LECTURE - Bacilli Flashcards
when do endospores form?
when nutrients are depleted or conditions are unfavorable for growth
- can last in soil for hundreds of years
Bacillus anthracis capsule
- Poly D-glutamic acid
- protein capsule (unique!)
- antiphagocytic
- Abs to capsule is not protective
T or F. Bacillus anthracis disease is more common in wild and domesticated animals, than in humans
T
Three types of anthrax
- cutaneous (spores enter cut; eschar; necrosis of tissue so black; death rare)
- gastrointestinal (spores ingested; undercooked meat; death rate high even with antibiotics)
- systemic (spores inhaled; germinate in lung phagocytes; septic shock)
Toxins of anthrax
- edema toxin
- lethal toxin
edema toxin
- B = Protective Antigen
- A = adenylate cyclase - calmodulin …
lethal toxin
- B = PA
- A = zinc-dependent protease that cleaves MAP-kinase = cytokine release = shock for macrophages
T or F. B. anthracis is resistant to many broad-spectrum antibiotics, including penicillin
F! susceptible
= CDC = ciproflaxin or doxycycline IV until antibiotic sensitivity tests are done
Process of forming an endospore
- DNA aligned into long filament
- DNA duplicated then divided into individual chromosomes; cytoplasmic membrane begins to invaginate
- DNA becomes completely surrounded by cytoplasmic membrane
- cortex formed and some of the spore coat beginning to form
- several layers surround internal contents; mature spore
- cell wall lyse = releases endospore
coonies on BAP look like medusa heads
B. anthracis
- also edges lift with loop like beaten egg white
chest radiograph og someone with inhalation anthrax
shows mediastinal thickening
- lymph nodes swollen in mediastinum = edema
second most common cause of anthrax
systemic anthrax
- lethal if successful spread from lungs to bloodstream
Exposure to anthrax
high density of spores inhaled from infected animal fur, hide, or wool
confirmed case of anthrax
compatible clinical illness plus positive culture or 2 other tests (PCR, immunohistochemistry, serology)
suspected case of anthrax
compatible illness plus one non-culture test OR epidemiological link
Main component of anthrax vaccine
B = protective antigen
Protective antigens of B. anthracis assembly
assemble into heptameric ‘prepores’ when bound to their ligands on the cell surface
Anthrax toxin entry into cells
- binding of PA to receptor
- proteolytic activation; dissociation of PA20
- self-association of PA63 to form heptameric prepore
- binding of either EF or LF to prepore
- endocytosis of complex
- pH-dependent conversion of prepore to pore, translocation of lifand to cytosol
B. anthracis virulence plasmids
pXO1 and pXO2
Bacillus cereus
- motile unlike B. anthracis
- diseases are toxicoses (food poisonings); fried rice
- two different enterotoxins = vomiting and diarrhea
T or F. There are three different types of toxins implicated in emetic disease of B. cereus
F! for diarrheal = Hbl, Nhe, CytK
toxins are preformed in food
emetic toxins
Foodborne illness due to B. ereus w rice as th vehicle is most likely associated with
diarrheal-type syndrome
Certhrax
- first anthrax-like mART toxin from B. cereus strain
- shares 31% sequence identity with anthrax lethal factor
- like LF, requires PA for host cell entry
- 60-fold more toxic to mammalian cells than anthrax LF
B. subtilis
- common contaminant of lab media
- killing of spores to check if autoclaving was good
- effective = 121 degrees C for at least thirty mins by using saturated steam under at least 15 psi
