Gram- Positive Bacilli Flashcards
It is both a human and animal pathogen
It is aerobic or facultatively anaerobic and non-spore formin
Listeria monocytogenes
It is motile with pretrichous flagella and exhibits a characteristic ―tumbling motility
Listeria monocytogenes
It can grow in a high salt medium with up to 10% NaCl
Listeria monocytogenes
It is recovered from the soil, dust, water, dairy products, and processed meats
It causes miscarriage or stillbirth in humans
Listeria monocytogenes
Virulence factors of Listeria monocytogenes
Listeriolysin O, catalase, supeoxide dismutase, phospholipase C, and p60
Mode of acquisition of Listeria monocytogenes
Ingestion of contaminated food such as meat, chicken, dairy products, and
vegetables
Microscopy: Coccobacillary in form and are arranged singly or in short chains that resemble
streptococci
Listeria monocytogenes
Culture: BAP-colonies are small, smooth, transluscent, grayish blue, and are surrounded by a
narrow zone of Beta hemolysis
Listeria monocytogenes
It is a serious infection that affects neonates, pregnant women, and immunocompromised hosts
Processed meat products should be thoroughly cooked or heated before consumption as a
primary preventive measure
Listeriosis
are the most important host defense against Listeriosis
Macrophages and T-lymphocytes
It usually occurs during the third trimester of pregnancy
It leads to miscarriage or stillbirth
Signs and symptom: Flu-like illness, fever, headache, and myalgia
Maternal disease (Pregnancy)
It is associated with an intrauterine infection due to the aspiration of infected amniotic
fluid
The infected infants are at full term and appear healthy at birth
It leads to meningitis that is usually seen by the third week of life
Neonatal disease
It develops though the ingestion of contaminated dairy products and processed meat
products
. Disease of immunocompromised host
SIM test: Has an ―”umbrella-shaped” or inverted Christmas tree‖ pattern at room
temperature at 25C but not at 35C
Listeria monocytogenes
Biochemical test for Listeria monocytogenes
(+) Glucose fermentation
(+) Catalase and motility
(+) CAMP reaction-―block type‖ hemolysis
(+) Hippurate and bile esculin hydrolysis
(+) growth in 6.5% NaCl
(+) Voges-Proskauer and Methyl red tests
(-) H2S production, nitrate reduction, and urease
Gram positive bacilli, the only catalase-negative, non-spore-forming, Gram-positive, rod-shaped bacterium that
produces hydrogen sulfide.
Erysipelothrix rhusiopathiae
It is isolated from wild and domestic animals like birds and fish
Erysipelothrix rhusiopathiae
Major: reservoir of Erysipelothrix rhusiopathiae
Domestic swine
Gelatin stab culture: Has a pattern of a ―”pipe cleaner” or a ―”test tube brush” at 22C
Erysipelothrix rhusiopathiae
Mode of transmission: Direct contact with infected excreta, blood, and flesh of animals through
skin breaks
Erysipelothrix rhusiopathiae
Predisposed individuals: Veterinarians and fish handlers
Erysipelothrix rhusiopathiae
Culture: BAP- Colonies are pinpoint with alpha-hemolytic zone
Erysipelothrix rhusiopathiae
Best specimens for Erysipelothrix rhusiopathiae
Tissue biopsies or aspirates from skin lesion
the best site for collecting specimens of Erysipelothrix rhusiopathiae
the outward margin of the lesion
a. Large and rough colonies-curled, slender, filamentous with a tendency to overdecolorize and become Gram-negative bacilli
b. Small and smooth colonies-transparent, glistening, and slender rods
E.rhusio
Culture: BAP- Colonies are pinpoint with alpha-hemolytic zone
The organism can grow on BAP and CAP for up to seven days
Erysipelothrix rhusiopathiae
curled, slender, filamentous with a tendency to overdecolorize and become Gram-negative bacilli
Large and rough colonies
transparent, glistening, and slender rods
b. Small and smooth colonies-
(+) H2S production in a TSI medium
(+) Glucose and lactose fermentation
(-) Catalase, oxidase, esculin hydrolysis, nitrate reduction, VP, and urease
Erysipelothrix rhusiopathiae
The species of this genus are classified Gram-positive rods as pleomorphic, non-motile, rod-shaped,
Arcanobacterium
Biochemical test: (-) catalase
Arcanobacterium
is both lipase-and lecithinase-positive and has a positive reverse CAMP
reaction due to phospholipase D
Arcanobacterium haemolyticum
Significant species of Arconbacterium
A. haemolyticum, A. pyoges, and A. bernardiae
Culture: BAP-Colonies have a narrow zone of Beta hemolysis; exhibit pitting of the agar with a
black opaque dot
Arcanobacterium
They can cause pharyngitis and endocarditis
arcanobacterium
Culture: BAP-Colonies have a narrow zone of Beta hemolysis; exhibit pitting of the agar with a
black opaque dot
Acranobacterium
is both lipase-and lecithinase-positive and has a positive reverse CAMP
reaction due to phospholipase D
A. haemolyticum
The members of this genus are obligately aerobic Gram-positive rods that are motile by
peritrichous flagella
Kurthia
BAP-Colonies exhibit a large ―”medusa-head” appearance
Nutrient agar- Colonies exhibit a rhizoid growth
Kurthia
Biochemical test: (+) Catalase; (-) gelatinase and oxidase
Kurthia
The mebers of this large and diverse group are composed of Gram-positive bacilli
Aerobic Actinomycetes
The members are classified as aerobes with a branching filamentous growth that extends along
the agar due to the substrate hyphae, and into the agar due to the aerial hyphae
Aerobic Actinomycetes
Microscopy: Filamentous Gram-positive rods with a “beaded appearance”
Aerobic Actinomycetes
Culture: Cells elongate to form branching, filamentous forms while some organisms form
hyphae on the agar surface or into the agar.
Aerobic Actinomycetes
Aerobic actinomycetes with a branching filamentous growth along the agar due to the?? and into the agar due to the?
Substrate hyphae; aerial hyphae
o Wet mount/hanging drop method: Exhibits a “tumbling motility‖ at room temperature
L.mono
SIM test: Has an ―umbrella-shaped‖ or inverted Christmas tree‖ pattern at room
temperature at 25C but not at 35C
L.mono
o Growth occurs at a wide temperature range of 0.5C to 45C
o It requires a slightly increased amount of CO2
L.mono
Their cell wall contains peptidoglycan, meso-diaminopimelic acid (DAP), and the sugars,
arabinose and galactose
Nocardia
The species grow on media that are used to recover fungi
Nocardia
Culture: Colonies exhibit wrinkled, chalk-like, and orange-tan pigmentation.
Nocardia
o It is a chronic, localized, painless subcutaneous infection that is characterized by the
presence of sulfur granules in the affected tissue
Actinomycetoma (Actinomycotic mycetoma)
Differential test: Resistant to lysozyme
Nocardia
o It is a confluent bronchopneumonia where the sputum is thick and purulent, although the
encapsulation of the abscess is absent
o The affected tissues do not have sulfur granules
- Pulmonary disease
Causative agent: N. cyriacigeorgica and N. farcinic
what agar is used to observe the morphology of actinomyctes, and to differentiate
branching Nocardia species from non-branching Rhodococcus species
Tap water agar
Incubation at ___ promotes the growth of Nocardia species
Incubation at 10% CO2
It is non-motile and partially acid-fast, and is composed of mycolic acid with longer carbon
chains
Rhodococcus equi
it can persist and replicate within macrophages
Rhodococcus equi
Microscopy: Coccobacilli with a ―zigzag‖ pattern and a filamentous form
Culture: BAP-Colonies exhibit a pale pink or yeloow color
Rhodococcus equi
It can infect immunocompromised individuals (HIV patients) and cause slowly progressive,
granulomatous pneumonia
Rhodococcus equi
The species of this genus vary from Gram-positive to Gram-variable rods
Gordonia
Culture: Colonies are smooth and slimy with irregular edges; but may appear as dry or rough;
and exhibit the presence of mycelia
Gordonia
Differential test: Susceptible to lysozyme
Rhodococcus equi
The members are slightly acid-fast when the kinyoun method is used
Tsukamurella
Culture: Colonies are circular with rhizoid edges; has no aerial hyphae; and exhibit white or
orange pigmentatio
Tsukamurella
Culture: Colonies are dry to chalky and heaped; some colonies exhibit a grayish white color and
a ―musty basement odor‖
Streptomyces
The microscopic and colony morphology of the species of this genus is very similar to that of the
Nocardia species
Actinomadura
It causes fungal wound infection that is known as eumycetoma
Actinomadura
The most common form of eumyctetoma is known as mycetoma pedis in which the infection is
localized on the patient‘s foot
Actinomadura
Culture: Routine agar-Colonies exhibit a ―molar tooth‖ appearance
Actinomadura
t is the etiologic agent of Whipple‘s disease that affects the gastrointestinal tract joints, and
muscles and is characterized by abdominal pain and diarrhea
Tropheryma whipplei
It is a gram-positive actinomycete and a facultative, intracellular pathogen
Tropheryma whipplei
It is isolated from human feces, saliva, and gastric secretions
Diagnostic test: (+) periodic acid Schiff staining (PAS) macrophages
Tropheryma whipplei
