Chapter 7: Corynebacterium and Listeria Flashcards
What is the general classification of Corynebacterium and Listeria?
Gram-positive rods
Non-spore forming
What is the main target group for Corynebacterium and Listeria?
Pediatric age group
Corynebacterium diphtheria is responsible for what?
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
Dark inflammatory exudate in child’s pharynx. Darker and thicker than strep throat. What is the cause? What should be done?
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
In order for Corynebacterium diptheria to have the deadly toxin, what must occur?
Must be lysogenized by a temperate bacteriophage which codes for the diphtheria exotoxin
What composes the diptheria exotoxin?
B subunit - binds
A subunit - blocks protein synthesis by inactivating EF2 (translation of eucaryotic mRNA into proteins)
Diphtheroids
Normal inhabitants of water, soil and the human skin and mucous membranes
Corynebacterium, arcanobacterium, brevibacerium, microbacterium
What complications do Diphtheroids cause?
Contamination of cultures
CA-infections
Nosocomial infections
Hospitalized pts: surgical wound infections, catheter and prosthetic device related infections, native and prosthetic valve endocarditis
Rhodococcus equi
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
What does Rhodococcus equi cause if inhaled by humans?
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
What are upper lobe lung nodules and cavities that form air-fluid levels characteristic of?
Rhodococcus infection
What are upper lung nodules and cavities that rarely form air-fluid levels characteristic of?
Mycobacterium tuberculosis
Rhodococcus may stain _____ ____ ___,
partially acid-fast
Listeria monocytogenes
small facultatively anaerobic, non-spore forming gram-positive rod
1-5 flagella
can grow in low temeratures
What is the major virulence factor of Listeria monocytogenes?
Listeriolysin O: allows it to escape the phagolysosomes of Mo and avoid intracellular killing
What groups does Listeriosis affect the most?
pregnant women, neonates, elderly and immunocompromised
Pregnant women and Listeria
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
Fetus and neonate, Listeria
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
What three bacteria are responsible for most meningitis acquired by neonate?
Listeria, E coli, and Group B strep
What is the most common cause of meningitis in people older than 50?
Pneumococcus
What is the second most common cause of meningitis in people over 50?
Listeria
What is the most common cause of meningitis in pts with lymphoma, on corticosteroids or receiving organ transplantation?
Listeria
What is the main reason why Listeria does no invade immune competent host?
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)
Since listeria can survive outside or within a cell, that makes it….
a facultative intracellular organism
