Flashcards in Chapter 6: Bacillus and Clostridium Deck (32):
Describe the organisms Bacillus and Clostridum
Gram-positive spore-forming rods
Does Bacillus or Clostridum like oxygen?
Bacillus is aerobic while Clostridum multiply in anaerobic environment
What is the ONLY bacterium with a capsule composed of protein?
How do humans contract Bacillus anthracis/
Direct contact with infected animals or soil
Handling infected animal products - hides or wool, drums, rugs,
Human-human contact NEVER been reported
Bacillus anthracis forms a spore which is resistant to what?
very stable and resistant to drying, heat, UV light, disinfectants, and can survive dormant in the soil for decades
The germination and expression of plasmid encoded virulence factors of Bacillus anthracis is found on what plasmids?
pXO1 and PXO2
What is pXO1 and pXO2 regulated by?
an increase in temperature to 37C, CO2, and serum proteins
*Spores only formed when introduced into the host
Where can Bacillus anthracis germinate?
skin abrasions, lungs, GI
What is a malignant pustule?
Exotoxin released by Bacillus anthracis causes a localized tissue necrosis, painless round black lesion with a rim of edema
What is Woolsorter's disease?
Spores taken up by Mo in the lungs and transported to hilar and mediastinal LNs where they germinate
Mediastinal hemorrhage occurs
What three proteins does the exotoxin encoded on plasmid pXO1 have?
Edema factor: EF - active A subunit, increases cAMP, Impaires neutrophil function and massive edema
Protective antigen (PA): promotes entry of EF into phagocytic cells
Lethal factor (LF): zinc metalloprotease that inactivates protein kinase. Stimulates TNF-a and IL-1b release from Mo
What does pXO2 encode?
three genes necessary for the synthesis of poly-glutamyl capsule
Inhibits phagocytosis of vegetative bacteria
How does Bacillus cereus differ from Bacillus anthracis?
motile, non-encapsulated and resistant to penicillin
Bacillus anthracis is NON-motile
What does Bacillus cereus cause?
food poisoning (nausea, vomiting, and diarrhea)
What enterotoxins can Bacillus cereus secrete?
Heat-labile toxin: Nausea, abdominal pain, diarrhea lasting 12-24 hrs
Heat-stable toxin: severe nausea, vomiting, and limited diarrhea
The toxin released by Clostridium botulinum causes what?
rapid fatal food poisoning
Blocks the release of ACh from presynaptic nerve terminals in the ANS and motor endplates
Causes flaccid muscle paralysis
Transmission: Smoked fish or canned veggies
S/S: b/l CN palsies causing double vision (diplopia), difficulty swallowing. general muscle weakness, sudden respiratory paralysis and death
Transmission: Honey, contaminated food
S/S: constipated for couple of days, Difficulty swallowing, muscle weakness, Floppy babies
Least common presentation of botulism
Similar to adult botulism except absence of prodromal GI symptoms and longer incubation period
Fever, Elevated WBC count
Clostridium tetani causes what?
tetanus: disease that classically follows a puncture wound by a rusty nail or other skin trauma
Spores found in soil and animal feces
Germinated in necrotic tissue
What is the exotoxin of Clostridium tetani?
tetanospasmin: causes sustained contraction of skeletal muscles
How does tetany occur?
tetanus toxin taken up at NMJ and transported to CNS
Toxins act on inhibitory Renshaw cell interneurons: prevents release of GABA and glycine (inhibitory NT)
Symptoms of tetany
Severe muscle spasms, lockjaw/trismus
Grotesque grinning expression = risus sardonicus
Mortality high after lockjaw
Describe Clostridium perfringens
Spores found in soil
Matures in anaerobic conditions
What are the 3 classes of infection with Clostridium perfringens?
Cellulitis/wound infection by Clostridium perfringens
Necrtoic skin is exposed, organisms grows and damages local tissue. Palpation reveals a moist spongy, crackling consistency to the skin due to pockets of gas (crepitus)
Clostridial myonecrosis by Clostridium perfringens
Secretes exotoxins that destroy muscle adjacent to wound entry
Ferment carbs, resulting in gas formation
Pockets of gas within muscles and subQ tissue
Thin blackish fluid exudes from skin
Fatal unless treated early
Diarrheal illness by Clostridium perfringens
Spores can germinate in foods (meat, poultry, gravy)
Ingestion of large amounts can lead to toxin in gut
What is responsible for antibiotic-associated pseudo-membranous colitis?
Severe diarrhea, abdominal cramping and fever
What can follow the use of broad spectrum antibiotics that leads to diarrhea?
Antibiotics wipe out part of normal intestinal flora, allows Clostridium difficile to superinfect to colon
Releases its exotoxins
What toxins does Clostridium difficile release?
Toxin A - causes diarrhea
Toxin B - cytotoxic to the colonic cells