24 Questions
What is the primary mechanism of listeriolysin O in preventing the killing of Listeria monocytogenes by macrophages?
It damages the phagosome membrane
What is the specific characteristic of Listeria monocytogenes that allows it to survive in certain conditions?
It can survive at refrigerator temperature under conditions of low pH and high salt concentration
What is the primary purpose of using McBride Medium in the laboratory diagnosis of Listeriosis?
To isolate Listeria monocytogenes from polymicrobial clinical specimens
Which of the following is a virulence factor of Listeria monocytogenes?
Phospholipase C
What is the primary role of the surface protein p60 in Listeria monocytogenes?
It induces phagocytosis
What is the characteristic of Listeria monocytogenes that allows it to be differentiated from other similar bacteria?
Hippurate hydrolysis positive
What is the primary group of individuals affected by Listeriosis?
Neonates, pregnant women, older adults, and immunocompromised hosts
What is the drug of choice for treating Listeriosis?
Vancomycin
What is the temperature at which Listeria monocytogenes grows, allowing for a technique called cold enrichment?
4°C
What is the characteristic of Erysipelothrix rhusiopathiae that allows it to form long filaments?
It is a pleomorphic rod
What is the typical route of infection for Erysipelothrix rhusiopathiae?
Through cuts or scratches on the skin
What is the characteristic of Arcanobacterium haemolyticum colonies on SBA?
A narrow zone of β-hemolysis
What is the characteristic of Erysipelothrix rhusiopathiae growth on gelatin stab culture?
A 'test tube brush-like' pattern at 22°C
What is the disease caused by Erysipelothrix rhusiopathiae in humans?
Erysipeloid
What is the characteristic of Trueperella (Arcanobacterium) pyogenes?
It is an animal pathogen
What is the characteristic of Arcanobacterium haemolyticum colonies on agar?
A black opaque dot
What is the primary concern for healthy individuals, particularly pregnant women, regarding Listeria monocytogenes?
Spontaneous abortion and stillborn neonates
What is the characteristic motility of Listeria monocytogenes at room temperature?
Tumbling motility
What is the optimal growth temperature for Listeria monocytogenes?
30°C to 35°C
What is the characteristic arrangement of Listeria monocytogenes cells?
Singly, in short chains, or in palisades
What is the characteristic hemolysis of Listeria monocytogenes on blood agar?
β-hemolysis
What is the primary laboratory diagnosis method for Listeria monocytogenes?
Microscopy
What is the typical outcome of Listeria monocytogenes infection in newborns?
Early-onset listeriosis
What is the preferred carbon dioxide (CO2) level for Listeria monocytogenes growth?
Slightly increased CO2
Study Notes
Corynebacterium
- Produces coccoid cells
- Corynebacterium diphtheriae has grayish white colonies
- Urease positive, differentiating it from Actinomycetes
- Corynebacterium urealyticum is most commonly associated with UTIs and is lipophilic and a strict aerobe
- Pinpoint, nonhemolytic, white colonies with characteristic coryneform microscopic morphology
- Nitrate negative, catalase positive, and urease positive within minutes after inoculation on a Christensen urea slant
- Drug of choice: vancomycin
Listeria Monocytogenes
- Virulence factors: hemolysin (listeriolysin O), catalase, superoxide dismutase, phospholipase C, and surface protein (p60)
- Can survive at refrigerator temperature under conditions of low pH and high salt concentration
- Culture media of choice: McBride Medium
- Infections: primarily affects neonates, pregnant women, older adults, and immunocompromised hosts
- Clinical infections: Listeriosis, newborns and immunocompromised adults, and pregnant women
- Spontaneous abortion and stillborn neonates can occur
- Newborns: early-onset listeriosis (can cause illness shortly after birth) and late-onset listeriosis (disease can occur from several days to two weeks)
Laboratory Diagnosis
- Microscopy: Gram-positive coccobacillus, found in singly, in short chains, or in palisades
- Cultural characteristics: grows well on SBA, chocolate agar, nutrient agars, brain-heart infusion medium, and thioglycolate broth
- Prefers a slightly increased carbon dioxide (CO2) and optimal growth temperature: 30°C to 35°C
- Colonies are small, round, smooth, and translucent, surrounded by a narrow zone of β-hemolysis
- Cold enrichment may be used to isolate the organism from polymicrobial clinical specimens
- Identification: hippurate hydrolysis positive, catalase positive, bile esculin hydrolysis positive, and motile at room temperature
- Wet mount preparations: “tumbling motility” (end-over-end motility) and produces a positive CAMP reaction
Erysipelothrix Rhusiopathiae
- General characteristics: three species in the genus Erysipelothrix, gram positive, catalase negative, non-spore-forming, and pleomorphic rod
- Usual route of infection is through cuts or scratches on skin, commensal pathogen on vertebrates and invertebrates
- Only species in this genus that can cause disease in humans, causing localized skin disease (Erysipeloid)
Arcanobacterium and Trueperella
- General characteristics: catalase negative, nonmotile, pleomorphic, aerobic or facultatively anaerobic
- Arcanobacterium haemolyticum (formerly Corynebacterium haemolyticum) and Trueperella (Arcanobacterium) pyogenes are associated with causing infections in humans
- Trueperella pyogenes is an animal pathogen, best known for causing infections in cattle
- Small colonies on SBA with narrow zone of β-hemolysis after 24 to 48 hours of incubation
- A black opaque dot is observed on the agar when the colony is scraped away
This quiz covers the characteristics of Corynebacterium, a genus of bacteria, including its morphology, growth, and enzymatic activities. Learn about the different species of Corynebacterium and their distinct features.
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