Bacteriology-40 Corynebacteria/ Listeria Infections*

Front 1

What are some basic characteristics of Corynebacterium and Listeria

Back 1

Both are aerobic, gram positive, non-spore forming rods

Front 2

What does Corynebacterium diphtheriae primarily cause

Back 2

Diphtheria, a model for toxin-mediated bacterial diseases. Immunization with diphtheria toxoid prevents disease, and treatment with anti-toxin is therapeutic

Front 3

What can Listeria monocytogenes cause

Back 3

Typically a food-borne pathogen and can cause miscarriage and stillbirths in pregnant women, severe systemic disease in the immunosuppressed, and occasionally gastroenteritis in healthy people.
Septicemia and/or meningitis in newborns (from mother)
Serves as model for how certain bacteria move within and between cells

Front 4

What are some Corynebacteria that cause disease in humans

Back 4

Corynebacterium diphtheriae
C. ulcerans and C. pseudotuberculosis- occasionally cause disease
C. jeikeium- infections in severely immunosuppressed patients and is frequently resistant to antibiotics
C. urealyticum- UTIs and alkaline encrusted cystitis.

Front 5

What are the properties of Corynebacterium diphtheriae

Back 5

URT and skin of humans
Gram-positive, club shaped bacteria that are nonmotile, nonsporulating, and produce catalase. Bacteria arranged in Chinese letters
Biotypes gravis, mitis, and intermedius
Grey to black colonies on selective medium containing tellurite. Must notify lab
Diphtheria toxin is a major virulence factor that is only produced by some strains

Front 6

How does diphtheria in an upper respiratory tract infection present

Back 6

Characterized by sore throat, low-grade fever, and an adherent pseudomembrane on the tonsils, pharynx, and nose. Respiratory diphtheria is usually caused by toxinogenic strains. Epidemic in Russia and the Ukraine

Front 7

How does Cutaneous diphtheria present

Back 7

It usually results from infection of insect bites, wounds, or other skin lesions by C. diphtheriae. Can present with deep ulcers containing typical pseudomembranes. Cutaneous diphtheria is often caused by nontoxinogenic strains

Front 8

What are complications caused by the systemic action of diphtheria toxin

Back 8

Myocarditis and polyneuritis. The lethal dose is about 0.1 ug/kg

Front 9

Where is the gene for diphtheria toxin present

Back 9

Several tox+ corynephages, including phage Epsilon. Toxinogenic strains of C. diphtheriae are lysogenic for tox+ phages (phage conversion)

Front 10

When is toxin produced by Corynebacterium diphtheriae

Back 10

Under iron-limiting growth conditions. Toxin synthesis is inhibited by an iron-dependent repressor

Front 11

In what form is toxin secreted by Corynebacterium diphtheriae

Back 11

As a single polypeptide. It is processed by proteolysis and reduction to form fragments A and B.

Front 12

What does Fragment B of diphtheria toxin do

Back 12

Binds to receptors on the plasma membrane of susceptible cells and initiates uptake of the toxin by receptor-mediated endocytosis

Front 13

What does Fragment A of diphtheria toxin do

Back 13

Once it is transported to the cytosol it catalyzes the transfer of adenosine diphosphate ribose from (NAD) to EF-2. The ADP-ribosylation of EF-2 causes inhibition of protein synthesis and death of the intoxicated cell. This is the same as exotoxin A of Pseudomonas aeruginosa, but the receptors are different

Front 14

How is immunity to diphtheria toxin given

Back 14

There is only one antigenic type of diphtheria toxin, and antitoxic antibodies neutralize its toxicity. Diphtheria toxoid is nontoxic, and when administered it elicits antitoxic antibodies. These prevent intoxication, but do not prevent colonization of C. diphtheriae

Front 15

What is the mainstay of treatment for diphtheria

Back 15

Passive immunization with horse antitoxin. Mortality increases each day the antitoxin is delayed. Allergic reactions can occur. Antitoxin is no longer made in the US. Antibiotics do not eliminate the need for antitoxin

Front 16

What is the mainstay for prevention of diphtheria

Back 16

Active immunization with diphtheria toxoid. Primary immunization during childhood is accomplished by administering a primary series of diphtheria and tetanus toxoids and pertussis vaccine (DTaP). Boosters given every ten years

Front 17

What does Listeria monocytogenes cause in domestic animals

Back 17

Septicemia and abscesses, meningoencephalitis, and infections of the uterus and fetus

Front 18

How does Listeriosis in humans often present

Back 18

Meningitis or septicemia, and is most likely to occur in immunosuppressed patients. Most infections foodborne, but infection in a pregnant patient can lead to abortion, stillbirth, transplacental infection, or infection of the infant during childbirth

Front 19

What are the properties of Listeria monocytogenes

Back 19

Psychrophilic or mesophilic and widely distributed in nature. Often foodborne
Short, gram-positive, motile rod that is nonsporulating, aerobic to microaerophilic and catalase positive. Has end-over-end tumbling motility
Beta hemolytic on blood agar. Grows on tellurite, may show palisades (Chinese letters)
13 serotypes based on somatic and flagellar antigens. Ia, Ib, IVb affect humans most

Front 20

Care must be taken to distinguish Listeria monocytogenes from what?

Back 20

Streptococci, Corynebacterium diphtheriae, and diphtheroid. Listeria monocytogenes is CAMP test positive, which helps distinguish it from environmental isolates

Front 21

What is the pathogenesis of Listeria monocytogenes

Back 21

It is a facultative intracellular pathogen. Enter cells via internalin which interacts with E-cadherin to promote internalization. Then produces a sulfhydryl-dependent hymolyin (LLO) that releases it from the phagosome into the cytoplasm. LLO is responsible for the hemolytic phenotype of L. monocytogenes on blood agar plates, and is an essential virulence factor.
Moves using host actin polymerization mediated by ActA. Spread from cell to cell without reentering the extracellular space. Encased in a double host membrane which is lysed

Front 22

What is important for development of Listeriosis

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Host factors. About 70% of cases in humans occur in immunocompromised patients. Meningitis is the most common presentation in humans. Bacteremia, focal infections, and perinatal sepsis can also occur

Front 23

How are infections by Listeria monocytogenes terminated

Back 23

Cell-mediated responses of the host

Front 24

What antibiotics are used to treat infections caused by Listeria monocytogenes

Back 24

Ampicillin or penicillin; combo of gentamicin with penicillin; combo of trimethoprim with sulfamethoxazole
Cephalosporins are not effective

Front 25

An outbreak of what microorganisms was linked to eating sliceable turkey deli meat

Back 25

Listeria monocytogenes. It caused seven deaths, and three stillbirths or miscarriages in eight states