

Toxic for many cells, including leukocytes, erythrocytes, fibroblasts, leukocytes, macrophages, and platelets
P-V leukocidin found in <5% of hospital acquired MRSA but in all strains of community acquired MRSA

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18
Q

List the different types of toxins found in S. aureus.

A

Cytotoxins

  • Alpha toxin
  • Beta toxin
  • Delta toxin
  • Gamma toxin -Panton-Valentine leukocidin (Dermo-necrotic)
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19
Q

What toxins act as Serine proteases that split desmoglein I (desmosome) for forming the intercellular bridges in the stratum granulosum epidermis? What disease to they cause?

A

Exfoliative toxins (ETA, ETB)

Staphyloccal scalded skin syndrome

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20
Q

Toxins that are known as Superantigens (stimulate proliferation of T cells and release of cytokines); stimulate release of inflammatory mediators in mast cells; increasing intestinal peristalsis and fluid loss, as well as nausea and vomiting
Enterotoxin A: food poisoning, B: staphylococcal pseudomembranous enterocolitis, C and D: found in contaminated milk products

A

Enterotoxins

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21
Q

Define superantigens:

A

(stimulate proliferation of T cells and release of cytokines)

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22
Q

What are some of the different types of enterotoxins from S. aureus and what type of diseases do they cause?

A

Enterotoxin A: food poisoning,

Enterotoxin B: staphylococcal pseudomembranous enterocolitis,

Enterotoxin C and D: found in contaminated milk products

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23
Q

This toxin is a superantigen (stimulates proliferation of T cells and release of cytokines); produces leakage or cellular destruction of endothelial cells

A

Toxic shock syndrome toxin-1

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24
Q

What is the mechanism of Superantigens?

A 
Toxins bind to class II major histocompatibility
complex (MHC II) on macrophages which interact with Variable Regions of β subunit of specific T-Cell Receptors (VβTCR)
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25
Q

What are the chemical mediators of superantigen interactions?

A

Macrophages release cytokines (IL-1β and TNF-α) and T cells (IL-2, IFN-γ and TNF-β)

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26
Q

What chemical mediators are the primary mediators of hypotension and shock in Toxic shock syndrome?

A

TNF-α and TNF-β hypotension and shock

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27
Q

What chemical mediators are the primary mediators of fever?

A

IL-1β

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28
Q

What cell-free coagulase reacts with globulin plasma factor (coagulase-reacting factor) to form staphylothrombin that converts fibrinogen to fibrin? This is a virulence factor.

A

Coagulase

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29
Q

What virulence factor of S. aureus: Hydrolyzes hyaluronic acids in connective tissue, promoting the spread of staphylococci in tissue?

A

Hyaluronidase

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30
Q

What S. aureus virulence factor: Dissolves fibrin clots

A

Fibrinolysin

Staphylokinase

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31
Q

What S. aureus virulence factor: Hydrolyzes lipids, ensure survival in sebaceous areas of body

A

Lipases

32
Q

What virulence factor of S. aureus: Hydrolyzes DNA

A

DNAse

33
Q

What organism causes: Scalded skin syndrome (Ritter Syndrome): disseminated desquamation of epithelium in infants; blisters with no organisms or leukocytes; Positive Nikolsky sign Cutaneous blisters.

A

S. aureus…

34
Q

List the different types of supperative infections:

A
  1. Impetigo
  2. Bullous impetigo
  3. Folliculitis
  4. Furuncles or boils
  5. Carbuncles
  6. Bacteremia and endocarditis
  7. Pneumonia and empyema
  8. Osteomyelitis
  9. Septic arthritis
    
35
Q

List two toxin mediated infection of Staphylococcal Diseases?

A

1) Scaled skin syndrome (Ritter’s Syndrome)
2) Food poisoning
3) Toxic shock syndrome

36
Q

What toxin mediated condition is described as:
disseminated desquamation of epithelium in infants; blisters with no organisms or leukocytes.

Positive Nikolsky sign: Blister has no bacteria. If test the blister you will not see any bacterial growth.

Cutaneous blister: Skin displacement…

A

Scalded skin syndrome (Ritter Syndrome)

Toxin:”Exfoliant” Toxin

37
Q

What is a Positive Nikolsky sign?

A

A blister that has no bacteria. If test the blister you will not see any bacterial growth.

38
Q

What type of organism causes this condition:

8 persons who attended a retirement party developed nausea (94%), vomiting (89%), and diarrhea (72%) 3-4 hours after eating after consumption of food contaminated with heat-stable enterotoxin (processed ham) with resolution within 24 hours

What is the name of the disease condition?
What toxin mediates this type of disease?

A

Staphylococcal organisms;

Disease: Food poisoning

Enterotoxin type A.
Food handler had cooked ham at home night prior and served next day cold: allowed to produce enterotoxin type A.

39
Q

A patient: All cultures negative except throat and vagina for S. aureus.
3rd day desquamation on face, trunk, extremities, then peeling of palms and soles on day 14 then stabalized by day 17.
High morbidity without prompt antibiotic therapy and elimination of the focus of infection.

What is the name of the disease described?

A

Toxic Shock Syndrome.

40
Q

What suppurative infections are described as : localized cutaneous infection characterized by pus-filled vesicle on an erythematous base then eventually turn into honey colored crusts?

What bacteria cause these infections?

A

Impetigo

Staphyloccoccal organisms. This is also called

41
Q

Describe the supperative infections is described as localized form of SSSS, Erythema does not extend beyond border of blister that are culture positive, Nikolsky sign not present?

SSSS = staphylococcal scalded skin syndrome.

A

Bullous impetigo

42
Q

What is the difference between Scalded skin syndrome (Ritter Syndrome) and Bullous impetigo?

A

Scalded skin syndrome (Ritter Syndrome): Nikolsky sign present / no bacteria

Bullous impetigo:Nikolsky sign not present

43
Q

What disease describes impetigo involving hair follicles.

A

Folliculitis,

If at base of eyelid: it is called a stye

44
Q

Describe this staphylococcal diseases / Suppurative Infections as a large, painful, pus-filled cutaneous nodules, drain spontaneously after surgical incision

A

Furuncles or boils

45
Q

A coalescence of furuncles with extension into the subcutaneous tissues and evidence of systemic disease (fever, chills and bacteremia).

A

Carbuncles

46
Q

What type of infection does this patient have: 21-year-old woman with history of IV drug abuse, HIV (CD 4 count 400 cells/mm3 who had 1 week history of fever, chest pain and hemoptysis.
Physical exam: 3/6 pansystolic murmur (endocarditis) and rhonchi in both lung fields.

A

Bacteremia and endocarditis:

The spread of bacteria into the blood from a focus of infection, usually skin infection; endocarditis characterized by damage to the endothelial lining of the heart

47
Q

Patient A: Bacteremia and endocarditis:
Chest X-ray: multiple bilateral cavitary lesions (pulmonary abscesses/septic emboli)

If the patient presents with culture of blood and sputum positive for methicillin-suspcetible S. aureus (MSSA) what would you treat the patient with?

A

Treated with Oxacillin for 6 weeks

48
Q

What condition describes:

Patchy infiltrates with consolidation and abscess formation in the lungs

A

Pneumonia and empyema

49
Q

Staphylococcus organism causes this disorder:
destruction of bones, particularly the metaphyseal area of long bone (Brodie abscess in adults). What is the name of the condition and what virulence factor is responsible for the spread of the disease?

A

Hyuranidase enzyme…

Destroy’s connective tissue…

50
Q

A patient mentioned sudden onset of an infection with no injury. The condition is described as painful erythematous joint with collection of purulent material in the joint space
Usually in adults receiving intraarticular injections or have mechanically abnormal joints. You take a sample and find a purulent aspiration.

What should be on your differential diagnosis?

A

Septic arthritis

51
Q

Describe this condition:

erythema and pus at site of traumatic or surgical wound; infections with foreign bodies can be caused by S. aureus and coagulase-negative staphylococci

A

Wound infection

52
Q

Describe this condition and the labs.

Dysuria (pain on urination) and pyuria (pus in urine) in young, sexually active women (S. saphrophyticus), in patients with urinary catheters (other coagulase-negative staphylococci), or following seeding of the urinary tract by bacteria (S. aureus)

A

Urinary Tract Infections:

Urinalysis = see white blood cells.
Catheters: coagulase negative staph
E.Coli is the most common cause of a UTI

53
Q

Describe this condition caused by coagulase negative staph:

chronic inflammatory response to bacteria coating a catheter or shunt

A

Catheter and shunt infections:

54
Q

Describe this condition caused by coagulase negative staph:

chronic infection of device characterized by localized pain and mechanical failure of the device. Fever and leukocytosis not prominent and blood cultures usually negative

A

Prosthetic device infections:

55
Q

List 4 common infections caused by coagulase negative staph:

A
  1. Wound infections
  2. Catheter and shunt infections
  3. Prosthetic device infections
  4. UTIs
56
Q

When see Pansystolic mumur: Differential: should include …

A

Endocardidits…

57
Q

Diagnostic tools for coagulase negative staphylococcus:

A

Diagnosis:

Microscopy useful for pyogenic infections but not blood infections or toxic-mediated infections

Staphylococci grow rapidly when cultured on nonselective media

THIS MEDIA SELECTS FOR Staph Aureus…Selective media (e.g. mannitol-salt agar-mannitol is fermented by S. aureus but not other staphylococci) can be used to recover S. aureus in contaminated specimens, also 7.5% sodium chloride (inhibits growth of most other organisms)
Nucleic acid amplification tests allow direct detection S. aureus (eg nasal MRSA PCR)

58
Q

What type of organisms: Cannot grow in presence of oxygen eg. Clostridium species

A

Obligate (strict) anaerobes

59
Q

What type of organisms: Grow in either presence or absence of oxygen eg. staphylococci, E. coli

A

Facultative anaerobes

O2 used as terminal O2 accepter. Most common infections. Generally referred to as aerobes.

60
Q

What type of organisms grow poorly aerobically but grow distinctly better under reduced oxygen tension
eg. Campylobacter jejuni

A

Microaerophilic

61
Q

Name: Gram-positive Rods, spore-forming

A

Clostridium spp.

62
Q

Name: Gram-positive Rods, non-spore-forming

A

Actinomyces spp.
Propionibacterium spp.
Lactobacillus spp.

63
Q

Name: Gram-positive Cocci

A

Streptococcus spp.
Peptostreptococcus
Peptococcus

64
Q

Name: Gram-negative Bacilli

A

Bacteroides spp.
Fusobacterium spp.
Prevotella spp.

65
Q

Name: Gram-negative Cocci

A

Veillonella spp.

66
Q

Name: Non-Spore-forming Anaerobic gram- positive cocci

A

Peptostreptococcus species

Normal flora , oral cavity, poly microbial infections

67
Q

Name: Non Spore-forming Anaerobic gram- positive rods

A

Actinomyces spp.

Propionibacterium spp. (associated with Acne and coag. neg. staph, prosthetic devices, gram + rods, in short chains or pairs; grows in 2-5 days.)

Lactobacillus spp. (GI and GU tract, probiotics, occasional associated with human infections..Isolated in urines or blood.)

68
Q

Name: Anaerobic Gram-negative Bacilli

A

Bacteroides spp.
Fusobacterium spp.
Prevotella spp. (not covered)

69
Q

Name: Anaerobic Gram-negative Cocci

A

Veillonella spp. (will not discuss in class)

70
Q

Define characteristics of Anaerobic infections:

A

Anaerobic infections are characterized by suppuration, abscess formation and tissue destruction

71
Q

List Different types of anaerobic infections:

A

Infections in which anaerobes are commonly involved:

  • Head and neck: odontogenic, chronic sinusitis, neck space infection
  • Pleuropulmonary: aspiration pneumonia, lung abscess
  • CNS: focal pyogenic infections (brain abscess, subdural empyema)
  • Intra-abdominal: peritonitis, intra-abdominal abscess
  • Female genital tract: Pelvic inflammatory diseases
  • Soft-tissue: decubitus ulcer (pressure sore), fasciitis, myonecrosis
72
Q

Name 2 poly-microbial types of infections:

A

1) Brain abscess

2) Pressure ulcers

73
Q

Key Clinical Indication of an anaerobic infection:

A
  • Anaerobic Infections
  • Foul odor of discharge
    Infections secondary to human or animal bites
    –Location of infection in proximity to a mucosal surface Major anatomical areas with predominant anaerobic flora - Oropharyngeal area
  • Female genital tract
  • GI tract
  • Classical clinical picture of anaerobic infections such as gas gangrene, lung abscess etc
    Gas in tissues or discharges
    Tissue necrosis, gangrene or abscess formation
74
Q

Name: Aerobic, non-spore- forming, gram- positive rod

A

Listeria spp

75
Q

Describe characteristics of gram negative non-sporeforming organisms:

A

Non-sporeforming

  • Motile and non-motile
  • Growth under aerobic and/or anaerobic conditions (facultative anaerobes)
  • Growth on non-selective(bloodagar) or selective (MacConkey agar) media
    - Simple nutritional requirements
  • Glucose fermentation,nitratereduction, lactose and

non-lactose fermentation
- Catalase positive,oxidase negative, cytochrome oxidase negative


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