LISTERIA, CORYNEBACTERIUM, AND SIMILAR ORGANISMS Flashcards by MAE AMOR D. CHIOCO

General Characteristics
* Catalase-positive
* Gram-positive rods
* Non-acid fast
* Non-spore-forming
* Mostly nonbranching rods

LISTERIA, CORYNEBACTERIUM, AND SIMILAR ORGANISMS

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CHARACTERISTICS NI Listeria monocytogenes

Widely distributed in nature and occasionally colonizes the human GIT

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HABITAT NI Listeria monocytogenes

Colonizer: animals, soil,
and vegetable matter; widespread in
these environments

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MODE OF TRANSMISSION NI Listeria monocytogenes

Direct contact: human GIT, ingestion of contaminated food (meat and dairy products)
Endogenous strain: colonized mothers may pass organism to fetus. Portal of entry is probably from GIT to blood and in some instances from blood and meninges

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Major virulence factor
Pore-forming toxin that reduced T-cell responsiveness

Listeriolysin O

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Bacterial surface protein
Induces host cell actin polymerization

Act A

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What are some localized infections caused by Listeriosis?

Stillbirth and neonatal death, meningitis, bacteremia, encephalitis, and endocarditis.

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What type of gastroenteritis is associated with Listeriosis?

Febrile gastroenteritis is associated with foodborne outbreaks of Listeriosis.

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What are some localized infections caused by Listeriosis?

conjunctivitis, skin infections, and lymphadenitis.

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Characteristics ni Corynebacterium diphtheriae

Only carried by humans

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Habitat ni Corynebacterium diphtheriae

Colonizer: human nasopharynx but only
in carrier state; not considered part of the
normal microbiota
Isolation from healthy humans is not
common

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MODE OF TRANSMISSION ni Corynebacterium diphtheriae

Primary mode of transmission: respiratory secretions or exudates from skin lesions

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extremely potent and lethal, blocking protein synthesis in human cells, causing the cells to die.

cytotoxic exotoxin

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What are the symptoms of respiratory diphtheria?

pharyngitis, dysphagia, low-grade fever, cervical and submandibular lymphadenopathy, fever, general malaise, and headache.

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What causes cutaneous diphtheria and what are its symptoms?

-toxigenic or nontoxigenic strains
-shallow, chronic skin lesions.

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CHARACTERISTICS OF Corynebacterium
jeikeium

Commonly encountered in clinical
specimens
Not considered highly virulent

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HABITAT NI Corynebacterium jeikeium

Colonizer: skin microbiota of hospitalized
patients, most commonly on the inguinal, axillary, and rectal sites

MODE OF TRANSMISSION Corynebacterium
jeikeium

Uncertain
Direct contact: may be person to
person
Endogenous strains: selection
during antimicrobial therapy, introduction during placement or improper care of IV catheters

s a nosocomial pathogen that causes cystitis in hospitalized patients, especially those who have undergone urologic manipulation and the elderly.

C. urealyticum

Name two other nosocomial pathogens besides C. urealyticum.

C. amycolatum and C. striatum.

known as “red coccus,” is isolated worldwide from water, soil, and manure of herbivores.

Rhodococcus

is used for processing specimens of L. monocytogenes from placenta and other tissues.

Cold enrichment

What is the primary direct detection method for Listeriosis?

Gram staining.

How do Listeria monocytogenes appear under a Gram stain?

short, gram-positive rods that may occur singly or in short chains resembling streptococci.

What media are used for cultivating Corynebacterium spp.?

Corynebacterium spp. are cultivated on 5% sheep blood and chocolate agar.

What selective media are used for C. diphtheriae?

Cystine-tellurite blood agar Modified Tinsdale agar (TIN)

What is the purpose of cystine in the selective media for C. diphtheriae?

enhances the growth of fastidious organisms, including C. diphtheriae.

How is C. diphtheriae presumptively identified on Tinsdale agar?

brown-black colonies with a gray-brown halo on Tinsdale agar

How is C. diphtheriae presumptively identified on cystine-tellurite blood agar?

black or gray

contains serum and egg, stimulates the growth of C. diphtheriae and the production of metachromatic granules in the cells

Loeffler's medium

How do colonies of C. diphtheriae appear on Leoffler’s medium?

Colonies of C. diphtheriae appear gray to white and translucent within 12-18 hours.

What molecular methods are used to identify C. diphtheriae?

Ribotyping, pulse-field gel electrophoresis, and multilocus sequence typing.

What tests can separate C. diphtheriae from other corynebacterial?

Halo in Tinsdale agar and urea hydrolysis.

Name some toxin detection methods for C. diphtheriae

-Guinea pig lethality test -immunodiffusion test (Elek Test) -tissue culture cells -enzyme immunoassays -PCR to detect the toxin gene.

How is Listeria monocytogenes presumptively identified?

By motility using a direct wet mount showing end-over-end tumbling motility, and an umbrella-shaped pattern after overnight incubation at room temperature in semisolid agar.

What biochemical tests are positive for Listeria monocytogenes?

-Ferments glucose, -Vogue's-Proskauer positive, -esculin positive, -CAMP positive.

What serodiagnosis method is used for Listeriosis?

Detection of anti-listeriolysin O antibodies (IgG).

How is diphtheria prevented?

Through immunization with a multidose diphtheria toxoid prepared by inactivation of the toxin with formaldehyde.

What is the treatment for diphtheria?

Diphtheria antitoxin (DAT) and either a single dose of IM penicillin or 14 days of erythromycin for symptomatic individuals.

What are some preventive measures for listeriosis?

-Properly washing raw vegetables and meat, -immunocompromised and pregnant individuals avoiding soft cheeses, and thoroughly heating -leftovers or ready-to-eat foods like hotdogs or cold cuts before consumption.