Bacteria: Gram Positive Bacilli Flashcards
List the Gram Positive Bacilli
- Bacillus Anthracis
- Bacillus Cereus
- Clostridium Tetani
- Clostridium Botulinim
- Clostridium Difficile
- Clostridium Perfingens
- Corynebacterium Diphtheriae
- Listeria Monocytogenes
Bacillus anthracis is a
- gram-positive
- spore-forming
- bacillus
- chains
Cutaneous anthrax
(the most common manifestation of Bacillus anthracis infection) presents with an area of central necrosis with surrounding erythema, edema, and eschar formation
Bacillus anthracis and cereus bacteria are
gram-positive bacilli that occur in chains
The capsule of Bacillus anthracis is composed of
poly-γ-D-glutamic acid (a polypeptide)
Bacillus anthracis needs
oxygen to sporulate (but can make ATP with and without oxygen; ie, aerobic or facultatively anaerobic)
Bacillus anthracis and cereus bacteria have
the ability to form metabolically inactive spores, which are resistant to decontaminants such as heat, chemicals, and radiation
The edema factor exotoxin of Bacillus anthracis
mimics adenylate cyclase → increase in cAMP → edema and dysfunction of phagocytes
The lethal factor exotoxin of Bacillus anthracis is
- a protease that cleaves mitogen-activated protein kinase (MAPK) → apoptosis, tissue necrosis multisystem physiologic disruption, and death
The lethal factor exotoxin of Bacillus anthracis is responsible for
the tissue necrosis seen in cutaneous anthrax
Wool sorters
are historically associated with pulmonary anthrax/inhalation anthrax (woolsorters’ disease) due to inhalation of Bacillus anthracis spores carried in animal wool (though this form of anthrax is rare in developed countries)
Pulmonary anthrax/inhalation anthrax primarily manifests as
hemorrhagic mediastinitis with bloody pleural effusions
Chest X-ray of patients with hemorrhagic mediastinitis from pulmonary anthrax/inhalation anthrax may show a
widened mediastinum or pleural effusions
_______ are effective against Bacillus anthracis
- fluoroquinolones
2. doxycycline
Bacillus cereus
ingestion of Bacillus cereus preformed toxin (classically associated with reheated rice) can cause early onset food poisoning → nausea/vomiting (early onset, within 6 hours) or watery diarrhea, abdominal cramps (onset within 6 to 15 hours)
Bacillus cereus is a
- gram-positive
- spore-forming
- bacillus
Bacillus cereus infection is classically associated with
reheated rice (warm temperatures → spore germination → enterotoxin production (preformed toxin)→ early onset food poisoning)
Clostridium tetani is
- gram-positive
- spore-forming
- bacillus
- obligate anaerobes
Clostridium tetani bacteria have the ability to
form metabolically inactive spores, which are resistant to environmental decontaminants such as heat, chemicals, and radiation
Clostridium tetani infection is classically associated with
- puncture wounds from barbed wire
2. puncture wounds from rusty nails
The metabolically inactive spores of Clostridium tetani are
ubiquitous in soil
The classic findings in tetanus include
trismus (a spastic paralysis of the jaw muscles (lockjaw)), and risus sardonicus (continuous contraction of the facial muscles resulting in an “evil smile” appearance)
The spasmodic contraction seen in tetanus can
extend to the neck and back → opisthotonos (backward arching of the head, neck, and spine)
The tetanus toxin of Clostridium tetani
- travels via retrograde axonal transport to the spinal cord
- protease that cleaves SNARE proteins
Tetanus toxin is called
tetanospasmin
The tetanus toxin (tetanospasmin) of Clostridium tetani functions to
the tetanus toxin (tetanospasmin) of Clostridium tetani cleaves SNARE proteins → inhibition of GABA and glycine release (inhibitory neurotransmitters) from Renshaw cells in the spinal cord→ muscle spasms, spastic paralysis, and hyperreflexia
The tetanus toxin (tetanospasmin) of Clostridium tetani acts on
the tetanus toxin (tetanospasmin) of Clostridium tetani acts on Renshaw cells (inhibitory interneurons in grey matter of the spinal cord) → inhibition of GABA and glycine release → muscle spasms, spastic paralysis, and hyperreflexia
Prevention of tetanus includes
administration of tetanus vaccine, which consists of deactivated tetanus toxin (often given with the diphtheria toxoid and acellular pertussis vaccine (DTaP))
Clostridium botulinum is
- gram-positive
- spore-forming
- bacillus
- obligate anaerobes
The anaerobic environment of improperly canned food allows
spore germination and growth of Clostridium botulinum
Clostridium botulinum bacteria have the
ability to form metabolically inactive spores, which are resistant to environmental decontaminants such as heat, chemicals, and radiation
Clostridium botulinum can cause
a descending flaccid paralysis (due to production of botulinum toxin) starting from the cranial nerves
Clostridium botulinum can cause a descending flaccid paralysis due to
production of botulinum toxin
Clostridium botulinum can cause a descending flaccid that may first affect
the eyes, causing ptosis and diplopia
Botulinum toxin of Clostridium Botulinum is a
botulinum toxin of Clostridium botulinum is a protease that cleaves SNARE → inhibition of presynaptic release of acetylcholine (an excitatory neurotransmitter) at the neuromuscular junction → flaccid paralysis
Infant botulism results from
ingestion of spores, which are able to colonize the GI tract of infants due to a not yet fully developed GI flora (in contrast to adults, who contract botulism from eating preformed toxin)
Honey
honey is frequently contaminated with Clostridium botulinum spores and it is advised that infants are not allowed to consume honey until they are at least 12 months of age
Clostridium difficile is
- gram-positive
- spore-forming
- bacillus
- obligate anaerobes
Clostridium difficile bacteria have the ability to
form metabolically inactive spores, which are resistant to environmental stressors such as heat, chemicals, and radiation
_______ is the most significant risk factor for Clostridium difficile infection
prior exposure to antibiotics (particularly clindamycin) is the most significant risk factor for Clostridium difficile infection
Prevention of Clostridium Difficile
contact precaution and infection control measures (hand hygiene with soap and water, use of gloves) help prevent spread of Clostridium difficile (and is especially important for protection of patients who are taking antibiotics, such and clindamycin)
toxin A (enterotoxin) of Clostridium difficile
toxin A (enterotoxin) of Clostridium difficile binds the brush border membranes of the gut → damage to the mucosal lining of the colon → diarrhea
Clostridium difficile can cause
watery diarrhea (often with abdominal pain, fever, and leukocytosis)
Toxin B (cytotoxin) of Clostridium difficile
- toxin B (cytotoxin) of Clostridium difficile disrupts the cytoskeleton via actin depolymerization → necrosis of colonic mucosal surfaces → pseudomembrane formation
- toxin B (cytotoxin) of Clostridium difficile causes pseudomembrane formation (toxin B disrupts the cytoskeleton via actin depolymerization → necrosis of colonic mucosal surfaces → pseudomembrane formation)
Diagnosis of Clostridium difficile infection can be made by
detection of its toxins (A and B) in the stool
_____ is effective against Clostridium difficile
- oral vancomyocin
2. metronidazole
Clostridium perfringens is
- gram-positive
- spore-forming
- bacillus
- obligate anaerobe
Clostridium perfringens infection is associated with
military combat wounds
Clostridium perfringens bacteria have the ability to
form metabolically inactive spores, which are resistant to decontaminants such as heat, chemicals, and radiation
the metabolically inactive spores of Clostridium perfringens are
ubiquitous in soil
Clostridium perfringens can cause
necrotizing skin and soft tissue infection, which can progress to myonecrosis and gas gangrene
The alpha toxin of Clostridium perfringens
- the alpha toxin of Clostridium perfringens is a lecithinase that cleaves lecithin (a phospholipid) molecules of phospholipid complexes → damage to cell membranes → myonecrosis and hemolysis
- the alpha toxin of Clostridium perfringens is a lecithinase that cleaves lecithin (a phospholipid) molecules of phospholipid complexes → damage to cell membranes → hemolysis
Clostridium perfringens produces a
double zone of beta-hemolysis when plated on blood agar (both the alpha and theta toxin of Clostridium perfringens have hemolytic activity)
The first-line treatment for Clostridium perfringens tissue infection is
surgical debridement and administration of antimicrobials, particularly penicillin
Ingestion of a large quantity of Clostridium perfringens spores can cause
late-onset food poisoning, characterized by watery diarrhea
Corynebacterium diphtheriae bacteria
- gram positive
- bacillus
- form V or Y shaped chains
The cytoplasm of Corynebacterium diphtheriae contains
metachromatic granules that stain with aniline dyes (the metachromatic granules stain red while the remainder of the bacillus stains blue)
Diptheria Toxin of Corynebacterium diptheriae
- diphtheria toxin of Corynebacterium diphtheriae inhibits elongation factor-2 by ADP ribosylation (a mechanism similar to that of exotoxin A of Pseudomonas aeruginosa)
- the diphtheria toxin of Corynebacterium diphtheriae causes cell necrosis → dense, grey tonsillar/pharyngeal pseudomembrane formation
Laryngeal diphtheria can
lead to severe lymphadenopathy → characteristic swelling of the neck known as “bull neck”
Corynebacterium diphtheriae is transmitted via
respiratory droplets
Presence of the diphtheria toxin of Corynebacterium diphtheriae in the bloodstream can result in
cardiac toxicity → myocarditis, arrhythmia, and heart failure
The diphtheria toxin of Corynebacterium diphtheriae can cause
nerve damage (demyelination) → paralysis that typically begins in the posterior pharyngeal wall and soft palate
Corynebacterium diphtheriae will grow as
dark black colonies on cystine-tellurite agar
Corynebacterium diphtheriae can be cultured in
Loeffler’s medium (where it develops metachromatic granules seen in the cytoplasm after staining with an aniline dye)
The ELEK test is used to differentiate
toxigenic from nontoxigenic Corynebacterium diphtheriae
The Corynebacterium diphtheriae toxoid vaccine is
typically only administered in developed countries and consists of inactivated diphtheria exotoxin (often given with the tetanus toxoid and acellular pertussis vaccine (DTaP))
Listeria Monocytogenes
- gram positive
- Bacillus
- facultative intracellular pathogens
- catalase positive
Listeria monocytogenes colonies are
weakly beta-hemolytic (surrounded by a small zone of complete hemolysis when plated on blood agar)
Listeria monocytogenes bacteria exhibit
tumbling motility in broth
Listeria monocytogenes bacteria form
“rocket tails” via actin polymerization that allow movement within and between host cells
Listeria monocytogenes bacteria are able to
grow in temperatures as low as 0°C and exhibit motility at temperatures between 22-27°C
Listeriosis outbreaks are associated with
dairy products like milk, soft cheese, and ice cream
the incidence of listeriosis is significantly higher in
pregnant women
Listeria monocytogenes is the third most common cause of
neonatal meningitis (following Streptococcus agalactiae (group B strep) and E. coli)
Listeria monocytogenes is a common cause of
meningitis in adults over 60 and immunocompromised patients
___ is effective against Listeria monocytogenes
ampicillin