Mhr Topic 16: Gram (+) Rods

Front 1

Gram (+) Rod types

Back 1

Corynebacteria
Bacillus
Listeria
Erysipelothrix

Front 2

Corynebacteria general characteristics (shape, motility, capsule)

Back 2

Shape - small, gram+ pleomorphic rods
Non-motile, non-encapsulated, non-spore forming
Except for C. diphtheriae, are normal skin and respiratory flora.

Front 3

C. diphtheriae: Who, How

Back 3

Who - Occurs in non-immunized countries (rare in US).
How - Spread by respiratory droplets. Causes local infection of throat and skin.

Front 4

Diphtheria Toxin Mech.

Back 4

Has an A and B subunit.
1) B subunit binds receptor on cell surface
2) Molecule brought into cell
3) A and B disassociate
4) A gets into cytosol and catalyzes addition of ADPR to EF-2, inhibiting protein synth.

Front 5

C. diphtheriae Pathology

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Causes Diptheria, acute respirator and cutaneous disease.
1) Respiratory - Produces thick, grey exudate called pseudomembrane, can produce bull neck, obstruct airways and lead to death.
2) Cutaneous - From simple pustule to chronic non-healing ulcer.
3)If gets into circulation, can have myocarditis > heart damage and failure and have paralysis of palate, eye and other muscles

Front 6

C. diphtheriae Treatment

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Disease resolves with formation of antitoxin Ab.
1) Antitoxin Ab from horse serum
2) Antibiotic therapy
3) Toxoid - vaccine against A portion of toxin. Immunization does not prevent carrier state.

Front 7

C. diphtheriae Diagnosis

Back 7

Usually clinically diagnosed. Labs only on request.
Requires tellurite to seperate from other corynebacteria. Tellurite makes them become black with brown halo.
When isolated colonies stained with mthylene blue, see red polychromatic granules
Definitive test requires proof of toxin production.

Front 8

C. jeikeium

Back 8

Causes problems in neutropenic patients
Associated with wound infection, speticemia, and endocarditis.
Usually multi-resistant to antibiotics.

Front 9

Corynebacter urealyticum

Back 9

Causes chronic or recurrent UTIs.

Front 10

Bacillis Anthracis Shape, motility, and culture characteristics

Back 10

Gram stain: Gram +, have box cars and bamboo rods. Usually grow in larger chains.
Culture: Large, non-hemolytic, grey to white, convex, tacky.
Non-motile

Front 11

Bacillus anthracis virulence factors

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Caused by vegetative bacilli that result from spore germination.
1) Capsule - Negative charge makes it inhibit phagocytosis
2) Edema Toxin - Edema factor + protective antigen
3) Lethal Toxin - Lethal factor + protective antigen.
Protective antigen mediates internalization of other factors by host cells.

Front 12

Edema Toxin

Back 12

Product of vegetative bacilli of Bacillus anthracis. Acts as a calmodulin-dependent adenylate cyclase. ^ intracellular cAMP changing membrane permiability causing edema.
X rays reveal widening in mediastinum with pleural effusions without infiltrates.

Front 13

Lethal Toxin

Back 13

Product of vegetative bacilli of Bacillus anthracis. Is a zinc-dependent protease. Interferes with signaling pathways in phagocytic cells. Induces apoptosis, necrosis, and hemorrhagic necrosis in tissues.

Front 14

Pathology of cutaneous anthrax

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Most naturally occurring cases are cutaneous. Papule develops evolving into a painless, black pustule = eshar.
Mortality if untreated is 20%

Front 15

Pathology of inhaled anthrax

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Incubation period = 2-14 days.
Early: malaise, fatigue, flu-like symptoms, cough
Intermediate: Positive blood cultures, mediastinal lymphadenopathy, pleural hemmorages, dyspnea, hypoxia, trachycardia, cyanosis.
Late: Respiratory failure, meningitis, shock. High fatality rate.

Front 16

Diagnosis of Bacillus anthracis

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History clinical symptoms, radiography.
Gram stain and culture. PCR of skin or tissue biopsy.
Cutaneous - swab vesicle fluid, ulcer
Inhillation - Blood (CNF if meningitis is involved)
GI - feces, vomit, blood

Front 17

Bacillus anthracis treatment

Back 17

ciprofloxacin or doxycycline for initial iv therapy.

Front 18

Non anthrax Bacillus

Back 18

Non-anthrax bacillus can cause opportunistic infections.
B. cereus produces a tissue destructive exotoxin and causes food poisoning.

Front 19

Listeria monocytogenes Culture characteristics

Back 19

Gram positive rod, looks like chinese characters.
On blood agar, produce small zone of beta-hemolysis. Different from Group B strep b/c is catalase positive.
Produces tumbling motility at room temp.

Front 20

Listeria monocytogenes who/how

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Who: Pregnant women. Newborns get the serious effects. Also, immunocompromised, cancer, diabetes, elderly, someone on glucocorticosteroids.
How: Usually unpasteurized dairy. Refrigeration does not prevent growth.

Front 21

Listeria monocytogenes pathology

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1) Septicemia
2) Meningitis
3) Granulomatous skin lesions
Neonates can get infection. Infection may result in abortion or preterm delivery.

Front 22

Listeria monocytogenes infection steps

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Is an Intracellular Pathogen
1) Is phagocytosed
2) Escapes phagolysosome via listeriolysin O.
3) Grows in cytosol, gets actin tail
4) Goes to cell surface forming pseudopod
5) Leaves Cell in a pod, therefore avoiding extracellular immune systme. Uses phospholypases to hydrolyze cell membranes

Front 23

Listeria monocytogenes Diagnosis

Back 23

Culture blood/CNF

Front 24

Listeria monocytogenes treatment

Back 24

Penecillin or ampicillin + gentamicin.

Front 25

Erysipelothrix rhusiopathiae

Back 25

Gram positive filamentous rod
Catalse negative
Causes skin infection called erysipeloid in people who handle animals: butchers, vets, fishermen.