Bacterial and Fungal Infections - Kozel

Question 1

What are the general features of Bacillus spa?

Answer 1

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

Question 2

Name two microbes that are spore forming.

Answer 2

1. clostridium spp

2. bacillus spp

Question 3

Are Bacillus bacteria encapsulated?

Answer 3

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.

Question 4

What toxins does the Bacillus species produce?

Answer 4

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

Question 5

What is protective antigen?

Answer 5

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.

Question 6

What is lethal factor?

Answer 6

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.

Question 7

What is Edema factor?

Answer 7

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.

Question 8

Bacillus anthracis causes several clinical diseases. What are they?

Answer 8

1. cutaneous anthrax
2. gastrointestinal anthrax
3. inhalation anthrax

Question 9

Describe cutaneous anthrax.

Answer 9

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

Question 10

Describe gastrointestinal anthrax.

Answer 10

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

Question 11

Describe inhalational anthrax.

Answer 11

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

Question 12

How is B. anthracis infection identified in the laboratory?

Answer 12

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

Question 13

Describe the epidemiology and control of anthrax.

Answer 13

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

Question 14

What is the vaccine for anthrax called?

Answer 14

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

Question 15

How is anthrax treated?

Answer 15

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

Question 16

What is a problem in treating anthrax with Ciprofloxacin?

Answer 16

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

Question 17

What are the general features of the Clostridium genus?

Answer 17

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

Question 18

Describe C. perfringens.

Answer 18

1. grows rapidly in tissues unlike other Clostridium species

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

Question 19

What is Alpha toxin?

Answer 19

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.

Question 20

What is enterotoxin?

Answer 20

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.

Question 21

What types of infections are caused by C. perfringens?

Answer 21

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

Question 22

Describe myonecrosis.

Answer 22

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

Question 23

Describe C. perfringens mediated food poisoning.

Answer 23

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

Question 24

Describe necrotizing enteritis mediated by C. perfringens.

Answer 24

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

Question 25

Describe the laboratory identification of C. perfringens.

Answer 25

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

Question 26

Describe the epidemiology of C. perfringens.

Answer 26

1. ubiquitous in soil, water and human GI tract | 2. often infection due to traumatic injury followed by contamination with spores

Question 27

How is C. perfringens infection treated?

Answer 27

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

Question 28

What are the general features of Borrelia burgdorferi?

Answer 28

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

Question 29

What is the disease caused by B. burgdorferi?

Answer 29

Lymes disease.

Question 30

What are the clinical features of Lyme disease?

Answer 30

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