Chapter 16: Aerobic Gram-Positive Bacilli

Question 1

What are the general characteristics of aerobic gram-positive bacilli?

Answer 1

Large diverse group of organisms, readily isolated from water and soil.

Question 2

What species is the most significant pathogen among Corynebacterium?

Answer 2

Corynebacterium diphtheriae

Question 3

What disease does Corynebacterium diphtheriae cause?

Answer 3

Diphtheria

Question 4

What are the characteristics of Corynebacterium species?

Answer 4

• Free-living saprophytes
• Resistant to drying
• Catalase positive
• Nonmotile
• Gram-positive, non–spore-forming rods
• Arranged in palisades

Question 5

How is diphtheria transmitted?

Answer 5

Acquired by droplet spray, aerosol or hand-to-mouth contact.

Question 6

What are the symptoms of diphtheria?

Answer 6

• Incubation period of 2 to 4 days
• Low-grade fever
• Malaise
• Mild sore throat
• Tough white to gray pseudomembrane

Question 7

What are systemic effects of the diphtheria toxin?

Answer 7

• Affects kidneys
• Affects heart
• Affects nervous system
• May cause demyelinating peripheral neuritis

Question 8

What is the treatment for diphtheria?

Answer 8

• Administer antitoxin
• Use antibiotics to clear the infection

Question 9

What culture characteristics are used for identifying Corynebacterium?

Answer 9

• Loeffler’s serum agar
• Cystine-tellurite blood agar (CTBA)
• Modified Tinsdale medium

Question 10

What is the Elek’s test used for?

Answer 10

Testing for toxin production by Corynebacterium diphtheriae

Question 11

Fill in the blank: Toxin production by C. diphtheriae is inversely proportional to _______.

Answer 11

iron availability

Question 12

What opportunistic infections can C. amycolatum cause?

Answer 12

• Prosthetic joint infections
• Sepsis
• Endocarditis

Question 13

What is the primary virulence factor of Listeria monocytogenes?

Answer 13

Hemolysin (Listeriolysin O)

Question 14

What is the typical source of human infection by Listeria monocytogenes?

Answer 14

• Dairy products
• Processed meats
• Contaminated cantaloupes

Question 15

What are the clinical infections associated with Listeria monocytogenes in adults?

Answer 15

• Septicemia
• Meningitis
• Endocarditis

Question 16

What are the cultural characteristics of Listeria monocytogenes?

Answer 16

• Grows well on sheep blood agar and chocolate agar
• Produces a narrow zone of hemolysis

Question 17

What type of motility is associated with Listeria monocytogenes?

Answer 17

Umbrella motility

Question 18

What is the treatment for infections caused by Erysipelothrix rhusiopathiae?

Answer 18

Drainage and surgery

Question 19

What are the culture requirements for Erysipelothrix rhusiopathiae?

Answer 19

Grows on blood or chocolate agar with CO2

Question 20

What type of bacteria is Gardnerella vaginalis?

Answer 20

Short, pleomorphic gram-positive rod or coccobacillus

Question 21

What is the main infection associated with Gardnerella vaginalis?

Answer 21

Bacterial vaginosis (BV)

Question 22

What is the primary laboratory diagnosis method for Listeria monocytogenes?

Answer 22

Microscopic morphology and cultural characteristics

Question 23

What is a significant characteristic of Nocardia species?

Answer 23

Aerobic, gram-positive filamentous rods, weakly acid-fast.

Question 24

What type of infections do Nocardia species primarily cause?

Answer 24

Pulmonary infections and cutaneous infections

Question 25

What is the identification method for Nocardia?

Answer 25

Microscopy, substrate hydrolysis, antimicrobial susceptibility profile

Question 26

What is the treatment for Nocardiosis?

Answer 26

Surgery and antibiotics, resistant to penicillin

Question 27

What disease does Bacillus anthracis cause?

Answer 27

Anthrax

Question 28

What is a key feature of Bacillus species?

Answer 28

Gram-positive large rods with endospores

Question 29

True or False: Bacillus species are predominantly pathogenic.

Answer 29

False

Question 30

What type of pathogen is Bacillus anthracis?

Answer 30

Facultative intracellular pathogen ## Footnote Fatal if untreated, causes diarrhea, weight loss, malabsorption, arthralgia, and abdominal pain.

Question 31

What are the characteristics of Bacillus species?

Answer 31

* Gram-positive large rods with 'empty' spaces * Endospores highly resistant to heat, drying, and chemicals * Catalase positive ## Footnote Most are saprophytic and isolated as contaminants.

Question 32

What disease does Bacillus anthracis cause?

Answer 32

Anthrax ## Footnote A disease primarily affecting livestock.

Question 33

How do humans acquire Bacillus anthracis infection?

Answer 33

By contamination of wound or ingestion/inhalation of spores.

Question 34

What is the morphology of Bacillus anthracis?

Answer 34

Large, spore-forming, gram-positive bacilli ## Footnote Spores are viable for over 50 years.

Question 35

What are the virulence factors of Bacillus anthracis?

Answer 35

* Polypeptide capsule * Potent exotoxin * Edema factor (EF) * Protective antigen (PA) * Lethal factor (LF)

Question 36

What is the incidence of Bacillus anthracis infection?

Answer 36

Very low, fewer than five cases per year.

Question 37

What is Woolsorter's disease?

Answer 37

Pulmonary anthrax acquired through inhalation of spores.

Question 38

What are the symptoms of pulmonary anthrax?

Answer 38

* Mild fever * Fatigue * Malaise * Sudden respiratory distress * Disorientation * Coma * Death ## Footnote Symptoms last less than 24 hours from onset to death.

Question 39

What is gastrointestinal anthrax?

Answer 39

Acquired by ingestion of contaminated raw meat. ## Footnote Symptoms include abdominal pain, nausea, anorexia, vomiting, and sometimes bloody diarrhea.

Question 40

What is injectional anthrax?

Answer 40

Acquired by direct injection of endospores into tissue. ## Footnote Commonly associated with injection drug use.

Question 41

What is the microscopic morphology of Bacillus anthracis?

Answer 41

Large, square-ended gram-positive rods with a bamboo appearance.

Question 42

What is the colonial morphology of Bacillus anthracis on blood agar?

Answer 42

Nonhemolytic, raised, large, grayish-white colonies with irregular, fingerlike edges. ## Footnote Described as 'Medusa head' or 'beaten egg whites'.

Question 43

How can Bacillus anthracis be differentiated from Bacillus cereus?

Answer 43

Bacillus anthracis is nonmotile, produces lecithinase, and exhibits a string of pearls morphology when exposed to penicillin.

Question 44

What is the treatment for anthrax?

Answer 44

Most isolates are susceptible to penicillin; ciprofloxacin is FDA-approved for treatment.

Question 45

What is the incubation period for B. cereus diarrheal syndrome?

Answer 45

8 to 16 hours.

Question 46

What symptoms are associated with B. cereus emetic form?

Answer 46

* Abdominal cramps * Vomiting ## Footnote Incubation period is 1 to 5 hours and resolves in 9 hours.

Question 47

What infections can B. cereus cause in immunosuppressed hosts?

Answer 47

* Endophthalmitis * Panophthalmitis * Keratitis * Meningitis * Septicemia * Osteomyelitis

Question 48

What are common Bacillus species that are usually contaminants?

Answer 48

* B. subtilis * B. licheniformis * B. circulans * B. pumilus * B. sphaericus

Question 49

List non-spore-forming, nonbranching, catalase-positive bacilli.

Answer 49

* Corynebacterium diphtheriae * Listeria monocytogenes

Question 50

List non-spore-forming, nonbranching, catalase-negative bacilli.

Answer 50

* Gardnerella vaginalis

Question 51

List non-spore-forming, branching, aerobic Actinomycetes.

Answer 51

* Nocardia spp.

Question 52

What are spore-forming, nonbranching, catalase-positive bacilli?

Answer 52

* Bacillus anthracis * Bacillus cereus