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Block 7 week 2 > Bacterial and Fungal Infections - Kozel > Flashcards

Bacterial and Fungal Infections - Kozel Flashcards

1
Q

What are the general features of Bacillus spa?

A
  1. gram pos rods
  2. areobes and facultative anaerobes
  3. spore forming
  4. 200 species
  5. B. anthraces and B. cereus are clinically important
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2
Q

Name two microbes that are spore forming.

A
  1. clostridium spp

2. bacillus spp

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3
Q

Are Bacillus bacteria encapsulated?

A

Yes. They have a polypeptide capsule (unusual - most are polysaccharide) that provides protection against phagocytosis. This capsule induces protective immunity in the host. Capsule genes are carried on a plasmid.

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4
Q

What toxins does the Bacillus species produce?

A
  1. They produce A-B type toxins. The A is the active portion and the B is the binding portion
  2. The toxin produced has PA or protective antigen, LF or lethal factor OR EF or edema factor
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5
Q

What is protective antigen?

A

Protective antigen is the binding portion of the A-B toxin produced by the Bacillus species. It binds cellular receptors and facilitates uptake of EF or LF - two other toxins produced by Bacillus. This antigen induces protective immunity.

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6
Q

What is lethal factor?

A

Lethal factor is an active component of toxin produced by Bacillus. Lethal factor is a protease that produces cell death. It is important in the pathology of inhalation anthrax.

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7
Q

What is Edema factor?

A

Edema factor is an active component of toxin produced by Bacillus. Edema factor is an adenylate cyclase that produces edema. It is important in the pathology of cutaneous anthrax.

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8
Q

Bacillus anthracis causes several clinical diseases. What are they?

A
  1. cutaneous anthrax
  2. gastrointestinal anthrax
  3. inhalation anthrax
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9
Q

Describe cutaneous anthrax.

A
  1. follows inoculation with B. anthracis spores
  2. presents with a painless papule that progresses to ulcer and then to a malignant pustule with a necrotic black eschar
  3. cutaneous form rarely progresses to a systemic form
  4. often seen with veterinarians due to their animal contact
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10
Q

Describe gastrointestinal anthrax.

A
  1. follows ingestion of spores of B. anthracis
  2. presents with local infection that may spread to systemic disease
  3. systemic symptoms are flu-like
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11
Q

Describe inhalational anthrax.

A
  1. follow inhalation of spores of B. anthracis
  2. spreads from lungs to regional lymph nodes and then becomes systemic
  3. causes hypotension, pulmonary edema, massive bacteremia and acute fatal toxic shock
  4. may have prolonged incubation period
  5. fatal if untreated
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12
Q

How is B. anthracis infection identified in the laboratory?

A
  1. specimen is taken from blood or eschar material
  2. specimen can be directly examined - gram stain of blood often positive, are gram-pos rods in chains. Capsule can also be stained.
  3. specimen can be grown on blood agar
  4. can identify by PCR and other specialized tests
  5. Bacillus spa are ubiquitous so just growing a culture may not be helpful. The Laboratory Response Network is equipped to test samples for B. anthracis specifically
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13
Q

Describe the epidemiology and control of anthrax.

A
  1. primarily a disease of herbivores
  2. not communicable
  3. humans normally infected by exposure to animals or animal products - called wool sorter’s disease
  4. potential for bioterrorism
  5. vaccine for humans and animals available
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14
Q

What is the vaccine for anthrax called?

A
  1. AVA - acellular vaccine adsorbed, has shown efficacy in wool sorter’s disease but has many issues
  2. animal vaccine is live vaccine
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15
Q

How is anthrax treated?

A
  1. main treatment is ciprofloxacin, also doxycycline can be given
  2. once there is massive toxin production, treatment is ineffective
  3. there is potential for monoclonal antibodies to protective antigen
  4. phrophylaxis in exposed individuals - ciprofloxacin or doxycycline for 40 days and vaccination with AVA
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16
Q

What is a problem in treating anthrax with Ciprofloxacin?

A

Cipro has many toxic side effects and can cause tendonitis and GI disturbances.

17
Q

What are the general features of the Clostridium genus?

A
  1. gram pos rods
  2. anaerobic
  3. spore forming
  4. ubiquitous in soil, water and sewage
  5. normal flora of human and animal GI tract
  6. produce numerous toxins
  7. C. perfringens is a clinically important species
18
Q

Describe C. perfringens.

A
  1. grows rapidly in tissues unlike other Clostridium species

2. Produces many enzymes and toxins such as alpha toxin and enterotoxin

19
Q

What is Alpha toxin?

A

Alpha toxin is a major lethal toxin associated with gas gangrene - produced by C. perfringens. It lyses numerous types of host cells and leads to massive hemolysis. Also called Lecithinase.

20
Q

What is enterotoxin?

A

This toxin is a superantigen produced by C. perfringens. It is released when cells undergo sporulation. This causes altered membrane permeability with loss of fluids and ions. It is associated with C. perfringens mediated food poisoning.

21
Q

What types of infections are caused by C. perfringens?

A
  1. soft tissue infections - cellulitis and myonecrosis
  2. food poisoning
  3. necrotizing enteritis
22
Q

Describe myonecrosis.

A
  1. also called gas gangrene
  2. caused by spores that are introduced by trauma or surgery
  3. causes muscle necrosis, shock and renal failure and is intensely painful
23
Q

Describe C. perfringens mediated food poisoning.

A
  1. follows ingestion of contaminated meat
  2. causes abdominal cramps and watery diarrhea
  3. enterotoxin is produced in the intestines
24
Q

Describe necrotizing enteritis mediated by C. perfringens.

A
  1. follows ingestion of enterotoxin (Beta toxin) -especially associated with ingestion of contaminated pork with sweet potatoes which allow toxin to get to GI tract
  2. causes necrotizing destruction of jejunum
25
Q

Describe the laboratory identification of C. perfringens.

A
  1. specimen is taken from fluid at site of infection
  2. can directly examine specimen and look for gram pos rods
  3. can culture - rapid anaerobic growth on agar or blood culture broth
  4. if taking specimen due to food poisoning then do immunoassay for enterotoxin in stool - must distinguish infection from colonization
26
Q

Describe the epidemiology of C. perfringens.

A
  1. ubiquitous in soil, water and human GI tract

2. often infection due to traumatic injury followed by contamination with spores

27
Q

How is C. perfringens infection treated?

A
  1. soft tissue infections - must treat rapidly (treated mortality is 40-100%), surgical debridement of infected tissue, high dose of penicillin + clindamycin
  2. gas gangrene can be prevented by proper wound care
  3. food poisoning - treat symptoms, antibiotics not effective
28
Q

What are the general features of Borrelia burgdorferi?

A
  1. weakly gram neg
  2. motile spirochetes
  3. can be grown in culture but have complex nutritional requirements
  4. several species cause disease but B. burgdorferi is only species in N. America
29
Q

What is the disease caused by B. burgdorferi?

A

Lymes disease.

30
Q

What are the clinical features of Lyme disease?

A
  1. three stages to infection
  2. post infection associated with post-lyme disease syndrome which has symptoms similar to chronic fatigue syndrome and fibromyalgia
  3. presents with erythema migrans - a characteristic rash that looks like a bull’s eye at site of tick bite
  4. may also present with acrodermatitis chronica atrophicans - bluish red lesions seen in late disseminated disease, more common in Europe
  5. long incubation period - 3-30 days after initial infection may see erythema migrans

Block 7 week 2 (5 decks)

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