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MCIM 224 > 23 Bacterial Pathogens II - Skin and Soft Tissue Infections, GI Infections > Flashcards

23 Bacterial Pathogens II - Skin and Soft Tissue Infections, GI Infections Flashcards

(60 cards)

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1
Q

The skin is dry and salty. What kinds of bacteria can survive these conditions?

A
  1. Staphylococcus
  2. Streptococcus
    (both gram pos)
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2
Q

Purpose of surface layer of skin?

A

Physical barrier against microbes

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3
Q

This bacteria is part of the normal flora of skin and nasal passages in 10-15% of ppl.

A

Staphylococcus aureus (gram pos)

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4
Q

How do S. aureus bacteria cause skin infections?

A
  1. They migrate down hair follicles into sebaceous glands
  2. They multiply
  3. Inflammation occurs
  4. WBCs are recruited
  5. Small pus-filled abscesses form
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5
Q

How can S. aureus skin infections present themselves on the skin?

A
  1. Folliculitis > small red bumps involving a SINGLE follicle per bump
  2. Furuncles (“boils”) > when infection of a single follicle spreads to nearby tissues (redness, swelling, +/- pain)
  3. Carbuncles > when several furuncles merge
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6
Q

Reservoirs: How many people are asymptomatic carriers of S. aureus?

Where does S. aureus tend to reside?

A

10-15% of ppl

S. aureus tends to reside on the SKIN and in the NASAL PASSAGES

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7
Q

Transmission: How can S. aureus be transmitted?

A
  1. Direct contact
  2. Fomites (objects/surfaces that can carry an infection)
  3. Respiratory droplets
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8
Q

Prevention: How can S. aureus be prevented?

A
  1. Good hand hygiene (esp. after nasal contact and esp. around elderly pts)
  2. Chlorhexidine > “de-colonize” pts
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9
Q

Treatment: How can S. aureus that has infiltrated the skin be treated?

A
  1. Surgically drain furuncles/carbuncles of pus

2. Antibiotics

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10
Q

Describe “scalded skin syndrome” (How it’s caused, and what its characterized by)

A

Caused by some strains of S. aureus

S. aureus produces “exfoliatin” toxin > this exotoxin destroys the material holding the epidermis to the dermis > S. aureus grows at site of infection > toxin is released into blood and spreads further

It’s characterized by redness and soft blisters that cover 20-100% of the body.

The skin peels away > wet, scalded-looking area remains > looks like a burn

This is a potentially fatal disease

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11
Q

Who is most susceptible to scalded skin syndrome?

A

Children < 2 years old

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12
Q

How to treat scalded skin syndrome? (3)

A
  1. Protective isolation
  2. Antibiotics
  3. Removal of dead skin tissue
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13
Q

Besides scalded skin syndrome, what other diseases can be caused by Staph. aureus?

A
  1. Endocarditis
  2. Bacteremia
  3. Pneumonia
  4. Osteomyelitis
  5. Toxic shock syndrome
  6. Gastrointestinal distress
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14
Q

T or F: All strains of S. aureus cause all diseases.

A

F

Not all strains cause all diseases

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15
Q

Biggest concerns w/ S. aureus? (2)

A
  1. Increased numbers of methicillin-resistant strains of S. aureus (MRSA)
  2. Increasing rates of “community-acquired” MRSA
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16
Q

About how many Staph. aureus infections are now caused by MRSA strains?

A

~60%

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17
Q

What’re ‘enteric’ bacteria?

A

Bacteria who use water/food to cause GI infections

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18
Q

Differentiate b/w food poisoning and food infections:

A

Food poisoning: Occurs when a TOXIN is consumed w/ food/water > rapid onset of symptoms

Food infections: Occurs when LIVE BACTERIA are consumed w/ food/water > slower onset of symptoms

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19
Q

How many hours does it take to show symptoms of…

  1. food poisoning?
  2. food infection?
A
  1. 4-6h

2. 18-24h

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20
Q

Name of S. aureus exotoxin that causes food poisoning?

A

Enterotoxin A

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21
Q

How will heating food help w/ Staph aureus colonization? Why might this not be enough to make the food safe?

A

Heating food to 100ºC WILL kill S. aureus, but it DOES NOT destroy the toxins that it produces (Enterotoxin A)

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22
Q

How long does it take to recover without treatment from an affliction by enterotoxin A of S. aureus?

A

~18 hours

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23
Q

How does enterotoxin A cause diarrhea, nausea, and vomiting?

A

Diarrhea: toxin acts on gut epithelial cells > fluid absorption is prevented

Nausea/vomiting: toxin stimulates gut receptors

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24
Q

How to prevent Staph. aureus contamination in food?

A
  1. Proper refrigeration

2. Known carriers of S. aureus should be careful when handling food

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25
What's the "enterohemorrhagic" strain of E. coli? What does ea. component of the strain designation mean?
O157:H7 O157: Type of LPS "O" side chain H7: Type of flagella antigen
26
Is E. coli O157:H7 ingestion considered to be a food infection or food poisoning?
Food infection
27
Where does E. coli O157:H7 usually reside?
Intestinal tract of cattle
28
Anything contaminated with WHAT can potentially lead to an infection with E. coli O157:H7?
Cow feces (since E. coli O157:H7 resides in its intestinal tract)
29
Pathogenesis of E. coli O157:H7 infection?
E. coli attaches to gut epithelia via pili > they multiply > they release exotoxins (Verotoxin) > these toxins damage intestinal tract lining by killing the epithelial cells > bloody diarrhea (among others)
30
Symptoms of E. coli O157:H7 infection? When do they get better?
1. Nausea 2. abdominal cramping 3. BLOODY diarrhea Symptoms get better after 5-7 days
31
How's E. coli O157:H7 diagnosed?
1. Look for tell-tale signs (e.g. bloody diarrhea) | 2. Stool culture
32
How should E. coli O157:H7 be treated? How should it NOT be treated? Why?
Treated w/ fluid replacement therapy Do not treat w/... 1. antidiarrheals > prolongs E. coli stay in gut 2. antibiotics > bacteria release more verotoxin when they die > worse symptoms
33
Possible rare complication of E. coli O157:H7?
Hemolytic Uremic Syndrome
34
What is Hemolytic Uremic Syndrome?
A rare complication of E. coli O157:H7 infection | -Verotoxin enters blood > RBCs destroyed + kidney damage
35
2 ways E. coli O157:H7 is controlled?
1. vaccination of cattle who act as reservoirs | 2. clean/cook food adequately
36
Diff b/w the toxin of S. aureus and E. coli O157:H7?
The Enterotoxin A of S. aureus is not destroyed by cooking, but the toxin of E. coli IS destroyed by cooking.
37
Diff b/w O157 and K12 strains of E. coli? (2)
``` O157 = pathogenic K12 = non-pathogenic ``` O157 has ~200 extra genes not found in K12
38
Name of bacteria that cause cholera?
Vibrio cholerae
39
How does Vibrio cholerae gets transmitted?
via fecal-contaminated water
40
V. cholerae gram stain and shape?
Gram -ve, curved rod
41
How do V. cholerae cause symptoms?
Attach to intestinal wall via pili and adhesion proteins > produce exotoxin during growth > causes hypersecretion of water and ions from gut cells into intestinal tract > severe diarrhea
42
T or F: V. cholerae exotoxin and the exotoxin of E. coli O157:H7 are similar in that they both damage the gut epithelia, causing similar symptoms.
F E. coli exotoxin causes epithelial damage, but V. cholerae's exotoxin does not cause epithelial damage
43
T or F: The cholera bacteria invades the gut's epithelial cells.
F
44
What happens to the blood of a person infected w/ cholera?
Increases in viscosity
45
Therapy req'd for inds with cholera?
Oral rehydration therapy
46
4 ways to prevent cholera?
1. Water purification 2. Reduce chances of contact b/w drinking water and sewage 3. Don't eat raw foods washed in contaminated water 4. Get the Dukoral vaccine
47
For how long does the cholera vaccine protect you?
Up to two years
48
Who should get the cholera vaccine?
Ppl traveling to high-risk areas
49
Most common virulence factor that cause gastrointestinal infections?
Bacterial exotoxins
50
T or F: Diagnosis based on symptoms alone is often enough to identify the bacterial species that cause gastrointestinal infections
F Need to do cultures for bacterial identification
51
Gram stain and bacterial shape of helicobacter pylori?
Gram neg Rod (also a motile bacterial species)
52
How many ppl carry H. pylori as part of their normal flora?
80%
53
Where do H. pylori tend to be found?
Mucosal lining of stomach and upper GI tract
54
What enzyme is produced by H. pylori?
Urease
55
What does urease do? How does this benefit H. pylori?
It breaks down urea to ammonia and CO2 > neutralizes stomach acids > allows H. pylori to survive
56
How does H. pylori cause stomach ulcers?
Bacteria attaches to mucosal layer's epithelial cells in stomach > causes localized inflammation > immune cells arrive > stomach epithelial and mucus-producing cells are destroyed > stomach gets exposed to gastric acid > ULCERS
57
How to diagnose H. pylori?
Invasive: Endoscopic biopsy > culture Non-invasive: "Urea Breath Test"
58
How does the Urea Breath Test work?
Ingest soln w/ isotope carbon-labeled urea > urea gets converted to CO2 and NH3 by H. pylori > CO2 is breathed out can get detected
59
What did old stomach ulcer therapies assume?
That stomach ulcers were caused by excessive stomach acid
60
Current therapies for stomach ulcers that're understood to be caused by H. pylori?
Antibiotics + acid-suppressing drugs

MCIM 224 (25 decks)

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