HRR: gram negative rods

Question 1

What is the shape and growth characteristics of Corynebacteria?

Answer 1

Corynebacteria are club-shaped, do not form spores, and exhibit aerobic growth on blood agar.

Question 2

What kind of colonies do corynebacteria form?

Answer 2

Corynebacteria form non-hemolytic colonies.

Question 3

Where can corynebacteria be found?

Answer 3

Corynebacteria are found as commensal flora on the skin, often referred to as diphtheroid.

Question 4

What is the virulence factor of corynebacteria?

Answer 4

The virulence factor is diphtheria toxin, which ADP ribosylates EF-2, blocking tRNA and thus protein synthesis.

Question 5

What encodes the DT gene?

Answer 5

The DT gene is encoded by a lysogenic bacteriophage.

Question 6

How is diphtheria toxin regulated by corynebacteria?

Answer 6

It is regulated by the corynebacterium repressor protein (DtxR), influenced by iron levels; low iron increases toxin production, while high iron decreases it.

Question 7

How is corynebacteria acquired?

Answer 7

Corynebacteria are acquired through inhalation of respiratory droplets.

Question 8

How can corynebacteria be prevented?

Answer 8

Corynebacteria can be prevented with DTP/DTAP vaccines.

Question 9

What is the clinical presentation of corynebacteria?

Answer 9

Corynebacteria are not invasive but can cause local and systemic effects of diphtheria, including fever, malaise, laryngitis, necrosis of oropharyngeal epithelial cells, and toxin-mediated myocarditis.

Question 10

How is corynebacteria diagnosed?

Answer 10

Diagnosis is primarily clinical; cultures are sent to reference labs for assay.

Question 11

How is diphtheria treated?

Answer 11

Diphtheria is treated with erythromycin and antitoxin (antibodies against DT). Skin infections may require antibacterial cleansers.

Question 12

What are the presentations of non-diphtheriae corynebacteria?

Answer 12

Non-diphtheriae corynebacteria typically cause minor skin infections.

Question 13

What is the shape and growth characteristics of Listeria?

Answer 13

Listeria are curved, beta-hemolytic on blood agar, catalase positive, can grow at refrigerator temperatures, and have flagella.

Question 14

How is listeria acquired?

Answer 14

Listeria is usually acquired through unpasteurized dairy or cold cuts.

Question 15

What happens if a pregnant person contracts listeria?

Answer 15

Transplacental and intrapartum infection can occur.

Question 16

What is the clinical presentation of listeria?

Answer 16

In most people, there are no symptoms; in the elderly, pregnant, or immunocompromised, listeria can cause meningitis and encephalitis.

Question 17

How is listeria diagnosed?

Answer 17

Listeria is diagnosed through blood and CSF culture.

Question 18

What are the virulence factors of listeria?

Answer 18

Virulence factors include intracellular growth, survival in macrophages, listerolysin O, and the actin tail.

Question 19

What is internalin?

Answer 19

Internalin induces the uptake of listeria by host cells.

Question 20

Describe listeria immunity.

Answer 20

Listeria immunity involves innate and adaptive immunity; cytokines and gamma interferon halt intracellular growth.

Question 21

How is listeria treated?

Answer 21

Listeria is treated with ampicillin and TMP/SMX.

Question 22

What are listeriae resistant to?

Answer 22

Listeriae are resistant to cephalosporins.

Question 23

What is the shape and growth characteristics of Bacillus?

Answer 23

Bacillus are rod-shaped, spore-forming, and exhibit aerobic growth.

Question 24

What is the infectious form of bacillus?

Answer 24

The infectious form of bacillus is the spores, which are highly resistant to inactivation.

Question 25

How are we infected with bacillus?

Answer 25

Infection can occur through inhalation, skin contact, or ingestion.

Question 26

What is the main threat of bacillus to humans?

Answer 26

Bacillus can be a bioterror agent.

Question 27

What are the virulence factors of bacillus?

Answer 27

Virulence factors include an anti-phagocytic capsule and a tripartite exotoxin.

Question 28

Describe the exotoxin in bacillus.

Answer 28

The exotoxin has a protective PA component, an EF component that causes edema, and an LF component that kills cells.

Question 29

Describe cutaneous anthrax.

Answer 29

Cutaneous anthrax manifests as a painless papule that progresses to an ulcer with edema and a black center.

Question 30

Describe pulmonary anthrax.

Answer 30

Pulmonary anthrax occurs after inhaling bacillus spores, leading to fever, cough, mediastinal edema, cyanosis, bacteremia, meningitis, and potentially death.

Question 31

Describe intestinal anthrax.

Answer 31

Intestinal anthrax results from ingesting bacillus spores, causing painful edema and necrosis.

Question 32

Describe bacillus cereus.

Answer 32

Bacillus cereus produces enterotoxin that causes food poisoning or ocular infection.

Question 33

How is bacillus diagnosed?

Answer 33

Diagnosis is made through culture of skin lesions, sputum, blood, and CSF.

Question 34

What does bacillus anthracis look like?

Answer 34

Bacillus anthracis appears as long chains of non-hemolytic, non-motile rods.

Question 35

What does bacillus cereus look like?

Answer 35

Bacillus cereus is beta-hemolytic and motile.

Question 36

How can we treat bacillus?

Answer 36

Cutaneous bacillus infections can be treated with doxycycline or ciprofloxacin, but pulmonary and intestinal anthrax are difficult to treat.

Question 37

How do we prevent bacillus?

Answer 37

Prevention includes ciprofloxacin if exposure is suspected and the beta anthracis vaccine, usually for military personnel.