chapter 7: corynebacterium and Listeria

Question 1

clinical presentation of corynebacterium diphtheriae

Answer 1

colonizes on the pharyx and forms grayish pseudomembrane

frome here releases powerful exotoxin that goes into the bloodstream and damages the heart and CNS

Question 2

appropriate culture medium for C diphtheriae

Answer 2

potassium tellurite agar: colonies become gray to black within 24 hours

loeffler’s coagulated blood serum: rod shaped pleomorphic bacteria

Question 3

antitoxin and c diphtheriae

Answer 3

inactivates circulating toxin which has not reached tissue

Question 4

DPT vaccine

Answer 4

need this even if child infected by c dip becasue being infected does not always result in immunity for future infection

DPT stands for diphtheria, pertussis (whooping cough), and tetanus

Question 5

how are group A beta hemolytic strep and corynebacterium toxins related

Answer 5

for the toxins to be released they need to be lysogenized by a temperate bacteriophage which codes for the diphtheria exotoxin

Question 6

C diphtheriae exotoxin subunit and function

Answer 6

B subunit binds to target cells and allows A subunit to enter

A subunit blockes protein synthesis by inactivationg EF2 (involved in translation)
-“human antibiotic” that can be lethal bc of damage to heart and neural cells

Question 7

other coryneform bacteria called diphtheroids

Answer 7

corynebacterium
aracnobacterium
brevibacterium
microbacterium

nosocomial pathogens
if postive in micro lab report doesn’t mean that there is an infefction bc normal inhabitants on human skin and mucous membranes

• can lead to infection in hospitalized patients
• pretty resistant to antibiotics

Question 8

rhodococcus equi

Answer 8

infects animals like sheep, deer, bears, dogs, cats

can form necrotizing pneumonia (that looks like mycobacterium tuberculosis or nocardia) in immunocompromised person

Question 9

rhodococcus equi clinical pearl

Answer 9

upper lobe lung nodules and cavities that form air fluid levels are characteristic
-stain partially acid fast
upper lung cavities caused by mycobacterium tuberculosis rarely form air fluid levels

Question 10

listeria monocytogenes virulence factor

Answer 10

listeriolysin O

allows escape of the phagolysosomes of macrophages and avoids intracellular killing

Question 11

Listeriosis LIST:

Answer 11

pregnant women
neonates
meningitis in the elderly and immunocompromised

Question 12

listeriosis list pregnant women

Answer 12

pregnant women

• infection at 3rd trimester,
• when cell mediated immunity has decreased
• avoid soft cheese and cold cuts bc these can be contaminated

Question 13

listeriosis list neonates and fetus

Answer 13

can be contracted in utero, or during vaginal birth
later = neonatal meningitis presenting about 2 weeks after pregnacny

-

Question 14

3 bacteria respnsible for most meningitis acquired by baby coming out of birth canal

Answer 14

listeria monocytogenes
e coli
group b streptococcus

Question 15

listeriosis list old and immunocompromised people

Answer 15

second most common cause of meningitis after pneumococcus in people over 50

Question 16

listeria is a facultative intracelluar organism

role with this and cell mediated immunity

Answer 16

in immune compotent host immune system can release factors that activate the macrophage that the listeria is liviving in and kill it (cell mediated immunityh)

• neonates and immunosuppressed pts cannot activate phagocytic cells–>infect meninges
• infects pregnant women bc immune system depressed