Aerobic Spore-forming, Gram positive bacili Flashcards
Charcateristic of Bacillus spp in general
- gram positive rods
- aerobic or facultative aerobic
- catalase (+); form non-pigmented colonies
- grow well in Sheep blood agar (or in enriched agars)
- non-branching
- sporulating (endospore - inactive form)
True or False:
Endospores are naturally active in the bacteria
False
- they only become active once they detect something that might possibly kill the bacteria
Bacillus spp can sometimes be confused with these bacteria
Clostridium
- since they are also gram-positive; spore-formin rods but are usually ANAEROBIC
Bacillus and Clostridium spp. can be differentiated by
Both - gram (+)
Catalase
Clostridium (-)
Bacillus (+)
Sporulation
Clostridium - anaerobic only
Bacillus - Anaerobic and aerobic
Best way to differentiate Clostridium spp from Bacillus spp.
Catalase testing
Catalase
Clostridium (-)
Bacillus (+)
Bacillus spp:
Bacillus cerues sensu lato group
- B. anthracis
- B. cereus sensu stricto
- B. thuringiensis
Bacillus spp. that is considered the most medically important, since it is considered a potential bioterrorism agent
B. anthracis
Bacillus spp: B. anthracis
Culture characteristics
- nonhemolytic - ground glass colonies on SBA
- nonmotile; encapsulated
- large, gray, flat with swirling preojections — “MEDUSA head”
- beaten egg white consistency of colonies
Causative agent of ANTHRAX ( a zoonotic disease) usully found in herbivores
- B. anthracis
B. anthracis:
Virulence factors
- capsule (D-glutamic acid)
- anthrax toxin
Capsule of B. anthracis can be visualized using
M’ Fadyean staining with methylene blue or India ink staining
The anthrax toxin of B. anthracis is made up of what proteins
- Protective antigen (PA)
- Edema factor (EF)
- Lethal factor (LF)
PA+ EF = edema
PA +LF = death
Bacillus spp: B. cereus
Culture characteristics
- beta-hemolytic on SBA
- nonecapsulated & motile
- Y - zone on egg yolk agar
- penicillin-resistant
- feathery and spreading resembling frosted glass
Bacillus spp. that often causes food poisoning and serious agentt of eye infections.
- B. cereus
B. cereus:
Virulence factors
- diarrheal enterotoxins
- emetic enterotoxin (cereulide)
A heat stable toxin produced by B. cereus which often cause nausea and vomitting in host.
- Emetic enterotoxin
Culture characteristics used to differentiate B. antracis to B.cereus
- Hemolysis on SBA
- Motility
- Resistance to penicillin
B. anthracis
- nonhemolytic
- nonmotile
- penicillin (S)
B.cereus
- beta-hemolytic
- motile
- penicillin (R)
True or False
B. anthracis is a potential terrorism thus they must be ruled out when isolated in clinical specimen
- TRUE
4 forms of Anthrax
- cutaneous
- inhalation
- gastrointestinal
- injectional anthrax
A form of Anthrax sonisdered as the most predominant form of anthrax and characterized by black “ESCHAR”
- cutaneous anthrax
acquired thru skin cuts, wounds,and insect bites
It is characterized by dark, crusty tissue at either the bottom or the top of a wound
ESCHAR
a derpressed black necrotic central area
A form anthrax also called as Woolsorter’s disease or Ragpicker’s disease
- Inhalation/ Pulmonary anthrax
True or False:
Injectional anthrax is associated with fomarion of eschar and is usually caused by drug abuse
FALSE
- no black eschar is seen
All about Food poisoning or diarrheal symptom caused by B.cereus
- incubation period 8-16 hrs
- duration 12-14 hrs
- ingestion of meat, poultry, vegetables , and pastas
Laboratory diagnosis:
B. anthracis
-gram (+) or gram-variable
“BAMBOO” rods
- clear xones may appear around cell indicating presence of capsule.
Laboratory diagnosis:
B. cereus
- similar to anthracis but without clear zone around cells since it’s not capsulated
Presumptive ID of anthrax
- stool culture in PEA, SBA. etc
B.cereus needs quantitative culture os suspected animal in cases of food poisoning
≥ 10 to the power of 5 = presumptive of B.cereus food poisoning
True or False
B.cereus can be accurately made thru stool cultures
- FALSE
we cannot use stool culture since this maybe part of noral gut flora.
Quantitative identificatio is used
Confirmation for ID of bacillus spp.
- direct flourescent antibody assays
