LISTERIA, CORYNEBACTERIUM, AND SIMILAR ORGANISMS Flashcards
General Characteristics
* Catalase-positive
* Gram-positive rods
* Non-acid fast
* Non-spore-forming
* Mostly nonbranching rods
LISTERIA, CORYNEBACTERIUM, AND SIMILAR ORGANISMS
CHARACTERISTICS NI Listeria monocytogenes
- Widely distributed in nature and occasionally colonizes the human GIT
HABITAT NI Listeria monocytogenes
- Colonizer: animals, soil,
and vegetable matter; widespread in
these environments
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
- Major virulence factor
- Pore-forming toxin that reduced T-cell responsiveness
Listeriolysin O
- Bacterial surface protein
- Induces host cell actin polymerization
Act A
What are some localized infections caused by Listeriosis?
Stillbirth and neonatal death, meningitis, bacteremia, encephalitis, and endocarditis.
What type of gastroenteritis is associated with Listeriosis?
Febrile gastroenteritis is associated with foodborne outbreaks of Listeriosis.
What are some localized infections caused by Listeriosis?
conjunctivitis, skin infections, and lymphadenitis.
Characteristics ni Corynebacterium diphtheriae
- Only carried by humans
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
MODE OF TRANSMISSION ni Corynebacterium diphtheriae
Primary mode of transmission: respiratory secretions or exudates from skin lesions
extremely potent and lethal, blocking protein synthesis in human cells, causing the cells to die.
cytotoxic exotoxin
What are the symptoms of respiratory diphtheria?
pharyngitis, dysphagia, low-grade fever, cervical and submandibular lymphadenopathy, fever, general malaise, and headache.
What causes cutaneous diphtheria and what are its symptoms?
-toxigenic or nontoxigenic strains
-shallow, chronic skin lesions.
CHARACTERISTICS OF Corynebacterium
jeikeium
- Commonly encountered in clinical
specimens - Not considered highly virulent
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.
