Chapter 7: Corynebacterium and Listeria

Question 1

What is the general classification of Corynebacterium and Listeria?

Answer 1

Gram-positive rods

Non-spore forming

Question 2

What is the main target group for Corynebacterium and Listeria?

Answer 2

Pediatric age group

Question 3

Corynebacterium diphtheria is responsible for what?

Answer 3

diptheria: colonizes the pharynx, forming a graying pseudomembrane composed of fibrin, leukocytes, necrotic epithelial cells, organisms cells
Exotoxin goes into bloodstream and damages heart and neural cells by interfering with protein synthesis

Question 4

Dark inflammatory exudate in child’s pharynx. Darker and thicker than strep throat. What is the cause? What should be done?

Answer 4

Diphtheria
Scarping off will cause bleeding and systemic absorption
TELL yoUR InTErn not to “LOAF around”
- swabs for culture on potassium tellurite agar and Loeffler’s coagulated blood serum media

Question 5

In order for Corynebacterium diptheria to have the deadly toxin, what must occur?

Answer 5

Must be lysogenized by a temperate bacteriophage which codes for the diphtheria exotoxin

Question 6

What composes the diptheria exotoxin?

Answer 6

B subunit - binds

A subunit - blocks protein synthesis by inactivating EF2 (translation of eucaryotic mRNA into proteins)

Question 7

Diphtheroids

Answer 7

Normal inhabitants of water, soil and the human skin and mucous membranes
Corynebacterium, arcanobacterium, brevibacerium, microbacterium

Question 8

What complications do Diphtheroids cause?

Answer 8

Contamination of cultures
CA-infections
Nosocomial infections
Hospitalized pts: surgical wound infections, catheter and prosthetic device related infections, native and prosthetic valve endocarditis

Question 9

Rhodococcus equi

Answer 9

formerly known as Corynebacterium equi
Gram positive, aerobic nonmotile, bacillary bacteria (rod-like that can grow long, curved, clubbed and even form branching short filaments)
Infect: cattle, sheep, deer, bears, dogs and cats

Question 10

What does Rhodococcus equi cause if inhaled by humans?

Answer 10

If human is immunocompromised, it can form a necrotizing penumonia that looks like Mycobacterium tuberculosis or Nocardia

Infection forms infiltrates, single or multiple nodules that cavitate and pleural effusions

Question 11

What are upper lobe lung nodules and cavities that form air-fluid levels characteristic of?

Answer 11

Rhodococcus infection

Question 12

What are upper lung nodules and cavities that rarely form air-fluid levels characteristic of?

Answer 12

Mycobacterium tuberculosis

Question 13

Rhodococcus may stain _____ ____ ___,

Answer 13

partially acid-fast

Question 14

Listeria monocytogenes

Answer 14

small facultatively anaerobic, non-spore forming gram-positive rod
1-5 flagella
can grow in low temeratures

Question 15

What is the major virulence factor of Listeria monocytogenes?

Answer 15

Listeriolysin O: allows it to escape the phagolysosomes of Mo and avoid intracellular killing

Question 16

What groups does Listeriosis affect the most?

Answer 16

pregnant women, neonates, elderly and immunocompromised

Question 17

Pregnant women and Listeria

Answer 17

Infection usually occurs in third trimester when cell-mediated immunity decreases 
Meningitis unusual for mother 
Infects fetus and 22% --> death
Premature and active infection 
Avoid cheese and cold cuts

Question 18

Fetus and neonate, Listeria

Answer 18

Infection acquired in utero or vaginal colonization
Infection by vaginal birth results in neonatal meningitis presenting abt 2 weeks post-partum

20% cause of all neonatal meningitis

Question 19

What three bacteria are responsible for most meningitis acquired by neonate?

Answer 19

Listeria, E coli, and Group B strep

Question 20

What is the most common cause of meningitis in people older than 50?

Answer 20

Pneumococcus

Question 21

What is the second most common cause of meningitis in people over 50?

Answer 21

Listeria

Question 22

What is the most common cause of meningitis in pts with lymphoma, on corticosteroids or receiving organ transplantation?

Answer 22

Listeria

Question 23

What is the main reason why Listeria does no invade immune competent host?

Answer 23

Listeria is a resistant organisms and able to hide out and survive withing certain immune cells (Mo and neutrophils)
It can survive outside or within cells
In immune competent hosts, the immune system can release factors that activate Mo so the organisms can be destroyed (cell-mediated immunity)

Question 24

Since listeria can survive outside or within a cell, that makes it….

Answer 24

a facultative intracellular organism