Lecture |Bacilli Flashcards
Spore formers
- Bacillus anthracis
- Bacillus cereus
Non-spore formers
- Corynebacterium
- Listeria
- Erysipelothrix
- Gardnerella
Branching, non-spore- formers
- Nocardia
- Aerobic actenomycetes
is Bacillus spp. aerobic, anaerobic, or facultative anaerobic?
aerobic & facultative anaerobic
Is Clostridium aerobic, anaerobic, or facultative anaerobic?
anaerobic
- Gram positive
- Aerobic or facultative anaerobic bacilli
- Endospores
- Catalase positive
Bacillus spp.
Clostridium spp. form endospores–
anaerobically
Bacillus spp. form endospores—
aerobically and anaerobically
causative agent of antrax.
Bacillus antracis
a disease of wild and domestic animals including sheep, goats, horses, and cattle.
Anthrax
Types of Anthrax
- Cutaneous Anthrax
- Gastrointestinal/Ingestion Anthrax
- Inhalation Anthrax (wool sorter’s disease)
- Injectional Anthrax
Causes a typical presentation of the ulceration is a black, necrotic lesion known as an
eschar
accounts for most human infections and is associated with contact with infected animal products.
Cutaneous Anthrax
results from ingestion of endospores
Gastrointestinal/Ingestion Anthrax
Gastrointestinal/Ingestion Anthrax presents in two forms:
oral or oro pharyngeal
Usually attributed to toxemia and sepsis.
Gastrointestinal/Ingestion Anthrax
Most fatal; previously referred to pulmonary anthrax, Woolsorters’ disease and ragpickers’ disease
Inhalation Anthrax (wool sorter’s disease)
Bacillus antracis virulence factor
- Lethal toxin (LT)
- Edema toxin (ET)
Each of virelence toxins consists of proteins such as
protective antigen (PA), lethal factor (LF) and edema factor
associated with food borne illness.
B. cereus group
organisms are often associated with infections in immunocompromised patients who have debilitating disease such as cancer or diabetes.
B. cereus
most common type of non gastrointestinal infection caused by B. cereus
endophthalmitis
also referred to as hemolysin IV
cytotoxin K
B. cereus group Virulence factors
- hemolysin BL (HBL)
- Nonhemolytic enterotoxin (Nhe)
- cytotoxin K (Cytk) (hemolysin IV)
- Cereulide
believed to act synergistically
hemolysin BL, nonhemolytic enterotoxin, and cytotoxin (hemolysin IV)
heat-stable, proteolysis, and acid-resistant toxin
cereulide
Specimen procession for Bacillus spp.
heat or alcohol shock
heat specimen 70°C for
30 minutes
heat heat specimen 80°C for
10 minutes
heat specimen 62°C to 65°C for
15-20 minutes (B. anthracis only)
only clinically relevant aerobic organisms capable of producing endospores in the presence of oxygen.
Bacillus spp.
inhibited by high concentrations of CO2
Sporulation
production of spores may be induced by
growth in triple sugar iron (TSI), urea, or nutrient agar containing 5 mg/L manganese sulfate.
a stain required to visualize endospores.
malachite green
appear pink from the secondary stain, safranin
vegetative cells
stains green
endospore
attributed by the fact that the endospores may appear as intra cellular or extracellular clear oval structures upon Gram staining.
Box car or bamboo rod appearance
selective agar for gram-positive organisms that isuseful for the removal of contaminating organisms and the isolation of Bacillus spp.
Phenylethyl alcohol agar (PEA),
used for selection and isolation from fecal contamination
Polymyxin-lysozyme-EDTA-thallous acetate (PLET)
used to induce B. anthracis capsule formation
Bicarbonate agar
an agar that should be incubated in increase carbon dioxide environment
Bicarbonate agar
in this agar, colonies of B. anthracis are nonhemolytic, large (2 to 5 mm), gray, and flat with an irregular margin because of outgrowths of long, filamentous projections.
SBA
has been used to describe the colony morphology of B. anthracis.
Medusa head
colonies of B. anthracis have what type of consistency
tenacious consistency
bacteria having the appearance or characteristic of beaten egg whites.
B. anthracis
ferments glucose
B. anthracis
produces lecithinase
B. anthracis
grows in 7% NaCl and pH<6
B. anthracis
susceptible to penicillin (10 U/mL)
B. anthracis
B. anthracis does not ferment ?
mannitol, arabinose or xylose
Grow on Egg Yolk Agar
B. anthracis
opaque zone around colonies
Lecithinase
oily sheen
Lipase
The hydrolyzed tube remain liquid even after freezing at 4°C
Gelatin Hydrolysis test
clearing of the x ray film
Gelatin Hydrolysis test
nonmotile bacterias
B.anthracis & B. mycoides
motility can be tested by either
- wet mount preparation
- inoculation into motility test medium.
Capsule production by B. anthracis can be detected by
- India ink staining on blood or CSF specimens
- on cells isolated in media supplemented with sodium bicarbonate
penicillin susceptibility of B. anthracis
susceptible
penicillin susceptibility of B. cereus
resistant
Lecithinase +
B. anthracis
Lecithinase -
B. cereus
motile -
B. anthracis
motile +
B. cereus
B. anthracis Hemolysis on BAP
none
B. cereus Hemolysis on BAP
Beta-hemolysis
B. anthracis gelatin hydrolysis
negative
B. cereus gelatin hydrolysis
postive
negative growth on PEA
B. anthracis
positive growth on PEA
B. cereus
Serodiagnosis of B. anthracis is typically available for the detection of the
PA antigen or toxin protein, LF, and EF
immunochromatographic test that presumptively identifies B. anthracis from blood agar within 15 minutes
Red Line Alert Test
most rapid detection method and differentiation of B. anthracis
PCR
recommended vaccine after aerosol exposure to B. anthracis, such as in a bioterrorist event.
Chemoprophylaxis with ciprofloxacin or doxycycline
gram positive “club-shape”
corynebacteria
- nonlipophilic/lipophilic
- catalase +
- Nonmotile
corynebacteria